About the boo k This plain and concise handbook is a useful instrument for Yacht Design students and an enjoyable reading for boat builders and boat owners who want to learn more about their yachts. The author takes the reader by the hand and leads him step by step through an overall check of all yacht design aspects, with useful suggestions and a few tricks of the trade.
The author Massimo Gregori Grgič experience starts in the 70’s with theWestlawn School of Yacht Design. In
1976 he founded Yankee Delta Studio and since then never stopped designing yachts. He has taught at the Yacht Design Master of Milan, Venice and Shanghai. For the same Publisher he has written two naval architecture handbooks: Il Progetto della Nave and Interior Yacht Design, the latter fourhanded with Professor Francesca Lanz. He lives and works in a farm on the Tuscany hills.
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Contents
Foreword Acknowledgements Chapter 1. The hull design 1.1. Abstract 1.2. The first moves
Chapter 2. The planning hu lls 2.1. Abstract 2.2. The reference network 2.3. The main hull lines 2.4. Some hints of hydrostatics 2.5. The ship’s weights 2.6. The “rule of thethumb” 2.7. A short preliminary check 2.8. More sections 2.9. Managingthe hull shape 2.10. Flank ahead
Chapter 3. The displacing hull 3.1. Abstract 3.2. The hull ines l 3.3. A short preliminary calculation 3.4. The weight modifications 3.5. Back to the drawing 3.6. The decks
Chapter 4. The mathematics of the hull 4.1. The displacement 4.2. The comparison coefficients 4.2.1. The prismatic coefficient 4.2.2. The block coefficient 4.2.3. The fineness coefficient 4.3. The unitary displacement
Chapter 5. Stability 5.1. The centre of gravity 5.2. transverse metacentric height 5.2.1. The metacentre 5.3. The effects of the transverse metacentric height 5.4. The stability 5.5. The inclining experiment 5.6. The longitudinal metacentric height
Chapter 6. The propulsion
6.1. The fixed pitch propeller 6.1.1. The propeller’s structure 6.2. The pitch 6.3. The slip 6.4. The pitch calculation 6.5. The diameter calculation 6.6. The cavitation 6.7. The As/Ad ratio 6.8. The clearance 6.9. The shaft line 6.10. The stern tunnels 6.11. The controllable pitch propeller 6.12. The jet propulsion
Chapter 7. Rudder 7.1. The rudderguideline effect 7.2. A design 7.3. The rudder machine
Chapter 8. The building materials 8.1. Abstract 8.2. The wood 8.2.1. Wood: a live substance 8.2.2. The building techniques 8.2.3. The strake planking 8.2.4. The clinker 8.2.5. The cross laminated wood 8.2.6. The marine plywood 8.2.7. The unfit wood composites 8.3. The light alloy 8.4. The steel 8.5. 8.6. The The fibreglass ferrocement 8.7. The fairing and the painting
Chapter 9. The engine room 9.1. The main engines (MMEE) 9.1.1. The characteristic curves 9.2. The gases exhaust line 9.3. The comburent 9.4. The ventilation trunks 9.5. Cooling water 9.6. The gen sets 9.7. The control room 9.8. More machineries and arrangement
Chapter 10. The plants 10.1. Abstract 10.2. The pumps 10.3. The bilges drain 10.4. The fresh water 10.5. The deck washing 10.6. The firefighting 10.7. The fuel supply 10.8. The black waters 10.9. The electric plant
10.10. The air conditioning 10.11. The lockers ventilation
Chapter 11. The tonnage Chapter 12. The mooring manoeuvres 12.1. Abstract 12.2. The equipment number 12.3. The chain 12.4. The anchor 12.5. The roadstead mooring 12.6. The windlass 12.7. The hawse pipe 12.8. The cleats and fairleads 12.9. The capstans
Chapter 13. The classification Registers Chapter 14. The general arrangement plan 14.1. Pinpoint the design parameters 14.2. The general arrangement plan 14.3. The lower deck layout 14.4. Is the arrangement aboard? 14.5. The main deck layout 14.6. Hints of ergonomics
Chapter 15. The executive plans 15.1. The feasible drawings and the essential information 15.2. The specifications and the bill of quantities 15.3. The owner’s cabin 15.4. The guests’ cabins 15.5. The toilets 15.6. The crew quarters 15.7. The kitchen 15.8. The pilothouse 15.9. The sitting room
Chapter 16. The details and the tricks 16.1. The differences from the household furniture 16.2. The doors 16.3. The natural lighting 16.4. The artificial lighting 16.5. The shower 16.6. The bathroom appliances 16.7. The curtains 16.8. The mirrors 16.9. The plugs and the sockets 16.10. The ceilings 16.11. The floors 16.12. The sofas and the armchairs
Chapter 17. The furniture mate rials 17.1. The marine plywood 17.2. The solid wood
17.3. The briar 17.4. The types of wood 17.5. The stonework 17.6. The fabrics 17.7. The leather 17.8. The leather imitation 17.9. The paint
Chapter 18. The deck arrangement 18.1. The aft cockpit 18.2. The sunbathing areas 18.3. The Fly bridge
Chapter 19. The safety on board 19.1. The emergency escapes 19.2. The life rafts and the life jackets
Chapter 20. The design for all The design for all: a call for ethics
Chapter 21. The refit The refit of an old vessel
Chapter 22. The draft ing 22.1. The drawings dimensions 22.2. The drawings scale
Chapter 23. The survey, the management and the sea trials Digest of Massimo’s principle s Conversion Table Bibliography
To Giulia and Leonardo, beloved grandchildren.
Quelli che s’innamoran di pratica sanza scienzia son come l’nocchier ch’entra in navilio sanza timone o bussola, che mai ha certezza di dove si vada *
Leonardo da Vinci
* Those who fall in love with practice without science are like the helmsman who sails without rudder or compass, and never k nows where he’s going .
Foreword
First of all let me apologize to all the readers of this book for its language, which might sound somehow weird to the English-speaking. I managed to write this text in English, which is not my mother tongue, and I’m sure that I made several mistakes, some of them possibly funny. In any case I tried to stick to a language as plain as possible: at the end of the day this handbook is addressed to the very beginner. Someone might wonder why I didn’t entrust the version of this book to a professional translator. There are several reason, but the main one is that only a vocational translator (not easy to spot), or the author himself, could render the technical parts. So: please forgive me and do focus on the content, not on the form. This text follows two former books of mine, written in Italian and printed by the same Publisher in 2009. I wrote one of them (namely “Interior yacht design”) four-handed, with the invaluable contribution of a co-author, professor Francesca Lanz. She took care of the priceless theoretical and cultural sections concerning the background of contemporary interior yacht design, which I have not included in this handbook, due to its inherently practical purpose. The students of Yacht Design courses or masters come from all-over the world: in my recent classes I had very few Italians while the majority of the students were from Brazil, Spain, Greece, Romania, Germany, Lebanon, Turkey, Mexico, Uruguay, Chorea, China … from everywhere. The only common language in this Babel is English, and this is the inspiring motivation for this handbook. For the formulas I have decided to use the simple symbols of “* ” as a multiplier, “ / ” for divisions, # for “number”.
Acknowledgements
Thanks to Jotun Marine Paints and Coatings, which is the main financial sponsor of this book. Jotun is a Company which employs some of the best people I ever met in my career. Not only competent and professional, but also kind and caring. I wish I could thank all of them, name by name, but it’s a crowd: let me remind (ladies first) Işil Celik, Başak Kanat, Gemma Gonzales Ferrer and then Albert Grau, Carlo Pertini… POLI.DESIGN of Politecnico di Milano runs a Yacht Design Master, called MYD, where I taught for several years: actually a large section of the srcinal text is nothing else but the collection of the lecture notes that I wrote for my lessons. I wish to thank the Politecnico and professor Andrea Ratti for choosing this text. A considerable help to address this book on its road. I’m grateful to Michele Stefàno and Gianni Bani: they work with me side by side, took care of the figures, tables, charts, designed the book cover: their help was invaluable for the final result of the book. Mss. Katia Forte is a professional translator: she lent a hand, having a quick (and yet qualified) look at the text, highlighting my worst mistakes. Many thanks. Thanks to Francesca Lanz, a professor, a professional and a friend, who allowed me to re-write a part of the book that we wrote together in 2009. Some of the figures of this handbook are taken from existing yachts or from different marine industry builders catalogues. Thanks to all of them. And I mainly wish to thank the readers of this book: this work would be useless without them.
Chapter 1 The hull design
1.1. Abstract
The word “hull” refers to the part of the ship made of the dead works, or topside (above the floating line, also called Load Water Line or LWL), and the quick works, or bottom (below the floating line). There are many types of hulls. The first and main difference is between merchant ships and pleasure crafts. I preliminarily wish to clarify that I use the words “ship” and “vessel” in an allinclusive meaning: don’t just think of ocean liners. Among professional hulls there are cargoes, chemicals, gas, oil and containers carriers, ferries, tug boats, supply vessels, pilot and fishing boats (among which there are several different types). There are professional hulls for military purpose, from submarines to aircraft carriers. Pleasure crafts belong to a few categories, almost consistent according to their propulsion: sailing boats (racers or cruisers), motorsailers, motor vessels including displacing or semi displacing hulls and planning boats. This list only refers to single hull vessels: but we shouldn’t forget the existence of catamarans, trimarans and hovercrafts. Besides, there’s no precise border between one type and another: there are pleasure submarines, fishing boats or tug boats converted into super yachts and so on. Several books have been written about the sailboats design, and I won’t therefore care about those vessels. The books dedicated to motor boats design are fewer: and this is what this text tries to take care of. 1.2. The first moves
The very first step is choosing which type of hull we’re going to design. We’ll go through two different hypothesis: a displacing hull and a planning one. This should clarify the differences. Shortly: every hull, while sailing through the water, creates a set of trochoidal waves. The first wave crest is near the bow. The distance of the second wave crest from the first is function of the vessel speed. The maximum possible speed for a displacing boat is function of the waterline length: as the ship’s speed increases, the second wave crest shifts backwards, till it reaches the transom. The bow tilts upwards, the resistance increases ... and there’s no way that a displacing hull can sail quicker than this: her displacing shape is such that she cannot overcome her limit-speed (see figure # 1).
Fig. 1
At maximum speed the resistance curve has a peak: exceeding this speed is not only a question o available power, but mainly of hull shape. There’s a formula to calculate with good approximation the maximum allowed speed for a displacing hull:V = K * . The speed V is in knots, WL is measured in feet. The K parameter equals roughly 1.34 for the type of displacing hull that we consider, but might be different for other kind of hull designs. Incidentally, I wish to mention that one knot speed is equivalent to 1.852 metres per hour and that a foot corresponds to 0.3048 metres. In the example of figure # 1 the WL (waterline length) is 22.75 metres, equal to 74.5 feet. The square root o 74.5 is 8.63. The limit-speed is therefore 1.34 * 8.63 = 11.56 knots. The planning hull shape, on the contrary, is such that it generates a lifting effect: in other words, the vessel can slide above the second ave crest and plane. The uplift force that supports this type of hull is no more simply hydrostatic, doesn’t only obey to Archimedes principle but, while sailing, produces an hydrodynamic lift which partly raises the boat above the water. We shall study two different hull lines: planning and displacing. The design parameters will change but the drafting method shall be the same.
Chapter 2 The planning hu lls
2.1. Abstract
The step to begin with is deciding the ship’s dimensions. How can a beginner decide which width (or beam) is fit for a given ship’s length? And which is the correct draft? In absence of experience, the only feasible way is gathering as many information as possible from magazines, books, brochures. It shall turn out clear that the Length All Out (LOA) versus Maximum Beam (B) ratio (L/B) is different for various hull families, and isn’t even coherent. I quote two examples of hulls designed by my Studio: • a displacing motor yacht, with a LOA of 42 metres: the beam is 8.50 metres and L/B is 4.941; • a planning motor yacht, with a LOA of 18 metres: the beam is 5.60 metres and L/B is 3.214. The above values and ratios should not be appraised as a truth. They only relate to particular hulls, designed by my Studio for specific needs. What really counts is understanding that the L/B ratio changes considerably on varying the ship’s dimensions. Let’s absurdly suppose that the 42 metres ship had the same L/B ratio of the 18 metres motor yacht. The result would beB = 42 / 3.214 = 13.06 metres, instead of 8.50. Such a width would be enormous and would cause an amount of problems. First it would arise an abnormal metacentric height (we’ll see later what it means); the main section area and therefore theoff, motion resistance grow; last butimagine not least, it ouldwould laughincrease, every sailor man’s head worldwide. As would anotherincredibly bizarre example, let’s that the smaller vessel had the same L/B ratio of the larger one: it would beB = 18 / 4.941 = 3.64 metres, kind of an unsteady torpedo, with no space inside for any arrangement. We deduce that the width of a hull doesn’t increase linearly with its length. The L/B ratio changes in different types or families o hulls: the ratio of displacing vessels is different from planning yachts and so on. A good help for a beginner is drafting a spreadsheet, showing dimensions, ratios and data concerning as many vessels as he/she comes to know: a lot of very useful curves will be generated. A few examples of ratios, besides L/B: • Waterline Length (LWL) versus Waterline Beam (BWL); • Length All Out (LOA) versus Displacement (Δ); • Weight (or Displacement) versus available P ower; • the above said ratio versus speed (S). The more input data, the more reliable the curves. Once you plot the curves, many points might result above or below the graph: discard them light-heartedly. 2.2. The reference network
Let’s presume that the main dimensions of the hull are set. The first vessel is a planning hull with
the following dimensions: • LOA 32.4 metres; • B 7.40 metres. A reasonable draft, as per the average data concerning existing yachts (see above), is about one metre and a half. Currently the project proceeds through a trail-and-error system, by approximation. Our target is to represent the three dimensional hull body by means of a two-dimensions drawing. Imagine it’s not a vessel, but a salami. We want to cut it with different planes and find out which shapes do come out. We set now a reference network: it shall be the guideline for all the subsequent design work. Two basic lines are: the centre line, aka the vessel’s axis of longitudinal symmetry; the base line, aka the ground line, a reference for all heights. We add several vertical lines: they stand for the planes, perpendicular to the centre line that cut across the hull. These lines are called “stations” and must positively be equidistant. They’re numbered, starting with zero aft: in other words, station # zero corresponds to the beginning of the designed floating line, or sometimes to the rudder stock position. In this example the common interval between them is 970 millimetres, or 0.97 metres (See Figure # 2).
Fig. 2
The stations of the body plan, or transverse sections, are somehow alike the regular knife-cuts of a salami lying down along the centre line and perpendicular to it, and the salami slices shape equals the shape of the ship’s “frames”. The frames are the actual “ribs” of the hull body and might be built out of steel, wood, light alloy and more. The stations are the geometrical shape of the vessel’s transverse sections. Frames and stations might or might not correspond in the real construction: at the end of the day, it’s the designer’s choice. My Studio’s policy is to have them corresponding. At the present design stage, the common interval of 970 millimetres is arbitrary, just an example. Let’s trace now some lines, parallel to the centre line and again equidistant: those are the “buttocks” and cut the hull ith planes parallel to the amidships plane. In a way, it’s like cutting the salami along the longer axis: unusual and yet possible. We use the same common interval: 970 millimetres. The buttocks are called ith letters: A, B and C. Please note that the same letters appear aside station # 14 in the upper part of the drawing. It’s because we will use station # 14 as the centre line of the body plan sections, as seen from bow and stern. There is also a strange symbol, cabalistic like: a circle, partly crossed by two symmetrical arches: it means that station # 14 is used as a centreline. Then we add more lines: those are the “waterlines”, they are parallel to the base line and their common interval is 300 millimetres. This time we plan to cut the hull with planes parallel to the ground: like slicing the salami with cuts parallel to the cutting board (see figure # 3), and mind your hands! We call these lines WL 3, WL 6 etcetera. The reference network is now complete and it’s the right time to introduce the Principle number one: the reference network must show, exactly alike, on each and every drawing of the ve sse l.
It’s somehow like a map for the explorer: it’s absolutely indispensable and no designer should ever forget it.
Fig. 3
2.3. The main hull lines
Let’s draw the main lines of the vessel, both in plan view and elevation: the sheer line, the keel and the chine (see figure # 4). We might wonder why these lines have such a shape and not another. The designer should acknowledge the existence of some fixed borders, before he/she frees his/her creativity. The lines must be “fair”, meaning that they shouldn’t show bumps, hollows, sharp edges; the lines must belong to the naval architecture logic. It’s a thousand-years-old science and no one expects a beginner to launch innovations, at the same time maverick and winning. The drawing’s lines need to be fair because they represent the actual, real lines of the vessel: if they’re bumpy, the hull will be equally uneven. As how to design such lines, I’m perfectly aware that nowadays a computer does it for us. But here is my Principle number two: a computer is not an intelligent machine that helps the fool: on the contrary, it’s a fool machine that only works in the hands of the intelligent.
This is why I shall spend some time explaining what old-time designers (such as me) used to do slowly, before we let a computer do the same quickly. The good old way of designing the hull lines started from the drafting table. The drawing used to be drafted on transparent tracing-paper and the lines were created by splines, handmade out of wood, plastic, light alloy. Some splines had a constant section: other had tapered ends. Some were more stiff, some more soft. Their length ranged from a few centimetres to three and even more metres. Every designer had his own accurately guarded stock of splines. The splines were held in the chosen position (curves and fair lines) by means of shaped eights, called “leads”. They had a kind of nail on one end. Probably, figure # 5 explains it better than words. The drafting table used to be perfectly horizontal, so that the lead weights wouldn’t fall from the splines. The designer would run his Indian-ink pen along the spline, avoiding ink stains. Some shapes couldn’t be designed by the splines and were traced by drawing curves, made of plastic or wood. Figure # 6 shows only a few of the existing hundreds.
Fig. 4
The ones in the figure are from my Studio and are made of mahogany: nowadays they are unobtainable, as the last craftsman who made them is sailing the heavens since long time. A complete
hull project required the designer some force and physical resistance. Now the same lines are generated by a computer in a fraction of a fraction of time: we have more free time, less headaches and maybe also less satisfaction. Coming back to the drawing: it shows only half of the sheer line plan view.
Fig. 5
Fig. 6
As a matter of fact we only design half of every vessel’s part that is symmetrical in respect to the centre line, or plane. Towards the bow the sheer line doesn’t end with a sharp edge but joins to a circle. This is not just an arguable aesthetic choice: a sharp-end bow would be difficult to build and ould be a weak spot, right in a highly stressed area. Let’s draw some transverse sections starting from the main frame, the wider one, the one that (in theory) holds the projection of all the other sections. In the example it’s section # 14. We know the height of the sheer line and its width. We also know the chine height, it’s inner and outer width (it has a small flat surface, a skid). The keel is on the centre line, and it’s height is known. Let’s join the sheer point with the outer chine. The outer chine ith the inner chine, and this point to the keel. We have a rough transverse section drawing of section
# 14 (see figure # 7). The hull side, as is now, is a flat surface and it will look ugly and bulky. We can therefore insert one or more “mouldings”, that is to say one or more small steps. Their line and the shadow that underlines them shall lighten the hull side. The line representing the hull side, as well as the one showing the bottom, is now straight, but generally is not. These lines are actually arches, convex or concave. The drawings shall report the value of their camber. Obviously every change o the sheer, the chine or the keel design shall sensibly modify the sections shape. 2.4. Some hints of hydrostatics
Let’s skip for a while the drawing to consider a few hydrostatics hints. As earlier said, part of the hull is above the load waterline (LWL) and it’s called dead works. Another portion lays below the LWL andvessel is theobeys quicktoworks, or bottom. The latter is the subject a fewbuoyant basic hydrostatic The floating Archimedes’ principle of flotation: «Theofupper force that hints. is exerted on a body immersed in a fluid is equal to the weight of the fluid that the body displaces». The ship in the water moves apart, or in other words displaces, a volume of water. The weight of this quantity o ater is equal to the weight of the vessel: neither more nor less. Equal. That’s why the vessel’s eight is called “displacement”. Just to make an example: if the boat weights 49 metric tons she will sink until she’ll displace roughly 49 cubic metres of water. “Roughly” because the specific weight o the water is different from lake to sea, from sea to sea, from summer to winter.
Fig. 7
Only distilled water weights exactly 1,000 kilograms per cubic metre. Lake water weights 1,012 kilograms per cubic metre, Mediterranean water weights 1,023, Persian Gulf water 1,032. The specific weight of the water is different, but the ship’s weight is still the same, as well as the weight of the water she displaces. She will just float higher above the water in the Gulf rather than in a lake. On small vessels the difference isn’t significant, while on a large ship it might considerably change the immersion. There are an infinite number of small forces, called vectors, which push the hull upwards. They converge in a single application point, which is inside the hull, somewhere along the centre plane and somewhere above the base line. It’s called Centre of Buoyancy, or CB. The weight of a yacht is the sum of a huge amount of unitary loads: some are permanent, such as the structure, the engines, the tanks (empty), the mooring equipment, the plants, the arrangements and much more. Some of the weights are variable, like the crew, the fuel, the fresh water, the bilge water. For our design ork we consider the half load weight: all the fixed ones plus half the variable. Every weight increase shall worsen the vessel’s performance, as the speed of every vehicle (a car, a bike, an airplane…) is highly influenced by the weight/power ratio. Out of my experience I feel like establishing
Principle number three: during my long career I’ve never seen a vessel that, at launching, proved to be lighter than expected.
All of them were heavier. To be honest, they all were also late on schedule and more expensive than expected. Therefore the designer should be cautious and lavish while estimating the vessel’s eight. And possibly also while committing himself to cost and delivery schedule. 2.5. The ship’s weights
All the single load forces, or vectors, converge in a single vector and its point of application is inside the hull, somewhere along the vessel’s centre plane and somewhere above the base line. It’s called Centre of Gravity, or CG simply G). “trim”, The design of the vessel foresees specific (half) load waterline position and(sometimes a planned longitudinal meaning that the ship must afloat on a straight line, not down by the stern or by the bow. The ship is straight on the designed waterline only if the longitudinal position of the Centre of Buoyancy corresponds to the longitudinal position of the Centre of Gravity. The ship would trim bow down in case CG were more ahead of CB, and stern down in the opposite event. Therefore it’s important to analyse carefully the vessel’s weights: in case of a mistake sometimes there is a remedy, and sometimes not. In any case mind the Principle number four: as a general rule, straightening a stern-down vessel is feasible, even if it might be difficult. Straightening a bow-down vessel is about impossible.
Similarly if the ship is heavier on one side of the centre plane she will list in the same direction o the load excess. In any case the hull will sink unevenly to compensate more weight with more displaced volume of water. Keeping under strict control the amount of weight and the position of CG is a designer’s duty: it’s not that difficult. Some of the weights are easy to evaluate, such as the engines, the gen sets, the pumps, the boilers, the shafts, the propellers, the anchors … a huge amount of items supplied by manufacturers who shall give the designer all the necessary data: namely the eight of each item and the position of its centre of gravity. Guessing the same for the arrangements is a little trickier. We might wonder which is the weight of a bed, or a sofa, or a wooden floor. The procedure is more boring than difficult. For example a bed: the dimensions of the top are 1,90 metres length by 0,80 metres width by 0,018 metres thickness. Please mind the units of measure: 18 millimetres equals 0,018 metres. Don’t ever mix metres with centimetres or millimetres: stick to one single unit, always the same, otherwise you’ll mess everything up. Coming back to the bed top dimensions: to get the top’s volume you multiply the three dimensions: 1.90 * 0.80 * 0.018 = 0.02736 cubic metres. If the bed were made of marine plywood, whose specific weight is roughly 450 kilograms per cubic metre, the top’s weight would be0.02736 * 450 = 12.312 kilograms. Its centre o gravity would roughly correspond to the centre of its geometrical figure. There’s more: the paint, the glue, the screws, some joining rulers: let’s round off to 13 kilograms. By the same system we can calculate the weight of the bed’s sides, the floors, the cabinets and so on. There’s a hidden item: it’s the network of rulers of cheap wood (mainly pine) that lies between the ship’s structures and the arrangements. A kind of interface. All in all the weights calculation is a long, demanding job. Thanks heaven there’s a shortcut, an useful rule of the thumb (I’ll spend later a few lines about this).
