List stability and stress data required to be supplied to ship under the current Load line Regulations, stating for each how such information might be used. The load line regulations require the master of the ship is to be provided with information relating to the stability of the ship. This usually takes the form of Stability Information Booklet which contains all that is needed to safely manage the vessel’s stability. stability. The required information is as outlined as below: !"
General Particulars This includes the ship’s name# official number# and port of registry# registry# tonnage# dimensions# displacement# deadweight and draught to the Summer $oad line. %seful as a reference in supplying information to various official organi&ations such as 'ort (uthorities# canal authorities etc
)"
General arrangement Plan
This usually consists consists of a profile and plan views of the ship showing the location of all compartments# tanks# store rooms and accommodation. %sed to locate and identify individual compartments. *"
Capacities and Centre of Gravity of cargo, fuel, water, stores stores etc:
This will show the the capacity and the longitudinal longitudinal and vertical vertical centre of gravity of every compartment available for the carriage of cargo# fuel# stores# fresh water and water ballast. This information is required for Transverse stability calculations +to calculate ship’s ,-" and $ongitudinal Stability calculations +to calculate ship’s $-". (lso used to calculate the space available for items of deadweight such as fuel# water# cargo etc. /"
stimated weight and disposition of passengers and crew:
0f particular relevance relevance to the passenger passenger ships. ships. 1or use in transverse transverse and longitudinal stability. 2"
stimated weight and disposition of dec! cargo including "#$ allowance for timber dec! cargo%
1or use in transverse stability calculations involving calculation of the ship’s ,,- and -3. %sed effectively so as to ensure vessel complies with the load line regulations throughout throughout the voyage.
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&eadweight scale
( diagram showing the load line mark and load line corresponding to the various freeboards# together with a scale showing displacement# T' and deadweight for a range of draughts between $ight and $oad condition. 'articularly useful when when loading cargo +eg# +eg# comparing draught to estimate estimate cargo loaded"
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'ydrostatic particulars particulars (&isplacement, )PC, *C)C, *C)C, LC+, LC, -*%
( diagram or table showing the hydrostatic particulars of the ship such as 5isplacement# T'# 3T# $B# $1# ,3 et. 'articularly useful for a variety of stability calculations including transverse stability and longitudinal stability stability +eg.# worksheets for the calculation of -3# trim and draughts forward and aft" !)"
ree urface /nformation (including an e0ample%
%sually in the form of 1ree Surface 3oments +1S3" for each tank in which liquids can be carried. The 1S3 given will be for a stated relative density of liquid +often !.44" which will need to be ad6usted if the liquid is of another density. density. %sed in transverse stability calculations in order to find the ship’s fluid ,- and fluid -3. There should also be a worked e7ample.
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-1 tables 2 Cross curves (including an e0ample% This will take the form of a diagram or table showing the righting levers for an assumed ,- +the ,; is the -< of the vessel assuming the ,- is &ero". There should also be a worked e7ample showing how a -< curve can be obtained using the tables = cross curves. ,; tables are used to obtain the value of -< +as -< > ,;>,-sin?" ross curves are used to find the -< of the vessel for any angle of heel.
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Pre3wor!ed hip conditions (Light ships, +allast 4rr2&ep, ervice loaded 4rr2&ep, homogenous loaded 4rr2&ep, &ry doc!ing etc%
To include include for each condition:a profile diagram indicating disposition of weighs.Statement of light weight plus disposition of weight on board.3etacentric height +-3"urve of statical stability +-< curve"@arning of unsafe condition. Aery useful in cargo planning since it is easier to use a ship condition similar to the proposed load condition. (lso useful where the ship’s tables are presented in a form unfamiliar to the ship’s officer who can now follow the method of calculation normally used on that vessel. Dry dock : nables officer to plan the stability condition for entering dry dock. Loaded : 'rovides officer an e7ample to establish stability condition of the vessel when loaded with relation to draught# trim# displacement# stress +S1 C B3" and also compliance with the loadline criteria. Ballast : 'rovides officer an e7ample to establish stability condition of the vessel when in ballast condition with relation to draught# trim# displacement# stress +S1 C B3" and also compliance with the loadline criteria.. Homogeneous loaded loaded : 'rovides an e7ample on cargo distribution for a given cargo to achieve a required stability criteria so as to enable the officer to plan for loading of various cargoes. !2"
pecial Procedures (Cautionary 1otes%
Sometimes known as autionary notes. These may take the form of procedures to maintain stability such as the partial or complete filling of spaces designated for cargo# fuel# fresh water etc. 7amples of this are: Sequence of ballasting during the voyage to maintain adequate stability# particularly to compensate for fuel=water consumption Ballasting to compensate for strong winds when carrying containers or other deck cargo. 3easures to compensate icing in (rctic waters (ny special features regarding the stowage behaviour of a particular cargo. !8"
/nclining e0periment report:
This will take the form of a report on the details of the inclining test showing the the calculation and other $ight Ship information. %seful in assessing the accuracy of the $ightship ,- given in the stability booklet# +which may change over time" !D"
/nformation as to Longitudinal tresses for vessels over "#5m in length
This applies to vessels over !24 mtrs in length and contains information on the determination of the longitudinal stresses such as Shear 1orce# bending moment and torsion. This will usually be in the form of comparison with ma7imum stress levels for the Seagoing condition and the Earbour condition. In this way the ship’s officer can assess the magnitude of the stresses before# during and after any loading# discharging or ballasting operations whether in harbour or in a seaway. seaway.
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)! 1ebruary )4!2
List the surveys required by the current Loadline Regulations for a vessel to maintain a valid Load line Certificate. !" )"
Initial Survey F Survey F $oad line (ssignment Periodic Surveys: Surveys: (nnual Survey Fwithin * months either way of the anniversary date of the load line certificate. The surveyor will endorse the load line certificate on satisfactory completion of annual survey.to be carried out every year year Genewal Survey F at interval not e7ceeding 2 years
The period of validity of the load line certificate may be e7tended for a period not e7ceeding * months for the purpose of allowing the ship to complete its voyage to the port in which it is to be surveyed.
List the items surveyed at a periodic Load line survey, describing the nature of the survey for 4C' item. The preparation for a load line survey will involve ensuring that the hull is watertight below the freeboard deck and weather tight above it +cargo tank lids on tankers must be watertight". The following are checked for condition and = or weather tightness +hose test as necessary": !" Supers Superstru tructu cture re = deck deck hous housee weath weather er tigh tightt door doorss F effect effective ive means means of clos closure ure and of secu securin ring g weather tightness +dogs# clamps# hinges# weather tight seal" )" Eatch Eatch cove covers rs F effect effective ive means means of of closu closure re and and secu securin ring g weath weather er tigh tightt +clea +cleats# ts# clamp clamps# s# wedg wedges# es# rubber sealing" *" Side Side scutt scuttles les +porth +porthol oles" es" F effec effectiv tivee mean meanss of closur closuree and and of securi securing ng weat weather her tight tight +cla +clamps mps## sealing# hinges# deadlight operation". /" Side Side cargo cargo doors doors F effec effectiv tivee mean meanss of closur closuree and and of of secur securing ing weathe weatherr tigh tightt +clam +clamps# ps# sealin sealing g arrangements" 2" 0ther 0ther deck deck openin openings gs such such as soun soundin ding g pipe pipe covers covers ullage ullage pipe pipe cover covers# s# tank tank lids# lids# sigh sightin ting g ports ports## manholes +deck scuttles" F effective means of closure and of securing water tight +hinges# clamps# sealing arrangements" 8" (ir (ir pipe pipess F per perma mane nent ntly ly att attac ache hed d mea means ns of of clos closur ure. e. -au -au&e &e to to fue fuell tank tanks. s. D" Aentilat ntilators ors F effec effectiv tivee means means of clos closure ure and securi securing ng weathe weatherr tight tight +unles +unlesss over over a spec specifi ified ed height". " 1ree 1reein ing g por ports ts in bulw bulwar ark k F free free movem ovemen entt of of fla flaps ps.. 9" Scup Scuppe pers rs## inle inlets ts and and dis disch char arge gess F effe effect ctiv iven enes esss of non nonr ret etur urn n = stor storm m valv valves es.. !4" (ccess (ccess F walkw walkway ays# s# ladd ladders ers## safety safety rails# rails# bulwa bulwarks rks in good good cond conditi ition on.. !!" !!" 5eck 5eck fitt fittin ings gs and and app appli lian ance cess for for timb timber er load loadli line nes. s. !)" $oadline $oadline and draught draught marks marks F measuremen measurements# ts# correc correctly tly positione positioned d and and clearly clearly visibili visibility ty +clarity +clarity"" !*" (ny chan changes ges to to hull hull or super super struc structur turee which which may may materi materially ally affect affect stab stabili ility ty +eg sign signifi ifican cantt increase in $ightweight of ship". !/" (ny depa departu rture re from from recorde recorded d Hondi Honditio tion n of (ssi (ssignm gnment ent’’ +as +as detail detailed ed in HGecor HGecord d of 'articu 'articular lars’" s’" !2" 'resen 'resence ce of of stab stabili ility ty inform informati ation on Bookle Booklett and and = or or $oadi $oading ng omput omputer er..
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)! 1ebruary )4!2
4 vessel assigned )imer load lines is to fully load with timber on dec! and in holds in a port in a )ropical 6one, for a destination in the 7inter 1orth 4tlantic 8one, during the winter months. (a% tate the minimum statutory requirements requirements for the ships stability throughout the voyage. "% Initial -3 The ma7imum righting lever +-<" (ngles of 3a7imum -<
not less than 4.!4 m +)4!! T5 ode" atleast 4.)4 mtrs not be less than *4 degs
4rea under the curve 4 to *4 degs 4 to /4 degs or ?f whichever is lesser Between *4 degs and /4 degs or ?f )" *"
not less than 4.422 mr not less than 4.49 mr not less than 4.4* mr
Stabi Stabilit lity y calcu calculat lation ionss to asse assess ss a vess vessel’ el’ss comp complia liance nce with with minimu minimum m stabil stability ity crit criteri eriaa shoul should d include a !2 increase in the weight of the timber deck cargo due to water absorption. (lternative ,; tables taking into account the increased freeboard due to timber deck cargo of a specified height may be used. Eowever such tables must assume a reserve buoyancy is only D2 of the deck timber because of the permeability of the timber deck cargo +assumed permeability )2".
(b% &escribe the various causes of any deterioration in the ship9s stability stability during the voyage. !" )" *" /" 2" 8" D" " 9" !4" !!" !!"