Following this rule, and out of experience, the weight of an arrangement (including floor, cabinets, partition walls, bulkheads, network, ceiling) ranges roughly from 95 to 110 kilograms per square metre. A minimalist set of furniture shall be lighter than a classic one. A kitchen or a bathroom shall be heavier than a sitting room. In other words: you multiply the area of a cabin, a saloon, a bathroom (in plan view, square metres) by the above said weight and you get the total weight of that room. The position of its centre of gravity would correspond, in plan view, to the centre of the geometrical figure, while its elevation shall be roughly one/third of the height above the floor. For instance: the saloon’s area is 23 square metres and it supposedly weights 105 kilograms per square metre. The total weight is therefore 23 * 105 = 2,415 kilograms. Let’s add 10% (241.5 kilograms) for the electric appliances, wiring, hardware, accessories, fan coils and we get 2,415 + 241.5 = 2,656.5. Remembering principle number three we round off the figure to 2,660 kilograms. Once all the weights and the position of their centres of gravity are detailed we list them into a simple chart, as in figure # 8. The first column shows which item we’re considering; the second lists its weight in kilograms; the third measures the longitudinal “arm”, aka the distance of its centre of gravity from a common point, usually station # 0; the fourth lists the “moments”, that is to say a force found multiplying the weight by the arm, measured in kilogram-metres. We sum up the weights (let’s call this figure Σw), we sum the moments (aka Σm) then we divide the sum of the moments by the sum of the weights m (Σ/Σw) and e get the position of the global centre of gravity along the centre line. Similarly we find the position of the vertical centre of gravity: just insert in the third column the distance of the centre of gravity o each weight from the base line and then proceed as ditto. In case we find out that the longitudinal position of the centre of gravity doesn’t correspond to the position of the centre of buoyancy we shall move some weight till we reach the perfect balance. But remember Principle number five: don’t ever attempt to balance the weights of a vessel by the fuel or the wate r tanks.
The ship might result even on the designed waterline with full tanks and out of balance when empty. It’s a lot wiser to try and move the batteries, may be the gen sets, the ater maker, the windlasses and so on. Perhaps we could still move the kitchen or a bathroom, the heavier rooms among the arrangements. The next principle states a general rule: Principle number six: the weight of a ship can roughly be divided into three main blocks. One third is the structure s; one third is the arrangements; one third is the machine ry and the plants. Joinery Weights and Centres of Gravity Item Bow cabin Guest Cabin 1 Guest Cabin 2 Bathroom Bow Guest Bathroom Astern Cabin Astern Bathroom Crew Cabin Crew Bathroom Galley
Weight[kg] 1100 875 875 530 410 1230 635 810 435 1350
Longitudinalarm[m] 12,3 9,5 9,5 11 8 6 5,5 14 13 6
Moment[kgm] 13530 8312,5 8312,5 5830 3280 7380 3492,5 11340 5655 8100
Main Saloon Wheelhouse Cockpit Joinery Bridge FlyJoinery
3565
5 630
980 1345 14770
7 2,5 6 7,31
17825 4410 2450 8070 107987,5
Fig. 8
2.6. The “ rule of the thumb”
It’s a worldwide known rule: it’s about measuring something by extending an arm in front of you, closing your fist and raising your thumb. Then you close one eye, turn your hand 90° and measure the dimensions… by the thumb. It’s a guesstimate and there is no accuracy. Yet, once it’s backed up by a few years’ experience, it’s a rule that works: you will realize how you get to the same results after days and days of drawings and calculations… or in a few seconds by the “rule of the thumb”. I wish to encourage my readers: you can initially skip the boring weight calculation: with a little practice you’ll be able to guess their amount and centre of gravity location. 2.7. A short preliminary check
Let’s go back to the first lines of the hull drawing. We have drafted the main section (# 14). Part o it lies above the waterline and part below. We must now check whether our design is congruent with the planned characteristics, namely whether the WL level (that for the time being we have drafted by the rule of the thumb) matches with the hypothetic 110,000 kilograms displacement we have in mind. We use one of the comparison coefficients: these parameters are normally calculated at the end of the design work and we shall see later how they’re found. For the time being let’s assume that we already know one of them: the Prismatic Coefficient orCp. It compares the immersed volume of the hull (aka ) to a solid which transverse section is the immersed area of the main section Am ( ) and which length is the waterline length (LWL). The formula to calculate it is Cp = /(Am * LWL). Naval architecture tells us that the Cp value for yachts having a hull similar to our design ranges from0.75 to 0.85. The hull is pretty “full”. Let’s therefore assume a0.80 figure: we’re now able to solve the formula. The variables are: Cp, and we’ve set it to be 0.80; LWL, and we just have to measure it on the drawing, finding 27.22 metres: we only miss . The inverse formula becomes = Cp * Am * LWL. Let’s introduce some numbers: Am, as measured on the drawing, equals to 2.599 m2. Please mind that the drawing only shows half of the transverse section: we must therefore multiply the area by two: the total is 4.5426 m2. The LWL length is 27.22 metres. Once we insert these figures in the formula it becomes: = 0.80 * 5.198 * 27.22 = 112.538 m3. Let’s multiply the volume by the specific eight of a cubic metre of Mediterranean salt water (see 2.4), aka112.538 * 1.023 = 115.126 kilograms. As first approach it’s acceptable and consistent with our design hypothesis. And even so, even if the figure shows that we’re on the right way, still it’s only a rough estimate. Let’s absurdly imagine that the final result was 80,000 kilograms, or 150,000: in the first case we should have to sink the hull, searching for the missing volume, and vice versa in the second event.
2.8. More sections
Let’s now draw two more sections, quite important for our design efficiency: station # 28, at the beginning of the LWL towards bow, and station # 0, at the LWL end backwards. On transverse view (see figure # 9), the half trace of station # 28 is on the right side of the centre line, while station # 0 is left of it. This happens because, customarily, the half stations from bow through amidships are drawn right of the centre line, while the stations from amidships through the stern are drafted on its left. It’s clearly seen that the stations towards bow have a deeper angle, or dihedral or deadrise, than the ones aft, and that there’s a progressive change in the bottom shape. The reason is intuitive: the bow sections crash into the waves and their shape must be such that they plough through them without hard blows. Near the stern, where the waves won’t hit, the hull needs flatter surfaces that give hydrodynamic lift to the vessel at speed. Let’s check which are the dihedrals of these stations, measuring their elevation angles relative to the base line. Station # 28 is 43.48°. Station # 14 is 16.15°. Station # 0 is 6.20°. Different dihedral values for the bottom stations shall seriously influence the vessel’s performance. There’s no magic formula, nor a set of numbers, to link the hull’s bottom shape to the vessel’s performance. It’s not just a question of speed: the ship must perform, but she must also be seaworthy in bad weather conditions: she must have a reasonable ratio between the engines power and her speed; she must sail safely also in a following sea and rough waves; she must have the right stability and so forth. The dihedral values mentioned above are ideal for a pleasure craft, meeting basic characteristics of comfort, safety, performance. An offshore, high speed craft would certainly need totally different and deeper dihedron. On the contrary the hull for a swamp hydroplane would need a completely flat bottom. As it goes, a deep dihedron hull is bound to be highly seaworthy but needs great power to achieve a good speed: on the contrary a flatter hull performs better at cruising speed, is less seaworthy and less stable in a following sea. Figure # 9 also shows the hull’s side. Its shape, near the stern, is about vertical but not quite. The hull would look boxy in case it’s too upright: a design showing an angle of 5° or less ould not be appropriate, even though it’s just an aesthetic issue which has nothing to do with the vessel’s performance.
Fig. 9
2.9. Managing the hull shape
What in case our first approach to the hull design is not satisfactory? May be that the sheer line, the chine and the hull position give for mediocre transverse sections. Perhaps too flat, or too deep. We must do some changes before we proceed. We need to figure the hull shape in three dimensions: it should be clear enough that raising the chine line would create a deeper dihedron. A larger sheer line ould «open» or flatten the side sections and so on. The hull is a solid body, even though its shape is irregular. Every change in one of its lines would necessarily bring a change in all the other forms. Sometimes a slightly convex or concave shape of the transverse sections is beneficial for the vessel’s performance. Convex bow sections reduce the impact into front waves, while concave sections amidships allow for a softer ride. 2.10. Flank ahead
The preliminary calculations confirm that our design work is on the right way. Let’s now complete the transverse sections design. The drawings in figure # 10 doesn’t show all the sections, namely only one over four abaft amidships: in case we draw all of them, the sections traces would show on top o each other, thus making the drawing an unreadable black spot. All the lines must be coherent and squared. That is to say, for example, that the cross point between a buttock and a waterline in plan view must correspond to the crossing point between the same forms in elevation and so forth. There must be a strict interdependence between all the hull sections: I know that a dedicated PC program does exactly this job but I believe that it should be clear why and how it happens. A computer is a tool that speeds up the designer’s work, but doesn’t replace his brains. Several slight modification shall be done in case the hull lines aren’t totally coherent, such as change the transverse sections, or the chine line or whatever else, with a patient trial-and-error procedure, until all forms are squared up. Please remind Principle number seven: yachts are made by centimetres, not by metres.
Fig. 10
That is to say, the modifications shall be made with a lancet, not with an axe. Once this design ork is completed we can draw all the missing sections, the lettering, the dimensioning and so on. The hull in figure # 11 has two spray rails on the bottom: they are intended to increase the hydrodynamic lift and pull the spray downwards.
Fig. 11
Chapter 3 The displac ing hu ll
3.1. Abstract
Let’s begin with a basic concept: there’s no sharp, absolute border between planning and displacing hulls. It’s rather a smooth and gradual shape transition from one type to the other. The drawing of a displacing hull is trickier than the previous one: we don’t have any more sharp lines oining sheer, chine and hull, but curved forms. The designer needs a great sensibility for the hull shape and the capability of figuring out a three-dimensional body: all things which only time and experience shall enhance. 3.2. The hull lines
The design work is similar to the one already described for the planning hull. The reference network is the same and such are the fundamental lines of the hull. This time the common interval is 840 mm and for sure it doesn’t coincide with the actual framing of the vessel. The vessel that we consider has a 25 m. LOA and 6.30 m. B. Figure # 12 shows some important differences with the drawing we saw before. The more evident is the transverse sections drawing: it’s not drafted on the vessel’s lines but apart, on the right side of the hull. It’s only a stylish choice. Another remarkable difference is the quick orks profile: it shows a kind of “nose”: it’s a bow bulb, and we shall examine it later on. Probably the most outstanding dissimilarity is the transverse section shape: once again we deal with the main section, # 9, which shape is totally unlike the planning hull form.
Fig. 12
Side and bottom aren’t anymore straight lines but fair polylines, joined by a roundish section, called “bilge”. In fact these kinds of vessels are known as “round bilge hull”. The lines show the vessel’s deck in plan view and elevation, and the topgallant bulwarks. The bulwark is a part of the hull which rises above the main deck. In figure # 13 it’s highlighted with a square box.
Fig. 13
3.3. A short preliminary calculation
We do a preliminary check like we already did in 2.7: in other words we verify whether the designed floating line (LWL in figure # 12) fits the forecasted displacement of the vessel. The average Cp for such a family of hulls ranges between0.5 and 0.6. Let’s assume a0.50 figure. We measure the half area of the immersed section, which equals 3.679 m2. The whole area is therefore 7.358 m2. The LWL length is 22.75 metres. The renown formula is: = Cp * Am * LWL : in other words
7.358 * 22.75 = 83.697 m3.
= 1.50 *
It’s a correct volume that we take for good as half load displacement, being = 83.697 * 1.023 = 85.622 kilograms.
3.4. The weight modifications
Let’s briefly suspend the displacing hull design to introduce an important concept: the vessel’s eight range and change between the empty and full load conditions. On such a kind of yacht we shall expect to have tanks for fresh water (3,000 litres), black waters (250 litres), white waters (400 litres), oily waters (500 litres), used engines oil (400 litres), new oil for machineries (200 litres), fuel… About the fuel topic we need to do a digression inside the digression: let’s suppose that the vessel has two four-stroke diesel engines releasing 600 hp each. This is the maximum output power, but at cruising speed we would only use 80% of it, aka 2 * 600 * 0.80 = 960 hp. The specific fuel consumption of any engine is shown on a chart, supplied by the engines builder. As a matter o principle it’s placed around 190 grams x hp x hour. The fuel consumption on the vessel of our design ould therefore be 190 * 960 = 182,400 grams per hour, equal to some 183 kilograms per hour. Such type of vessel is normally equipped with two diesel engine electric generators. Lets’ presume that one generator releases 30 Kw/h (aka 30 kilowatts per hour) and the second one 12 Kw/h, for a total of 42
Kw/h. Also in this calculation we presume that the generators work at 80% of their maximum load, therefore do roughly release 34 Kw/h. The ratio between Kw and Hp is 1.341: therefore 34 Kw/h equal 45.6 hp. The generators fuel consumption shall be190 * 45.6 = 8,664 grams per hour, equal to some 8.7 kilograms per hour. The total fuel consumption on a hourly base is.183 + 8.7 192 kg.The maximum speed of the vessel comes from the renown formula , or knots. We deem a consistent speed reduction, as we plan to use only 80% o the power, thus assuming a constant speed of 10 knots. So, the vessel covers 10 nautical miles in an hour, burning 192 kilograms of fuel. Let’s figure out the vessel range as 450 nautical miles: it takes 45 hours to cover this distance at 10 knots speed. During this time lapse the fuel consumption shall be45 * 192 = 8,640 kg. Unfortunately this is not the amount of fuel that we need to board: as it goes, part o the fuel cannot be drawn because it remains in the tanks bottom and part of it fills the pipes, the filters etcetera. The percentage of unusable fuel is roughly 10%: thereafter the total amount of fuel we need is 8,640 + 864 = 9,504 kg. I wish to highlight that, up to now, the unit of measure has always been kilograms: but at the fuel station you buy diesel by the litre, not by the kilogram. Diesel fuel is lighter than water, on equal volume: it actually weights 850 kilograms per cubic metre. To accommodate 3. 9,504 kilogram of fuel we need a total tanks volume of 11.2 m Coming back to the variable weights calculation we have 4,750 kilograms between miscellany tanks and 9,500 kilograms of fuel, for a total amount of 14,250 kilograms. The huge difference between full load and empty vessel conditions affects many parameters: the centre of gravity position, the stability, the draft, the speed. Actually the ship is never completely empty, thus for the stability calculations a 10% load is assumed, and this condition is called “ship at arrival”. It’s not difficult to calculate how the draft changes with the weight modifications: an issue that will be later debated. ≅
3.5. B ack to the drawing
Similarly to what we already did with the planning hull, let’s add more elements to the drawing. We decide what we want station # 0 and station # 18 look like. We also introduce a new element: the mark of waterline # 10. We have now four points through which the waterline must surely pass: three half breadths that we measure at the intersection of the transverse sections # 0, 7, 13, 18 and 23 with the LWL, plus the LWL beginning (see figure # 14). Let’s assume that the WL 10 mark is good for the design we’re determined to achieve: this trace gives us the half breadth on the waterline of all the stations. Now we add stations # 5 and # 14. One might be puzzled by the ostensible arbitrariness of waterline # 10 shape. Actually, the trick is examining body plans of similar existing vessels and gathering how, why and which parts our design ork assimilates, which ideas it’s worth blending into our project and which are the elements o innovation. Going back to figure # 14: there’s a brand new section, 45° inclined, which starts from the transverse sections centreline. This section is called “diagonal”: its srcin position and tilting angle are totally arbitrary. It’s a very useful section to verify the fairing of the round bilge area. The designer can trace as many diagonals as he wants: the more you have, the easier is the control of the hull shape trend. Figure # 14 shows the line generated by the intersection of the diagonal with the transverse sections. It goes without saying that the diagonal line, as well as all the remaining lines
representing the hull, must be fair: in case it isn’t we’ll have to go over an adjustment work, as described for the planning hull. Now we add more transverse sections, waterlines and buttocks, always checking the fairing of lines and the collation of the intersections in the three views, till we get to the complete hull lines drawing. I highlight a new element, in the aft section of the hull: it’s kind of a fin or a centreboard, called “skeg”. Its main purpose is to increase the vessel’s course keeping attitude in following sea, but also to protect from impacts the appendages, such as the propellers, the brackets, the rudders. And what about the bulb bow? Books have been written and designers have severely fought about this appendage, about its benefits and its shape. No doubt that the bulb bow improves the performances of very large ships, where it has remarkable dimensions and its effect on the waves generated by the hull is substantial. On the contrary its usefulness on minor vessels is controversial. As for the form, in our design example it has an egg shape. Yet the debate on the topic is open. 3.6. The decks
We design the deck and the deckhouse exactly with the same criteria we used to draft the hull, naturally overlooking any hydrostatic issue. We cut the deck and deckhouse by means of the same stations that we used for the hull, drafting this part of the vessel in three views.
Fig. 14
Chapter 4 The mathematics of the hull
4.1. The displacement
In 2.7 and 3.3 we used the Cp reverse formula to check, with rough approximation, whether the immersed volume of the hull matches a realistic displacement for the type of yacht that we’re designing. It’s time now to calculate exactly the hull displacement. I’m afraid I’ve to say it again: I know that all the dedicated design programs on every computer will supply the designer with the data about volumes, displacements, stability and many more elements for several different immersion values, both for a straight hull and for an inclined one. Yet I feel that understanding the process through which it happens is fundamental, and it might also help to compensate for the contingent lack of the beloved computer. Imagine that the Aliens have taken over our Earth and that no more computer is working: we still have some elementary tools, such as paper, pencil, fingers for counting, the multiplication table by heart and our brains. Please note that figure # 15 shows that part of the transverse sections lies below the LWL (it’s the quick works), while another part is above it (the dead works). Let’s forget about the latter: our target is to establish what immersed volume results from the integration of the transverse sections below the LWL. We use the Simpson’s rule: we’re talking of Mr. Thomas Simpson, not of Homer, of course. This rule for the integral is simple enough andGerman was named after the competed 1700 British mathematician, but the Italiancalculus Bonaventura Cavalieri and the Johannes Kepler for its authorship.
Fig. 15
It’s one of the many possible rounded-up ways to calculate the volume of an irregular-shaped body. All systems (Simpson’s or the trapezoidal rule) are based on the averages law. First of all we divide the LWL in an even number of spaces, which gives an uneven number of stations. Let’s have a look at the hull in 3.5: the common interval is 0.84 metres. As for the Simpson’s rule we should set the last station in correspondence to the LWL forward end: but there’s a bow bulb, which sticks out and needs to be considered while calculating the immersed volumes. Therefore we exceptionally set the last station in correspondence to the bulb edge. We get 28 spaces and 29 stations, numbered from # 0 to # 28 (see figure # 15). It’s time now to draw the Simpson’s chart table, as per figure # 16: and yes, I must acknowledge that a computer spreadsheet would be helpful (provided the Aliens allow us to use it). The first column on the left, which title is “Stations”, lists the numbers of the transverse sections, or stations. The second column’s headline is “1/2 areas” and it is void, for the time being. The third column is assigned to “SM”, which stands for “Simpson’s Multipliers”. The rule is simple but binding: the first and last numbers must be 1 and all the other shall come in succession: 4, 2, 4, 2, 4 …
Column # 4 title is “SF”, which stands for “Simpson’s Functions”: it’s empty now, but we shall fill it with the product obtained multiplying each half area by the corresponding Simpson’s Multiplier. The fifth column is assigned to “M”, meaning “Multiplier”. This time the numbers are the same as the stations. Column six is entitled “Sm” (please note that “m” is now a lower case letter) and stands for “Simpson’s moments”: it shall later list a number of “moments” (I wish to recall that a “moment” is the product of a force by a distance, or “arm”). The top right corner reminds that the “CI” (aka “Common Interval”) is 0.84 metres. The cells that shall brief the figures of volume, Mediterranean displacement, Gulf displacement and LCB are already set at the left bottom corner of the chart table. We must now fill the second column with the half areas of the immersed sections, corresponding to each station. Yes, I know that nowadays any computer program will measure these areas quickly and with extreme accuracy, but before the birth of these processors, designers used a “planimeter” (see figure # 17).
Fig. 16
The draftsman had to follow the contour of a two-dimensional figure, centring the line with a small red dot within a magnifying lens. Then the reading was to be multiplied by a correction factor for the scale and the result was the area of the figure. The values were plotted on a chart, to check that there ere no blatant misreadings (see figure # 18). In my office there’s still planimeter, hidden in a drawer: you never know (the Aliens could be behind the corner). Nowadays reading the half areas figures by means of a computer dedicated program is a lot easier and quicker, of course. In any case I suggest that you double check, following Principle number e ight: checking twice neve r killed anybody.
Or, if you prefer, confidence is good, checking is better.
Fig. 17
We insert the half areas values, either read from the curve or from the computer, in the second column of the chart table (see figure # 19).
Fig. 18
Now let’s multiply the half areas figure by the corresponding Simpson’s Multiplier and write the result in the Simpson’s Functions column: for example (let’s take an easy one) the figure corresponding to station # 7 shall be 2.008 * 4 = 8.032 . The chart table looks now like in figure # 19.
Fig. 19
We sum all the Simpson’s Functions, getting a 174.357 figure. We are now able to calculate the immersed volume of the hull: the formula is (∑SF * CI *2)/3.
Fig. 20
We need to multiply by 2 because we have only read half the areas: dividing by 3 averages the
Simpson’s Multipliers. The actual formula becomes(174.357 * 0.84 * 2)/3 = 97.640 m3 which, multiplied by the specific weight of sea water gives for a97.640 * 1.023 = 99,885 kg displacement. I wish to highlight the importance of keeping the units of measure under control: if it’s metres, let it always be metres and let kilograms always be kilograms. Don’t change horse halfway the race.
Fig. 21
Let’s finally check where is the longitudinal centre of buoyancy, aka LCB. We multiply the Simpson’s Functions (SF) by the corresponding Simpson’s multipliers (Sm), hich determine the distance of each value from a common srcin, aka station # 0. See figure # 21. The formula is ∑Sm * CI/∑SF or, in other words, we multiply the sum of the Simpson’s moments by the Common Interval and then divide the result by the sum of the Simpson’s Functions. In the case in point we have 2453.558 * 0.84 / 174.357 = 11.82, meaning that for the designed waterline the LCB position is 11.82 metres ahead of station # 0. It goes without saying that the LCB positions changes considerably once we consider different immersions of the hull. It’s actually necessary to re-do the complete procedure for waterlines set at different levels and plot the results on a curve. Let’s then hope that Alien never bothers our computer, so that it does the dirty job while we play 18 golf holes! We now know the longitudinal position of the Centre of Buoyancy: we need its vertical position too (aka VCG ), to ascertain the vessel’s stability. It’s not difficult: just boring. We must repeat the same procedure using the waterlines areas instead of the stations areas. 4.2. The c omparison c oefficients
We can verify the efficiency of the hull design by means of the “comparison coefficients”. These are numeric values, typical for each family of hulls. Please note that they shall substantially change for the same hull, once we examine different immersions.