The vesse vessell is loadi loading ng timb timber er in tropi tropical cal &one &one and and in most most case casess the the carg cargo o will will be be in a dry dry state state condition. (s the the vess vessel el prog progres resses ses toward towardss the the dest destina inatio tion n in the loaded loaded passag passage# e# she she proc proceed eedss to the @;( @;( area. It is is poss possibl iblee that that the the timb timber er carg cargo o may may abso absorb rb more more moistu moisture re whic which h may may incr increas easee the the weig weight ht more than !2. This reduces the -3 and therefore -< curve. 1ree 1ree surfa surface ce effe effect ct when when fuel fuel and and wate waterr is consum consumed ed from from the full full tank tankss whic which h redu reduced ced -3 and and therefore -< curve. onsum onsumpti ption on of of fuel# fuel# stores stores## 1@ during during the the passa passage ge will will cause cause - to ris risee there thereby by redu reducin cing g the the -3 and therefore -< curve 5uring 5uring winter winter season seasons# s# as as the the vesse vessell moves moves toward towardss highe higherr latit latitude ude## will will enco encount unter er seri series es of of depression resulting in bad weather. Seas Seas on on deck deck will will cause cause raise raise in - due to adde added d weig weight ht and also also caus causee 1S 1S whic which h redu reduces ces -3 a nd -< curve @hilst @hilst e7peri e7perienc encing ing heavy heavy seas# seas# if if any any of of the the lash lashing ing gives gives way way and and cargo cargo break break loo loose# se# it can result in catastrophic result due to deterioration of the stability of the vessel. If the the vess vessel el is is e7per e7perien iencin cing g sever severee wind wind and and spra spray y on on one one side# side# it can can resu result lt in in unsy unsymme mmetric trical al icing on deck and superstructure (s a resu result lt of of this this the the vess vessel el may may list list or or loll loll over over to to due due to incr increas easee in weig weight ht on on one one side. side. This This lis listt or los losss will will red reduc ucee the the vess vessel el’’s sta stabi bili lity ty by by way way a" reduction in -3i
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)! 1ebruary )4!2
!)" !*"
b" produces heeling arm c" redu reduct ctio ion n in in (re (reaa und under er the the curv curvee or the the 5yna 5ynami mica call stab stabil ilit ity y d" Gedu Geduce cess the the rang rangee of of pos posit itiv ivee sta stabi bili lity ty of the the rig right htin ing g lev lever er curv curve. e. e" Geduces the ma7imu imum ri righting lever. If the the vessel vessel is lolled lolled over over## then then the situat situation ion is furthe furtherr worse worsened ned.. This This is beca becaus use# e# if the the vesse vessell is e7per e7perien iencin cing g severe severe weat weather her and and is is lolled lolled over over then then wind wind and and wave motion will further heel the vessel.
4n unstable vessel lying at an angle of loll to starboard has an empty double bottom tan! subdivided into four watertight compartment of equal width. )he tan! must be ballasted to return the vessel to a safe condition. &escribe the sequence of action to be ta!en and the possible effects throughout each stage. (n angle of loll is caused due to the vessel being in an unstable condition with negative -3 when upright and the vessel may heel to port or starboard. !. ). *.
Since Since the the angl anglee of loll loll is is cause caused d by - being being too high# high# effo efforts rts is to to be direc directed ted toward towardss lower lowering ing it (s a first first means means of of corre correcti cting ng meas measure ure## one one shoul should d look look toward towardss lowe lowerin ring g weig weight ht and reduci reducing ng the free surface effect where possible. Since Since the the vessel vessel has an empty empty doub double le bot bottom tom tank tank subd subdivi ivided ded into into four four water water tigh tightt comp compart artmen mentt of equal width following ballasting sequence must be carried out to return the vessel to a safe condition: SJ. !: Ballast the inner low side completelyF marked ( on the following figure. SJ. ): Ballast the inner high side completely F marked B SJ. *: Ballast the outer low side completely F marked SJ. /: Ballast the outer high side completely F marked 5
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)! 1ebruary )4!2
": !. ). *. /.
;: !. ). *. /.
The fi first rst se sequence is is to to ba ballast th the in inner lo low si side ta tank ma marked (. (. @hile hile fill fillin ing g up up the the tank tank## due due to the the int intro rodu duct ctio ion n of of mor moree fre freee sur surfa face cess the the situ situat atio ion n wil willl initially worsen. 3ore 3oreo over an in increa creasse in in th the in initia itiall li list wil willl hap happe pen n du due to to the the off cent centre re weig weight ht.. Eowe Eoweve verr as the the tan tank k sta start rtss to to fil filll furt furthe her# r# the the - wil willl sta start rt lowe loweri ring ng down down and and the the list list will will star startt to reduce. The se second se sequence is is to to fill th the in inner hi high side ta tank B. B. The The con condi diti tion on of the the ves vesse sell whi while le fill fillin ing g up up this this tank tank is some some what what sim similar ilar to SJ SJ !. In this this sequ sequen ence ce alth althou ough gh ther theree is is fre freee sur surfa face ce eff effect ect ini initi tial ally ly## the the ,- of the the ves vesse sell wil willl decrease as the tank is filled up due to concentration of weight at the lower part of the ship. (s the the tank tank is fina finall lly y fil fille led# d# the the fre freee sur surfa face ce effe effect ct is elim elimin inat ated ed and and the the ,- will will redu reduce ce even even further thereby improving the vessel’s stability.
<: !. ). *. /. 2. 8. D.
1ill up the outer low side tank marked . The purp urpose ose is is to to fur furth ther er redu reduce ce the the ,,- an and im impro prove the stab tabilit ility y of of the the vess vessel el.. 0ne 0ne of of the the main main reas reason on the the low lower er ,- is to have have posi positi tive ve -3 so as to elim elimin inat atee the the angl anglee of loll. (s th the ta tank is is fi filled up up it it wi will ha have fr free su surfaces initially. ly. Eowe Eoweve verr by by now now tank tank ( and and B are are fill filled ed full fully y whi which ch has has red reduc uced ed the the ,,- cons consid ider erab ably ly.. By fill fillin ing g thi thiss tan tank k the the star starbo boar ard d lis listt mom momen entt crea create ted d by by fil filli ling ng tank tank ( and and B ini initi tial ally ly will will be counter set by the port moment produced by filling this tank. (t the the sam samee tim timee the the - wil willl be be fur furth ther er conc concen entr trat ated ed down down impr improv ovin ing g the the -3 of the the ves vesse sel. l.
=: !. ). *.
This This will will be the the fin final al sequ sequen ence ce of ball ballas asti ting ng whic which h wil willl be be the the oute outerr hig high h sid sidee tan tank k mar marke ked d 5. 5. By fill fillin ing g up up thi thiss tan tank k the the -3 is furt furthe herr imp impro rove ved d and and the the por portt mom momen entt pro produ duce ced d by by thi thiss tan tank k will offset the starboard moment produced by filling tank ( and B. The The - of the the ves vesse sell wil willl be be low lower ered ed suff suffic icie ient ntly ly and and the the ship ship shou should ld be com complet pletel ely y upr uprig ight ht condition when this tank if completely filled.
&>19)s: !.
). *.
5o not not fil filll the the oute outerr hig high h sid sidee tan tank k fir first st beca becaus usee the the adde added d wei weigh ghtt may may caus causee the the vess vessel el to suddenly and violently roll over to the other side with a possibility of the moment of the roll carrying the ship over past the angle of vanishing stability and therefore capsi&ing the vessel. This This is beca becaus usee gen gener eral ally ly at loll loll the the por portt lis listt mom momen ents ts is equa equall to to the the star starbo boar ard d lis listt mom momen ents ts and there is no list. It is only with the case of list it is prudent to fill the high side tank. ven ven if the the ves vesse sell doe doess not not caps capsi& i&e# e# such such a sud sudde den n rol rolll may may resu result lt in in6u in6ury ry to pers person onne nell or or shift of cargo with its implications on ship’s stability.
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)! 1ebruary )4!2
&escribe how a vessel lying at an angle of loll may be returned to a safe condition. (n angle of loll is caused due to the vessel being in an unstable condition with negative -3 when upright and the vessel may heel to port or starboard. !" )" *"
/" 2" 8"
D"
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9"
nsu nsure re tha thatt the the hee heell is due due to the the nega negati tive ve -3 -3 rath rather er tha than n off off cen centr tree weig weight ht.. That That is is to ensure ensure that that the the port port listi listing ng mome moment nt is is equal equal to the the starbo starboard ard listin listing g mom moment ent.. Since Since the the angl anglee of loll loll is is cause caused d by - being being too high# high# effo effort rt is is to be dire directe cted d towar towards ds lowe lowerin ring g it. it. a" This This can can be be do done by shif shiftting ing wei weig ght onb onbo oard. ard. b" If the vessel has high ballast ballast tanks then these these may be emptied by discharging discharging the ballast from high side tank first. 0nce the high side tank is emptied then empty the lower side tank. 0ne should should look look towar towards ds lowe lowerin ring g the the weigh weights ts and and redu reducin cing g free free surf surface ace effect effect where where poss possibl iblee i.e.# by pressing up tanks. Should Should it be nece necessa ssary ry to to fill fill the the doub double le bot bottom tom## it is is impor importan tantt to choose choose a divid divided ed tank tank first first so so as to minimi&e the free surface effect 0ne tank tank shoul should d be filled filled at a time time and alway alwayss fill fill the the lower lower side side first first.. This This will will probab probably ly caus causee an initial increase in the list because of the off centre weight and generated free surface effect# but after that the list will start to reduce as - is lowered. @here @here a doub double le bottom bottom is subdiv subdivide ided d into into three three equal equal water water tight tight compar compartme tments nts## then then a" it is is logi logical cal to fill fill the the cent centre re tank tank first first since since the the adde added d weig weight ht will will caus causee the the - to move move vertically downwards and the heel will therefore reduce as the tank f ills. b" ;either it will cause cause the vessel to roll over to the the high side since the the added weight is not off centre. c" 1ill th the lo low side ta tank co completely d" 1inall 1inally y fill fill the the high high side side tank. tank. By By the the tim timee this this tank tank is com comple pletely tely full full the the vesse vessell will will be in upright condition as the vessel’s stability is improved by this time and -3 being positive. @her @heree the there re are are fou fourr ath athwa wart rtsh ship ip tank tank the the ord order er reco recomm mmen ende ded d is: is: a" Ballast the in inner lo low si side fi first. b" Ballast the inner high side side completely c" Ballast th the ou outer lo low si side co completely d" Ball Ballas astt the the outer uter high igh side com complet pleteely 'rior 'rior cons conside iderin ring g any any of of the the abov above# e# if if the the vess vessel el is at at sea sea wher wheree the the ship ship is lolled lolled over over then then following shall be carefully observed. a" (lte (lterr cou cours rsee to to put put the the shi ship’ p’ss head head into into the the pre predo domi mina nant nt wave waves. s. b" It is essential that the the ship stays in lolled lolled to the same side.
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)! 1ebruary )4!2
0plain why the information provided by a curve of statical stability, derived from -1 values should be treated with caution !"
-< curv curves es are are the the best best way of asse assess ssing ing a ship’ ship’ss stab stabili ility ty but but they they do have have limita limitatio tions ns as as they they are are based upon theoretical theoretical values. )" This This is is beca becaus usee no accoun accountt is is take taken n of of what what may happen happen in prac practic ticee at at large large angle angle of heel heel e.g.# e.g.# flooding through ventilators# shifting of cargo# etc. *" The ,; values values are tabula tabulated ted for variou variouss angle angless of heel heel for for a rang rangee of displa displacem cement ents. s. Thes Thesee value valuess are derived based on the fact that it would be convenient to consider the -< that would e7ist if were at ,eel# termed ,;. /" The ,- of the the vess vessel el is is assum assumed ed to to be &ero# &ero# ther therefo efore re all all ,; ,; value valued d need need to to be correc corrected ted in orde orderr to take into account the actual ,- of the vessel. 2" The The -< -< val value ue is pred predom omin inan antl tly y dep depen enda dant nt upon upon the the ,-. ,-. 8" Eence Eence in in orde orderr to obtai obtain n the the actual actual -< for a give given n valu valuee of ,-# ,-# a corr correct ection ion need need to to be be made made for the actual height of - above the keel. D" -< > ,;, ,;,-si -sin?. n?. ,; value value must must be interp interpola olated ted betwee between n two two sets sets of of displ displace aceme ment nt to to arri arrive ve at a desired displacement. ,- values dependant upon displacement and the displacement is dependant upon accuracy of weights onboard including the lightship displacement and ,-. " The light lightshi ship p ,,- and and disp displac lacem ement ent is is no longer longer the same same that that was was calcu calculat lated ed when when the ship ship was was built. 9" -< valu values es are are base based d upon upon an an assum assumed ed trim trim condit condition ion which which may not be the the vess vessel’ el’ss actu actual al trim trim## although some vessels have different ,; tables for different trim conditions. !4" ( furt further her com compli plicat cation ion is is that that of 1ree 1ree trim trim where where the the vesse vessell change changess its trim trim as it heel heels. s. !!" !!" This This condit condition ion is is very much much obvi obvious ous in in case case of small smaller er vessel vessel’s ’s like like offsho offshore re suppl supply y vessel vessels. s. Trimming Trimming by stern on such vessels will reduce the water plane area especially when vessel’s vessel’s low stern goes into the water and the aft deck floods. !)" Geduction Geduction in water water plane plane area area reduces reduces the vessel’ vessel’ss stability stability and therefore therefore the ,; ,; values values for that angle of heel. !*" Thus Thus the -< -< curve curve obtai obtained ned usin using g ,; valu values es of fi7 fi7ed ed trim trim## then then the curv curvee obtain obtained ed will will be incorrect one and will tend to show that the vessel has better stability. stability. !/" @ater @a ter shipp shipped ed on on deck deck will will not not be be account accounted ed for. for. Such water will change change the the vessel’ vessel’ss ,,- creating free surface moment as the vessel rolls in seaway. !2" (lso dynamic dynamic factors factors such as synchrono synchronous us rolli rolling# ng# parametric parametric rolling rolling and loss of stabil stability ity cannot cannot be appreciated by inspection inspection of a curve of statical stability such as righting righting lever or righting righting moment curve.