4.2.1. The prismatic coefficient
We have already met the “prismatic coefficient (akaCp). We used it in 2.7 and 3.3 for some preliminary check. Basically Cp compares the immersed volume of the hull to a solid which transverse section is equal to the main station area and which length is equal to the waterline length (see figure # 22). Let me recall the formula:Cp = /(Am * WL) . Converted in figures, for the hull e’ve designed, it gives: 97.64/ (7.538 * 22.75) = 0.58329 that we’ll informally call 0.583. This figure is fit for this kind of hulls: more than satisfactory.
Fig. 22
4.2.2. The block coeffi cient
The “block coefficient” (aka Cb) compares the immersed volume of the hull to a parallelepiped hich three dimensions are: the waterline length, the draft T( ) and the width on the waterline (or BWL) (see figure # 23). The formula isCb = /( BWL * T * LWL) . As for our hull, it gives 97.64 / (6.22 * 1.5 * 22.75) = 0.460007 or better 0.46. This is also an average, acceptable figure.
Fig. 23
4.2.3. The fineness coeff icient
The “fineness coefficient” (or Cf) compares the LWL area (that we call AWL) to a rectangle hich sides are the LWL and BWL dimensions (see figure # 24). The formulaCf is = AWL/(BWL * LWL). In our case we have 106.057 / (6.22 * 22.75) = 0.74949 but we assume 0.75. And this is also good.
Fig. 24
4.3. The unitary displacement
We have just measured the area of the waterline A ( WL) of the hull we’ve designed, and it is 106.057 m2. It should be plain: as the hull sinks one centimetre below the waterline, or floats one centimetre above it, the displacement changes of one hundredth of cubic metre, that is to say106.057 * 0.01 = 1.06057 m3, or 1.0146 * 1023 = 1084.9631 kg. In other words: for small neighbourhoods of a waterline we can consider the hull as a parallelepiped. In the case in question: if the weight varies of 1,085 kg the hull sinks one centimetre; if the hull sinks one centimetre it means that there’s been a weight increase of 1,085 kg. It goes without saying that the same calculation needs to be done for all the waterlines and that the results must be plotted on a curve.
Chapter 5 Stability
5.1. The c entre of gravity
Please see figure # 21: we have found the positions of the LCB and VCB. We need two conditions for our vessel to float exactly on the designed waterline. First: the ship’s weight must equal the eight of the water that she displaces, diving to the desired draft. Second: the centre of gravity must be on the centre plane and its longitudinal location must correspond to the LCB position. As for the first point, it’s plain that the ship would dive more if she were heavier than forecasted, and vice versa. In case the transverse position of the centre of gravity TCG ( ) was not on the centre plane the vessel would list on the same side where the centre of gravity actually is. If the LCG would not correspond to the LCB location the hull would heel bow down or stern down, depending from the centre of gravity position. Therefore we need to verify the vessel’s weight. Let’s list on a chart all the parts of the vessel, their estimated weight, their LCG position in respect to station # 0 and their VCG, measured from the base line. The more items we list, the more precise is the output of our calculation. We positively know the weight and the CG position of some parts: namely the engines, the machinery, the anchors, the chains, the rudders, the shaft line, the propellers and so on. The suppliers shall give us such specifications. We need to estimate many other: for example the plants, the joinery work, the paint, the filler forth. I wish to example. highlight that the following chart doesn’t relate to the hull that e drafted. It’s and just so a working method
Fig. 25
The first column on the left lists the items, starting from the fibre glass structure and going ahead ith the mooring equipment. The second column shows the items weight in kilograms. Columns # three and four give the positions of the LCG and VCG of each item. The sixth and seventh columns show the “moments”, that is to say the product of each weight by its arm, or distance, from a common srcin (station 0 or base line). Let’s now sum all weights: it’s plain that the figure we get should be very near to the vessel’s displacement that we have guessed. In case there’s a difference, we can calculate the draft change as per 4.3. In the same way we add all the vertical and longitudinal moments. Now, the result of the division of the sum of the moments by the sum of the weights is the distance in metres of the LCG from station # 0 and of the VCG from the base line.
I wish to highlight that there are considerable differences between the conditions of “ship at arrival” and “ship at departure”, aka light ship and full load. This method is more boring than difficult: it’s time consuming and involves some ability and experience. But it’s fundamental for all projects accuracy and for the vessel’s stability assessment and survey. A serious implementation to the “rule of the thumb”. 5.2. The transverse metace ntric height
While studying a vessel’s hull we consider two metacentric heights: transverse and longitudinal. We shall overlook the latter simply because it wouldn’t build up any hassle, while we shall analyse in detail the transverse metacentric height. 5.2.1. The metacentre
Let’s specify what is the metacentre (aka “M”) of a ship. She can be assimilated to a pendulum: ith a little fantasy, you might think of the metacentre as the fulcrum around which the ship rolls, for heel angles below 10°. The reciprocal positions of the transverse metacentre (Mt), of the centre o buoyancy (B) and of the centre of gravity (G ) (figure # 26) are fundamental for the initial stability o the vessel.
Fig. 26
The position of Mt is function of the moment of inertia of the waterline figure. I’m sure that our beloved computer shall easily and quickly give us this datum: but do we really want to sell our souls
to technology? Are we sure that this stupid machine can replace our intelligence? I love to ask mysel question when I know the answer, which is no! Let’s therefore see how to calculate the momentum o inertia of a waterplane figure and, as final result, how to find theMt position. In a simple way and mainly with our computer switched off. We use a chart table and a calculation method very similar to the renowned Simson’s rule (see figure # 27): we refer to the hull in figure # 15. As usual the first column on the left lists the stations. The second one shows the half breadths of the waterline figure from the centre line, in metres, for each station. The third column lists each of these figures raised to the third power (aka cubed). The fourth column shows the dear, old Simpson’s Multipliers (do you remember? 1, 4, 2, 4, 2…). The last column lists the result of the multiplication of the figures o column three by the Simpson’s Multipliers, that is to say the momentum of inertia functions Fi).( The formula to calculate the momentum of inertiaI)( is I = (ΣFi * CI * 2) / 9. In other words, we multiply the sum of the momentum of inertia functions Fi by 2, as we have only measured the half breadths. Then we multiply by the common intervalCI and we finally divide by 9, to average the figures. In our case the result is 245.838 m4. The formula to calculate the distance fromB (remind it’s the centre o buoyancy) and Mt is BMt = I / . We’ve already found the immersed volume of the hull (see figure # 20) and it is 97.64 m3. The figures in the formula therefore give:BMt = 245.838 m4 / 97.64 m3 = 2.518 m. BMt is also called “ r” or “transverse metacentric radius”. We’ve also already calculated the position of B (see 4.1) and the weights table chart (see 5.1) gives the G position. The span between G and Mt gives the transverse metacentric heightGMt: some call it “r-a”. 5.3. The effects of the transverse metacentric height
It’s plain that the transverse metacentre position is strictly bound to the shape of the hull, particularly to the waterplane shape. The only way of changing the Mt position is modifying the hull lines. It’s also evident that the metacentre position changes for different hull drafts, which in turn modify the waterlines shape, their momentums of inertia and the immersed volumes. Changing the position of G is a lot easier: we can move some weights or add ballast. The value of GMt cannot be lower than a minimum figure, and it’s inappropriate that it’s too high. I wish to highlight that the transverse metacentric height is an independent value, not bound to the vessel’s dimensions: in other ords it could be 80 centimetres for a 20 metres yacht as well as for a 300 metres cargo ship.
Fig. 27
The Registers of Shipping determine the minimum value of GMt, below which the ship is not allowed to sail: it’s 0.15 metres, and believe me it’s very, very low. In case the GMt figure is between 0.40 and 0.60 metres the rolling of the vessel is very slow and accentuated. The vessel is instable and lists easily, even for the wind pressure alone. The leeward side definitely ships water and the crew feel unsafe. For GMt figures between 0.70 and 0.90 metres the vessel rolls normally, even with high waves, and she gives a sense of safety and comfort. If GMt is between 1.00 and 1.20 metres the decks tend to remain horizontal, the vessel fights the aves and rolls hard. The rolling period is quite short, walking around the decks is difficult, the crew needs to grab constantly to handrails and seasickness is behind the corner. For GMt values above 1.30 metres the vessel is so “hard” that is ships water on decks, the rolling is so tough and quick that moving around is pretty impossible and the inner ear is so stressed that even an experienced crew would be seasick. Thereafter gather limits: too lowwe is bad, too that muchstability, is worse.as alcohol and refined food, must keep within reasonable 5.4. The stability
The “stability” of a vessel is her ability to straighten up after that, for some reason, she listed on
one side. The centre of gravity (G ) position doesn’t change when the ship rolls under the wind or o the waves force. On the other hand the distribution of the immersed volumes changes: the hull sinks by the listing side and emerges by the opposite side. The centre of buoyancy ( B) position therefore changes, and moves from the centre plane towards the listing side B1 ( in figure # 28). As we can see from the figure, there are two forces, or vectors, with the same value but pushing in opposite directions: one is the weight-force; the other is the buoyancy-force. When the vessel lists on one side, they’re no more aligned, as they are when the hull is even. The distance between these two vectors is the “righting arm” or GZ. We get the “righting moment” by multiplying the vessel’s displacement by GZ.
Fig. 28
The righting armGZ value is function of the sine of the listing angle and the formula isGZ = GM sen α.
The position of Mt remains on the vessel’s centre plan for listing angles below 10 degrees. Above this figure Mt moves away from the centre plane. The reason is plain: the waterplane shape of a vessel listing more than 10 degrees becomes asymmetric to the centre line: as a consequenceMt flies somewhere in space, giving birth to what is called “metacentric swirl” which calculation is quite difficult and is not in the scope of this handbook. What really counts is studying the vessel’s stability between 0 degrees listing and the capsizing point: the designer shall therefore draft the “stability chart” which shows the GZ values for all listing angles. The figure should always be positive (above
the x-axis): if and when the curve should cross the x-axis and become negative… «Houston, we have a problem». In other words: it might happen that a vessel with aGMt higher than another ship proves, in the end, to have a worse transverse stability. It’s plain that: GMt is not the only parameter by which we determine a vessel’s stability. 5.5. The inclining experiment
Let’s assume that we have accurately calculated the positions ofG and Mt. Once the vessel is about finished we need to do an “inclining experiment”. It’s absolutely necessary, and the Registers o Shipping deem it mandatory: the scope is to ascertain theGMt figure by means of an experimental method. We must respect a few conditions to be able to run the experiment: the vessel must be afloat, moored in calm water, in absence wind, we must thereduced displacement. Mainly there be no free-surface liquids inside the tanksof(or at least they know must be to a minimum). Themust movement of free-surface liquids during the experiment would change the position ofG in an unknowable way and make useless the figures that we will read. As a consequence all tanks (fuel, fresh water, oil, oily aters, sewage and so on) must be either empty or completely topped up. The pipes connecting all tanks shall be intercepted. Pools and tubs must be empty. We must fix a pendulum to a point situated on the centre plane of the vessel, such as a deck overhang or the lower part of a signal mast. In case the length of the vessel is more than 35 metres it’s mandatory to use two pendulums, one near the bow and the other near the stern. Each pendulum carries a load at its extremity, which should end up into a basin filled with water or oil (the only free-surface liquid allowed), to dampen its movements. The perpendicular position of the pendulum shall be clearly identified and marked before we incline the vessel: this way we’ll be able to measure the gap ( S) when the ship lists. It’s equally important to know ): it’s is the The pendulum, theofgreater shallaccept be thea offset,the thelength easierof arethethependulum readingsL(and theplain betterthat is the longer test quality. Registers Shipping listing angle between 1 and 3 degrees and a minimum pendulum offset of 100 millimetres. To list the vessel we board a weight ( P), which amount changes with the ship’s dimensions. The necessary eight can be achieved by means of sand bags, old oil barrels filled with stones, iron or lead bars, concrete blocks or else. We must know the amount of weight and the distanceB)( of its centre o gravity from the centre line. I deliberately accentuated the heel angle in figure # 29, just to make the symbols, values and letters easily readable. The actual ship shall list a lot less. To summarize: • G is the centre of gravity of the vessel even on her keel; • G1 is the centre of gravity, shifted aside after boarding the weightP; • Mt is the transverse metacentre position; • P is the weight that we board to list the vessel; • B is the distance, or arm, from the centre line of the centre of gravity ofP; • L is the pendulum length; • S is the offset of the pendulumend when the ship lists; • α is the heel angle; • D is the vessel’s displacement, including the weightP. The listing vessel’s equilibrium condition is given by the formula: P * B = G G1 * ∆ Since we assume that the listing angle is very small, we can also assume that the offset ofG to G1
is perpendicular to the centre plane. We can therefore say thattan α = G G1 / G Mt or G G1 = G M * tan α.
Let’s go back to the equilibrium formula and let’s replace theG G1 figure with GMt * tan α and e get P * B = GMt * tan α * . Thereafter, if we isolate GMt, we get GMt = P * B / tan α * . We know the values ofP, B and D (please remind that it’s the srcinal vessel’s displacement plus the weight P). To solve the formula and find the experimental value ofGMt we still lack the tan α figure. We deduce it from the length of the pendulumL() and from its offset (S) by the formulatan α = S / L.
For the sake of clarity let’s do a numeric example: the vessel has an initial displacement of 40 metric tons. We board a 2 tons weight (P), raising the total displacement to 42 tons. The centre o gravity of the weight we board is 2.5 metres from the centre line. The length of the pendulum is 3 metres and its offsets, when the ship heels, is 0.4 metres. The tan α value is 0.4 / 3 = 0.13. The formulaGMt = P * B / tan α * becomes GMt = 2 * 2.5 0.13 = 0.915.
Fig. 29
5.6. The longitudinal metacentric height
Wewaterplane have seen shape, that theinposition of the the centre transverse function ofmetacentre the momentum of inertia of the respect to line. metacentre To find the is longitudinal we should go through the same calculations we did before, but this time the moments of inertia must be calculated in respect to a transverse axis, being therefore a lot higher than the transverse readings. As we have seen, the readings are cubed and it’s plain that the result shall save us from every possible surprise. Actually, to a first approximation, the longitudinal metacentric height is assumed to equal the LWL. That’s why all vessels roll more than they pitch. The following figure # 30 shows an example
concerning an actual hull: please note that all the data are plotted on curves which are function of the ship’s draft (Y axis).
Fig. 30
Chapter 6 The propul sion
6.1. The fixed pitch propeller
The propeller is the more classic way to drive a vessel, but it’s not the only one. Propellers are such a huge topic that whole books are dedicated to their study: this handbook only gives basic information. The paragraph is dedicated to “fixed pitch propellers”, which means that there are also “controllable pitch propellers” (CPP). We’ll see them later. 6.1.1. The propeller’s structure
The propeller is built with metal: sometimes it’s stainless steel but more often it’s casted of an alloy of copper, magnesium, aluminium and other metals. In other words, bronze. The propeller is made of a hub and of a certain number of blades: motor vessels generally have three, four or five blades (see figure # 31). The hub is hollow and the cavity is conical: in the inner face there’s a slot for a steel key. The shaft holds the same slot, so that propeller and shaft are integral. Abaft the propeller there’s a nose cone, screwed to the threaded shaft end. The cone is made of zinc, which is used as sacrificial anode. In other words: sea water, which is salty, is a natural electrolytic solution. The propeller which is an alloy of copper, aluminium and magnesium: the “nobility” scaleisofmade metalsofisbronze, the following: • Lithium; • Sodium; • Magnesium; • Titanium; • Aluminium; • Manganese; • Zinc; • Chrome; • Iron; • Cadmium; • Nickel; • Tin; • Lead; • Copper; • Stainless steel; • Silver; • Mercury;
• Platinum; • Gold. The so called “nobility” of a metal stands for its major or minor aptitude to lose ions during an electrolytic passage. Gold is on top, lithium is the “poorest”. Zinc is in between. It’s therefore plain that copper would lose ions to the advantage of stainless steel, unless there’s a less noble metal to sacrifice: aka the zinc anode.
Fig. 31
6.2. The pitch
The main characteristic of a propeller is the pitch (P), aka the progress of the propeller in one revolution. Modern propellers have a progressive pitch: in other words, near the hub it’s higher than the nominal pitch while it’s lower near the blade’s tip. The nominal pitch is measured at 70% of the blade length. 6.3. The slip
The propeller works like a screw its geometrical pitchturning corresponds to itswood progress revolution: in theory. Practically, the and propeller is not a screw in a solid plank.forIt each works in water: there’s therefore a difference between its geometrical, or nominal, pitch and its actual progress for each revolution. We call this difference “slip” (S), it’s a variable, influenced by many parameters such as the rate of revolutions per minute, the type of hull, the vessel’s speed, the position of the propeller, the appendages (shaft, bracket…) and more. As a rule of the thumb we can assume the slip to be roughly:
• • • •
20% for high speed planning hulls; 25% for planning cruising vessels; 30% for displacing hulls; 40% for sailing boats.
6.4. The pitch calculation
It’s a wise idea to leave the final decision about the propellers characteristics to their builder: it’s a complicated matter and it’s prudent to let the last word to who knows better. Yet we need to set up a preliminary calculation, at least of pitch and diameter. Now, between the engine and the shaft line there is a gear box. It changes the rotation of the propellers from forward to aft and reduces the engine revolutions: the reduction depends from type vessel. Let highlight pullingN that drives every vehicle, ratio including boats, it’sthenot justofthe power Ne ( me ) but mainlythat thethe “torque” (force m). The torque formula is Nm = (K * Ne) / RPM where K is a parameter and RPM (Revolutions Per Minute) the revolutions, either of the engines or of the shaft, depending what we’re looking at. RPM is a numerator: therefore the higher the revolutions, the lower the torque. Torque is therefore a force, and in fact its value unit is Newton x metre: it could be defines as the aptitude of an engine to generate ork. It’s plain that a vessel having a low weight/power ratio, therefore able to achieve high speed, doesn’t need high torque values. On the contrary a tug boat, slow but powerful, needs high torque to do her work. These simple criteria shall help the choice of engines for every type of vessel. Thereafter we shall use a reduction ratio between 1: 1.5 and 1: 2 for a planning vessel, while we shall use a higher reduction ratio (i.e. 3: 1 or 3.5: 1) for a displacing, slow motion ship. Let’s nowfrom calculate the propellers We start the design speed V( ):pitch. let’s figure out it’s 30 knots. Remember that a knot equals one nautical mile per hour, aka 1,852 m/h. 30 knots equals30 * 1,852 = 55,560 metres per hour. Let’s imagine that our vessel is equipped with two marine diesel engines, with a maximum rotation speed of 2,300 RPM, and that the reduction ratio R ( r) is 2: 1. The propellers therefore rotate at 2,300 / 2 = 1,150 RPM. The propellers do 1,150 * 60 = 69,000 revolutions per hour. Provided that, during that same hour, 69,000 rotations of the propellers shall cover a distance o 55,560 metres, every revolution should cover a distance of 55,560 / 69,000 = 0.805 metres. This ould be the necessary pitch to run at 30 knots, were not for the slip. We must thereafter add 20% to the value above said, which becomes 0.805 * 1.20 = 0.966 which we round up to 1 metre. We can transform all this long and boring calculation in a formula:P = (V * 1,852) / [(RPM / Rr) * 60 ] * S that can be simplified intoP =[(V * 30.8666) / (RPM / Rr] * S. 6.5. The diameter calculation
The propeller diameter is function of its design, its number of blades, of the shaft revolutions. The diameter of a four blades propeller can be gathered from the chart of figure # 32. It correlates (right) the propeller revolution (let me highlight: not the engines revolutions but the
shaft speed) with the power (left). Draft a line joining the revolutions with the power: the reading on the middle column gives, with good approximations, the propeller diameter. Using the same data o 6.4 we join the shaft revolutions (1,150) with the power (let’s say it’s 2,300 Hp), we read a diameter value D of 1.13 metres. The propellers of pleasure crafts might have five blades: in this case we can reduce the diameter about 10%.
Fig. 32
6.6. The cavitation
Every point of the blade surface rotates with the same angular velocity, but it’s plain that the blade tip has a linear speed much higher than it has near the hub. The local pressure drops as the blade tip cuts through the water at high speed: the drop of the pressure below the vapour pressure produces bubbles of vapour. These cavities quickly explode, generating noise, vibrations, local corrosion o the blade and a reduction of the propeller’s performance. The theoretical calculation concerning cavitation is quite complex and we shall leave it to experts: knowing the basics is enough for our purpose. The cavitation is influenced by the propeller diameter: the larger the propeller, the higher the linear speed of its tip; by the number of revolutions per minute: the higher, the worse; by the blade design, by the shaft angle, by the draft of the propeller, by the appendages in front of the propeller and by tens other parameters. 6.7 . The As/Ad ratio
There’s another parameter which influences the propeller performance: it’s the ratio between the expanded surface of the propeller (As) and the disc surface (Ad), meaning the circle which inscribes the propeller. Figure # 33 shows how As might be considerably higher than Ad (drawing on the left),
here each blade “covers the” other.
Fig. 33
6.8. The clearance
The propeller tip should not be too near to the hull surface. There is a laminar water flow below a running hull: the water in this area has a different speed compared to the surrounding, still water. In case the propellers blades cross this theyupgeta astrong strokevibration, which, multiplied by the number of blades and by the revolutions perlaminar minute,flow builds which might shake the hole vessel. Besides, the propellers lose efficiency. Thereafter, there must be a space, or “clearance”, between the blade tip and the hull. As general rule, this span must equal 15-20% of the propeller diameter D. The higher the vessel’s speed, the greater the clearance must be. 6.9. The shaft line
The propeller is connected to the gear box by means of a cylindrical shaft, made of stainless steel. Both ends of the shaft are threaded: the aft end is bolted to the propeller, while the forward end is bolted to the coupling flange, which in turn is bolted to the gear box flange (figure # 34), and also here there’s a slot with a key. There is a stuffing box where the shaft crosses the hull: it allows the shaft rotation and is tight to the sea water. The shaft needs at least one support, called “bracket”: in case it’s very long the brackets could be two or even three. The bracket (built either in bronze, steel or light alloy) is bolted to the hull bottom. Its lower end is a cylinder, inside which there is a rubber bushing, which holds the shaft. The upper face of the bracket is shaped like the hull (see figure #35). The span between the aft end of the bracket and the forward face of the propeller’s hub should not be more than 50% of the shaft diameter: this avoids vibrations. The shaft diameter is function of the power, or to say better, of the twisting moment (or torque) and depends upon the mechanical
characteristics of the steel, namely its torsion breaking load. The shaft line is seldom horizontal: its angle depends from many parameters, such as the engine dimensions, the propeller diameter, the hull shape. Due to the shaft angle, the propeller pulling force splits into two vectors: one horizontal and forward, the other vertical upwards. The larger the angle, the greater the loss of driving forces: besides, a too large angle is a cause of cavitation. The maximum allowed angle is therefore 12°. The horizontal distance between the propellers should be at least two diameters: this shall avoid unwanted interferences. Please remind that all vessels, during a quick sharp turn, list on the same side of the turn. This brings one of the propellers near the water surface: in case it’s too far from the centreline it might cavitate. 6.10. The stern tunnels
Some vessels can be equipped with stern tunnels, near the aft end of the hull (see figure # 36). Tunnels reduce the draft, increase the propellers efficiency and lower the resistance. Practical tests show that tunnels allow roughly 10% speed increase.
Fig. 34
Fig. 35
Fig. 36
6.11. The co ntrollable pitch prope ller
Controllable pitch propellers ( CPP) are mainly used on workboats. The blades turn around a pin fixed to the hub and the pitch can be positive (forward drive) or negative (backwards). CPP are very complicated pieces of machinery and are seldom used on pleasure crafts. 6.12. The jet propulsion
The “jet” is kind of a high pressure pump: the engine pulls a rotary pump, which suckles water from below the hull and pushes it backwards through a stern drive. It’s one of the more efficient propulsion systems. There are no rudders or gear boxes: on the stern drive there’s a pivoting shell hich diverts the water flow, or bends downwards to re-direct the gush forward, to pull the vessel back. It’s quite an expensive system and easily suckles debris when it operates in shallow waters. Also manoeuvring in restricted water, such as in a harbour, isn’t easy: the crew needs to run the engines lively to handle the vessel. This moves huge amounts of water, builds waves, and other sailors might be very unhappy. See figure # 37.
Fig. 37
Chapter 7 Rudder
7.1. The rudder effect
Examining the rudder effect might sound strange: it’s plain what it does. It steers the vessel. Yet one thing might not be carefully considered: the bow doesn’t turn, when a ship hauls off. It’s the stern that moves aside under the rudder effect. The ship then changes course, yet you’d better remember this hile manoeuvring in restricted waters. The rudder is an appendix which increases the resistance: not much when it’s centred, quite sensibly while it turns to steer the vessel. The rudder use reduces the vessel’s speed. Finally, at high speed, the rudder raises the stern and the vessel lists in the same direction of the turn. 7.2. A design guideline
The rudder surface must be proportionate to the type, dimension and speed of the ship. Giving a general rule is therefore impossible, even if there are empirical and debatable formulas. Experience and good sense suggest that the rudder surface of a displacing ship should equal 2.5 to 5% of the projection of the immersed hull, while for a high speed planning vessel an area of 1 to 2.5% should be enough. The rudders must not be installed right abaft the shafts, but need to be misaligned, with enough offset from the shaft line to allow its disassembly. There should be enough space between the propeller and the rudder to allow the dismantling of the propeller. The rudder stock dimension depends from the material it’s made of, from the rudder dimension, from the number of stands. The vessel’s structure must be well reinforced in the neighbourhoods of the rudder stock: it’s a particularly delicate and stressed area. Part of the rudder blade is ahead of its shaft: it reduces the ork load on the rudder machine and it’s called “compensation”. It’s dotted in figure # 38.
Fig. 38
7.3. The rudder machi ne
The rudder movement is either mechanic or hydraulic, generally backed up by an electric motor. The rudder machine (see figure # 39) must have a by-pass position, to allow the use of an emergency tiller in case of failure of the main system. The automatic pilot works together with the rudder machine and grants a constant course.
Fig. 39
Chapter 8 The buil din g materials
8.1. Abstract
The vessel’s structure is made of many elements, some transverse and some longitudinal. A atertight outer skin, called plating (or planking) encloses all these structures and makes a barrier for the surrounding water. All the elements which build a structure must be continuous: figure # 40 shows that the longitudinal stringers of the bottom correspond with the structures of the bulkheads and of the deck. The same applies to the transverse sections, where the floors, the frames, the beams build up a continuous ring. The vessel’s structure is therefore made of “rings” which tie the ship in both planes. Please note the names of the structure parts: they must become familiar. Figure # 41 shows a similar structure during a vessel building. The weight of the structure is only from 25 to 35% of the total eight of the ship: there is a substantial dissimilarity between different building materials, but the range only involves a small percentage of the whole displacement of the vessel. In all vessels, but for the wooden constructions, the tanks are structural, hosted in a double bottom structure. Metal built ships (either out of steel or aluminium alloy) must have plugs (that can be opened from outside) below the fuel tanks, as all repair works which need welding must follow a complete and careful emptying of the fuel tanks. The maritime authority checks the vessel before the works start and releases a “gasonfree” certificate” only in case the tanks are empty and clean. These plugs must be clearly shown a dedicated drawing.
Fig. 40
Fig. 41
8.2. The wood
Wood, as boatbuilding material, has been neglected since a long time, and it’s a real pity. It requires well-seasoned wood, qualified manpower, great experience, and long construction time. Besides, the wood structure is quite large and cuts space for the arrangements. Finally, a wood vessel requires a lot of maintenance. Yet, no other material has the same appeal and scent. 8.2.1. Wood: a live substance
Wood is a live material: its characteristics change considerably depending from the area where the trees grow, from the period of the year of their felling, from the way the logs are sawn into planks, from the drying system and from the seasoning. Planks sawn parallel to the log’s axis do contort (shrinks and twist) more than planks sawn with a “quarter cut”, that is to say with a 45° angle (see figure # 42). The wood should be preferably seasoned in an open space, exposed for enough time to the inclemency of the weather. This way the wood gradually loses the interstitial and intercellular moisture, till it reaches the ideal humidity, that is to say roughly 12% of its weight. Like this wood reaches its dimensional stability. For commercial reason and to cut time, wood is often oven seasoned: a method that sometimes brings some bad surprise. Commonly used woods are: oak, douglas fir, pine, cypress, and naturally the classic mahogany and teak. Each of these species is fit for some specific parts of the boat.
Fig. 42
8.2.2. The building techniques
Wooden vessels, alike all other boats, are made of transverse and longitudinal structures. The 2) are not comparable mechanical properties of wood (its ultimate tensile strength is @ 60/65 N/mm ith the steel ones (ultimate tensile strength @ 480 N/mm2) or with those of aluminium alloy (ultimate tensile strength @ 320 N/mm2). As a consequence the dimensions of the floors, of the frames, of the stringers etcetera must be larger, heavier and would cut space inside the boat. The parts of the structure are joined by means of marine glue, screws, bolts and nails. Naturally all the metalware is made either of copper or of stainless steel. 8.2.3. The strake planking
Solid wood planks, opportunely shaped, are fixed on the structure. It’s the oldest and more classic building method and it’s still used for small boats, mainly in emerging Countries. It’s quite strong and heavy. It needs a careful caulking to be waterproof. 8.2.4. The clinker
The planking strips are put one above the other: it’s typical of small boats, i.e. the Dinghy 12’ (see figure # 43). 8.2.5. The cross laminated wood
The building starts from the inner structures: some of them permanent, such as bulkhead and floors, and some provisional, like several transverse frames that shall be later demolished. From five to six layers of wood sheets are glued upon this framework: the sheets thickness is only 4 to 5 millimetres hile their width is 300 to 500 millimetres. The wood is normally mahogany. The sheets cross at a 30° angle. It’s an elastic and light structure, fit for round hulls, such as sailboats.
Fig. 43
8.2.6. The marine plywood
Marine plywood can only be used for hard-chine boats, as the sheets only bend following a conic or cylindrical generatrix and don’t yeld. The structure is quite heavy. 8.2.7. The unfit wood composites
There are two main composites which are totally unfit for boat building purposes. One is the domestic plywood, because the glue which is used would give away with the sea humidity. The other is the medium density fibreboard: it’s a cheap material, heavy, inconsistent.
8.3. The light alloy Light alloy is commonly called “aluminium” but it’s’ not correct. Actually marine industry uses an alloy made of aluminium, magnesium, manganese, silicon and other metals even though the percentage of aluminium is by far the highest. Marine industry uses two light alloys: one belongs to the ISO 5,000 series, namely AlMg4.5Mn, and the other to the ISO 6,000 series, in particular AlMgSiCu. The 5,000 series alloys are fit for welding, while the 6,000 series are either glued or riveted or both. The ISO 5083 alloy is the most commonly used: it’s sold in plates and bars. It can have different annealing status which give diverse mechanical characteristics: the most commonly used are H32, H 321 and H 111. Light alloy needs inert gas welding and qualified manpower. Light alloy boat building has many advantages and only two handicaps. Aluminium is a self-protecting metal: its exposed face oxidises ith a very strong ceramic surface. It doesn’t rust and doesn’t degrade. It’s quite light: let’s remember that its specific weight is @ 2.66, while steel is @ 7.85. The mechanical characteristics of aluminium aren’t, of course, the same of steel (see 8.2.2 for the ultimate tensile strength): therefore all structures of an aluminium alloy vessel must be oversized, compared to a steel building. The weight saving (mind: for the structure alone) is roughly 40%, compared to steel. Building a steel hull and aluminium alloy decks is convenient for some types of ships: the weight is less and the centre of gravity is lower. Steel and aluminium cannot be directly welded. Therefore they are coupled by means of a bi-metallic special welding system. One commercial brand is “Detaclad”: it’s made of a steel sheet and an aluminium sheet, one above the other, joined by explosion. For what above said, it would seem that
aluminium alloy was the best possible boat building material. It would be so, if it were not for two issues. One is the cost: aluminium is much more expensive than steel. Even though in terms of weight there’s a saving, at the end the construction is more costly. A pity because it’s even cleaner than steel and easier to handle. As for the second problem, that is to say corrosion, please go back to 6.1.1 and see the electrolytic scale of metals, or galvanic series. You might notice that aluminium’s position isn’t much fortunate, not a very noble metal. Crucial precaution must therefore be used: no nobler metals should come in contact with the aluminium structure. AISI 316 stainless steel is mainly used. Just out of curiosity, AISI stands for American Iron and Steel Institute. Figure # 41 shows a light alloy construction. 8.4. The steel
Steel used for boatbuilding is commonly Fe 42, where Fe is its official name in the periodic table and 42 is its ultimate tensile strength in Kg/mm2, equal to 412 N/mm2. Steel is an old building method: several years ago the structures used to be riveted, while nowadays they’re only welded. Ship building in steel is classic for large vessels, where the structure weight doesn’t influence the total weight of the ship and her performance. As a matter of fact, steel construction is one of the heaviest, simplest and cheapest. Unfortunately steel quickly oxidizes and corrosion keeps working below the surface rust layer, up to the point that whole thin sheets of steel drop off. 8.5. The fibreglass
This term includes various building methods such as fibreglass, sandwich and composite. I personally deem this material as devoid of any appeal, smelly, amorphous, and lacking of any particular quality. Its ultimate tensile strength is from 150 to 200 N/mm2. Yet it’s essential for mass production. The cost of boats dropped since fibreglass was used, which allowed many people to approach yachting and boats. Every new fibreglass boat building begins with the construction of scale one-to-one wood models of hull and decks. Cheap wood is used, such as pine or poplar: at the end o the works it will be cast away. These models are the exact picture of what the finished boat shall look like: all details and particulars must be carefully foreseen and inserted at this stage: for example the manholes necks, the windows housing shapes, the raised areas for the mooring equipment installation, the anti-skid weave areas etcetera. The surface of such models must be perfect, without bumps or hollows and must be mirror polished, like a new car body. It’s plain that every flaw will show on each boat built afterwards. The construction of the moulds starts as soon as the models are finished, checked and approved. A detachant chemical product is sprayed on the models, and then the gelcoat is applied.allGelcoat is asmall hard flaws. resin, fitLayers for surfaces. Generallyglass it’s black red,then because these colours enhance possible of resin-soaked fibreorare applied above the gelcoat. The weight of these glass woven is quite variable: lamination starts with a very light one, called “mat” , made of short fibres, arranged at random, glued together. More layers are applied afterwards, increasing the woven weight, till several heavy roving are laid. “Roving” is made of long and regularly crossed fibres, sawn together. It’s mandatory to use a sufficient weight of mat before laying the roving, unless the mould surface (and later the boats skin) shows a horrible weft in relief.
The Registers of Shipping rule the glass weight per square metre, both for the moulds and for the actual boat building. The weight changes depending on many parameters and on the different vessel’s areas. Similarly the Registers of Shipping rule the percentage of glass and resin which the panels are made of. As for the rule of the thumb, the glass weight shouldn’t be less than 30% of the total weight. A steel structure is now fastened to the outer part of the mould, to avoid deformation. The moulds and the wood model are taken apart, the wood model is thrown away, the moulds are mirror polished and are now ready for the boats production. The moulds are the female, or negative, mark of the boat. The completion of the process above described with a few lines actually needs a long time. The resins are either polyester of epoxy: in any case they harden by means of a catalyst. The completion o the catalysis needs a “cure time” which goes from several days to some weeks. Once the moulds are ready, the building procedure is the same as above ditto: first the gelcoat (this time it shall have the chosen final colour of the boat), then the mat and so on. When the shell is made the structures (floors, frames stringers etcetera) are installed. The structures are made of laminated fibreglass beams, with a “C” shape, built of fibreglass above an inner core, such as wood, hard paper, polyurethane foam: the core isn’t part of the structure, it’s only a useful shape. Parts of the arrangement can be built o fibreglass, such as floors, showers trays, beds structure and much more. Fibreglass doesn’t’ require maintenance, doesn’t rust, doesn’t rot, doesn’t chip, doesn’t dent, and doesn’t need repainting. It’s the ideal building material from the point of view of the customer: it’s cheap and long lasting. It’s the ideal building material for the Builder: it’s easy to build and doesn’t create problems. Yet I don’t love it. 8.6. The ferrocement
I writecrafts aboutbuilding. it only because it exists but, also outwas of personal experience, I wouldn’t suggest it for pleasure It’s a cheap method which used during Wold War Two to build cargo ships (the “Liberty”, see figure # 44) following the steel shortage, as this metal was mainly bound for military constructions. The vessel’s structure is made of small diameter steel bars, the same used to reinforce concrete pillars, and steel net with square or hexagonal knit. The net is fastened by means o steel wire to the longitudinal and transverse steel bars network. Once the load-bearing structure is finished, the concrete is placed. Workers apply the concrete from outside and from inside at the very same time, carefully filling all hollows and pressing the concrete from both sides. The procedure is very similar to the reinforced concrete construction, but no gravel is added to the concrete: only portlandite and sand. The specific weight of such a structure is @ 3: it’s not bad, mainly when compared to steel. But the very high thickness which is necessary do frustrate this advantage. Ferrocement doesn’t rust, doesn’t rot, doesn’t smell and it’s easily repairable. On the other hand it easily transmits vibrations and noise and every modification to holes and passageways is impossible once the concrete hardens. Fairing the hull and deck is a time consuming procedure and paper sanding is about impossible. Yet it’s probably the cheapest ship building method.
Fig. 44
8.7. The fairing and the painting
Only fibreglass boats don’t need painting. All the remaining yachts, ships, vessels need paint. Let me recall an old, short and nice rhyme which tells about a boat: She scorns the man wh ose heart is f aint And doesn’t show him pity. And like a girl she needs the paint To keep her looking pretty.
Let’s start from the bare surface, be it either steel, aluminium alloy or wood. The first thing to do is to build a scaffolding structure all around the vessel, which could take some time. All surfaces need to be thoroughly cleaned: there must be no traces of grease or dust. Often the paint supplier specifies that a first layer of epoxy interface needs to be sprayed before the filler is used. Then an applicator smooths all surfaces by applying some filler, which thickness should not exceed a few millimetres. But naturally it depends upon the initial quality of the construction. Once the filler is hard enough (it’s actually a resin which needs a catalyst), the painter sands the filler, leaving it in the hollows and scraping it away above the bumps. It usually is a time consuming procedure. At the end the surfaces must be cleaned again and then the first layer of paint can be applied, only when the fairing work is satisfactory: it’s called a “primer” and is an interface between the filler and the paint. Two more layers of paint follow: a so called “undercoat” and finally a “topcoat”. I suggest you to contact a plaster and paint supplier and discuss the painting procedures with its technical staff. The painting process can be pretty different depending upon the material that the vessel is made of. The supplier will also decreeand the timing. environmental conditions to respect while painting: paragraph mainly humidity, temperature, thickness It’s plain from the “Acknowledgements” that our favourite paint supplier is Jotun Marine Paints and Coatings. We choose the paint for a vessel for its colour, but another criteria is the “gloss”, which measures the opacity grade of a surface: 100 is extremely shiny, 0 is absolutely matt. Both values are purely theoretical (see also figure # 89). Please remind that the darker the paint and the higher the gloss, the easier is spotting all minor flaws on a surface.
I wish to suggest that the colours choice criteria shall follow this policy: after the customer’s and the designer’s indication, several samples of the colours shall be painted on aluminium sheets, 30 by 40 cm and supplied to the customer and his consultants for approval. With the colour chosen among them, a 1 m. by 1 m. aluminium sheet shall be painted. Once the colour is approved in writing by the customer and/or his consultants, two wide samples, 2 m. by 4 m. shall be painted on the ship (hull and deck) for final approval in writing. Sometimes a colour sample on a small plate doesn’t look the same when it’s painted on the vessel: it might be the light incidence or a change in the mood… I might therefore now introduce Principle number nine: spoken words fly, written words remain.
Chapter 9 The engine room
9.1. The main eng ines (M MEE)
Fig. 45
The engines (sometimes a single one) are the beating heart of the vessel. Position, easy access and maintenance, reliability are fundamental for every vessel and for her safety at sea. There are several criteria leading to a choice: the power, the speed (RPM), the weight, the fuel consumption, the noise, the exhaust smoke, the cost but also the service and its availability worldwide. Marine engines are mainly four-stroke diesel motors: I shall therefore write only about this family, even though there are also two-stroke diesel motors, gasoline engines etcetera. The main engines, shortly MMEE, fill most of the engine room volume. All engines burn fuel, which in the diesel case is gasoil. I wish to remind that the fuel combustion inside the cylinders is just a very quick oxidation which releases power, under the form of heath. Two elements are necessary for the reaction to happen: the combustible and the comburent. The combustible is the fuel: provided that the crew fills the tanks in due time, there should be no problem. Some issue might arise with the comburent, that is to say air, or to say better the oxygen which is part of the gas blend that we call “air”. The engine room must be water and eather tight: therefore the MMEE work in a sealed room, which volume is not very big. The air
flow into the engine room (through dedicated ventilation trunks) must supply the engines with enough air to burn the fuel and also enough air to ventilate the room, keeping the temperature within acceptable values.
Fig. 46
All engines suppliers rate the parameters which must be respected to guarantee the MMEE performance: air pressure and temperature, humidity, sea water temperature etcetera. The marine engines are unusually big: for example see figure # 46, which shows two valves. The smaller is the valve of an average city car. The larger one is the valve of a tug boat engine. I think that a picture explains more than words the difference between these engines. 9.1.1. The characteristic curves
Every engine goes with a technical specification which lists its characteristics, among which the most important, at least to all appearances, is the power it releases: it’s specified both in Kw and in Bhp (Brake horse power), being the ratio 1 Kw = 1.341 Bhp. The engine showing in figure # 45 is a MTU 16 V 2000 M 93. MTU stands for Motoren und Turbinen Union, 16 is the number of cylinders (you might try and count them on the picture), V is their angle in respect to the crankshaft: the rest is marketing nomenclature. The MTU handbook states that this engine has a speed of 2,450 RPM; that its specific fuel consumption is 209 grams per Kw/h (or @ 188 grams per Hp/h), that is to say roughly 450.7 litres per hour. The manual then lists all the dimensional data, such as weight, with and without gear box, it says that the stroke is 156 mm, the bore is 135 mm and that the total displacement is 35.7 litres. “Displacement”, in this case, has nothing to do with the vessel’s weight: it’s the total volume o the cylinders. The handbook tells more: for example that the average work load must be 60% of the maximum output power and that the engine should not overcome 3,000 work hours per year. It goes ithout saying that other engines from other brands would have totally different specifications. Engines with low speed (or RPM) are fit for work boats, good for running endlessly. The general figures of the manual aren’t sufficient for the designer’s work. What we really need is a set of curves, such as in figure # 47, where the torque curve is the more important. DBR curve shows the usable power for reduced periods, while the MCR curve shows the maximum continuous rating. Please mind that every engine builder relates the given parameters to special conditions: in the MTU case they are: • Air intake temperature 25°; • Cooling water temperature 25°;
• Atmospheric pr essure 1,000 mbar; • Intake depression 15 mbar; • Exhaust backpressure 30 mbar; • Fuel intake temperature 25°; • Antifreeze 40%. Unless we have a great luck, all of these parameters won’t prove real in practice and we shall therefore expect minor changes in the engine performance. What in fact negatively influences the performance is the back pressure in the exhaust line: this happens for example in case the gases outlet is well below the waterline. Almost all vessels have the gas exhaust pipe below the waterline: back pressure can be avoided simply by keeping the outlet near the surface. Another very effective way is to build a secondary, small dimension gas exhaust line above the waterline: it’s very useful when the vessel is at rest or sailing slowly, and the gases below the hull aren’t extracted by the laminar flow as it happens at speed. Sometimes, before everything works well, the designer and the builder must go through a lengthy trial and error procedure. The engine builder technical representatives attend to the sea trials and carefully check all the engine parameters, there including the exhaust gas temperature.
Fig. 47
May be that the engine can’t reach its maximum speed (RPM); or that, even if it does, the exhaust gas toothe high. Both things that is thetoo load on the is too event high, (which which in turn temperature could meanisthat propeller pitch might and/ormean diameter large. In engine the opposite seldom happens) the propeller might result too small. 9.2. The gases exhaust line
As I wrote above, most of the vessels have the gas exhaust line below the hull. Like this the fumes mix with the water and are consistently abated. Each engine has one or more exhaust lines which end up in a silencer: the temperature of the exhaust gas is quite high, therefore all pipes must be protected by means of insulating material (see figure # 48).
Fig. 48
The pipes hang from the deck beams: in between there are anti-vibrating supports. The exhaust gases head into the silencer, where they mix with the sea water which comes from the heat exchanger (see figure # 49). Inside the silencer drum there are several steel bars which break the water flow, mixing the gas with the spray. This way the gas temperature and the fumes drop. The silencer and the exhaust line are connected by means of a heat-resistant elastic pipe which dampens the vibrations. The diesel-electric generator exhaust gas ends up in the same silencer, from which starts the secondary exhaust line. I wish to highlight that the system above described is only one of the many possible ways to design an exhaust line: the designer might want to discharge the exhaust gas through the stern or on the vessel’s sides. The trend is to address the generators exhaust gases towards the top funnel of the vessel: like this the guests swimming around the yacht won’t be bothered by the burnt fuel fumes. On the other hand, the fumes shall bother the sunbathing passengers on top deck, which proves that perfect happiness doesn’t exist.