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)! 1ebruary )4!2
&escribe the effect of a heavy list on a vessel9s stability. !" )" *" /" 2" 8" D" "
@hen @hen a vess vessel el is is lis liste ted d the the - lie liess off off the the cent centre re lin linee to to port port or sta starb rboa oard rd.. -< is is actu actual ally ly cap capsi si&i &ing ng lev lever er wit with h a nega negati tive ve -< -< when when the the ves vesse sell is upri uprigh ght. t. -< is is ne negative un until th the an angle of of li list. (t angle of list -< is &ero. If the the ship ship is heel heelss beyo beyond nd angl anglee of list list## posit positive ive -< is is produ produced ced and it is is now now a righ rightin ting g momen moment. t. 3a7i 3a7imu mum m res resid idua uall -< -< is is red reduc uced ed.. The The loss loss of -< due due to to lis listt > -- E 7 os? (s os? os? > !# !# the the loss loss of -< is ma7i ma7imu mum m whe when n the the ship ship is upri uprigh ght. t. (rea (rea under under the the curve curve +dynam +dynamical ical stabi stabilit lity" y" is is decre decrease ased d due due to losing losing the the area area unde underr the the heeli heeling ng arm curve. 9" (ngl (nglee of of ma7 ma7im imum um -< valu valuee is is inc incre reas ased ed by a sm small all amo amoun unt. t. !4" Gan Gange of stab stabil ilit ity y is red reduced uced.. !!" !!" ;o chang changee in the the angle angle of deck deck edge edge imm immers ersion ion but but it it is easil easily y reache reached d on the the liste listed d side side when when acted upon by the e7ternal forces. !)" Since Since the ship ship is is already already listed listed## e7terna e7ternall forces forces can can easily easily heel heel the the ship ship to more more dang dangero erous us angle angle of heel on the listed side. +If this question forms part of a question where they have asked to show the -< curve with list condition# only the above answer will suffice. If asked as a stand alone question then curve need to be drawn"
&iscuss the use, limitation and relative accuracy of 4C' of the following means of stability assessment. Simplified Stability tables (e.g., a! "#$
?se: +a" +b" +c" +d" +d"
These These are are inco incorpo rporat rated ed in in the the ship’ ship’ss stab stabili ility ty book booklet let either either as a diagra diagram m or a table table.. ( quic quick k assess assessmen mentt of the ship ship’s ’s stabil stability ity as as to wheth whether er or not not all stat statuto utory ry criter criteria ia are are compli complied ed with is achieved by means of a single diagram or table limi liminat nates es the the need need to use use cros crosss curve curvess or -< curv curves es for for diff differe erent nt load loading ing condit condition ions. s. Thre Threee met meth hods ods of of pre pressent entati ation are: are: 3a7imum deadweight moment or table 3a7imum permissible ,- diagram or table. 3inimum permissible -3 diagram or table.
/nitial *etacentric 'eight (G*% ?se: +a" +b" +c"
%sed %sed to deter determi mine ne the the initi initial al stabi stabilit lity y of the the vessel vessel i.e. i.e.## the stab stabili ility ty of the the vess vessel el at sma small ll angl angles es of heel. I30 $oad $oad $ine $ine Gegula Gegulatio tions ns stip stipula ulates tes the the mini minimu mum m value value of of Initi Initial al -3 -3 for diffe differen rentt type type of vessel. Eence Eence at a glan glance ce of init initial ial -3 -3 for that that ty type of vesse vessel# l# once once can can ascert ascertain ain the the stabi stabili lity ty condi conditio tion n of the vessel. Eowever in order to comply fully with the regulations there are other criteria which needs to be complied with.
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)! 1ebruary )4!2
0plain the meaning of ree )rim and its particular reference to offshore supply vessels. 1ree trim is the sudden and significant moment suffered by the offshore supply vessels after a certain angle of heel due to the shift of $B and $1 forward. The bow is up and the stern in trimmed down. This effect is e7plained as follows: follows: !. ). *. /.
2. 8. D. . 9. !4. !!. !!.
1ree 1ree trim trim effe effect ct is obse observe rved d in offsh offshore ore supply supply vessel vesselss with with high high foreca forecastl stlee +norm +normally ally forwar forward d superstructure" and a low working after deck. @hen @hen ship ship is heeled heeled over over to immers immersee the the after after deck deck line line## the the forec forecast astle le rema remains ins well well over over the water line. The water water plan planee area area aft on the low side side has been been lost lost causin causing g the the 1 to to move move forwar forward. d. The The ship ship starts to trim by the stern. (s the the ship ship progre progressi ssivel vely y heel heelss furth further er the the rese reserve rve buoya buoyancy ncy of of the the forwa forward rd supe superst rstruc ructur turee takes takes effect# volume of buoyancy being transferred from the high side aft where it is not being used to the low side on the heeled side. This causes the $ $B to move fo forward. This This acco accomp mpani anied ed by the contin continui uing ng forwar forward d move movemen mentt of the $1 causes causes the ship ship to to trim trim significantly further by the stern as it continues to heel. This This situ situat atio ion n lea leads ds to a dan dange gerr of of afte afterr dec deck k bei being ng floo floode ded. d. The stabi stabilit lity y of of the the vess vessel el is is grea greatly tly reduce reduced d due due to to the the redu reducti ction on in the the wate waterr plane plane area area and and hence reduction in the ,; value. If the the ship ship’s ’s ,; valu valuee has has been been calc calcula ulated ted for fi7ed fi7ed trim trim they they will will result result in an an incor incorrec rectt -< curve curve and will tend to show that the vessel has better stability than it actually has at large angles of heel. 1i7ed 1i7ed trim trim ,; data data will will give give grea greater ter -< -< values values than than what what the the ship ship will will actua actually lly have have when when heel heeled ed beyond the angle of deck edge edge immersion stability stability will be overestimated. overestimated. Theref Therefore ore it it is pref prefera erable ble that that the the ,; valu values es of the the ship ship be derive derived d on a Kfree Kfree to to trim trim basis basis and and the the ,; tables should have the statement Korrected for 1ree trimL.
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)! 1ebruary )4!2
4 vessel with a high dec! cargo will e0perience adverse affects due to strong beam winds on the lateral windage areas. 0plain how the effects of steady and gusting winds can be determined and state the minimum stability requirements with respect to wind heeling under the current regulations !. ). *. /. 2.
8. D.
.
( vessel vessel with with high high deck deck cargo cargo may may have have thei theirr stabi stabilit lity y cons conside iderab rably ly redu reduced ced when when sub6e sub6ecte cted d to strong beam winds. ( heel heel angle angle will will be be prod produce uced d by by the the stron strong g beam beam winds winds upon upon larg largee late lateral ral areas areas of the the ship ship.. This This late lateral ral area area may may be be a combin combinati ation on of high high free freeboa board rd and and tiers tiers of contai container nerss on on deck deck.. The wind wind heelin heeling g mome moments nts are the moments moments produ produced ced by this this force force## mult multipl iplied ied by a heeli heeling ng lever lever## tending to incline the vessel. The The co compone ponen nts of wind ind hee heelling ing mom momen ents ts are: re: a" @ind 1orc 1orcee +1" +1" F 1or 1orce per uni unit area area +kg +kgs=m)". ) b" @indage area +(" +(" F (rea (rea +m ". c" $ever +d" 5istance of of centriod of windage area fromt omthe ce centriod of buoyancy +B"
Eeel Eeelin ing g mom momen ents ts > 1or 1orce ce 7 dis dista tanc ncee > 1(d M !444 !444 tonn tonnes es.. 3et 3etre res. s. The vesse vessell will will contin continue ue to to heel heel until until an equa equall and and oppos opposite ite force force is is prod produce uced d i.e. i.e.## right righting ing moments of equal value to the heeling moments# resulting in a steady angle of heel. Gighting moments
>
@ind Eeeling moments
N 7 -<
>
1(d !444
>
Eeeling 3oment M N
>
1(d M !444 7 N
Therefore -< loss at angle of heel
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)! 1ebruary )4!2
9. !4. !!. !!. !).
The The -< -< los losss du due to to wind wind heel heelin ing g pro produ duce cess a heel heelin ing g arm arm The wind wind heelin heeling g moment momentss are usua usually lly repr represe esente nted d by a strai straigh ghtt hori&o hori&onta ntall line line on the the curve curve of statical stability. This This is due due to the the presu presump mptio tion n that that the wind wind heelin heeling g moment momentss do not not change change as as the vess vessel el heels heels.. In pract practice ice the the wind wind heel heeling ing mome moments nts will will tend tend to reduc reducee as the the vessel vessel heel heelss due due to the the inclin inclinati ation on of the windage area reducing the heel force. Eowever for the purpose of stability it is assumed that the wind heeling force remains constant throughout# resulting in the hori&ontal heeling arm across the curve.
*/*/1?* )4+/L/)@ R?/R*1): !. ).
*. /. 2. 8. D.
(ppl (pplie iess to cont contai aine nerr shi ships ps.. @here @here the height height of the latera laterall windage windage area from the the load load water water line line to the top top of the contain containers ers is is greater than *4 of the beam# the regulations require that the ship builder produces a curve of righting moments for the worst possible service conditions together with the total windage area# the position of its centroid centroid and the lever to half half draught. Steady Steady wind wind Eeel Eeeling ing 3oment 3oment +O" > 1.(.d .(.d M !444 !444 +t.m." +t.m."## where where 1 > /.2 /.2 kgs= kgs=m m ). @ind @ind forc forcee is dyn dynami amicc which which is is equal equal to to -usti -usting ng wind wind P 24. 24. -usti -usting ng wind wind heel heeling ing moment moment > Stead Steady y wind wind Eeel Eeeling ing 3om 3oment ent +O" +O" 7 !.2 !.2 Ther Theref efor oree Eeel Eeel arm arm ma7 ma7im imum um > -< los losss 7 !.2 !.2.. 1rom 1rom the the fol follo lowi wing ng cur curve ve # it it is requ requir ired ed tha thatt a" Steady wind heel ? ! is not more than 82 of the (ngle of deck edge immersion +? de". b" (ngle of dynamic Eeel +?dy" not more than (ngle of progressive flooding +? f " c" (rea (rea KS) KS)’ is eq equal ual to to or or mor moree th than (rea rea S! S! up up to to ?f
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)! 1ebruary )4!2
7ith regard to the modern shipboard stability and stress finding instrument: (a% (a%
tate tate the the hydro hydrosta static tic and and stabi stabili lity ty data data alre already ady pre pre3pr 3prog ogram ramme medd into the instrument.
!" )" *" /" 2" 8" D" " 9" !4" !4" !!" !)"
Shi Ship’s p’s dim dimen ensi sio ons and and gene eneral ral par parti ticu cula lars rs.. apacity of of al all in internal sp spaces. AA- = $$- = 1S3 1S3 of all all int inter erna nall spac spaces es +ca +carg rgo o spac spaces es## ball ballas astt tank tankss fuel fuel # 1@ 1@ etc etc"" Eydro Eydrost stat atic ic part partic icul ular arss F 5isp 5ispla lace ceme ment nt## dra draug ught ht## T' T'## 3T 3T## $B $B## $1 $1## ,3 $igh $ightt shi ship p data data F $igh $ightt shi ship p disp displa lace cem ment ent and and ,-. ,-. ,; data Stab Stabil ilit ity y lim limits its +$oa +$oadl dlin ine# e# -rai -rain# n# Timber mber etc" etc" Sim Simplifi lifies es Stab Stabil ilit ity y 5at 5ata +e.g +e.g.# .# 3(Q 3(Q ,-" Structural Stress $imits -rai -rain n $oa $oadi ding ng data data +as +as in in gra grain in load loadin ing g boo bookl klet et"" @ind Ee Eeeling 5ata Ice (llowance 5ata
(b% (b%
&escri &escribe be the the infor informa matio tionn to be enter entered ed into into the the instr instrum ument ent by by the ship ship9s 9s officer.
!" $ocati $ocation on and and weigh weightt of indi individ vidual ual item itemss of deadw deadweig eight ht F cargo cargo## fuel# fuel# balla ballast# st# stor stores# es# fres fresh h water water## passengers etc. )" $oadline &one *" G.5. of seawater = dock water /" G.5. G.5. of liqu liquid idss F fuel fuel## bal balla last st## liq liqui uid d carg cargo o etc etc.. 2" S.1. .1. of bulk cargoes +e.g. .g. grain"
(c%
&escribe the output information information
!" )" *" /" 2" 8" D" "
5eadweight su summary. Trim rim and and drau draugh ghtt +fo +forw rwar ard# d# aft# aft# mid midsh ship ips# s# fre freeb eboa oard rd"" Eeel Stab Stabil ilit ity y (sses ssessm smen entt F -m# -m# -< -< cur curve ve## dyn dynam amic ical al stab stabil ilit ity y etc etc.. Simp Simpli lifi fies es Stab Stabil ilit ity y diag diagra ram m and and asse assess ssm ment. ent. Stre Stress ss (sses ssessm smen entt F Shea Shearr for force ce## Ben Bendi ding ng mome moment nt## To Torsio rsion. n. -rain lo loading as assessment. $oad $oad line line asse assess ssm ment ent F e.g. e.g.## con conta tain iner er stac stack k wei weigh ghtt
The stress data is usually given as a percentage of the ma7imum allowable at that particular point along the length of the vessel. Eence two variables are the actual stress encountered and the corresponding strength of the vessel at that point which resists that particular stress.
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)! 1ebruary )4!2
tate the purpose of the inclining e0periment. The purpose of performing inclining e7periment on vessel is to determine the value of the ,- in the lightship condition. The determination of light ship ,- is required because the light ,- changes over a period of time. 3oreover# the lightship ,- and displacement displacement value are the basis from which the ,- is determined for every other condition. (n error in the ,- calculated for any condition of loading will result inaccuracy in all stability parameters dependant on this value F -3# -< values and dynamical stability stability.. (lso during the e7periment# the $- for light condition will also be determined.
&escribe the precautions to be ta!en by the '/P9s >/CR before and during the inclining e0periment. !" )" *" /" 2" 8" D" " 9" !4" !!" !!" !)" !*" !*" !/"
The ship ship must must be moor moored ed in in quie quiett shel shelter tered ed waters waters free free from from the effect effectss of of passi passing ng vessel vessels. s. There There must must be adequa adequate te dept depth h of of water water under under the the keel keel so that that the the botto bottom m of of the the ship ship does does not touch the sea bed on inclination. inclination. There There shou should ld little little or no no wind wind.. If there there is any wind wind the the ship ship shou should ld be head head on on or or stern stern to it. it. The The ship ship sho shoul uld d be be floa floati ting ng free free.. The There re sho shoul uld d be no bar barge gess alon alongs gsid ide. e. 3oo 3oorin rings shou hould be sl slacke acken ned righ rightt dow down n. Shor Shoree side side gang gangwa way y if if any any mus mustt be land landed ed to to all allow ow unre unrest stri rict cted ed hee heeli ling ng.. (ll loos loosee wei weigh ghtts mus mustt be be rem remov oved ed or secu ecured. red. (ll fittin fittings gs and and equi equipm pment entss such such as as accom accommod modati ation on ladd ladder er # derr derrick icks=c s=cran ranes es shou should ld be be stowe stowed d in their normal sea going positions. 1ree 1ree surfa surface ce shou should ld be be minim minimi&e i&ed. d. (ll (ll tank tankss shoul should d be verifi verified ed as as being being comple completel tely y empty empty or ful full. l. Bilges should be dry. 5eck 5eck should should be be free free of water water.. (ny (ny water water trap trapped ped on on deck deck will will move move durin during g the test test and and reduc reducee the accuracy of the result. The ship ship shoul should d be be upri upright ght at the commen commencem cement ent of the e7peri e7perimen ment. t. (ll person personnel nel not direct directly ly conc concern erned ed with with the e7peri e7perimen mentt should should be sent sent ashore ashore.. In tid tidal al con condi diti tion ons# s# con condu duct ct e7p e7peri erime ment nt at at slac slack k wate waterr. ffici fficient ent two two way way commun communica icatio tion n must must be estab establis lished hed betw between een a pers person on in char charge ge of of the operation and the central control station# the weight handlers and each pendulum station.
0plain why a vessel9s Lightship -G may change over a period of time. !" )" *" /"
onsta onstant nt of of the the vess vessel el keep keep chang changing ing due to accu accumu mulat lated ed slud sludge ge in in fuel fuel tank tanks# s# mud mud and and rust rust in in ballast tanks +unpumpables" +unpumpables" Aariou riouss sto stores res rema remain inin ing g unc uncon onsu sume med d mig might ht add add to to the the cons consta tant nt.. (ny struct structura urall chan changes ges will will affe affect ct the light light ship ship ,,- and and light light ship ship disp displac laceme ement nt $ight $ightshi ship p ,- for a pass passeng enger er vess vessel el will will change change consid considera erably bly over over a peri period od of time time mainl mainly y because of the left over baggage baggage etc will accumulate accumulate over a period of time and add to the the constant considerably.
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List the circumstances when the inclining e0periment e0periment is required required to ta!e place on passenger vessel. !" )" *" /"
@hen the vessel is built. @hen @hen any any ma6o ma6orr modif modifica icatio tions ns are are made made to the ship ship so so as to materi materially ally affect affect the stabi stabilit lity y. very 2 years. If any any sign signifi ifican cantt chang changee is is found found F $igh $ightt displ displace aceme ment nt chan changed ged by ) ) or $ights $ightship hip $changed by ! of ship’s length.
tate the formula to determine the virtual loss of G* due to a free surface liquid within a rectangular tan!, e0plaining each of the terms used The formula to determine the virtual loss of -3 due to free surface liquid is given by 1ree surface surfa ce correction correcti on +1S" > $oss in -3 > $ 7 B * 7 G5 of liquid liquid in tank !) 7 N 7 n) @here $
$ength of the rectangular tank. $oss of -3 is directly proportional to the length of the tank so will be the value of f ree surface moments +loss of -3". B Breadth of the rectangular tank. 1rom the formula it can be seen that breadth of the tank is the most critical factor which determines the amount of loss in -3 i.e.# loss of -3 is directly proportional to the the cube of the breadth of the tank. tank. 5ensity Gelative density of liquid filled in the tank. tank. $oss of -3 is directly proportional proportional to the G5 of the liquid# greater the density of the liquid# greater the loss in -3. N 5ispla 5isplacem cement ent of the the vess vessel. el. -reate -reaterr the the disp displac laceme ement nt of of the the vess vessel el less lesser er the the loss loss of of -3 and vice vice versa. !) It is is part part of of the the form formul ula. a. The The fre freee surf surfac acee corr correc ecti tion on can can als also o be giv given en by by 1ree Surface 3oments +1S3" 5isplacement 1S3 > 3oments of Inertia of the free surface liquid 7 G5 of the liquid > $ 7 B* 7 G5 of liquid !) n number of longitudinal longitudinal subdivision of the tank. The longitudinal subdivision of the tank greatly reduces the 1S as it is indirectly proportional to the square of number of subdivision. subdivision. 1urther it can be seen that if the tank is divided into two equal subdivision then the 1S will reduce by a quarter and * equal division will reduce the loss by one ninth and so on. on.
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)! 1ebruary )4!2
0plain the effects on the virtual loss of transverse G* due to the free surface effects when the slac! tan! is subdivided (a% )ransversely: 1ree surface surfa ce correction correcti on +1S" > $oss in -3 > $ 7 B * 7 G5 of liquid liquid in tank !) 7 N 7 n) !. ). *. /. 2.
(lthou (lthough gh the the tank tank is tran transve sverse rsely ly sub sub divi divided ded yet yet the the effe effecti ctive ve leng length th and and brea breadth dth of the the tank tank still still remains the same. 0ne should should not mista mistake ke Hn’ Hn’ in the formul formulaa for for trans transver verse se sub subdi divis vision ion as it refe refers rs to to the the longitudinal subdivision. subdivision. The The area area ava avail ilab able le for for the the free free mov movem emen entt of the the liqu liquid id sti still ll rema remain inss the the same same.. The The fre freee sur surfa face ce effe effect ct rem remains ains the the sam samee as it was was bef befor ore. e. The follo followin wing g diag diagram ram shows shows an e7am e7ample ple of tank tank tran transve sverse rsely ly subd subdivi ivided ded into into two two equal equal parts. parts.
(b% Longitudinally Longitudinally
$
1ree surface surfa ce correction correcti on +1S" > $oss in -3 > $ 7 B * 7 G5 of liquid liquid in tank !) 7 N 7 n) !. ). *. /.
$ongit $ongitud udina inall subdi subdivi visio sion n of the tank tank great greatly ly redu reduces ces the free free surfa surface ce effe effect ct and and henc hencee the the loss loss of of -3. (S it it can can be be seen seen from from the formu formula# la# that that the the $os $osss in -3 is is inver inverse se prop proport ortion ional al to to the the square square of ) the number of subdivision +n ". 1or e7amp e7ample# le# if the the tank tank is divi divided ded into into two two equal equal subdiv subdivisi ision on then then the the 1S 1S will will reduce reduce by a quarter and * equal division will reduce the loss by one ninth and so on. The follo followin wing g figur figuree illus illustra trates tes an e7am e7ample ple of tank tank longit longitudi udina nally lly divide divided d into into two two equa equall parts parts..
n
n
B
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)! 1ebruary )4!2
0plain why a vessel laden to the same draught on different voyages may have different natural rolling period. Golling period +T" in seconds is the time taken for the ship to complete one complete oscillation i.e.# the time it takes for the ship to roll from one side back through the upright to the e7tent of its roll on the other side and back again. +port F starboard F port".