Fig. 49
9.3. The comburent
The engine needs air to run: in principle, the amount of air in the engine room is never overestimated. Let’s find out which is the necessary volume of air. Each of the MTU engines of the previous example has a @ 36 litres displacement. As they have 16 cylinders we shall have four cylinders in induction stroke for every half rotation of the crankshaft (four shall be in compression, four in expansion and four in exhaust stroke). Therefore the necessary air shall be36 / 4 * 2 = 18 litres per revolution. This figure would be correct it the engine sucked air at atmospheric pressure: but it’s outfitted with two turbo compressors and the pressure of the air reaching the cylinders is therefore higher. I wish to digress slightly to say a few words about turbochargers. The stoichiometric ratio between combustible and comburent cannot change. Therefore, the higher is the amount of the first, the higher the volume of the latter must be. It follows that, for equal engine displacement, we can burn fuelFor if we higher of air. engines, Burning awhich higherdrive quantity means getting moremore power. thisintake reasona we usequantity turbocharged one of or fuel more compressors, operated by the exhaust gas. The engine therefore intakes compressed air. In the MTU case the air pressure is 3.5 times higher than the atmospheric. The air volume at atmospheric pressure becomes 36 / 4 * 2 * 3.5 = 63 litres per revolution. The engines speed is 2,450 RPM: it needs 63 * 2,450 = 3. As the vessel has two engines we 154,350 litres of air per minute, which we round up at 155 m shall need @ 310 m3 of air per minute, for the MMEE alone. The designer can avoid all of this boring
calculation: he can find the same data on the technical sheet supplied by the engine builder. In the MTU case the sheet lists a 2.6 m3 per second for each engine: if you like, check the calculation and you’ll see that the figures match. The designer must remember to air-feed the diesel-electric generators: let’s imagine that we get by ith 350m3 of air per minute, for engines and generators. We must now allow 70 complete air 3: we renewals, each hour, in the engine room. Let’s figure that the engine room volume equals 75m need 70 * 75 = 5,250 m3/hour, that is to say @ 88 m3 per minute. The total amount of air is thereafter 350 + 88 = 438 m3 per minute, or @ 7.5 m3 per second. The ventilation trunks must be accurately shaped and sized: the air flow through the ventilation ducts must not exceed 9 metres per second, otherwise it whistles, rumbles and is quite noisy. As per the calculation above, the total section of the ventilation trunks should not be less than7.5 m3 / 9 m = 0.83 m2. My suggestion is to double this value because, as I wrote before, air in never enough, and it’s also free of charge. For the time being. 9.4 . The ventilation trunks
The section shape of the ventilation trunks is not important: they can be round, oval, square… what counts is that they don’t have sharp bends or angles. Ideally they should be straight. The ventilation trunks are equipped with high power fans which work two ways, in and out. These fans must be fitted ith remote-control shutters, to cut of air in case of fire in the engine room. The control must be clearly indicated, easy to handle, quickly reachable. The end of the trunks on deck needs a careful design work: some noise shall necessarily come from the engine room, and the trunks must be protected from sea spray or waves. Each trunk must have a water interception system to keep the engine room dry. Finally there must be enough space around the trunks to install noise and fire insulation material. 9.5. Cooling wa ter
The MMEE and the diesel generators need a cooling system. Each engine has a heat exchanger, cooled by sea water. In practice, fresh cooling water flows around the water jacket of the cylinders block, which in turn gets cooled by sea water, by means of a radiator. The engine builder shall specify the cooling water pipes size, which is generally quite large. The vessel is normally provided ith two sea water intakes, set below the hull, equipped with bulb valves. Filters are provided on the main pipes line: a set of valves and secondary pipes shall provide the cooling sea water to all machinery. 9.6. The gen sets
The ship is similar to a small city which produces the electricity needed for its life. The choice o the electric generators (or gen sets) depends upon the energy balance, meaning the sum of the electrical absorption of motors, lights, refrigerators, air conditioning etcetera, in different conditions of use and various times of the day. In principle the designer needs to consider the following users:
• Deck systems: rudder machine, davits, capstans, windlasses; • Navigation and safety systems: instruments, radar, gyrocompass, firefighting pumps, radio communication; • Food service: dumb waiter, fridges, freezer; • Comfort system: air conditioning and heating; • Kitchen service; • Cabins system: fresh water pumps; water maker, boiler, elevator; • Lights system: inside lights, deck lights, emergency lights; • Engine room service: blowers, bilg e pumps, fuel pumps. Vessels generally have more than one electric generator, depending from the needed power: they must also work in parallel. Let me remind that the parallel between more generators sums their power, which unit is kW/h. A small generator could be installed for night use: it should release just enough power to light the vessel and to run the air conditioning. Gen sets are enclosed by noise reducing boxes (see figure # 50).
Fig. 50
9.7. The control room
Larger vessels are equipped with a “control room”. It’s a small and well organized office, soundproof, air conditioned, at one end of the engine room which it overlooks through large windows (see figure # 51). The control room allows the crew to survey the engine room in perfect comfort and safety.
Fig. 51
9.8. M ore machineries and arrangement
The engine room houses most of the vessel’s machinery: a short list includes: • Water maker; • Air conditioning pumps and compressor; • Boiler; • Fresh water pumps; • Firefighting pumps; • Bilge pumps; • Deck washing pumps; • Fuel pumps; • Rectifier; • Main electric boards. But there might be much more, such as the stabilizers machinery, the CPP controls etcetera. All the machinery which builds up vibrations, such as the pumps, should be installed on silent-blocks or similar anti vibrating devices. The structure of the vessel is like a resonance box and it might spread vibrations and noise even to cabins quite far from the engine room. It goes without saying that all machinery and plants must be easily accessible for inspection and maintenance. The engine room must have at least two entrances (it’s mandatory for the Registers rules) and at least one of them must be large enough to allow the passage of bulky loads, spare parts etcetera. There should be a work bench, ith sufficient tools for every emergency repair: machinery might break on board, and sometimes it’s not kind enough as drill, to crack down inmachine, a harbour a maintenance workshop. shouldand be at least a vice, a pillar a welding an or airnear compressor and a complete set There of wrenches tools. Mind that some machinery might need a dedicated kind of tooling, supplied by the builder and not available on the market. The designer should forecast a locker to store everything in perfect order. The vessel should finally board all the necessary spare parts, such as drive belts, filters, gaskets etcetera: the designer shall find a dedicated place for all of these items.
Chapter 10 The plants
10.1. Abstract
A common basic guide line characterizes all synoptic plant drawings: the target is to identify all the users and their position (bilges, living areas, machinery, tanks etcetera) and thereafter design the net of the necessary pipes, pumps and valves. The plans I shall examine are “synoptic”, meaning that they’re just functional schemes, in opposition to “topographic” plant which would show the actual position of each component. The latter is generally responsibility of the installer, under the designer’s supervision. Drawings called “as-is” shall be drafted at the end of the shipbuilding works: they are the actual on-board survey of the plants. The plants can be made of various materials: stainless steel, iron, copper, polypropylene, teflon, fibreglass: the material choice depends upon technical and economic considerations. 10.2. The pumps
The pumps have two main characteristics: the capacity and the head. The capacity is the amount o liquid that the pump can drive for unit of time: the unit of measure is litres per minute or 3mper hour. The head is the height difference between the intake and the delivery points. The unit of measure is metres of water column. These values are in inverse relation: the same pump might drive more liquid at less height, or less liquid at greater height. For example: the data from a pump-builder technical sheet state that the same model has a 0.9 m3/h capacity with 10 m/H2O head, or 2.7 m3/h capacity ith 2 m/H2O head. The designer must keep these criteria in mind while choosing a set of pumps for a vessel. Therefore a high head pump shall be used for firefighting purpose, as the water must reach areas o the ship much higher than the engine room, where presumably the pump is placed. On the contrary, a low head pump can be enough for the bilges service, as intake and outlet points are about level. Pumps aboard a vessel must be self-priming: that is to say, the pump must be able to suckle liquid even if the intake pipe is empty. It’s a fundamental feature: on the contrary, the crew would have to manually fill the pump body with liquid in case it’s been out of work for a long time. Most of the pumps are electric driven, by means of a dedicated electric motor: they can be fed by 12 or 24 V. d.c. or 220 or 380 V a.c. It mainly depends from the pump dimension and from the electric plant on board. Some pumps are mechanical, driven by the MMEE. 10. 3. The bilge s drain
The bilges are divided by watertight bulkheads which separate various compartments of the vessel (see figure # 52). Some water usually drips from condensate, from the sea chests, from small spill from the machineries, from fortuitous shipping of sea water. In each of the vessel’s compartments there must be a bilge suction rose, that is to say a pipe connecting the bilge with the pump, with a filter at its end to stop solid debris. In figure # 52 I have enlarged the pumps area. Please note that there are two bilge pumps: they can work together or one can backup the other. The suction roses are connected to a manifold with non-return valves. The bilge water flows into the sea, but for the engine room bilge water which is supposed to be oily and must be collected in a dedicated tank. All plants drawings must include a legend (see figure # 53) which explains the symbols, lists the machinery and possibly the dimensions. A high capacity mechanical bronze pump should be prudently installed on one of the MMEE: quite useful in the unfortunate case of engine room flooding. For the same reason, a three ways valve can be installed on the main sea water intake pipe: this valve allows the MMEE to suckle the cooling water from the bilge instead that from the sea. It’s an emergency item only, to be used in case of major leak.
Fig. 52
Fig. 53
10.4. The fresh water
Structural double bottom tanks hold the fresh water. The water is boarded from the pier through large size pipes, placed on both the vessels’ sides. As all boarding pipes, they must be provided with ventilation pipes. But fresh water is also produced on board by means of reverse osmosis water makers. We’re talking of electric driven machinery which purifies sea water, making it drinkable. Their output capacity ranges from a few hundreds litres to some thousands per hour: boarding water from the pier becomes therefore useless. The fresh water that they produce is collected in the tanks and once they’re full, the excess production is discharged overboard. In fact it’s convenient not to stop and restart the water makers too often to keep them in top shape. The fresh water pump is fitted ith a surge tank: this keeps a constant pressure and smooths the impeller’s pulses, so the water flow to the taps is continuous and uniform. Also the fresh water pump should have a backup pump, so that the fresh water supply is granted also in case of failure or maintenance of the main pump. It’s plain that the fresh water pump must have a sufficient head to grant enough pressure also to the top decks users. Hot water must also feed the wash basins, the bidets, the showers, the tubs, the kitchen: the arm water comes from one or more boilers. The water is heated by means of electric resistances and/or by means of exchangers with the heath of the gen sets cooling water outlets. Large vessels should be provided with a hot water circulating pump: this way the hot water is immediately available, also on upper bridges, avoiding long waits. The designer should not forget some users hich are peculiar for vessels, such as a shower on the aft bathing platform, a wash basin in the engine room, the water supply to ice makers, the deck pools, the windshield washer. Decks washing on large yachts is done by means of fresh water: in this case a water sweetener is appropriate: the ater, devoid of calcar, won’t leave unaesthetic white stains on the vessel’s paint.
10.5. The dec k washing
The crew washes the decks either by sea water or by fresh water: all experienced Captain knows that the teak planking must only be washed by salt water. A sea water pump is therefore necessary: it’s also used for washing the mooring chains: they might be messy with mud, sand, algae coming from the sea bed and would dirt the deck and the chains locker. The deck washing pump can be used to back-up the firefighting plant in case of emergency. 10. 6. The firefighting
Fire on board is possibly the worst nightmare of all sailors. For this reason the vessels are fitted ith several fire prevention and extinguishment means. The simplest are the manual fire extinguishers: their number, capacity and position follows the Registers rules. In principle they must not be hidden inside lockers, or in case they are, their position must be clearly identified by a dedicated sign. There’s a main firefighting plant: the outlet pipes end up in boxes, assigned for the purpose, placed around the decks in strategic positions. Fire hoses are placed in the same boxes. All cabins and rooms on board a vessel are provided with one or more heat and smoke sensors: automatic water sprinklers are installed on every ceiling. The engine room is fitted with a carbon dioxide automatic and manual remote-control firefighting plant: the gas bottles are placed in a dedicated room. I already wrote in 9.4 about the automatic or remote-control shutters, to cut- off air in case of fire in the engine room: the same principle applies to the fuel pipes, which valves must be shut to cut-off fuel from the engine room. The Registers require that some vessels are fitted with a portable emergency pump, equipped with its own independent engine and portable by two people. 10.7. The fuel supply
I wrote in 8.1 that the vessel is fitted with structural double bottoms, which host the fuel. Besides the main tanks, there’s a smaller reservoir, placed near the MMEE, called “daily tank”: the MMEE and all the machinery are fed from this tank. The fuel is carefully filtered before it gets to the users: the filters remove water and other impurities. Larger vessels are fitted with one or more rotary filters: this machinery pumps the fuel in a filter, round the clock, also when the vessel is moored. It draws the fuel from the furthest tank, filters it and pours it in the nearest tank. Condensate water and sludge might gather in the tanks bottom: in a calm sea the water, which is heavier than fuel, would not create problems. But in a rough sea, as the vessel rolls and pitches, the water might mix with the fuel, thus reducing the MMEE power or even stopping them, right when the crew needs all the available power to thethe bad weather. Pleaseinsee as bottom. I wrote, The roughly 10%don’t of the used, it fills thefight pipes, filters or remains the3.4: tanks MMEE usefuel all cannot the fuelbethat the as injection pumps suckles: some of it goes back to the fuel tank. It is hot and a good idea is to connect this excess line to the farthest tank, so that the fuel has time to cool. The fuel tanks are all connected and the crew, by means of a dedicated pump, can move the fuel from a tank to another. Like this the crew can control and adjust the vessel’s trim.
10.8. The black waters
The international rules don’t allow any vessel to release the WCs black waters into harbours or coastal waters. The vessels are therefore provided with sewage tanks and treatment machinery. The black waters tank is fitted with a level alarm, although it must be emptied only manually by the crew. The black waters must be discharged into a cistern aground, through a dedicated collector. Like all tanks, also the black water tank needs an outlet air vent which, for obvious reasons, must be placed as far as possible from the areas dedicated to guests and crew. A good idea could be through the mast top. 10.9. The electric plant
The sources of energy are essentially three: the batteries, the electricity supply from the pier and the diesel-electric generators. The batteries are gathered into gas-proof boxes: they’re used for the MMEE start and as a source for the 24 and 12 V. d.c. lines. The Registers require, for some types o vessels, that an emergency set of batteries is fitted on board. This set is bound for emergency radio communications and lights. As an alternative to the batteries there must be an emergency generator, placed on the highest bridge and independent from all the other energy sources. The pier supply is alternate current. Some of it feeds directly the a.c. users and some, by means of a rectifier, charges the batteries and feeds the d.c. users. Finally the diesel-electric generator feed the ship with all the electric power she needs. The electric plant on small vessels is generally quite simple and all d.c, either 12 or 24 V. On large yachts, on the contrary, the plant is 220 V, a.c. In each cabin or group o cabins there might be a rectifier to allow the use of d.c. users, such as the lights. Only very large vessels usebuilding 380 V a.c. choice lamps is quite wide since we stick to d.c.doesn’t There happen are several producers, highThe quality and of lovely design lamps. Unfortunately the same with a.c. lamps, but the designer can easily put the issue right by placing local rectifiers and going back to d.c. lamps. The electric plant has a general control panel which is usually placed in the engine room. Please mind that it might be quite large and heavy. There are also secondary control panels, for each group of cabin, out of which the most important is in the pilothouse. The electric plant should be built in sections, each leading to a control box. A dedicated colour and label marks each wire. Let me highlight a truth that tends to be neglected Principle number ten: for each metre of the vessel’s length there is a kilometre of wires and pipes.
That is to say: the lack of clarity of a plant design or construction makes the maintenance and repair impossible. 10. 10. The a ir co nditioning
This plant has two functions: the change of air and the cooling and heating of the cabins. A machinery called “primary air treatment group” filters the external air, dehumidifies it and minimally
cools it. The air is then lead into the cabins by means of high diameter insulated pipes. Once the primary air fills the rooms, it is cooled (or warmed) by the air conditioning plant. A set of chillers and pumps is placed in the engine room, while each cabin is fitted with one (or more) local machinery, called “fan coil”. The air conditioning supplier shall help the designer choosing the number and type of fan coils, which power depends on the room’s volume and environmental conditions. It’s up to the customer to decide whether some particular rooms, such as the toilets or the engine room, must be air conditioned or not. All fan coils must have an air outlet and intake: they produce an incredible amount of condensate, such that these machineries are fitted with a tray below. These trays must be connected to the white waters tank. A thermostat for each cabin controls the temperature. The designer shall indicate its position on the plans: it shouldn’t be near the portholes, neither near the fan coils and in any case it must be visible and accessible. The fan coils, as well as the primary air pipes, are quite voluminous. Therefore the designer must carefully plan their position. 10. 11. The loc kers ventilation
Every closed volume, such as bilges, chain locker, carbon dioxide room etcetera must be sufficiently aired by means of ventilation ducts and openings. This way the vessel won’t stink o damp, the rooms shall be healthy and the vessel’s structure will last for long.
Chapter 11 The tonnage
“Tonnage” is one of the most abused and mistreated terms: whoever isn’t familiar with ships often confuses the tonnage with the displacement (see 4.1 and successive). It’s by now plain that the displacement equals the vessels’ weight. Instead the tonnage is a measure of volume which includes the hull and the decks and is only used for vessels having a LOA > 24 metres, therefore “ships”. The tonnage calculationshe is must only necessary to ascertain some “legal” of loading the ship,capacity such asand the safety regulations abide to, some technical features shecharacteristics must have, her the fees she must pay when docking or crossing straits or canals. There are various tonnage rules, such as the Panama Tonnage, the Suez Tonnage or the International Tonnage. All rules take into consideration the whole volume of the ship, but some allow for deductions, like the engine room volume, the kitchen and other technical spaces. The unit of measure of the tonnage is the “gross ton” (GT), which doesn’t equal 1,000 kilograms weight, or a cubic metre: a GT roughly equals 2.6 3m. Actually, the real formula is GT = K1 * V , where K1 is a multiplier which varies in function of the volume. It’s indicated in the tonnage handbooks. The tonnage has two important steps which influence the designer’s work: 300 and 500 GT. Above the latter value the regulations are very strict and bounding for what concerns the safety appliances, the building methods, the crew characteristics and the ship’s operation. I guess that everybody is familiar with the “12 metres SI” that used to race for the Cup. belongraced to a in family of metricgames. tonnage sailboats beenlooking famousand in the past,America’s such as the 5.50They SI which the Olympic They’re for that sure have the best more graceful sailboats ever built.
Chapter 12 The mooring manoeuvres
12.1. Abstract
A vessel, like a car, is born to travel. But, as the car, sooner or later she shall need a parking place. The ship can be kept still in a bay, by means of anchor and chain, or moored to a pier. 12.2. The equipment number
The Registers rule the number and weight of the anchors, the diameter and type of chains, the diameter and length of the mooring lines for each vessel. All of this is listed in a chart table and the input datum is the “equipment number” (En). The formula to calculate En is more boring than difficult: it considers some parameters like the side area of the hull and of the decks. As per the chain, the Registers state whether it must be studless of with stud link. 12.3. The chain
54 shows a stud studless andbetween a shackle the and linkthe diameter. “B”Figure is also# the head link in alink stud(A), linkachain andlink it’s (B) placed the(C). last“D” studislink swivel crown, just before the anchor. The swivel crown is a revolving shackle which allows the anchor and the chain to turn. Small diameter chains are available in long sections and therefore no joint link is necessary, while large diameter chains (typically stud link chains) are produced and sold in “lengths”. Each length equals 27.50 metres and the segments are joined by means of a special assembled link, called “Kenter” link (see figure # 55). The ultimate tensile strength of the steel by hich the chain is made of can be “grade 1”, “grade 2” or “grade 3” and naturally it makes a difference in the chain’s diameter. Grade 3 steel would allow for a lighter chain: even if the mechanical characteristics comply with the rules, I wouldn’t feel like suggesting such a solution because what holds the vessel is not the anchor, but is the chain’s weight. The chain is made of zinccoated steel: on some vessels, just for the look of it, the first few metres of the chain could be made o stainless steel.
Fig. 54
Fig. 55
12.4. The anchor
Figure # 56 shows which parts the anchor is made of and how it’s linked to the chain. “A”, “B” and “C” are the same links of figure # 54, even though the “C” link is generally swivelling. Like this the anchor is free to turn and to find its position into a recess of the bow, called “pocket”. “E” is the shank, “F” is the fluke, “G” is the crown plate. Anchors are made of zinc-plated steel, but they might sometimes be made of stainless steel for aesthetic purposes. I wish to highlight that the anchor shape of figure # 56 is only one among the many existing: danforth, flipper, hall and more.
Fig. 56
12.5. The roadstead mooring
Anchoring a vessel in a bay has several benefits. And brings a few problems. It’s a calm mooring, far from noises, from pier neighbours and from meddling crowds. There’s only the sea and the bay’s banks, fishes and seagulls. And no port fees. The drawbacks are: you need a tender to reach dry land; the gen sets must run all the time; the Captain must pay careful attention to the weather conditions. A vessel windward to a rocky shore is in a very dangerous position in case a strong wind begins blowing. All good sailors know that what holds the anchor from dragging is the chain’s weight. Please note that the vessel tends to traverse and that the chain crawls on the bow, scraping the paint. The bow should therefore be protected by means of a stainless steel plate. 12.6. The windlass
The chain on large size vessels is quite heavy and cannot be hauled on board by hand. Thereafter a indlass is necessary. In case there are two anchors and two chains, two windlasses are needed. The portside one shall turn counter clockwise while the starboard side one shall rotate clockwise. The main part of the windlass is the wildcat, or “gipsy wheel”. It’s a drum, integral to the windlass shaft, hich hosts the chain links. It goes without saying that there must be a perfect coincidence between the links (diameter, length, width) and the shape of the drum’s marks.
Fig. 57
To avoid unpleasant last minute surprises I suggest to supply the windlass builder with a sample o the actual chain. As figure # 58 shows, above the wildcat there’s a drum, or capstan. Its purpose is hauling ropes and warping. The windlasses are in sight and even though they’re pieces of machinery they need a good design and finishing touch to fit on a yacht deck. The part of chain which falls into the chains locker must be long enough, and heavy enough, to pull down the chain, keeping it close tight to the wildcat. An insufficient weight might cause the chain to come off the wildcat and slip. Type and power of the windlass are function of the weight and dimensions of the anchor and chain. The “up” and “down” controls are placed near the windlass and in the pilothouse.
Fig. 58
12.7. The hawse pipe
On large vessels the chains pass through structural pipes, called “hawse pipes”. Figure # 59 shows how the chains roll on a spool which cuts the friction. The chains need stoppers which hold the chain: in other words, the wildcat is not supposed to hold the chain load. It can be a devil’s claw or a sash stopper: the wildcat has a brake but it’s unfit to keep the chain from turning. One or more water nozzles should be set in the hawse pipes to wash the chain. Figure # 59 shows kind of a tray, made o stainless steel, all around the windlasses: it holds the dirt which flows from a drain plug. The designer should not forget manholes on deck to access the chain locker.
Fig. 59
12.8. The cleats and fairleads
The mooring ropes are belayed to cleats which need to be installed in a comfortable, rational place. There must be four cleats at the bow, four at the stern and two on the sides. The mooring ropes cross the bulwark through stainless steel fairleads: they have rounded edges and sometimes rollers, to protect the ropes from wearing. The vessel mooring must be safe, strong and elastic at a time: figure # 60 shows an example. 12.9. The c apstans
It’s unthinkable warping an heavy vessel by hand: capstans must therefore be installed also near the stern to haul the mooring ropes.
Fig. 60
Chapter 13 The classification Registers
Every vessel building must be surveyed and certified by a classification Register, approved by the Maritime Authority. The best known Registers are: • Registro Italiano Navale (R.I.Na.); • Lloyd’s Register of Shipping; •• American Bureau of Shipping (ABS); Bureau Veritas; • Det Norske Veritas; • Germanisher Lloyd’s; • Nippon Kaji Kyokai. All Registers release an incredible amount of publications, both on paper and electronic. This set of rules determines the building methods, the safety appliances guideline, settles limits to the vessel’s operations, gives her the “class” and so on. The Registers don’t take responsibility for the ship’s outcome: they only check that the project complies with the rules, and that the vessel is built as per the project. At the end of the building the Register releases a compliance certificate after which the Maritime Authority issues the documents which enable the ship to sail. There are more bodies which release further certifications, sometime mandatory and sometimes discretionary: for example MCA (Maritime and Coastguard Agency) and SOLAS (Safety of Life at Sea).
Chapter 14 The general arrangement plan
14.1. Pinpoint the design pa rameters
We have started a dedicated design exercise: we must therefore presume that we have a customer, be it a private owner or a boat builder. In any case, when it comes to design the arrangements, the designer shall get a guideline: several demands that shall include the number of cabins, their location, the furniture style and so on. The customer often gives the designer a full outfit of leaflets, pages ripped from yachting magazines, picture of yachts which belong to dear friends or, in case it’s a builder, which are built by competitors. Frequently this iconography concerns boats much bigger than the one the designer is taking care of. Typically the customer asks for a number of cabins, o bathrooms, of saloons that would hardly fit in a yacht twice as large. Well: after all this is the reason hy he pays a professional. If it were easy, he could have done it alone. The designer, after a few years work, shall have his own pictures portfolio of yachts that he designed and built, which might be useful to take inspiration from (drawing inspiration from ourselves is not against professional ethics…) and helpful to find out which are the customer’s taste and wishes. In other words, to plan the job. It’s an important stage of the designer’s work, somehow as he was a tailor sewing a custommade dress. Several meetings with the customer might be necessary to fulfil this design stage, yet the importance understand arrangementstoplan drafting. perfectly his needs is plain. The designer can then skip to the general 14.2. The gene ral arrangement pl an
We have seen how to design the hull and the decks. Let’s now start drafting the arrangements inside these volumes. The position of the frames, of the bulkheads, of the double bottoms is already set: this actually means that the designer, when drafting these elements, had already in mind what the vessel’s layout would look like. And in fact this brings us to Principle number eleven: no single part of the vessel lives an independent life, but they’re all strictly linked together such that every modification done to one will necessarily bring a change to all the others.