2)
*" /"
2" 8" D"
+!" The natural rolling period in still water is given by the formula: T > ) R , A-3 7 g @here T > period of roll in seconds g > acceleration due to gravity +9.! mtrs = sec )" , > Gadius of -yration. -3 > 3etacentric height of the ship. Radius of Gyration is the distance from the centre of gravity or the rolling a7is at which the total weight +@" would have to be concentrated in order to give the ship same moment of inertia as it actually has. 1or an any particular sh ship th the Radius of Gyration can be changed b y altering the distribution of deadweight about the rolling a7is. If the the weig weights hts are moved moved away away from from the the rolli rolling ng a7is a7is## the the radiu radiuss of gyrat gyration ion is incr increas eased ed resu resulti lting ng in the longer period of roll and the ship will roll slower +moving weight outwards towards the side of the ship is known as winging out weights" onver onversel sely y# movin moving g weigh weights ts inw inward ardss towar towards ds the the rol rollin ling g a7is a7is will will cause cause the the ship ship to roll roll faster faster.. The roll roll perio period d varie variess inver inversel sely y as the -3. Eence Eence larg larger er the the -3# -3# sho shorte rterr the the rolli rolling ng peri period od +sti +stiff ff ship" and smaller the -3# longer the rolling period +tender ships". (lso (lso the the roll roll peri period od will will change change when when weigh weights ts are are load loaded# ed# discha discharg rged ed or or shift shifted ed## since since both both the the -3 and the moment of inertia +measure of distribution of weight about the rolling a7is" will be affected.
1rom the above statement it can be seen that although the laden vessel has the same draught for different voyages# yet its rolling period will change because of the following reasons:
C'41G /1 G* >R )' 4* &R4?G'): !" )" *" /" 2"
1or the same same draug draught ht## the the -3 -3 of the vessel vessel may not necess necessari arily ly be be the the same same.. -3 of the the vessel vessel varies with concentration of weight distributed on the ship with reference to the keel. ( vessel vessel loaded loaded with with high high densit density y carg cargo o +low +low S1" will will have have large large -3 +reduct +reduction ion in ,-" ,-" compared to when loaded with low density cargo F both resulting in same draught. It is is possi possible ble that that the the vesse vessell may have have loade loaded d sligh slightly tly less less carg cargo o but but may may have have bunk bunker er tank tankss fully fully filled which cause the - to move down resulting in increase -3. (lso (lso the the ,- of the the carg cargo o loade loaded d has has direc directt effec effectt on the result resultan antt -3 of the the vess vessel el +1or +1or e7ampl e7amplee a vessel with more deck cargo will have less -3" So the the chang changee in -3 for for the the same same draugh draughtt will will resul resultt in change change in rollin rolling g peri period od as as dis discus cussed sed above.
&/)R/+?)/>1 > 7/G') 7/)' RPC) )> R>LL/1G 4B/: !" )"
The Gadiu Gadiuss of -yrat -yration ion may vary vary for for every every voyage voyage +with +with same same draug draught ht"" as the distr distribu ibutio tion n of weight with respect to rolling a7is may vary. Eenc Eencee the the roll rollin ing g per perio iod d wil willl cha chang ngee for for each each voy voyage. age.
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)! 1ebruary )4!2
Eowever it should be borne in mind that the period of roll is not affected by the amplitude or magnitude of the roll.
&escribe the different rolling rolling characteristics of a vessel in a stiff condition and a vessel in tender condition. condition. The natural rolling period for the vessel is given by T > ) R , A-3 7 g @here T > period of roll in seconds g > acceleration due to gravity +9.! mtrs = sec )" , > Gadius of -yration. -3 > 3etacentric height of the ship.
tiff hip: !" )" *"
a" b" c" d"
( stif stifff shi ship p is is one one wit with h a very very larg largee -3 -3 caus caused ed by by the the ,- bei being ng too too sma small ll.. This This occu occurs rs if too too muc much h wei weigh ghtt is is pla place ced d low low down down with within in the the shi ship. p. The ship ship will will be e7c e7cess essive ively ly stab stable# le# righti righting ng mom moment entss will will be be so large large as as to cause cause the the ship ship to return to the upright very quickly when heeled. Rolling characteristics characteristics : It can can be be seen seen from from the the above above form formula ula that that the the rolli rolling ng peri period od is is inver inversel sely y prop proport ortion ional al to to the the -3 of the vessel. Since the stiff ships ships have large -3# the rolling rolling period will be short. short. The ship ship will will offer offer grea greater ter resist resistanc ancee to being being rolled rolled and will will be be rolle rolled d to lesser lesser angles angles of heel heel.. -enera -enerally lly a ship’ ship’ss natu natural ral rollin rolling g perio period d is greate greaterr than than the the wave wave period period.. Since Since sti stiff ff ship shipss have have shorter rolling period they are more vulnerable in the beam sea.
)ender hips: !" )" *" /"
( tend tender er ship ship is one one wit with h a very very smal smalll -3 -3 cau cause sed d by by ,,- bei being ng too too lar large ge.. This This occu occurs rs if too too muc much h wei weigh ghtt is is pla place ced d hig high h up up wit withi hin n the the ship ship.. The ship ship will will have have less less stabil stability ity## righ rightin ting g mome moments nts as com compar pared ed to to the the stiff stiff ship. ship. This This caus causes es the the ship ship to be slug sluggi gish sh and and slo slow w ret retur urn n to to the the upri uprigh ght. t.
Rolling characteristics: characteristics: a" Becaus Becausee of small small right righting ing moment momentss the the ship ship will will only only offer offer limite limited d resis resistan tance ce to to being being rolled rolled## causing the ship to be rolled to larger angles of heel. b" (lso from the Golling period period formula# Golling period period varies inversely as -3. c" Sinc Sincee the the tend tender er ship shipss hav havee sma small ll -3# -3# thei theirr roll rollin ing g peri period od will will be long long.. d" The ship ship will will be slow slow to retu return rn to to the the uprig upright ht and and will will tend tend to remain remain at at the the e7ten e7tentt of the roll roll for for a comparatively long time.
The Gadius of -yration also has effect on the ship’s rolling rolling characteristics. Eowever in both Stiff and Tender Tender ship it varies with the circumstances as the distribution of weight with respect to rolling a7is is not the same at all times.
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)! 1ebruary )4!2
&iscuss how a vessel9s still water rolling period is affected by changes in the distribution of weight aboard the vessel. The distribution of weight aboard the vessel can be discussed with respect to following factors: +!" +)" +)" +*" +*"
5istri 5istribut bution ion of weig weight ht with with respec respectt to the ,eel ,eel of the vessel vessel +,- of the the weig weight ht"" The The rela relati tive ve dens densit ity y of of the the weig weight ht dist distri ribu bute ted. d. 5ist 5istri ribu buti tion on of weig weight ht with with resp respec ectt to to the the roll rollin ing g a7i a7is. s.
Distribution of weight weight with respect to the Keel of the vessel vessel (KG of the weight)
If the weight is distributed high up within the vessel# then the resultant -3 if the vessel will be reduced due to increase in the resultant ,- of the vessel +because the ,- of the weight distributed will be more". The relative density of the weight distributed. The relative density or the S1 of the weight distributed will contribute a ma6or factor in determining the -3 of the vessel. 1or e7ample# if a high density cargo is loaded in a ship then the -3 of the vessel will increase as compared to loading a low density cargo in the same hold.
Thus it can be seen that both the above factors are aecting the GM of the vessel. Distribution of weight weight with respect to the rolling rolling ais
The distribution of weight with respect to the rolling a7is affects the Gadius of -yration. If weights are distributed inwards inwards towards the rolling a7is then the Gadius of -yration -yration is reduced. onversely if the weights are distributed away from the rolling a7is the radius of gyration is increased. The natural rolling period for the vessel is given by T > ) R , A-3 7 g @here T > period of roll in seconds g > acceleration due to gravity +9.! mtrs = sec )" , > Gadius of -yration. -3 > 3etacentric height of the ship. %sing the above formula in con6unction with the e7planation of above section it can be seen that: !" )" *"
The The dist distri ribu buti tion on of of weig weight ht abo aboar ard d the the vess vessel el can can cha chang ngee the the -3 of of the the vess vessel el.. The Gollin Golling g peri period od varies varies inver inversel sely y as as the the -3 -3 and and hence hence chang changee in -3 chan changes ges the rollin rolling g period. (lso (lso dist distrib ributi ution on of of weigh weightt with with resp respect ect with with the the rolli rolling ng a7is a7is affec affects ts the the Gadi Gadius us of of -yrat -yration ion.. Therefore the distribution of weight is such that if the Gadius of -yration is increased then the rolling period is increased as it is directly proportional and vice versa.
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)! 1ebruary )4!2
0plain the term ynchronous rolling and describe the dangers, if any associated with it. Synchronism is the name given to the condition when the ship’s natural natural period of roll is the same as the apparent period of wave. !" )" *" /" 2" 8" D" "
@hen @hen this this occu occurs rs the the wave wavess give give the the ship ship a push push each each time time she she rolls rolls +like +like a swing" swing" causin causing g her her to roll more and more heavily. Theo Theore reti tica call lly y thi thiss cou could ld caus causee the the vess vessel el to even eventu tual ally ly caps capsi& i&e. e. Eoweve Eoweverr Synch Synchron ronism ism is is less less like likely ly to to happe happen n as the rollin rolling g perio period d of the the ship ship incr increas eases es with with the angle of roll at large angles of heel. 3ore 3oreov over er the the per perio iod d of of sea sea wave wavess ten tends ds to vary vary over over time time.. The The ship ship’s ’s natu natura rall roll rollin ing g per perio iod d will will be gre great ater er tha than n the the wave wave per perio iod. d. Ship’ Ship’ss whic which h has has a long long natura naturall rolli rolling ng peri period od are are less less vulner vulnerabl ablee in a beam beam swe swell ll than than the stiff stiff ships with their short periods of roll. If the the sea sea is is forwa forward rd of of the the beam beam the the appa apparen rentt perio period d of of waves waves will will be reduce reduced d whil whilst st the the sea sea abaf abaftt the beam will increase the apparent period of waves. Ther Theref efor oree the the sea sea on the the qua quart rter er wil willl incr increa ease se the the lik likel elih ihoo ood d of sy synchro nchroni nism sm..
Dangers associated associated with !ynchronous rolling: a" 5anger of of ca capsi&ing the ve vessel. b" Eeavy roll may cause shift shift of cargo# especially deck deck cargo which is at greater greater distance from the rolling a7is. c" The vesse vessell will will then then roll roll in a fashio fashion n dicta dictated ted by righ rightin ting g mome moment# nt# heel heeling ing the vessel vessel e7cess e7cessive ively ly to the listed side and increasing the chances of subsequent shift of. argo. d" The dynam dynamical ical stabi stabilit lity y of the vessel vessel will will be greatl greatly y reduc reduced ed unde underr these these circum circumsta stance ncess and and there there is always a risk of capsi&ing. e" Stru Struct ctur ural al dam damag agee to the the ves vesse sell +rac +racki king ng## surg surgee of liq liqui uids ds". ". f" 'ersonal in6ury. g" 5own flooding.
tate the action to the ta!en by the ship9s officer when it becomes apparent that the vessel is e0periencing ynchronous rolling. rolling. !" )" *" /" 2"
(lter (lter cou course rse## ideal ideally ly towa towards rds the the wave wave since since this this short shortens ens the apparen apparentt perio period d of of the the waves waves.. (lte (lterr spe speed ed e7ce e7cept pt when when the the wav wavee is is no not on on the the beam beam.. (lte (lterr ver verti tica call dis distr trib ibut utio ion n of of the the weig weight ht so as to chan change ge the the -3. -3. (lter (lter the the vert vertica icall and and tran transve sverse rse distri distribut bution ion of the the weig weight ht aboa aboard rd the the vess vessel el so so as to chan change ge the the ship’s radius of gyration. .g.# winging out weights. The later later two two measur measures es can be achiev achieved ed by ballas ballastin ting# g# deball deballast asting ing or shifti shifting ng other other items items of deadweight such as fuel or fresh water.
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)! 1ebruary )4!2
&escribe the methods of improving the initial stability if the G* at the critical instant is found to be inadequate. The ma6or considerations that should be borne in mind during dry docking are !" that that the the ' forc forcee is is kep keptt to to an an acc accep epta tabl blee lev level el and and )" that that the the Shi Ship p main mainta tain inss an acc accep epta tabl blee posi positi tive ve -3 -3 duri during ng the the cri criti tica call peri period od.. $oss of -3
' Q ,+0G" ' Q ,3 F ' If it is found that the -3 at critical instant is found to be inadequate the following measures to be taken to improve the initial stability. !"
)" *" /" 2"
>
The loss loss in in -3 is dire directl ctly y propo proporti rtion onal al to to the the ,- of the the vess vessel. el. Eence Eence lowe lowerr the the effe effecti ctive ve ,,- of the vessel by lowering the weights within the vessel# discharging weights from the high up or taking on an acceptable amount of ballast in the double bottom tanks. mpty th the hi high wi wing ta tanks if if po possible. Stow Stow derr derric icks ks## cra crane ness and and rigg riggin ings gs in stow stowed ed posi positi tion on.. limi liminat natee or mini minimi& mi&ee free free surfa surface ce effe effects cts by topp topping ing up or or empty emptying ing slack slack tank tankss where where possib possible. le. ,eep ,eep mini minimum mum stern stern trim trim as reco recomm mmend ended ed by by the the dry dry dock docking ing plan. plan. Smalle Smallerr the the trim trim## small smaller er the the ' force and hence smaller the loss of -3.
0plain why the values of trim and metacentric height in the freely afloat conditions are important when considering the suitability of a vessel for drydoc!ing. )rim: !" )" *" /"
2" 8" D"
The The trim trim of of the the vess vessel el play playss a very very vita vitall roll roll in vess vessel el’’s dry dry dock dockin ing. g. The vesse vessell shou should ld ent enter er the the dry dry dock dock with with a small small stern stern trim trim as recomm recommend ended ed by by the the dry dry dock docking ing plan available on the ship. H'’ force force or or the the upthr upthrus ustt gener generate ated d at the block block when when the vessel vessel’s ’s stern stern firs firstt touch touches es the the bloc block k continues to increase as the buoyancy force is reduced. The The fo formul rmulaa for for calc calcul ulat atio ion n of of th the H'’ H'’ forc forcee is is giv given en by '> hange of Trim Q 3T $1 1rom 1rom the the for formu mula la it it can can be seen seen tha thatt grea greate terr the the ster stern n trim trim mor moree the the H'’ H'’ forc force. e. (lthou (lthough gh the the ster stern n frame frame is is desig designed ned to take take force force e7ert e7erted ed on on it during during drydoc drydockin king# g# ther theree is a ma7imum limit that must not be e7ceeded. If the the H'’ H'’ forc forcee is is e7c e7cee eede ded d the then n it it wil willl lea lead d to to str struc uctu tura rall dam damag age. e.
*etacentric 'eight (G*%: !" )" *"
$oss $oss of stabil stability ity +$oss +$oss of of -3" -3" comm commenc ences es as as soon soon as as the the ship ship touc touches hes the block block aft aft and and cont continu inuee to worsen as the value of the ' force increases. The ma7imu ma7imum m loss loss of -3 -3 occur occurss at the instan instantt immed immediat iately ely prior prior to to the the ship ship settli settling ng on the blocks forward and aft F known known as ritical Instant. Instant. The vesse vessell must must have have positi positive ve stabil stability ity +posit +positive ive -3" at this this critic critical al instan instant. t.
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)! 1ebruary )4!2
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2" 8" D"
"
That That is to say say that that it is is essen essentia tiall that that the the righ rightin ting g mome moment nt affo afforde rded d by the upward upward acti acting ng buoy buoyancy ancy force +remaining F due to pumping out of dock water" remains greater than the capsi&ing moment afforded by the upthrust of ' force acting at the keel at all times prior to the ship touching the blocks forward and aft. If this this is not not so# so# then then the ship ship will will becom becomee unsta unstabl blee resul resultin ting g in negati negative ve -3 -3 and and would would topple topple over in the dock. Theref Therefore ore the the meta metacen centri tricc heigh heightt of of the the vesse vessell when when she is in freely freely afloat afloat condit condition ion is very very important when considering the suitability of the vessel for drydocking. The The form formul ulaa for for los losss of of -3 -3 at at cri criti tica call ins insta tant nt is give given n by $oss of -3 > ' Q ,+0G" ' Q ,3 F ' 1rom 1rom the the formu formula la it it can can be seen seen that that loss loss of -3 -3 is direc directly tly propo proporti rtiona onall to the ' forc forcee and and the the ,of the vessel.
Eence the values of trim and metacentric height of the vessel in the freely afloat conditions are important for the purpose of dry docking the vessel.
&escribe the two methods of determining the upthrust (P force% during the critical period. The two methods of calculating the ' force are a" alc alcul ulat atio ion n of of ' forc forcee at at any any stag stagee dur durin ing g dry drydo dock ckin ing g pro proce cess ss.. b" alculation of ' force during the critical critical period when drydocking. drydocking. "alculation of # force at any stage during dry$doc%ing process. !" Throug Throughou houtt the the dry drydoc dockin king g proc procedu edures res the true true mean mean draugh draughtt of of the the vessel vessel reduce reduces. s. )" This This situa situatio tion n is simila similarr to the vessel vessel rising rising out of wate waterr due due to weight weightss being being discha discharg rged. ed. *" Gis Gise in in cms cms is is given iven by the the form formul ulaa w+t w+t"" D T'. /" The H'’ force force may may be consi consider dered ed to to have have the the same same effe effect ct on on Tru Truee mean mean draug draught ht as as if weight weight had been actually discharged. discharged. 2" Ther Theref efor oree red reductio ction n in T35 +cm +cms" > ' forc forcee +t" +t" T' 8" Transp anspos osin ing g th this fo formu rmula we can can fin find tha thatt
P force (t% E Reduction in )*& (cms% 0 )PC
D"
This This formu formula la can can be used used at any draugh draughtt befor beforee or after after the the crit critica icall inst instant ant since since what what is bein being g found is the loss in buoyancy due to the reduction in the draught.
"alculation of # force during the critical period when dry$doc%ing.
a" b"
c"
In the the peri period od betw between een the ship ship touch touching ing the block block aft aft +sta +start rt of of criti critical cal perio period" d" and and touc touchin hing g the the blocks forward and aft +critical +critical instant" the ship ship undergoes a change change of trim. The change of trim at any stage stage during the critical period period may be considered to be be the same as the change of trim that would have occurred when a weight Hw’ has been discharged from a position at the aft perpendicular equivalent to the upthrust H'’ in tones. The The fo formu rmula to fin find d ch chang ange of of tri trim m is is giv given en by 0T +cms" > Trimming Trimming 3oment > w 7 $1 3T 3T
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)! 1ebruary )4!2
d"
e"
If the the ' forc forcee is con consi side dere red d to hav havee the the same same eff effec ectt as a wei weigh ghtt disc discha harg rged ed at at the the aft aft perpendicular# perpendicular# then 0T +cms" > ' 7 $1 3T Tran Transp spos osin ing g the the abov abovee form formul ulaa we can can fin find d ' as give given n und under er H'’ force force at any instant during during critical period > 0T+cms" 7 3T $1 foap
0plain why it is beneficial to have small stern trim when entering dry doc!. !. ). *. /. 2. 8. D.
The critic critical al peri period od duri during ng dry drydoc dock k is betwee between n when when the the ship ship touche touchess the the block blockss aft aft and and event eventual ually ly comes to rest on the blocks along its entire length. 5uring 5uring the critic critical al peri period od prio priorr to taking taking the the block block fully fully forw forward ard and aft# aft# the the ' force force will will be acti acting ng at a single point on the stern frame of the ship. The stern stern frame frame is is stren strength gthene ened d to accept accept the force force e7er e7erted ted on it it durin during g the the drydo drydocki cking ng but but ther theree will be a ma7imum limit that must not be e7ceeded. If the the ' forc forcee bec becom omes es too too lar large ge## str struc uctu tura rall dam damag agee wil willl occ occur ur.. It is usua usuall to to hav havee acce accept ptab able le nea nearr lig light ht cond condit itio ions ns for for dry drydo dock ckin ing. g. (n obvi obvious ous method method to limi limitt the the ' force force duri during ng crit critica icall perio period d is to keep keep the initia initiall trim trim by by stern stern small. The The form formul ulaa for for calc calcul ulat atin ing g the the ' for force ce duri during ng the the cri criti tica call per perio iod d is is giv given en by '>
. 9. !4. !!.
hange of Trim Q 3T $1 It is is clear clear from from the the above above formu formula la that that ' forc forcee is direct directly ly prop proport ortion ional al to to the the chang changee of trim trim that that the ship will undergo. $imiti $imiting ng the trim trim will will theref therefore ore limit limit the the ma7im ma7imum um load load that that will will be e7peri e7perienc enced ed by by the the ster stern n frame. The grea greater ter the the ship’ ship’ss displ displace acemen ment# t# more more import importanc ancee will will be needed needed to to limit limit the dock docking ing trim trim.. The The fo formu rmula to fin find d the the loss loss of -3 is : $oss of -3
!). !*. !/
' Q ,+0G" ' Q ,3 F ' 1rom the above formula# clearly greater the trim# greater the ' force greater the ' force# greater the loss of -3. If the loss of -3 results results in negative -3 then then the ship ship will fall over in the dock before the shores were properly set up. Thus it is beneficial to have small stern trim on entering drydock so as to avoid structural damage due to e7cessive ' force and to have effective control over the ship’s stability stability by having positive stability stability at all times till the the vessel sits on the blocks blocks fore and aft.
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)! 1ebruary )4!2
4 ship is loading in a port in a tropical 8one for one in the 7inter 1orth 4tlantic 8one during winter months. &escribe the various precautions and considerations considerations which must be borne in mind at the loading port in order that the voyage is accomplished safely and in accord with the statutory requirements, requirements, for e0ample the Load Line rules. !"
)" *" /" 2" 8" D" " 9" !4" !!" !!" !)" !*"
The prima primary ry cons conside iderat ration ion is to to have have the vessel vessel comply complying ing with with the the load load line line regu regulat lation ionss throughout the voyage voyage for ensuring intact reserve buoyancy argo hatches# ventilators# ventilators# sounding pipes# air pipes# freeing port" Since Since the the vess vessel el is is going going to anot another her $oad $oad line line &one &one## the the vesse vessell shou should ld be be loade loaded d in such such a way way she she does not breach the load line requirements. (lthou (lthough gh she is loadin loading g in Tropi Tropical cal &one# &one# yet yet she she canno cannott immer immerse se the the marks marks more more than than a lever lever i.e.# @inter load line P due allowance for consumables P bunkers. To calcul calculate ate the bunker bunker consum consumpti ption on and and 1@ 1@ cons consum umpti ption on up up to a poin pointt on the vessel vessel’s ’s intend intended ed route where it enters the winter load line &one. (lso (lso the the loadi loading ng shou should ld be be in such such a way way that that the vessel vessel will will have have adeq adequat uatee stabi stabilit lity y throu througho ghout ut the voyage. If the the ship ship is less less than than !44 !44 mtrs mtrs in in lengt length h she she canno cannott immer immerse se more more than than winter winter north north atlant atlantic ic mark when in winter &one. Aessel ssel need need to have have suffic sufficien ientt bunk bunker er rese reserve rve to meet meet bad bad weat weather her and conti continge ngenci ncies. es. (ll (ll der derri rick ckss and and cran cranes es must must be stow stowed ed in posi positi tion on.. lim limin inat atee free free surf surfac acee effe effect ctss by emp empty tyin ing g or pre press ssin ing g the the tank tankss if pos possi sibl ble. e. (dequa (dequate te lash lashing ing arrang arrangeme ements nts for for deck deck carg cargoes oes partic particula ularly rly for heavy heavy lifts. lifts. Stow Stow heav heavy y car cargo go as low low as as pos possi sibl blee to to bri bring ng down down -. Aessel’ essel’ss loading loading and and stability stability condition condition throughou throughoutt the the voyag voyagee must must take take into account account ice accretion. Sheari Shearing ng force force## bendin bending g moment momentss and To Torsion rsional al stres stresses ses must must be be well well within within limi limits. ts.