The project is like a vase full of golf balls: there is no way you can move one without changing the equilibrium of all the remaining balls. This kept in mind, let’s go back to the general arrangement plan, also called GA. This plan must show the entire vessel: it must therefore include an elevation view (or “profile”), the plan view of all decks, a longitudinal section and if ever possible a significant transverse section. This set o
drawings gives to all the parties involved with the project (customer, builder, suppliers…) enough information to build up a realistic idea of what the vessel must be like. Besides, the designer can check with sufficient accuracy the heights, the functionality of stairs, aisles and passages, the ergonomics. Yes, because there’s Principle number twelve: the human body dimensions do not shrink only because the boat’s rooms are narrow.
Beds, therefore, must have a standard length: not less than 195 centimetres. Their width must be at least 85 centimetres for a single bed, twice as much for a double one. Doors must have a minimum net span of 58 centimetres. Aisles should not look like horror-movie corridors and their width must not be less than 68 centimetres. The ceilings height should be at least 190 centimetres: it’s an acceptable figure on small vessels, hile on large yachts, which rooms are larger, it shall be between 200 and 220 centimetres. Customarily a large room with a low ceiling gives an uneasy feeling of oppression, of incumbent threat and is clearly out of proportion. Unfortunately there’s no mathematic rule which ties the room area to the ceiling height: at the end of the day it’s a question determined by the designer’s taste and delicacy… and by the available space. Unfortunately we must sometimes come to compromises, as in all jobs, and do the things that are feasible, not the ones we like. The designer, while drafting the GA, must carefully study the vessel’s planning scheme, that is to say decide which are the owner and guests paths, which are the crew paths, where are the emergency escape routes. It’s plain that this feature doesn’t apply to small vessels, but it becomes fundamental once the ship has three or more bridges. On large yachts the designer must consider one or more “muster stations”: these are the gathering places where the persons meet in case they have to abandon the ship. It’s should be an easily accessible place, far from likely sources of fire (such as the engine room and the kitchen) near to the life rafts, not too high above the water (see also Chapter 19). 14.3. The lower deck layout
Figure # 61 shows the lower deck layout of the same yacht which hull we’ve seen in Chapter 2. It’s only one of the many possible layouts, but it’s what the customer chose. I have to say that the general setup of the project might considerably vary from a cultural area of the world to another. This is a “Mediterranean” kind of yacht: an Arab, a Chinese, a Russian, an American or a Finnish customer would certainly want something quite different. Students of the Universities where I teach often ask me where they have to set the cabins, the bathrooms and the rest: the univocal answer is that I don’t’ know. Who’s in charge of the design work makes the decisions, apart from the customer’s requests. In this case, starting from the bow, we have a bathroom and a shower, just abaft the collision bulkhead. Two stairs coming from the upper bridge suggest that it pertains to a cabin placed above. Behind a bulkhead there is a VIP cabin with separated toilet and shower. Then two double bed cabins, mirror like, each with its own toilet. There’s a central stair which leads to the main deck. A further bulkhead divides the guests cabins from the kitchen. A stair on the left connects the kitchen ith the upper deck. The kitchen is a topic which needs further attention. May be that your customer usually only eats two salad leaves and a boiled shrimp (let alone what his partner eats, that is to say
nothing), yet he will want a kitchen suitable for a small hotel. The kitchen can be placed below, as in our case, or on the main deck level. It can be an open space or have glass walls. In any case it must be rational, functional, well equipped. Behind the kitchen there is the captain’s cabin (right) and two double beds cabins for the crew (left). Abaft there is the engine room. The crew cabins don’t seem very comfortable: it’s an acceptable compromise because on such size vessels the crew don’t live aboard all year round, but only for short periods. On larger yachts, where the crew would spend aboard eleven months a year, their quarters should be different and much more comfortable. There seems to be a void space between the sheer, the floors border and the beds. It’s not wasted space: drawing the arrangements starting exactly from the sheer line would be a mistake, one of the most common the beginner does.
Fig. 61
14.4. Is the arrangement aboard?
Or is it outside the vessel? It might seem a bizarre question but it’s not. Let’s have a look at figure # 62: the transverse section shows that the hull narrows below the sheer line, as it has a “vee” shape.
The more we move towards the base line, the narrower it becomes. Therefore it would be a mistake to design the berth too near the sheer line: either the berth was so high to be unusable (case A), or it as out of the boat, if at the right height (case B). What we need is a compromise between width and height (case C): like this the berth will be on board the vessel. There’s a span between the outer end of the berth and the sheer line projection. In plan view this might appear as a drawing mistake, giving the impression of wasted space, but it’s not like this. Some experience and practice shall help the designer to deem whether the arrangement he’s drafting is aboard or not. In any case, throughout the executive plans drafting, all transverse sections shall be thoroughly checked: not just to make sure that all pieces of furniture fit inside the vessel, but also to allow some extra space for the passage o pipes, wires and for the hands of a maintenance operator.
Fig. 62
14.5. The main deck layout
Figure # 63 shows the main deck layout: starting from the bow we find the steel tray upon which the windlasses are installed (see 12.7). Behind there’s a sitting area. Now, moving inside, we see again the twin stairs coming from the bathroom below. In the centre there’s a walk-in cabinet and then a double bed owner’s cabin. Abaft there’s the pilothouse: it’s raised above the main deck floor level and we shall see it later in detail. On the left side there’s the stair leading down to the kitchen, and naturally, just abaft, there’s the dining room. The main saloon ends with a large sitting area. The aft cockpit on deck is equipped with a further sitting area and a folding table. Strange that it might seem e have Principle number fourteen: the yacht is always designed with her bow to the right.
Why? It’s a mystery, but it’s been like this since our ancestors engraved log canoes on their cavern alls. The more attentive reader might have realised that I skipped from principle number twelve to principle number fourteen: it’s not superstition, just elementary prudence, the same attitude after hich in our line of business we don’t “catch fire” but only get upset, and we don’t “get to the bottom” but just thoroughly examine the problems. We don’t want to deal with fire and bottoms, in any
circumstance.
Fig. 63
14.6. Hints of ergonomics
Fig. 64
People’s “dimensions” are listed by percentile: in other words, there’s a majority of individuals that meet some criteria and a minority which doesn’t. The designer should take into consideration the ninetieth percentile in case his customer is a builder and the vessel is bound to be sold to people that he’ll never encounter. Like this he would meet the needs of the largest amount of people. If, on the contrary, the designer is working for a private owner, a basketball champion for example, he’d better adjust the project on his customer’s size. Please keep in mind that, sooner or later, the yacht of your design will certainly have to face the market demands, be it second hand yachts or new ones. I suggest that you avoid odd dimensions and/or style. This brings us to Principle number fifteen: every new design starts from the ending point of the previous one.
In other words: don’t expect a beginner to jump up and overturn the history of design. Be humble and start every time from the point that you (or others) have last reached. Only small steps at a time lead to lasting, sensible and serious innovations. Coming back to ergonomics, please consider that children will enjoy the vessel too. Kids would never reach the light switches in case the designer specifies that they’re placed on the ceiling (which actually means that the designer forgot to find them
a clever location, from the very beginning). Figure # 64 shows the ninetieth percentile of men and omen, from 45 to 54 years-old, aka the category of people who buys and uses a yacht. I personally disagree about the “weight” figure, but I might go on a diet. Don’t get mad with figures: get a tape metre and measure the common objects around you and around your house. Measure a bed, the chair’s height, the rise and the tread of a step, the sofa’s seat cushion, the kitchen’s height. Ask a relative or a friend to seat at the dining table and check the space that he/she needs for dining in full comfort, make a note of the door handles height from the floor… then ask yourself why all of this should be different on a boat. It shouldn’t. Certainly, the ceilings height won’t be 3 metres, like in our house. In 14.2 I already gave some figures for the ceilings span. These figures concern the “clear height”, that is to say the distance from the finished floor to the finished ceiling. Therefore, to a clear height of 200 centimetres we must add (above) the thickness of the ceiling panelling, the framework, the structural beam, and (below) the finishing material, the raw floor, the framework. Let’s say that this brings our figure up to 230 to 240 centimetres (see figure # 65 and 66). Mind that some of the plants (wires and pipes) shall pass below the floors and above the ceiling panels, and they need some space. I suggest that you don’t specify ceiling lamps or handrails sticking out below the ceiling: I spent the best years of my youth hitting my head into the lamps of a small sailing boat and I wouldn’t see other human beings suffer that way.
Fig. 65
Fig. 66
Chapter 15 The executive plans
15.1. The feasible drawings and the essential information
The designer shall start the set of feasible drawings only after the customer officially approves the GA. You better be prepared: the GA might go through several modifications before it’s finalized. Let’s imagine we were able to agree with the customer about all the vessel’s characteristics. It’s now time to say the famous words, the sentence that every respectful designer shall put before his work, hich is Principle number sixteen: in this *** boat there’s not enough space.
Where, in the place of ***, you’re free to insert some picturesque, informal and explicit connotation. It’s incredible, but when the time comes to draft the feasible plans all vessels seem to shrink, to be too small and there’s no space for most of the things we want to fit on board. Unlike our previsions, the floors are narrower, the structures bulkier, the plants take too much space… while the GA allows some approximation, the feasible drawings must be precise, coherent and collated. “Collation” means checking that the same information are correctly shown on all the drawings, that they match with the technical specifications, with the bill of quantities and with the weight calculation. For example: you draw a stair that goes from the lower deck to the main deck. If it has eleven steps on one drawing, it must have eleven steps on all the remaining drawings. If a door opens inside a cabin in a drawing, it shall open inside in all the other drawings. If there is a 70 by 70 centimetres manhole on the deck drawing, the same manhole must show on the cabin ceiling below and must be listed in the technical specifications and in the bill of quantities. I know: it sounds evident, clear and obvious. But it’s not. So many times you modify a drawing and forget to copy the same change on all the other drawings, which brings chaos to the whole project. To avoid such a mess there’s Principle number eighteen: all modifications done to a drawing must immediately be copied on all the others.
In case my readers wonder where principle number seventeen is, please be informed that it’s in the same place of number thirteen. The feasible drawings must convey information clearly and efficiently. Put yourself in the shoes of the people who will receive your drawings and ask yourself whether they’re readable, plain, complete. Ask yourself which info you’d need if you were to build the boat (or the cabin, the door, the bed, the ceiling…). Your drawings should be the answer to these questions. Consider that the worker who receives your drawings is not in your head, might not have your preparation, might not even speak and read your language. The designer’s commitment is
releasing plain, unambiguous, thorough information. Unfortunately there’s not a unique rule. Some shipyards have decennial experience, in-house competent technical office and skilled manpower. These builders might construct the vessel just by means of the GA, a few survey visits of the designer and a set of finishing materials samples. Others might need much more information: at the bottom o the scale there are those who even need the drawings of the screwdriver and the screw plus a short handbook explaining how to use them (see figure # 67).
Fig. 67
Fig. 68
Usually the feasible drawings of the arrangements must show each room in several views: • a plan view of the whole room; • a plan view of the floor, without the furniture; • a plan view of the ceiling; • a left side longitudinal section; • a right side longitudinal section; • several transverse sections. Let’s see a few examples: the following figures make reference to the same vessel that we saw in 14.3 and 14.5. Figure # 68 shows the plan view of one of the twin cabins. Please note some interesting details: the centre line and the stations (17, 18, 19, 20) show in the upper part of the drawing, as per principle number one. The legenda (which I have omitted on the following figures for the sake of clarity) on the right lists several useful information, such as which lamps must be installed, which finishing materials shall be used, the colours, the hardware (handles, portholes…) and the suppliers brands. There is a small scale drawing of the whole lower deck: the cabin in question is highlighted (dotted, actually). This little trick helps workers to understand quickly which cabin the drawing makes reference to.
Fig. 69
It keeps workers from wondering “Where the heck are we?” when they deal with large vessels. There are a few notes: unfortunately they’re not readable due to the printing scale, and besides they’re in Italian. Shortly they say: “All dimensions must be verified on board”; “All dimensions are in millimetres”; “All drawings must be approved by the joiner before the works start” and more. The floor height is 1,450 millimetres from the base line. The portholes seem to be horizontal, but naturally they’re not: it’s just a drawing expedient to show their position and dimensions. Figure # 69 shows
the cabin’s ceiling, the dimensions of the finishing panels, the lights and how they’re linked together in groups. The next drawing (figure # 70) shows the floor without the furniture and explains which ood it’s made of, the wood strips dimensions and mainly indicates that there’s a manhole under the bed. It’s an inspection manhole for the double bottom tanks.
Fig. 70
Please mind that the inspection manholes are fundamental and that no piece of furniture or partition bulkhead should fall above them, or else they could be opened. The following two figures (# 71 and # 72) are the longitudinal and transverse sections of the same cabin. Note that we left some void space aside for the plants. Finally figure # 73 shows a mix of drawings of the bathroom.
Fig. 71
The partition bulkheads reach to the vessel’s structure and the floors are fixed to these bulkheads, never vice versa. Let me highlight that all the drawings are perfectly collated: each element occupies its place in all the views, the dimension coincide, the portholes are in the same position and they’re listed in the technical specification and bill of quantity, together with all the lights, hardware etcetera.
Fig. 72
The correct procedure to design a cabin is working on the three views at one time. There’s no way a designer could draft the complete plan view first and then skip to the sections: it wouldn’t work. The drawings must progress together and there will be thousands of modifications: please remember principles number eleven and eighteen! The designer must have clear in his mind what he wants to achieve: at the end of the day, a drawing is only a way to convey your ideas to others. Therefore: first have ideas, and then design.
Fig. 73
All the “workshop details” (like the rulers, the mortises, the tenons, the minute hardware) are missing in the feasible drawings of the cabin shown above. The designer should leave such information to the joiner who, in any case, will follow his own traditional working method. If you do the detailed drawings they would probably be totally neglected: so, let’s spare the hustle. 15. 2. The spe cifica tions a nd th e bill of q uantities
A written document must go with the feasible drawings: it’s the technical specifications booklet (briefly called which describes vessel in detail. mainthedimensions, where how she’s built,“Tech whichSpec”) material is made of, thethepainting cycle, theHer plants, arrangements, theand trials and so on. The Tec Spec could be made of only a few pages, up to a few hundreds, depending on the amount and the importance of the works. Figure # 74 shows an example: it’s just the index of a Tec Spec and gives a rough idea of which are the arguments. The Tec Spec booklet certainly is an extremely boring text, both for the compiler and for the reader. Yet it’s absolutely essential. It goes ithout saying that also the Tec Spec needs to collate with the drawings: whatever appears in the Tec
Spec must also show in the plans. TECHNICAL SPECIFICATION INDEX G) GENERAL G.1) MAIN CHARACTERISTICS G.2) DIMENSIONS AND PERFORMANCE G.3) RULES – CLASS – CERTIFICATE G.4) STABILITYAND TRIM G.5) TESTS AND TRIAL G.6) MATERIALS AND MANPOWER - WORKMANSHIP G.7) TECHNICAL DOCUMENTS G.8) TOOLS AND SPARES G.9) EXCLUSIONS G.10) ALLOWANCES H) HULL H.1) HULLFORMS – SUPERSTRUCTURES H.2) MATERIALS – TYPE OF STRUCTURE – WELDING H.3) H.4) WATERTIGHT D.B & TANKS BULKHEADS H.5) UNACCESSIBLE AREAS H.6) LOCAL STRENGTHENING H.7) NON DESTRUCTIVE TESTS H.8) CATHODIC PROTECTION H.9) MAST STRUCTURE H.10) STRUCTURAL FURNITURE – RECESSES AND LOCKERS O) OUTFITTING O.1) ST.STEEL OUTFITTING PARTS O.2) EXTERNAL DECKS LINING – MISCELLANEOUS WOOD-WORK O.3) PAINTING O.4) THERMO-ACOUSTICAL INSULATION O.5) INSIDE PARTITION BULKHEADS – LININGS – GRATINGS O.6) GROUND TACKLE – DECK MACHINERY O.7) PORTHOLES – W.T. DOORS – SCUTTLES – WINDOWS O.8) STEERING – VESSEL CONTROL O.9) VENTILATION (OUTSDE E.R.) ANDAIR CONDITIONING O.10) PIPING – MACHINERY– PUMPS O.11) SAFETYAND SALVAGE O.12) ELECTRICAL INSTALLATION O.13) ELECTRONIC NAVIGATION AND COMMUNICATION SYSTEMS O.14) TECHNICAL AREAS INTERIORS AND OUTFITTING O.15) MAST O.16) MISCELLANEOUS P) PROPULSION P.1) MAIN PROPULSION ENGINES P.2) REVERSE/REDUCTIONGEARBOXES P.3) ENGINES AND GEARBOXES MOUNTING P.4) SHAFTING AND PROPELLERS P.5) ENGINE ROOM VENTILATION P.6) ENGINE ROOM GRATINGS P.7) WORKSHOP A) ACCOMMODATION A.1) GENERAL A.2) FLOORS A.3) LININGS A.4) ACCOMMODATION AND BATHROOMS OUTFITTING A.5) ACCOMMODATION AND PUBLIC AREAS LAYOUT M) MAKERS LIST – MATERIALS SPECIFICATIONS
Fig. 74
Besides the Tec Spec the designer must compile a spreadsheet, called “bill of quantities” (or BOQ). This document lists all and every item that the vessel is made of: it goes without saying that all these items are listed in the Tec Spec and show in the drawings. The chart’s columns are:
• Item: it tells what we are dealing with (engine, generator, chair, porthole etcetera); • Category: the vessel’s components are grouped by homogeneous kinds, like “machinery”, air conditioning”, “kitchen “and so on; • Supplier: lists the builder or supplier which the designer suggests; • Addre ss, city and nation: of the above said suppliers; • Contact person: sometimes a purchase is easier if you personally know who to deal with; • Telephone, fax, e-mail: no comment; • Catalogue code: this piece of information makes the life of the shipyard’s purchasing manager much easier, and reduces the risk of misunderstandings; • Dimensions: quite useful for the designer and for the builder; • Number of items: lists how many portholes, how many reading lights, how many chairs and so forth; • Reference drawing: tells which drawings show the item; • Unitary and total we ight: keeps under control the vessel’s weight; • Delivery, outfit and test: the builder shall fill this column, listing the dates to keep the building schedule under control. The list of items amounts to some hundreds entries: it’s an in-progress document. Some components might not be available, or the delivery schedule is too long, or the owner has changed his mind. Be ready to re-do the work several times: six or seven is the average standard. In any case all changes must be carried on the drawings and the Tec Spec, and vice versa. 15.3. The owne r’s cabin
Fig. 75
The owner spends a lot of money for his new yacht. The designer should try and give him as much comfort and luxury as possible, like a spacious, quiet, cosy and elegant cabin. If the vessel’s size allows it, the owner’s cabin should have an independent bathroom and a walk-in closet like in figure # 75. If the yacht is large enough there might be more luxuries, like a sauna, even though the classification Registers tend to make a fuss about saunas. Perhaps the designer could fit-in a dedicated corner for a computer, or even a separate studio. A safe is necessary, and it should be hidden. May be behind a painting: who would ever imagine that the picture hides a safe? All thieves in the world. Well, if you have a better idea, write to me. We’ve already installed safes all over the yachts of our design: inside the hangers, below the beds, behind the bathroom’s mirrors. We run short of ideas by now. It goes without saying that the safe must be solidly fixed to a structure of the ship. The owner guards his precious belongings and cash in the safe and then he forgets the combination. Is it his wedding date? The first or the second? His wife’s birthday? Which wife? If the designer is allowed to do so, he’d better make a confidential note to help the owner in the time of needs. The cabin must be bright. If ever possible, the designer should fit a manhole on the cabin’s ceiling: much better if it’s large enough to serve as an emergency escape. There could be one or more skylights, that is to say fixed windows, flush with the deck. They should be fitted with curtains, or may be made of a special liquid crystals glass: when it’s electrified it’s transparent and when the power is off, it turns
black. Portholes or windows must be fitted on the cabin’s sides: the curtains must be two. One light, to filter the daylight; another, opaque, to darken the room. 15.4. The guests’ cabins
People enjoy yachts only if they’re comfortable, with the possible exclusion of sailors (including myself), who savour pain, sufferance and inconvenience. The owner will want to lodge his guests at the very best. Often the “guests” are the owner’s kids. Everybody knows that children don’t love to spend their holidays with parents: if, moreover, their cabins are pokey, low, dark and noisy… the family peace is at risk. More than this, there could be an awful difference between the “nice” cabin, the “less nice” and the “horrible” one. The designer should therefore try to plan similar guest cabins: in case cabin it’s not really possible, he should compensate flawcabin withwith a quality. For beds example, lowa ceiling might have two portholes instead of one; ora the transverse mightthe have private toilet. See figure # 61: you might notice that two guest cabins are mirror like. 15.5. The toilets
The toilets of a vessel are also called “heads”. I shall write later about the bathroom features, hich are somehow different from the house ones, and yet a yacht toilet must have the same equipment, that is to say one or two wash basins, a WC, a bidet, a shower. Large vessel might be fitted with a bathing tub or even a Jacuzzi pool. The designer should not draft the wash basin alongside the sheer line: there must be a mirror above the wash basin and it would be in the porthole’s way. The WC and the bidet should be set along the vessel’s side: like this there’s more space for the intake and outlet pipes. The design shall include several lockers and drawers to hold all the necessary gadgets which help men to be less disgusting and women to be more attractive. Remember that nothing can be left around: whatever is free to do so would fall due to the vessel’s motion (see figure # 73). 15.6. The crew quarters
I wrote about it in 14.3: let me add that often the captain has the last word when it comes to buy a yacht. Apart from all other reflections, it’s wise giving the crew a comfortable arrangement. A happy crew, well fed and refreshed does a better service to the yacht, grants a higher safety standard and is kinder towards the owner and his guests. Privacy is a must both for the owner and for the crew: the designer must therefore carefully study the paths and pay special attention to the sound-proofing of the divisional bulkheads. 15.7. The kitche n
The kitchen design depends on the boat’s dimensions and on her destination: one thing is the small sailboat for the week-end cruise, another is the large charter vessel. The design for a guzzler’s
kitchen shall be different from the salad-and-shrimp-eater’s one. In any case the kitchen must include all the features that allow to cook food, to preserve it, to extract the fumes, to dispose of the waste, to clean everything spic and span and to renew the air. As safety is the designer’s main concern, the kitchen (a dangerous place) must have pan-stoppers on the cooktop and handrails all around. In the foreword I wrote that a yacht designer should also be a sailor, unless he/she wouldn’t know the problems he’s supposed to deal with: similarly I wonder how a designer could draft a really functional kitchen unless he/she has ever cooked or washed the dishes (see figure # 76).
Fig. 76
15.8. The pilothouse
The pilothouse is the vessel’s core. It’s also the place of dreams and imagination, where the vessel becomes an airplane or a spaceship. The designer has the responsibility of blending the navigation, communication and electronics instruments into a pleasant and exciting design (see figure # 77 and # 78).
Fig. 77
There are red lights for night service (they won’t blind the crew) and all the instruments are the same listed in the Tec Spec and BOQ. The view from the pilothouse must be perfect: the designer must therefore pay careful attention to the ergonomics: all instruments must be at hand and easily readable. The MMEE controls should be placed right of the wheel, unless the captain is left-handed. The VHF radio, which is often used, needs to be near the wheel too. Don’t’ get mad about the wheel: on many large size vessels it’s not there anymore. There’s only a joystick, because large yachts usually sail under the automatic pilot control at large and the captain manoeuvres from the fly bridge in restricted waters only.
Fig. 78
15.9. The sitting room
The readers of this handbook might think that the sitting room is the area where the owner and his guests live. But they would be wrong. The vessels that we design are mainly used in summer: during the day the passengers live on the decks and at night they change and go for dinner at a restaurant. Yet, it’s the first room that everybody sees when boarding the vessel, and the first impression is the most important. The sitting room also includes the dining area (see figure # 79). The room should be bright, ith large windows shaded by light curtains. Some of the arrangement (which is known as “loose equipment”) might come from the household market, such as armchairs, sofas, coffee tables, provided that the wood they’re made of is suitable for marine use and that the hardware (screws, hinges etcetera) is made of stainless steel.
Fig. 79
Chapter 16 The details and the tricks
16.1. The differenc es from the household furniture
The boat moves and the house does not: this is the main and most obvious difference. There are several other differences, more elusive and deceptive. Let’s focus on the movement: as I wrote before, a yacht designer who doesn’t’ sail and therefore doesn’t experience what a really bad tempered sea can do, can’t reasonably take all the necessary measures in his design work. All pieces of furniture should be fitted with some kind of anti-rolling device. No matter how it’s done: it might be a simple wood stripe glued and screwed or something a little more complex, as per figure # 80.
Fig. 80
A sailboat, which lists sensibly when sailing close to the wind, must have higher anti-rolling features. Anti-rolling devices could be unsightly, mainly in a refined, rarefied interior design. The designer might then suggest the use of dedicated trays. A sheet of anti-skid material could be glued below the trays and they should not fall from the countertops. It’s more a farmer’s solution than a sailor’s, but it’s better than collecting objects from the floor. All the drawers and the lockers must have some kind of latch which prevents them from opening when the vessel rolls and pitches. The drawers might have a fall-down type of rails. The doors must be fitted with stoppers to hold them
open (see figure # 81). The boat is a humid space: all the lockers, the kitchen cabinets, the cupboards, the drawers should have some kind of air intake to avoid mildew. It could be simple holes on the shutters, or a straw network front, or wooden venetian blinds. The wise owner should let all lockers and drawers open when he leaves the boat for a long period, but sometimes he forgets to do so. As the boat moves, the people on board often lose balance and hit the furniture which therefore should have rounded or soft edges.
Fig. 81
Bruises are part of the sailor’s attire, but broken bones should be avoided. Yachting magazines show recent yachts interiors all made of sharp corners, steel and crystal dihedron, extremely minimalistic, without any anti-rolling device or handrail. Yet, this handbook concerns vessels designed to sail the sea, not to be kept moored to a pier to show off. Finally we have Principle number nineteen: all the closed volumes of the vessel must be easily accessible.
Meaning that the back panels of every hanger, locker and closet must be removable for inspection and maintenance. 16.2. The doors
Please remember principle number twelve: the boat ergonomic doesn’t change only because the space and the volume are smaller than at home. Yet we must sometimes compromise: at the end of the day if there’s no space, there’s no space! The doors (see 14.2) should have a minimum net span of 58 centimetres, but also should not be larger than 75. Wider doors would be hard to use and to fit:
besides, they wouldn’t get along with the arrangements. The doors height should be approximately 180 centimetres, compatibly with the ceiling height. The doors on old vessels used to have a sill, some 15 centimetres high above the floor. It was due to stop water, to preserve the bulkhead holeness and to trip the non-sailors, thus separating the tares from the wheat. The most recent trend is to cancel doors sills: it’s more elegant and allows also mountain shepherds to sail without stumbling. The hinges and the rabbet could be on-sight or hidden inside the doorpost. The doorpost could be made of the same wood of the furniture, or made of varnished wood or finally bought from a supplier who builds them in light alloy. The hinges and the rabbet might be set inside the bulkhead thickness, without a doorpost. This design solution is more elegant and clean, but it’s feasible only in case the bulkheads thickness is at least 50 millimetres. Naturally the bulkheads won’t be made o marine plywood: they would be too heavy. The partition bulkheads are made of a light material: two thin marine plywood sides and rigid polyurethane foam inside. They’re made and sold by several qualified and certified suppliers. The designer might also use sliding doors. I’m personally against sliding doors, apart from the design for physical impairment (see chapter 20). Sliding doors don’t close well and leave open splits: therefore they don’t stop smell and noise. There’s always an engine frequency which will make the doors rattle. Finally the sliding doors must be somehow fixed in the open position, but sooner or later somebody might forget to fix the door, which might close abruptly hen the vessel rolls. And it’s very dangerous. Sliding doors should be the second best choice: in any case it’s better to install them in a longitudinal opening instead that on a transverse bulkhead, because the ship rolls more than she pitches. Doors can have rounded or squared corners: rounding the corners used to be a way not to create possible cracking spots in a bulkhead, and it could still be a good idea. The designer should not choose the handles, the lockers, the hinges and all the minute hardware from household production. Everything must be in stainless steel and besides the bulkheads (and doors) thickness is quite lower than it is at home: there are several specialised suppliers that use the right materials and know how to stop the vibrations. Please don’t forget a door-stopper (see figure # 81). The final precision adjustment of all doors must be done only when the vessel is afloat: even i the yacht is quite large, her trim will slightly change once she leaves the bilge blocks to float in the ater. 16. 3. The natura l lighting
A boat with bright rooms is liveable, cosy and cheerful. The designer task is to find as many natural light sources as possible. These are the windows, the manholes, the skylights and the portholes. Let’s begin with the windows: the surfaces of a vessel’s hull and decks are curved, while the glass sheets are flat. The windows must therefore be installed into flat recesses. The glass is glued to the structure. The glue might change its chemical and physical characteristics due to a long exposure to sunlight. It should be protected from the ultraviolet rays by means of a black printed strip running around the edges (see figure # 82). In case the designer doesn’t like the black strip, a stainless steel (or bronze) frame could be glued above the printed area. Please note that the lower edge of the recess is inclined downwards to let water flow. The glass type and its thickness are outlined by the classification Registers. Coloured glasses are not allowed in the pilothouse. Talking about the pilothouse: sometimes the front windows are flat but the designer might want them curved. It’s feasible: the glass must be curved in an oven, above a steel mould. Feasible but expensive and time
consuming. Most of the windows on the deck sides cannot be opened: at the end of the day the vessel is air conditioned (see 10.10), and besides fixed windows are for sure watertight. The manhole (see figure # 83) is an opening on the deck, generally square, large enough to allow an average size person to pass through. It has two frames: one is fixed to the deck and the other, hinged to the first, holds the glass or, to say better, a sheet of coloured methacrylate. The skylight is a smaller opening, and sometimes it’s of the fixed type. The portholes are placed on the hull sides, which are curved while the porthole flange is flat. Like the windows they must be installed into flat recesses.
Fig. 82
Fig. 83
The structure which connects the outer opening on the hull and the porthole is called “neck” (see figure # 84 and figure # 85). The portholes shape is up to the designer’s choice: they can be
rectangular, round, oval … All portholes have a device to keep them open: it’s either a friction on the hinges or a simple hook hanging from the ceiling.
Fig. 84
They should be fitted with micro switches: a panel in the pilothouse shall inform the captain hether the portholes are closed or open. Mosquito nets are a useful accessory. The Register might impose that the portholes are fitted with a storm shutter. The designer must indicate the portholes position on all drawings: they must be ergonomic, that is to say easily reachable by an average person, not just by Spider Man. The designer should consider that the portholes contribute to the throughout look of the vessel. They should be placed in such a way that fits into the external boat’s design and, at the same time, is coherent with the arrangements. Please remember principle number eighteen: quite often, during the design work, the designer might need to move one or more portholes. Abiding to principle number eighteen shall save the designer from one of the great evergreens o (careless) yacht design: ending up with a porthole inside a locker or across a bulkhead. The Registers impose a minimum height of the portholes lower edges above the LWL: in case their position is deemed critical, they might ask that the portholes are fitted with a “captain’s key” instead of the usual ing nuts. In other words, it’s the captain’s responsibility to decide whether they can be open or not, depending from the conditions of the weather.
Fig. 85
16 .4. The artificial light ing
The skilful use of the artificial lightning can generate a particular mood; it can even enhance some volumes and hide others or give a feeling of larger or narrower volumes, changing the perception o reality. The designer needs some experience to design this kind of lighting. A simple lamp, hanging from the wires of a ceiling, is more than enough to light a room. Everybody has experienced this kind of lighting in the first days after relocation. And maybe even for a longer time than just for the first days. Possibly for a few months. Yet, this is not what customers expect from our design work. Let’s fix a milestone: electric power feeds the lights on a vessel. I should actually call it “tension”, but I ant this handbook to be as plain as possible. Therefore: electric power, either 12 or 24 V. d.c. (see 10.9). The source of light is the lamp: its lighting capacity is measured in Watts. For the same power, the light can be whitish or yellowish or in other words, cold or warm. These adjectives don’t mean that the lamp is iced or hot, but make reference to a scale called CCT (Correlated Colour Temperature), measured in Kelvin grades. The higher is the Kelvin number, the colder is the light. The designer should pay attention to such details, because a wrong light colour could spoil an emotional effect. Most of the household light aren’t’ fit for marine use. The materials the lamps are made of must resist in the humid and saline environment, which is not the case of domestic appliances. Luckily enough, there are several specialized suppliers of marine appliances. The overhead light is the most commonly used (see figure # 86). It could stick out from the ceiling, whole or in part, or else be completely recessed into the ceiling panel: in the latter case the designer should pay attention to the heath dispersion.
Fig. 86
The lamp might even burn the ceiling’s upholstery. Apart from the overhead lamps, the designer could use some diffused lights for a softer effect. The lamps might be hidden above a counter ceiling, behind a vertical panel, or may be strategically placed below the beds or finally concealed in a dedicated recess into the partition bulkheads, a few centimetres above the floor. The old, classic abat-jour might be used to create cosy corners, where to read a book or listen to the music. Courtesy
spot-lights should be used in the passageways and on the stairs rises. The lights on deck must o course be watertight. A number called IP (International Protection) measures the capacity of an electric appliance to stand up to humidity and water spray. See figure # 87: it’s a short digest of the protection scale. IP 20 is enough for cabins lights, while for the showers it should be IP 44 or 54. Lights on deck must be at least IP 65. Optical fibre can give peculiar light effects. It’s made of an illuminator (it’s a lamp) which can be placed above a ceiling or inside a locker, provided it’s easily accessible for maintenance. Several optical fibres depart from the illuminator: their final diameter is few millimetres. They don’t’ light much but can create design patterns, or highlight a furniture detail. Their light is completely cold, and this time I mean the real temperature. Optical fibre lighting has two issues: one is the cost, because it’s pretty expensive. The other is the maximum possible length o the fibres: only from six to seven metres. The designer must remember to draft courtesy spot-lights inside the hangers, with a micro-switch linked to the lockers shutters. IP44 IP54 IP55 IP65 IP66 IP 67 IP68 IP 68-XX
Protection against spray Protection against spray Protection against low press ure jets of water Protection against low press ure jets of water Protection against powerful jets o f water and heavy seas Protection a gainst the effect of “temporary” immersion b etween 15 cm and 1 m Protection agains t long periods of immersion under pressu re Protection against long periods o f immersion at XX m
Fig. 87
16.5. The shower
notmy going to bother my readers with #the88:detailed description of for thethe showers hardware. and Let it’s me ustI’m point finger to the shower of figure it’s clearly a feature pleasure-loving only fit for large vessels, where there’s a water maker and no supply shortage. The shower floor is made of a teak grating. It’s not slippery and lets the water flow. The shower floor should conveniently be one centimetre lower than the bathroom’s, so that the water won’t spill off.
Fig. 88
16.6. The bathroom appliance s
The wash basins are the same as in our houses. Never ever use flat bottom basins. The vessel is never exactly even and some water shall always remain in a corner. At home the inlet and outlet pipes of the bathroom features disappear into the wall or under the floor. On a vessel there are no such thick alls and the designer must forecast a piece of furniture to host and hide the pipes. The WC doesn’t flush by gravity as it does at home. A dedicated pump, placed just behind the bowl, drives the black into with a sewage tank design. (see 10.8). The bidets’ style must be equal to the WC: they generally belong toater a series the same 16.7. The curtains
One of the worse accidents that can happen to a vessel is fire on board. The statistics say that the hottest starting points of a blaze are the kitchen, the engine room and the curtains. For this reason some of the materials the vessel is made of are fire-resistant. These materials are classed: from “0” to “5”, where “0” is the more fireproof. The curtains should be “Class 1”. They should have two rails: one above and one below: like this they won’t wave when the ship rolls. Waving curtains are among the best and safest ways to get everyone seasick. The designer might prefer venetian blinds: in such case they must have two taut side lines to avoid beatings and vibrations. The curtains could be fixed by means of snap buttons in case the windows have irregular shapes. 16.8. The mirrors
I only mention the mirrors to recommend not using them. Even old seadogs get seasick when looking at their mirrored image, when the ship rolls.
16.9. The plugs and the sockets
Finally a nice surprise: they’re the same we use at home. Certainly not the grandmothers’ pearswitch above the bed, but the wall boxes and the switches are the same. The boxes take some space: their depth is roughly 4 centimetres. Therefore they must be installed where there’s enough room. That is to say: it wouldn’t work placing the switch on a 20 millimetres marine plywood wall. The box ould stick out on the opposite side. The designer should place the switches on lockers sides, or he could forecast a double partition bulkhead where necessary. Generally the right position for the switch is near the cabin’s door, on the same side of the handle of course. One thing not to do is disregard the switches position while drawing the plans and later tour the vessel with the electrician, trying to find a feasible solution. One generally ends up placing the switches on the ceilings: and the kids? (See 14.6). Please mind the difference between a switch and a deviator. The customer will ant to enter his cabin and switch the light on, and then will want to switch off the same light from his bedside. In this case he doesn’t need a switch, but a deviator. 16.10. The ceilings
The ceilings upholstery cannot be made out of a single piece. It must be done with separate panels, covered with the material that the designer has chosen. The raw panels are made of a thin marine plywood layer: roughly from 5 to 10 millimetres. The finishing material can be leather, imitation leather, fabric. The panels might be just painted. In any case the joining lines between the panels are a delicate issue. The whole work outcome is ugly unless they’re perfect. The panels are fixed to the framework by means of flasks and bayonets, dedicated snap buttons or simply by means of Velcro strips. ever design flat a flatceilings ceiling,give mainly it’s a large of one. Alwaysindesign a little camber. For a strangeDon’t optical illusion, theifimpression “falling” the middle. The designer should “work” the ceiling, drafting areas with different heights, inserting hidden lights, slightly changing the colours. Finally: remember that light colours seem to raise the ceiling. On the opposite, dark colours give the impression of a lower span. 16.11. The floors
As I wrote in 15.1, the partition bulkheads reach to the vessel’s structure and the floors are fixed to these bulkheads. Therefore the floor rests against the bulkheads, and not the bulkheads on the floors. Please go back to figure # 66: a raw layer of marine plywood rests upon the framework. This provisional floor, unfinished yet, shall be used during the building works. The installation of the final floor one ofthethetools last fall, works be undertaken. During the building the workers comethe andnecessary go with heavyisshoes, thetoglue and paint drip… a mess. The designer must draw openings in the floor, in correspondence of the double bottoms manholes. Floors can be made o several materials. The carpet floor is the easiest, quicker and sometimes cheaper. It’s not slippery and it doesn’t require a huge amount of work. The market offers beautiful carpets made of wool, cotton and even synthetic fabric. The carpet should be fire-resistant and comply with “Class1” (see 16.6). The contraindications are the cleaning difficulty, the water retention and the lack of design srcinality.
The floor might be finished with one of the hundreds wood types: to name a few, teak, mahogany, alnut, oak or wengè. The wood could be installed in strips: longitudinal, traversals, 45° inclined. Or it could come in tiles, large or small. In case the wood seems too predictable, the designer might use thick leather tiles. It has a beautiful look, a lovely scent and a soft touch. Like all gorgeous things, it’s very, very expensive. And certainly, a Coke split on a leather floor by a careless guest might put an end to an old friendship. If the vessel is very large, the designer might use stone or marble for the floors. The increase of weight wouldn’t be significant if compared to the whole displacement of the ship. There’s no real reason to design the same floor finishing for a saloon and for the cabins. I would say that, on the contrary, they should be different. And a carpet floor is quite suitable for the cabins: it also dampens noises. 16.12 . The sofas and the armchairs
Sofa and armchairs should be fixed features: that is to say, they should be secured to the ship’s structure, unless they’re bought and installed as loose equipment (see 15.9). In case they’re part of the oiner supply, the designer should forecast some opening in the structure, so that the hollow lower part of the sofas can be used as storage volume. The upholstery is made of polyurethane foam with different densities. There should be a hard inner core surrounded by a softer layer. The final layer should be made of tetrapolyethylene. Like this the sofa’s cushions would look and feel soft, but would resist to a sitting person weight. Before making a final decision the designer should have some raw cushions made, with different sizes, design and hardness. Sometimes what looks comfortable on the drawings it’s actually not once it’s built.
Chapter 17 The furniture materials
17.1. The marine plywood
It’s the most commonly used wood in the boatbuilding industry. Most of the arrangements are made of marine plywood. As it name suggests, it’s made of several thin “plies” or layers of wood. Each ply crosses the following one at 90° angle. This solution compensates for the wood deformations. The plies are glued together under high temperature and pressure. The glue is resistant to humidity. The outer final surface of the panels is made of a noble wood, such as okoumè. The designer will later chose how to finish the surface: it could be covered with Formica, fabric, leather of a thin layer o ood called scaleboard, roughly 2 millimetres thick, which could be teak, mahogany, walnut etcetera. The plywood edges absorb water: they should never be left on sight but should be finished by means of glued wood slats. The designer might need to insert wood gratings in his design, like for the fancoils inlets and outlets, or for the lockers ventilation. Gratings should not be cut from a plywood panel: the wood layers would show on the edges. It’s cheap but ugly. Gratings should be made o solid wood. Marine plywood is quite heavy: its specific weight is 0.45. As an alternative the designer could use the light material I mentioned in 16.2. 17.2. The solid wood
The solid wood isn’t much used for boatbuilding, apart for the framework and for some details o the furniture. Solid wood has the annoying tendency to shrink, to bend, to crack, to stretch. In other ords, it might bring a lot of headaches if it’s not perfectly seasoned. The example in figure # 80 shows a rounded edge, made of solid wood. It goes without saying that the same wood type must be used for the scaleboards and the solid wood details. 17.3. The briar
The real “briar” comes from the root of the homonymous plant. Pipe smokers know it well because it’s what the chamber of their pipes is made of. Several other types of wood are called “briar”, but they come from different trees and never from their roots. The briar comes from sections of the trees here branches have been cut or where parasites have caused some kind of illness. These parts are machine-sliced and the outcome are thin wood sheets with beautiful patterns. The size of the sheets o briar wood is small (roughly 25 by 35 centimetres) and the producer must tie them together with the same order by which they were cut, so that their pattern is consecutive. Briar should be used with moderation. First of all, the briar wood is beautiful if it appears here and there, as a precious element of decoration. A whole arrangement made of briar is sickening, like an indigestion of caviar. Then:
the briar wood sheets are small and have irregular shaped edges. Therefore the woodworking is time consuming and needs very qualified manpower. The briar wood sheets are full of small holes: these imperfections need repairing, and it’s a wearing procedure. Briar wood is a rare material, and the designer should avoid choosing some kind of wood that’s not easily available: please stay down to heart. Commonly used briar woods are the Brazilian walnut, the manzanita, the myrtle, the mahogany, the walnut, the oak and the California redwood. All of these names might sound unfamiliar, unless one of my readers is the woodworker’s son. I suggest that the beginner visits a joiner’s workshop and humbly asks to be given some scrape of wood, may be also asking for more info, such as how, why and where it’s used. I’m sure that nobody would refuse a piece of waste. The same procedure could be used in a marble workshop because Principle number twenty: you cannot be an interior designer unless you’re familiar with the materials.