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)! 1ebruary )4!2
&escribe )ype F49 vessel under the current Load line Regulations, including the flooding, tability and assumed damage requirements for a newly built vessel. ( type ( ships any ship designed to carry liquid cargoes in bulk such as tankers# chemical carriers# $'and $;- carriers. (ccording Gegulations )D of $oadline Gegulations a type H(’ ship is defined as one which: !" is desi design gned ed to carr carry y onl only y liqu liquid id carg cargoe oess in in bul bulk. k. )" Eas a high high inte integri grity ty of of the the e7pos e7posed ed deck deck with with only only sma small ll acce access ss open opening ingss to cargo cargo compar compartme tments nts## closed by watertight gasketed covers of steel or equivalent material *" Eas a low low pe permea rmeabi bili lity ty of lo loaded aded com compartm artmen ents ts..
looding requirements: !"
)"
If the the vessel vessel is over over !24 !24 mtrs mtrs in length length and has an empty empty comp compart artmen mentt when when full fully y load loaded ed at at the the Summer loadline# the ship should be capable of remaining afloat after flooding of such a compartment with an assumed permeability permeability of 4.92 and shall remain afloat in a satisfactory condition of equilibrium. equilibrium. If the the vess vessel el is is over over !24 !24 mtrs mtrs in in leng length th then then the the machi machiner nery y space space shall shall be be treat treated ed as as a floo floodab dable le compartment# with an assumed permeability of 4.2.
tability requirements: 3 Condition of quilibrium !"
)"
*" /" 2" 8"
D"
The final final wate waterli rline ne afte afterr flood flooding ing## takin taking g into into acco account unt sinkag sinkage# e# heel heel and trim# trim# is is below below the lower lower edge of any openings such as air pipes# top of a ventilator coaming# door sill and openings which are closed by means of weathertight doors or hatch covers through which progressive progressive flooding may take place. If pipe pipes# s# duct ductss or or tunne tunnels ls are are situ situate ated d with within in the the assum assumed ed e7te e7tent nt of of dama damage ge pene penetra tratio tion# n# arrangements shall be made so that progressive flooding cannot thereby e7tend to compartments other than those assumed to be floodable in the calculation for each case of damage. The The ange angell of of heel heel due due to unsy unsymm mmetr etric ical al flo flood odin ing g does does not not e7ce e7ceed ed !2 !2 deg degs. s. If no no par partt of of the the dec deck k is is imme immers rsed ed## an ang angle le of of upto upto !D !D deg degss may may be be acce accept pted ed.. The metac metacent entric ric heigh heightt +-3" +-3" in in the the floode flooded d condi conditio tion n must must be posi positiv tivee and and must must be atle atleast ast 4.42m. The The ves vesse sell mus mustt hav havee ade adequ quat atee res resid idua uall sta stabi bili lity ty afte afterr flo flood odin ing g The right lever curve must have a minimum range of stability of )4 degs. The ma7imum righting lever +-<" must be at least 4.! mtrs within this range of stability. The area area unde underr the the righ rightin ting g leve leverr curve curve withi within n this this range range shal shalll not not be less less than than 4.4!D2 4.4!D2 mr. mr.
&amage assumptions: !" )" *"
The verti vertical cal e7tent e7tent of damage damage in all cases cases is is assu assumed med to be from from the the base base line line upwa upwards rds withou withoutt limits. ,eel to to deck The transv transvers ersee e7te e7tent nt of damage damage is equal equal to to )4 )4 of beam beam or !!. !!.2 2 mtrs mtrs which which eve everr is lesser lesser.. $ongit $ongitud udina inally lly F Betw Between een transv transvers ersee bulk bulkhea head d +B!4 +B!44 4 to to incl include ude one one bulkh bulkhead ead other other than than machinery space bulkhead"
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)! 1ebruary )4!2
&escribe the provisions of the current Load Line regulations governing the ability of some )ype + vessels to withstand flooding due to damage and the stability in the final conditions. !" )" *" /" 2"
( type type B ship ship is one one whic which h is not a Ty Type ( ship ship Fnot Fnot desi designe gned d to carry carry liqu liquid id car cargoe goess in Bulk. Bulk. Eas a gre greaater ter fre freeb eboa oard rd than than type type ( vesse essell. Eas le lesser de degree of of su subdivision. Eas Eas lar large ge deck deck open openin ings gs whic which h are are only only weat weathe herr tig tight ht.. (cce (ccess ss to to unde underr deck deck com compa partm rtmen ents ts in in Ty Type B vess vessel elss is thr throu ough gh lar large ge hat hatch ches es..
There are two classification classifica tion of Type Type B vessels vi&.# Type Type B84 and Type Type B!44 Type &$': !" (ny typ type B ship ship whic which h is is ove overr !44 !44 mtrs trs lo long. ng. )" 'rov 'rovid ided ed with with stee steell hat hatch ch cove covers rs whi which ch are are wea weath ther er tig tight ht.. *" Since Since prov provide ided d with with stee steell hatch hatch covers covers## quali qualifie fiess for for a redu reducti ction on in in the the tabul tabular ar free freeboa board rd of of 84 84 the difference between type ( and type B freeboards# hence the term B84.
=%
looding re requirement
a"
@hen @hen loade loaded d in accord accordanc ancee with with the the init initial ial condit condition ion of load loading ing## shall shall be able able to wit withst hstand and the flooding of any single compartment with an assumed permeability of 4.92 and shall remain afloat in a satisfactory condition of equilibrium.. If the vessel is over !24 mtrs mtrs in length then the machinery machinery space is regarded as a floodable floodable compartment with assumed permeability of 2
b"
Type & +a" +a" (ny typ type of of B 84 shi ship ove overr !44 !44 mtrs trs lon long. g. +b" +b" 'rov 'rovid ided ed with with stee steell hat hatch ch cove covers rs whic which h are are weat weathe herr tig tight ht.. +c" +c" (cce (ccess ss to the the eng engin inee roo room m fro from m dec deck k pro prote tect cted ed by hous house. e.
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)! 1ebruary )4!2
+d" +e" +e" +f"
(g% a.
b.
'rovid 'rovided ed with with open open rails rails for 24 of the the leng length th of the the vessel vessel and not bulwar bulwark. k. rew rew acce access ss by gang gangwa way y or or und under er deck deck pass passag age. e. Jualif Jualifies ies for a reduct reduction ion in the the tabu tabular lar free freeboa board rd of of !44 !44 the the diffe differen rence ce betwe between en type type ( and typ typee B freeboards# hence the term B!44.
looding requirement:
@hen @hen load loaded ed in in acco accorda rdance nce with with the the initia initiall condi conditi tion on of of load loading ing## shall shall be able able to wit withst hstand and the flooding of any two fore and aft ad6acent compartment with an assumed permeability of 4.92 and shall remain afloat in a satisfactory condition of equilibrium.. If the vessel is over !24 mtrs mtrs in length then the machinery machinery space is regarded as a floodable floodable compartment with assumed permeability of 2
Condition of quilibrium 4pplicable all class of )ype + vessels. !"
)"
*" /" 2" 8" D" " 9"
The The fina finall wate waterl rlin inee afte afterr floo floodi ding ng## taki taking ng int into o acco accoun untt sink sinkag age# e# hee heell and and trim trim## is belo below w the the lowe lowerr edge of any openings such as air pipes# top of a ventilator coaming# door sill and openings which are closed by means of weathertight doors or hatch covers through which progressive progressive flooding may take place. If pip pipes es## duct ductss or or tun tunne nels ls are are sit situa uate ted d wit withi hin n the the assu assume med d e7te e7tent nt of of dama damage ge pen penet etra rati tion on## arrangements shall be made so that progressive flooding cannot thereby e7tend to compartments other than those assumed to be floodable in the calculation for each case of damage. The The ange angell of of hee heell due due to unsy unsymm mmet etri rica call floo flood ding ing doe doess not not e7ce e7ceed ed !2 degs degs.. If no no par partt of of the the deck deck is imme immers rsed ed## an angl anglee of of upto upto !D degs degs may may be be acc accep epte ted. d. The The met metac acen entr tric ic hei heigh ghtt +-3" +-3" in in the the flo flood oded ed con condi diti tion on mus mustt be posi positi tive ve and and mus mustt be atle atleas astt 4.42m. The The ves vesse sell mus mustt hav havee ad adequa equate te resi residu dual al stab stabil ilit ity y aft after er floo floodi ding ng The The rig right ht leve leverr cur curve ve must must hav havee a min minim imum um ran range ge of sta stabi bili lity ty of )4 degs degs.. The The ma7 ma7im imum um righ righti ting ng leve leverr +-< +-<"" mus mustt be atle atleas astt 4.! 4.! mtrs mtrs with within in this this rang rangee of stab stabil ility ity.. The The area area und under er the the rig right htin ing g lev lever er cur curve ve wit withi hin n this this ran range ge sha shall ll not not be les lesss than than 4.4 4.4!D !D2 2 mr. mr.
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)! 1ebruary )4!2
7hen converting tabular freeboard freeboard into assigned reeboard as specified in the Load Line rules a number of corrections have to be applied. 7ith the aid of simple s!etches describe each of the corrections and indicate how each may be applied. ( tabular freeboard is the freeboard that would be assigned to a standard ship built to the highest recogni&ed standards having specific characteristics as laid down in the $oad $ine regulations. The following corrections required to be applied in order to convert Tabular Tabular freeboard to assigned freeboard. Type &$' * &$ correction + ,or type & vessels only: !" If the the ship ship qualifi qualifies es for for the reduction reduction in tabula tabularr freeboard freeboard## either either 84 84 or !44 then this correctio correction n is applied. )" Jualifica Jualification tion requires requires provision provision of steel steel hatches# hatches# subdivis subdivision# ion# improved improved water freeing freeing arrangements# crew protection etc. -ooden -ooden atch correction + for type & vessels only: The tabular freeboard is increased if the vessel has hatches other than those of the steel pontoon type on the e7posed freeboard deck = raised quarter deck or the forward )2 of the super structure deck +i.e.# 'osition !"
,lush dec% correction + only Type & ships: !" This correction is applicable if : a" The length of the the vessel is less than or equal equal to !44 mtrs mtrs and b" The effective effective length of the superstructure superstructure is less than or equal equal to *2 of ships length. )" The The tab tabul ular ar free freebo boar ard d in this this case case is incr increa ease sed. d.
&loc% co$efficient correction: correction: !" The The blo block ck coe coeff ffic icie ient nt is meas measur ured ed at 2 2 of of the the summ summer er drau draugh ght. t. )" 3odifi 3odified ed tabu tabular lar freebo freeboard ard is incr increas eased ed if if the the block block coeff coeffici icient ent of the the vess vessel el e7ce e7ceeds eds 4.8. 4.8. *" 1reeboard is multiplied by +4.8 +4.8 P b" M !.*8.
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)! 1ebruary )4!2
Depth correction: !" The The sta stand ndar ard d fre freeb eboa oard rd dept depth h of a shi ship p und under er the the Gul Gules es > $ M !2 )" If the the free freebo boar ard d dep depth th is more more tha than n $ M !2# !2# then then the the fre freeb eboa oard rd is is inc incre reas ased ed *" If the the freebo freeboard ard depth depth is less less than than $ M !2# !2# the the free freeboa board rd may may be be decre decrease ased d prov provide ided d that that the the superstructure is at least 84 of length amidship position or trunk over entire length of the vessel.