The market offers a poorer material which might look similar to the briar wood, at least for the unexperienced eye. Several layers of wood are glued one above the other, inclining the veining at random. The thin wood layers cut from this pack look somehow like briar, but it stands to the real thing like the surimi stands to the lobster. 17.4. The types of wood
Books have been written about the hundreds existing types of wood. Some of them are fit for boatbuilding, some must be avoided. The classic woods are teak and mahogany. Mahogany is rare and expensive. The market has found two cheaper and more available types of wood which resemble mahogany. They’re called “assie mahogany” and “sapele mahogany”. Actually assie and sapele have nothing to do with real mahogany but I must honestly admit that they’re quite similar to the srcinal. Also walnut has an alter ego, called anegrè. Even teak has a lookalike: the iroko. This wood is more yellow that teak and its cutting dust is highly allergenic. The surface of all woods can be processed in several ways: it can be whitened, painted or even sandblasted. The outcome is very different and the designer had better have some sample done before making a final decision. It’s impossible to write a short summary about all the existing types of wood: I just wish to highlight that pale woods, such as birch, ash, linden and oak tend to change colour when exposed to direct light. Try and leave a magazine for a week on an ashwood table under the sunlight. Its mark will clearly show when you remove it. Some types of wood are harder than others and less workable, some aren’t available in long boards, but only in short ones etcetera. The topic is vast and fascinating: I suggest the beginner to examine it in depth, not only for professional reasons but also for personal culture. It could be the discovery of a fabulous world. 17.5. The stonework
Three families actually fall under the name “stone”: marbles, granites and stones. They’re different for their genesis, mechanical characteristics, grain, solidity, workability and mainly for their
hardness. The hardness of a stone is measured in “Mohs” grades: the soft talc value is 1, the hard diamond is 10. Marble goes from 3 to 4; granite from 6 to 7. The designer should not choose a stone ust from a small sample. This should be only a primary criterion, after which the designer should visit the marble workshop and check the actual stone leaf because the colour and the veining might sensibly change from one stone block to another. The designer can find the most complete catalogue of stones in cathedrals. Go there and try to identify the marbles, the granites and the stones. The most commonly used stone is marble. There are plenty, of different types, with an incredible variety o colours and patterns. They range from the Carrara pure white to the light blue of the macauba and Bahia; from the Portugal pink to the Siena yellow; from the Indian absolute black to the Greek crystal, hich is semi-transparent. The total weight of the ship should be kept under strict control: to save eight, the marble leafs are cut in thin slices and then glued on a bee-nest aluminium and epoxy resin structure. Only a few details are made of solid marble, like the torus. Granites are much harder than marble, and therefore less workable. Stones are much softer and less lasting. Their microcrystalline cohesion is feeble and they easily break, and yet some of them are beautiful. Some stones aren’t fit for use on board a vessel: for example the limestone or even the Carrara pure white, which is stunning but far too delicate. The stone surface can be treated in several different ways, thus getting quite diverse colours and effects. What follows is a short list of the possible treatments: • smoothing; • sandblasting; • bushhammering; • chipping; • polishing. The designer should have some samples of the surface treatment done: they’re all handmade and the result might be sensibly different from one hand to another. 17.6. The fabrics
As I wrote before, the fabrics must be fire resistant (Class 1). The fabrics are among the most noticeable features of an arrangement: there are the curtains, the sofas, the bedspreads and much more. The final decision about the vessel’s look is up to the designer’s sensibility and to the customer’s taste. The upholstery could be made of classic damask cloths, or of a monastic white linens sequence. I just wish to suggest that, in any case, the designer should specify that the fabrics must be wetted before they’re cut and sawn. This way the fabric won’t ever shrink and the customer on’t complain. Please check which is the height of the cloth: if it’s too low, a lot of joints will be necessary. The design pattern must match and it can become a serious headache. Besides, there are a lot of scraps. Check also the cloth weight: some fabrics are extremely light, and others are as tough as a tin foil. The choice depends from what they’re used for. 17.7. The leather
The leather is a wonderful and noble material. It smells good and transforms all rooms into a cosy nest. The leather quality and thickness changes with the part of the animal’s skin it’s made of, and also
ith the way it’s treated. Commonly it’s cows leather, but it could be pigs, horses, goats, snakes, eels, toads and much more. Its top quality is the “fine grain” which saves the srcinal porous surface of the animal’s skin. Then there is the “coarse grain”, which is lightly fluffed. Then again the “nubuk”, with velvet-like surface. The “split” can be used for cladding pieces of furniture. The upper part of the leather cut through its thickness becomes the fine grain and the lower part is the split, less precious. “Leather” is the natural uncut skin. The industry offers embossed leathers; dotted, striped, with relie patterns… you name it. The use of leather depends from the designer’s taste and, why not, from is ethic position towards animals. In case, my suggestion is to use only the fine grain, the best and softer leather. The leather upkeep needs more care than the fabrics’, but on the other side it’s elastically isotropic. In other words it resists and stretches homogenously in all directions, while fabric resists ell in the warp sense, much less in the weft sense and it deforms very much in diagonal. To cover a sofa, for example, all pieces of fabric must be cut and sawn in the same sense, while leather allows for much more freedom. Unfortunately the best leather is also the more delicate. Finally, also leather must be fireproof. 17. 8. The leathe r imitation
The leather imitation doesn’t have the scent and preciousness of real leather. Yet there are some imitations that are as soft and pleasing to the touch as real leather. Sometimes they’re also more expensive. These imitations are fit for some uses, like for the ceilings upholstery. They’re produced and sold in rolls, while animal skin has limited dimensions, which means joining several skins to get large pieces. The leather imitation is easily washable: sometimes using it for sofa upholstery would relax the vessel’s owner while kids run around wearing wet bathing suits and handling soft drinks. 17.9. The paint
Please see 8.7. I only wish to add that the deck teak must not be painted. The paint choice follows several criteria. To mention just two, one is the colours: each one of them is internationally indicted by a number called RAL (Rechtsausschuß für Lieferbedingungen). The RAL scale is divided in HR for the matt colours and GL for the shiny ones. There are more than 2,000 colour codes. Another criterion is the “gloss”, which indicates the grade of opacity of a painted surface. A totally opaque surface has value “0”, a perfectly shiny one has the hypothetic value “100”: see figure # 89. It goes ithout saying that the shinier is the surface, the easier is to spot every flaw. VOpaque ery Opaque Medium Opaque Semi Opaque Semi Shiny Shiny
Fig. 89
Gloss value from Gloss value from Gloss value from Gloss value from Gloss value from Gloss value from
1
to
10
11 31 41 51 80
to to to to
30 40 50 80
Chapter 18 The deck arrangement
18.1. The aft c ockpit
The vessel’s owner and his guests primarily enjoy the yacht in the open air, mainly in the aft cockpit. It’s near the main saloon door and there is no interruption between these areas. The cockpit must be fitted with some pieces of furniture: a dining table, some chairs, possibly a sofa and a few comfortable armchairs (see figure # 90 and # 91). There must be a set of dedicated lights and two or more loudspeakers, connected to the hi-fi plant. The designer must foresee a locker, near the cockpit, to store the shoes, which are forbidden on board. There might be a further locker for the gangway commands, for the garage door, for an electric panel: but naturally it depends on the vessel’s size. 18.2. The sunbathing areas
Usually a set of large cushions is placed on the deck, ahead of the pilothouse. This position is sheltered from the wind, as it tends to raise above the deck, and it’s private, because it’s far from the stern and therefore from the pier. There could be sunbathing cushions also on the fly bridge. In any case, the filling of the cushions must be made of a material which allows the water to flow thru, so the cushions wouldn’t be constantly soaked. The cushions shall be covered with imitation leather and reupholstered with washable terry cloth (two sets). The cushions should rest on a teak grating, not directly on the deck, to avoid the stagnation of water and humidity. In any case the cushions must be fixed by means of snap buttons or else they would sure fly away. The designer must foresee a storeaway locker for the cushions.
Fig. 90
Fig. 91
18.3. The Fly bridge
It’s the top bridge of a vessel: in 15.8 I wrote that the crew manoeuvres from this bridge in restricted waters. Therefore there should be a second, external pilothouse. It shall have less instruments than the main cockpit: at least the engines commands and gauges, the bow thruster joy stick, the VHF radio and naturally the rudder wheel. All of this must be sheltered from the rain and
the spray. A feasible solution is shown in figure # 92: the instruments panel is covered by a removable Plexiglas sheet. The fly bridge area should be furnished withchaises longues , some ouffs , a bar, a dining table, may be a BBQ: whatever the designer might think of, to allow the customer and his guests enjoying life in the open air. There could be a med-arch, which is a structure crossing above the fly bridge: it might host a foldable or rolling set of canvas to protect the bridge from the night damp.
Fig. 92
Chapter 19 The safety on board
19.1. The emergency escapes
The cabins could be far from a door leading outside, a stair, any kind of exit from the vessel. There could be a long aisle, possibly also a flight of stairs to go from the lower deck to the main deck. The crew and the guests must be able to reach safety in case of distress: the designer must foresee enough emergency escape routes and escape hatches. It might happen that an emergency hatch from a lower cabin ends up in a room on the upper bridge. It’s plain that no piece of furniture should be designed and placed in its way. The escape from the cabins shall be hidden below an easily removable ceiling panel. The space between the ceiling and the upper floor must host a foldable stair or, if it’s not feasible, a rigid portable stair could be hidden below a bed or inside a locker. In any case it must be clearly signalled. For larger vessels the Registers require an emergency escape plan showing the routes, the hatches and the muster stations: a set of labels shall be placed around the ship to direct the passengers towards safety. 19.2. The life rafts and the life jackets
The Registers rule the number of emergency features for each vessel. The life rafts, also called “inflatable rafts”, are large gears, either held in soft bags or hard shells. They must be placed in easily accessible areas of the vessel, far from the bow (in case of collision) and far from the most commons sources of blaze (the engine room and the kitchen). They should not be too far from the LWL: the passengers should be enabled to jump into them without breaking their necks. The designer must mandatory foresee (on the drawings and in the Tec Spec) a bolt-eye for each life raft. Each raft has a pulling line which stretches when the raft is launched from the vessel, opens the gear and inflates the raft. The same line holds the raft near the vessel while the passengers board it. The line must be tied to the bolt-eye: if not, the raft would not inflate and would sink. Some rafts are fitted ith a pressure gauge: once it sinks, the gauge feels the water pressure and inflates the raft. Yet the raft wouldn’t be tied to the vessel and the wind would quickly push it far. A cheap feature like a bolteye could save several human lives: therefore the designer should not forget it. There must be a life acketvessel for each on board. There must also be a sufficient number lifetojackets for children. The mustperson be fitted with one or more life buoys with a long line,oftied the vessel, and an automatic light. Finally: some vessels have an EPIRB (Emergency Position Indication Radio Beacon). It’s a floating buoy which switches on automatically in case of distress (mainly sinking): it transmits a code signal to a satellites network and shows the ship’s position to the rescue teams.
Chapter 20 The design for all
The d esign for a ll: a ca ll for e thics
The World Health Organization’s definition for disability is “…a complex interaction between eatures of a person’s body and features of the environment in which he or she lives …” Anyone o us might be considered disabled once he finds himself in an unusual and uncomfortable situation. As for physical disability in a situation that we consider “normal”, it’s up to doctors and caretakers to help the special needs of a person, while it’s the designer’s duty to work on the environment. The first motivating principle for a project dedicated to a disabled person is that only the knowledge o problems and the design exploration brings to solutions. The second guideline is understanding that people’s abilities change depending on the contest. The third and last approach is that design work is bound to depend largely on constraints. On top of this there’s a special ergonomic concept. The theme that the designer must develop is easy to understand and difficult to achieve: the ship shall have no ergonomic barriers and all parts of it shall be accessible by the customer. To begin with, all decks must be steps-free. There must also be no steps throughout the inside arrangements, and so between the aft cockpit and the saloon on main deck. This is a design issue which involves the ship’s official certification, which the designer must keep as essential and easy as possible. The Maritime and Coastguard Agency (MCA),concept for example, for sill-free doors on the weather deck. The side passageways on all would decks isnever out ofallow the ordinary: theirside width at deck level must be 95 centimetres and 110 centimetres at handrails level. The handrail itself should be 120 centimetres high from the deck (instead of the standard 100 centimetres). This span would allow the customer to use the handrails as a gym tool. The side doors on the passageways must be recessed into the deck structure (figure # 93). This extra space gives enough room for a wheelchair to turn. It goes ithout saying that such wide passageways reduce space inside: that’s why it’s wise to design a large hull, somehow beamier than usual.
Fig. 93
On the other side, slimmer decks help keeping the ship’s Gross Tonnage within the 500 figure hich, as I mentioned in Chapter 11, is our bugaboo. When a disabled customer docks he uses an electric vehicle (figure # 94): it’s a wonderful, helpful, functional tool and yet it’s not designed to resist sea water spray. The designer must therefore find the space for a dedicated garage on main deck. The tool must be at a time sheltered and easily available. The market offers kind of a chair, electric driven, easily removable, which helps the person with special needs to dive either in the sea or in the Jacuzzi pool. This feature should be used in more than one place of the vessel, like on the aft bathing platform and near the Jacuzzi pool (see figure # 95). A good way to connect the aft platform to theheelchair cockpit is(figure by means of one two horizontal platforms and dimensioned to hold # 96). Theorgangway shouldelectric be specially builtshaped and have a floor width of 90a centimetres, plus two safety rails to guide the wheels.
Fig. 94
The vessel should be fitted with an electro-hydraulic elevator which serves all the bridges. The cabin must be large enough to host the wheelchair and one caretaker.
Fig. 95
All the doors inside must have a net span of 85 centimetres and naturally have no sills. Some o them might be sliding because this feature gives for an easier use to a disabled person.
Fig. 96
The toilet and shower shall comply with dedicated ergonomic standards and must foresee ample space for caregivers to work (figure # 97). A small gym area might be forecasted somewhere in the vessel. The spaces between coffee tables, couches and chairs must be carefully studied, and so the dining room. The disabled customer should be entitled to choose any place at the table. All writings, instructions, labels must also be printed in Braille, because the design should foresee all further
aspects of possible disability, like visual impairment, besides the motor disability. All materials and furniture details should be chosen for the sake of safety and simplicity: hidden fixing hooks to hold the heelchair, no sharp corners, hard carpet floors, non-skid wooden floors. The crew is quite important for such a design, dedicated to the disabled. Their areas should be designed following their demands and their necessary will to go the extra mileage to be helpful. There should be an easy and quick connection between the crew quarters and the customer’s cabin. The annex must have a square pull-down bow to allow for an easy boarding of the wheelchair. Finally, we might call this attitude “design for all”.
Fig. 97
Chapter 21 The refit
The refit of an old vessel
Sometimes, too few times actually, an inspired customer comes up with the idea of bringing back to life an old vessel. She usually is an old tug boat, or a military ship, or a discharged cruise vessel. The designer must be able to see below the old paint and the rust and ascertain whether a pearl is sleeping there or if it’s only a wreck, just good for the foundry. In fact, most of these vessels are made of steel: the wood ones tend to decay and disappear, but when they last long enough they are real masterpieces of art. The steel structures of ships built up to the mid-fifties were riveted: more recent vessels are welded. The first case creates a huge problem: nowadays it’s hard, not to say impossible, to find workers who can rivet, and the type of steel used in the fifties isn’t much good for welding. The designer’s first task is to check whether the ship is still in a throughout sufficient shape: too much restoring work might not be cost-effective and sometimes it’s worth abandoning the project. Quite often the srcinal building plans, calculations and paperwork concerning the ship are nowhere to be found. When it happens it’s a hassle for the designer, who shall do a huge survey work to reconstruct the necessary drawings and documents. To begin with, the designer should have an ultrasonic inspection done. It reveals the thickness of the frames, of the floors, of the decks and of the plating. Some corrosion should be steel state platesmight replacement is common. The engineThey (or engines), the machinery, theexpected shaft lineand andsome the plants rise another possible headache. might or might not be working, but quite surely they won’t abide to the present regulations. To name a few, the wiring of the electric plant would not be to class, the exhaust gases would not comply with the environment protection rules, the instruments would be out-of-date, the heat insulation material comprises asbestos etcetera. The srcinal arrangements shall be demolished, also to reach the vessel’s structure and do the necessary repairs and maintenance. When the works start, every day brings a surprise, something unexpected and unpredictable. The designer has to face so many problems, and he must find a solution for each of them. It’s about impossible to outline a budget for the works or a delivery schedule for the vessel. Somebody might onder why a customer, a designer, a builder would ever put themselves in such a trouble: simply because the satisfaction of restoring an old boat is priceless. Because she shall finally have a charm that no new boat has. Because she’s a piece of history, marine knowledge and culture. Because transforming an old wreck into a beautiful ship is worth every sacrifice. Figures # 98 and # 99 show a vessel that we refitted: at the beginning and at the end of the works.
Fig. 98
Fig. 99
Chapter 22 The drafting
22.1. The drawings dimensions
A drawing to scale is not a sufficient source of information for the workers who shall build the vessel. The designer cannot expect the workers to measure an old, worn, dusted and stained print by means of a folding rule inside a darkish cabin: and then get the beautiful result he has in mind. The designer must dimension every part of his drawings. The srcin of the measures should always be the same: the centre line, the base line or the cabin floor. I know it sounds obvious, but please mind not to change unit of measure between different drawings: if you choose millimetres, let it always be millimetres. The builder will be grateful to the designer if he unifies the rounds radiuses, the shutters dimensions, the drawers fronts and so on. 22.2. The drawings scale
The most commonly used scale is 1:10. It’s intuitive for whoever is familiar with the metric system. The vessel could be very large: in this event the scale of the drawings might be reduced to 1:20. Only the GA could be in scale 1:50 or even 1:100. In case the designer works with AngloSaxon customers, the drawings scale should be 1”:1’, that is to say 1:12 in the metric system. Usually the designer doesn’t give the builder printed drawings but just electronic files. In any case the drawings must be organized so that the prints (sooner or later they’ll be made) wont’ have a bed-sheet size. Indicatively the prints should not exceed the A1 dimension. Like this the workers will be able to stick the print on a thin sheet of plywood, hang it somewhere or move it around the boat. Figure # 100 shows the UNI table of dimensions. Some drawings might be out of scale: typically the renders, the details and the perspective drawings. And sometimes it’s suitable delivering out-of-scale drawings: for example when the designer doesn’t want the customer to go around the drawing with a metre tape measuring the bedside tables, the chairs or other minor details of a GA (a useless headache) or he’s afraid that someone might… be inspired by his drawings. Size A0 A1 A2 A3 A4 A5 A6
Fig. 100
mm 1189 ×841 841×594 594×420 420×297 297×210 210×148 148×150
inches 46.8 33.1 × 33.1 23.4 × 23.4 16.5 × 16.5 ×11.7 11.7×8.3 8.3 × 5.8 5.8 × 4.1
Chapter 23 The survey, the management and the sea trials
The designer’s task doesn’t end with the drawings. The building works must be surveyed. The surveyor’s assignment is to ascertain that the building works correspond to the drawings, to the Tec Spec and to the BOQ. The designer acts as a project manager on behalf of his customer, and he might have to deal with other managers, who work for the builder or for the suppliers. The good project manager should have a problem-solving not a the problem-arising one.building Quite often project manager’s tasks, a delicate one, isattitude, to authorize settlement of the workone stateofothe progress. It’s a great responsibility, both towards the party who pays and towards the one who cashes-in. The frequency and number of accesses of the designer to the builder’s premises is ruled by the contract. Please remember that the shipyard is somebody else’s property. At his arrival, the designer should show up to the owner or to his representative and ask their permission to access the building site. He should always beg permission to take pictures. The designer should never comment the job with the workers or give them direct instructions. If the designer feels that the work isn’t well done, that there’s some problem or if he wishes to do some modification, he should talk with the production manager. Make it clear: during the construction works nobody is allowed to smoke on board. The main reason is safety: so many vessels have been blazed during the building. Around the ship there’s glue, paint, thinner, wood scraps. The cigarette butts end up everywhere and pop out for months after Let’s the vessel is delivered. Thea good designer shouldThe always wearshould a helmet, without caring i others don’t. say that he’s giving example. designer listen to experienced orkers: sometimes they know better. Out of my experience I can say that for each work I did, I learnt two things for each one that I taught. The time will come when the vessel is afloat: be it still under the builder’s responsibility, or under the captain’s, please abide to Principle number twe nty one: ALWAYS beg permission before boarding a vesse l.
The designer should also witness the vessel’s tests, which are: • FAT or factory acceptance tests (all the features and machinery that can be tested aground); • HAT or harbor acceptance tests (all the machinery that can be tested with the vessel afloat, moored to a pier); • SAT or sea acceptance trials (speed, seak eeping, noise, vibrations, steering etcetera).
Digest of Massimo’s principles
Principle number one: the reference network must show, exactly alike, on each and every drawing of the ve sse l. Principle number two: a computer is not an intelligent machine that helps the fool: on the contrary, it’s a fool machine that only works in the hands of the intelligent. Principle number three: during my long career I’ve never seen a vessel that, at launching, proved to be lighter than expected. Principle number four: as a general rule, straightening a stern-down vessel is feasible, even if it might be difficult. Straightening a bow-down vessel is about impossible. Principle number five: don’t ever attempt to balance the weights of a vessel by the fuel or the wate r tanks. Principle number six: the weight of a ship can roughly be divided into three main blocks. One third is the structure s; one third is the arrangements; one third is the machine ry and the plants. Principle number seven: yachts are made by centimetres, not by metres. Principle number e ight: checking twice neve r killed anybody. Principle number nine: spoken words fly, written words remain. Principle number ten: for each metre of the vessel’s length there is a kilometre of wires and pipes. Principle number eleven: no single part of the vessel lives an independent life, but they’re all strictly linked together such that every modification done to one will necessarily bring a change to all the others. Principle number twelve: the human body dimensions do not shrink only because the boat’s rooms are narrow. Principle number fourteen: the yacht is always designed with her bow to the right. Principle number fifteen: every new design starts from the ending point of the previous one. Principle number sixteen: in this *** boat there’s not enough space.
Principle number eighteen: all modifications done to a drawing must immediately be copied on all the others. Principle number nineteen: all the closed volumes of the vessel must be easily accessible. Principle number twenty: you cannot be an interior designer unless you’re familiar with the materials. Principle number twe nty one: ALWAYS beg permission before boarding a vesse l.
Co nversion Table Length
inch 1 foot 1 yard 1 mile 1 kilometre 1 metre 1 metre 1 centimetre 1 millimetre 1 nautical 1 mile
= = = = = = = = = =
2.54 centimetres 0.305 metre 0.9144 metre 1.61 kilometres 1000 metres 100 centimetres 3.28 feet 0.3937 inch 0.039 inch 1852 metres
kilolitre 1 litre 1 1fluidonce US 1 gallon 1Imperialgallon
= = = = =
1000 litres 1000 millilitres 29.57millilitres 3.785 litres 4.546litres
= = = =
1000 grams 1000 milligrams 0.45 kilogram 28.35 grams
= =
25.4 millimetres 30.48 centimetres
= = =
5.280 feet 0.6214 statute mile 1000 millimetres
= = =
10 millimetres 0.1 centimetre 1.852 kilometres
= =
cubic 1 metres 1000 cc
= = =
2.2 pounds 0.035 ounce ounces 16
Volume
kilogram 1 gram 1 pound 1 ounce 1
Weight
Power
kW1 bhp 1
= =
1.360 PS 1.014 PS
=
1.341 bhp
Bibliography
AA.VV. (1988),Man uale dei marmi, pietre, graniti, 3 vol., Vallardi Editori, Milano. Bobrow J., Jinkins D. (1986),Classic Yacht Interiors, Concept Publishing, Westbrook. Bobrow J., Jinkins D. (1992),The World’s Most Extraordinary Yachts, Concept Publishing, Westbrook. Cairncross C. (1972), Ferrocement Yacht Construction , Adlard Coles, London. Caprino G., Teti R. (1989),Sandwich Structure Handbook , Edizioni Il Prato, Padova. Consiglio Nazionale delle Ricerche (1985), Il manuale dell’Architetto , Consiglio Nazionale delle Ricerche, Roma. Costaguta U.F. (1981), Fondamenti di idrodinamica, Statica e dinamica della nave, carene e propulsione , Hoepli, Milano. Du Cane P. (1974),High Speed Small Craft , David & Charles, Devon. Gregori Grgič M. (2009),Il progetto della nave , FrancoAngeli, Milano. Gregori Grgič M., Lanz F. (2009),Interior yacht design , FrancoAngeli, Milano. Levi R. (1990),Dhows to deltas, A. & A. Editori, Milano. Levi R. (1992),Milestones in my design , Kaos Service Editore, Milano. Lord L. (1963),Naval Architecture of Planing Hulls , Cornell Maritime Press, Cambridge, Maryland. Mannella G. (2005),Elementi di tecnica navale : per gli istituti nautici e per i naviganti, Mursia scuola, Milano. Marchi N. (1989),Il mobile in legno , Editrice La Scuola, Brescia. Nicolson I. (1971), Small Steel Craf t, Adlard Coles, London. Palutan E. (1992),Monografie dei legni più impiegati nelle industrie d el legno e del mobile , Palutan Editrice, Milano. Palutan F. (1986),Radiche, Palutan Editrice, Milano. Panero J., Zelnik M. (1983),Spazi a misura d’uo mo , Be-Ma Editrice, Milano. Pieresca G. (1991), Il legno e l’arte di costruire mobili e serramenti, Hoepli, Milano. Pullin G. (2009),Design meets disability, MIT, Cambridge, Massachusetts. Registro italiano navale (1995),Regolamento p er la costruzione e la classif icazione delle unità da diporto, Registro italiano navale, Genova. Romano F. (1972),La barca in ferro-cemento: manuale di costru zione e d’informazione , Nistri-Lischi, Pisa. Sims E.H. (1978),Boatbuilding in Aluminium Alloy, Nautical Publishing Co. Ltd., Lymington, Hampshire. Skene N. (revised by Francis K.) (1977),Skene’s Elements of Yacht Design, A. & C. Black, London. Slade K.A. (1979), Steel boat Contruction , Newnes Technical Books, London. Steward R.M. (1970),Boatbuilding manual, International Marine Publishing, Camden, Maine. Walker M. (1980),Down below. Aboard the World’s Classic Yachts, Chronicle Books, San Francisco.
The author Massimo Gregori Grgič was born in Florence too many years ago. His experience starts in the 70’s with the Westlawn School of Yacht Design. he founded StudioVenice and since then never stopped designing yachts. He has taughtInin1976 the Yacht DesignYankee MastersDelta of Milan, and Shanghai. He lives and works in a farm on the Tuscany hills. Massimo’s e-mail address is max@maxgregori.it.
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