"orrection for position of dec% line: !" 1ree 1reebo boar ard d mus mustt be be cap capab able le of vert vertic ical al meas measur urem emen ent. t. )" If the the vess vessel el is is havin having g a roun rounded ded gunwal gunwale# e# then then the freebo freeboard ard must must be corr correct ected ed by by the the verti vertical cal difference between the actual position of the deck line and the correct position.
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)! 1ebruary )4!2
!uperstructure correction: correction: !" 1reeboard will be reduced if: +a" The ship is with sufficient sufficient standard standard height superstructure +0G" +b" Eas sufficient water tight trunking to a minimum height and width. )" This This reduc reductio tion n will will vary vary acco accordi rding ng to to the the leng length th of of the the super superstr struc uctur turee = trun trunk k as a perce percenta ntage ge of of the vessel’s length. *" If the the supe superst rstruc ructur turee or trunk trunk is is of less less than than the the stan standar dard d heigh heightt = brea breadth dth then then the the corre correcti ction on will will be reduced proportionally proportionally.. /" If it is not not of of suf suffic ficien ientt heig height ht or leng length th or width width then then no no redu reducti ction on in freebo freeboard ard..
!heer correction: !" $oad $oad line line regul regulat atio ions ns assu assume me a sta stand ndar ard d she sheer er for for the the vess vessel el.. )" If the the ves vesse sell has has a grea greate terr shee sheerr than than sta stand ndar ard# d# the the bas basic ic free freebo boar ard d is dec decrea rease sed. d. *" If the vessel vessel has a les lesser ser sheer sheer than than the the standa standard# rd# the basic basic freebo freeboard ard is increa increased sed.. /" If the vessel vessel’s ’s amids amidship hipss super superstr struct ucture ure is less less than than !4 !4 length length## then then there there is reduct reduction ion in freeboard.
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)! 1ebruary )4!2
&ow height correction:
!" )"
The load load line line rules rules cont contain ainss a formul formulaa for for calcu calculat lating ing the minimu minimum m bow bow heigh heightt base based d on the vessel’s length and block coefficient. If the the bow bow hei heigh ghtt is les les than than the the cal calcu cula late ted d hei heigh ght# t# fre freeb eboa oard rd is is incr increa ease sed. d.
!u//er ,reeboard : (ssigned only upon 0wners request F only increase in freeboard. ,reeboards /ay also be increased at the owners request or where there are no openings or cargo port holes below the freeboard deck
orrections are then applied to the (ssigned Summer 1reeboard in order to determine the Tropical# @inter# 1resh @ater and Tropical 1resh water freeboards.
7hen converting )4+?L4R R+>4R& to +4/C R+>4R& as specified in the Load line Rules a number of corrections corrections have to be applied. (a%
List the geometric features of of the ship which give rise to these corrections.
The ship which are required for these corrections are Type Type B vessels. !" )" *" /" 2"
( typ typee B ship ship is is one one which which is not not a Ty Type ( ship ship Fnot Fnot desi designe gned d to carry carry liquid liquid cargo cargoes es in Bulk. Bulk. Eas Eas a great reater er free freebo boar ard d th than type ( vess essel. el. Eas lesser de degree of of su subdivision. Eas Eas lar large ge deck deck open openin ings gs whic which h are are only only weat weathe herr tig tight ht.. (ccess (ccess to under under deck deck com compar partm tment entss in in Ty Type B vessel vesselss is is thro through ugh large large hatch hatches. es. There are two classification of Type B vessels vi&.# Type B84 and Type B!44
Type &$': !" (ny (ny type type B sh ship which ich is is ove overr !4 !44 mtrs trs lon long. g. )" 'rov 'rovid ided ed wit with h stee steell hatc hatch h cov cover erss whi which ch are are wea weath ther er tig tight ht.. *" Since Since prov provide ided d with with steel steel hatc hatch h cover covers# s# qual qualifi ifies es for for a reduct reduction ion in the the tabu tabular lar freebo freeboard ard of 84 84 the difference between type ( and type B freeboards# hence the term B84.
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)! 1ebruary )4!2
Type & !" (ny ty type of B 84 sh ship ov over !4 !44 mt mtrs lo long. )" 'rov 'rovid ided ed wit with h stee steell hatc hatch h cov cover erss whi which ch are are wea weath ther er tig tight ht.. *" (cce (ccess ss to the the eng engin inee roo room m fro from m dec deck k pro prote tect cted ed by hous house. e. /" 'rovi 'rovide ded d with with ope open n rail railss for for 24 24 of the the leng length th of of the the vess vessel el and and not not bul bulwa wark rk.. 2" rew rew acce accesss by by gan gangw gway ay or under nder deck eck pa passag ssagee. 8" Jualif Jualifies ies for for a redu reducti ction on in in the the tabula tabularr freebo freeboard ard of of !44 !44 the the diff differen erence ce betwe between en type type ( and type type B freeboards# hence the term B!44.
(b% 0plain the reason for each of these corrections and indicate how each correction should be applied to )abular )abular reeboard (actual values not required% Type &$' * &$ correction &$' : Since provided with steel hatch covers# qualifies for a reduction in the tabular freeboard of 84 the difference between type ( and type B freeboards# hence the term B84. &$: Jualifies for a reduction in the tabular freeboard of !44 the difference between type ( and type B freeboards# hence the term B!44. -ooden atch correction: The tabular freeboard is increased if the vessel has hatches other than those of the steel pontoon type on the e7posed freeboard deck = raised quarter deck or the forward )2 of the super structure deck +i.e.# 'osition !"
,lush dec% correction: !" This corre rrection is applicable if : a" The The len lengt gth h of of the the vess vessel el is less less than than or equa equall to to !44 !44 mtrs trs and and b" The effective length length of the superstructure superstructure is less than or equal to *2 *2 of ships length. length.
)"
The The tabu tabula larr free freebo boar ard d in this this case case is incr increa ease sed. d.
&loc% co$efficient correction: correction: !" The The blo block ck coe coeff ffic icie ient nt is meas measur ured ed at 2 2 of of the the summ summer er dra draug ught ht.. )" 3odified tabular freeboard is increased if the block coefficient of the vessel e7ceeds 4.8. *" 1reeboard is multiplied by +4.8 P b" M !.*8.
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)! 1ebruary )4!2
tate with the aid of a labeled s!etch, the minimum stability criteria required by the current Load line Rules. Initial -3 The ma7imum righting lever +-<" (ngles of 3a7imum -<
not less than 4.!2 mtrs atleast 4.)4 mtrs not be less than *4 degs
4rea under the curve 4 to *4 degs 4 to /4 degs or ?f whichever is lesser Between *4 degs and /4 degs or ?f
not less than 4.422 mr not less than 4.49 mr not less than 4.4* mr
)he current Load line rules permit a reduction reduction of the permissible minimum initial G* for some vessels with timber dec! cargo and the inclusion of the volume of this cargo in the derivation of the cross curves. >utline the circumstances under which this reduction is allowed and e0plain why this reduction is permitted. !" )" *" /" a"
b" c" d" 2" 8"
The The vess vessel el mus mustt have have tim timbe berr cert certif ific icat ate. e. 3ust 3ust hav havee (ss (ssig igne ned d Tim Timbe berr 1ree 1reebo boar ard. d. 3ust 3ust have have soli solid d stow stow of of deck deck carg cargo o full full leng length th of of deck. deck. The vessel vessel must must have have positiv positivee stability stability at all times times and should should be calculat calculated ed with with regard regard to: to: the in increase of of ti timber we weight due to to absorption of water. Ice accretion if applicable. variations in consumables. consumables. 1ree 1ree surfac rfacee ef effect ects of of the the liqu liquid idss in in tan tank ks. @eight ight of wate waterr trapp trapped ed in in the the broke broken n space spacess withi within n the the timb timber er deck deck carg cargo o espec especial ially ly logs logs.. The stabil stability ity calculat calculations ions shoul should d include include !2 increa increase se in weight weight due due to water water absorptio absorption n during during the voyage. ,; values values may may be increase increased d for addit additiona ionall freeboard freeboard B%T B%T only only D2 D2 of the the deck cargo cargo volume volume may be used for additional additional reserve buoyancy. buoyancy.
The reason for reduction in the minimum permissible -3 is as follows: !" The deck deck carg cargo o secu secured red stowed stowed on full full leng length th of free freeboa board rd deck deck acts acts as additi additiona onall reser reserve ve buoyancy. buoyancy. )" The additi additiona onall reser reserve ve buoy buoyancy ancy is appl applica icabl blee only only when when the the deck deck cargo cargo is well well secure secured d and and covers the entire length of the ship’s cargo deck up to alteast standard superstructure height. *" The timber timber carg cargo o also also prov provide idess a grea greater ter degree degree of prot protect ection ion for the hatch hatches es agai against nst the sea. sea. /" The ,; valu values es may be incr increas eased ed for additi additiona onall freeb freeboar oard d howe however ver only only D2 D2 of the the timb timber er volume must be considered as reserve buoyancy. 2" The princ principl iplee of inclus inclusion ion of the the tim timber ber as as reser reserve ve buoy buoyancy ancy in the the deri derivat vation ion of the the alte alterna rnativ tivee ,; data is illustrated in the following figure.
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)! 1ebruary )4!2
-
-
<
B
B
1ig H(’
<
1ig H+’
1rom the above above diagram !" In figu figure re ( when when the the vesse vessell is heeled heeled beyond beyond the the angl anglee of deck deck edge edge imm immers ersion ion## -< valu values es are are small when reserve buoyancy of the timber is not included i.e.# the -< values are derived from ship’s ordinary ,; values. )" In figure figure B we we can can see that that by using using ,; value valuess whic which h incl include ude D2 of the volum volumee of the immersed timber as reserve buoyancy caused an outward movement of B which increased the -< values. *" This This incr increas easee in in -< -< valu valuee incr increas eases es the range range of of stabi stabilit lity y of of the the vesse vessell and and the the dyn dynami amical cal stability.
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)! 1ebruary )4!2
7ith regard to Load Line rules distinguish a )ype 4 vessel from a )ype + vessel and e0plain why they have different )4+?L4R freeboards. )@P 4
)@P +
!"
5esig esigne ned d to to car carry ry liqu iquid car cargo in in bu bulk
)"
(llo (llows ws a smal smalll free freebo boar ard d i.e. i.e.## less less rese reserv rvee buoyancy. buoyancy. The The long longit itud udin inal al hul hulll fram framin ing g in Type ( vessels results in a high degree of sub divisions 7po 7pose sed d wea weath ther er deck deck has has hig high h deg degre reee of of integrity. (ccess to under deck compartment is through small deck openings which are watertight steel covers Eigh Eigh degr degree ee of safe safety ty agai agains nstt flo flood odin ing g because of low permeability permeability of loaded cargo spaces. Eas high degree of subdivision
0the ther th than Type ( vess essels els F whic hich are are not designed to carry liquid cargo in bulk Eas a greater freeboard than Type (
*"
/"
2"
8"
Eas less degree of subdivision.
7posed weather deck has low degree of integrity as compared to Type ( vessel (ccess to under deck compartment is through large hatch openings which are only weather tight. Aulnerable in heavy weather to flooding
$ess degree of subdivision
Type ( vessel and Type B vessel have different tabular freeboard because: !" The The str struc uctu tura rall lay layou outt of of bot both h ves vesse sels ls are are dif diffe fere rent nt )" Types of carg cargo o carri arried ed are are diff ifferen erent. t. *" 3oreov 3oreover er the the perm permeab eabili ility ty of of the cargo cargo tank tankss in Ty Type ( ships ships are are low low as comp compare ared d to the the Ty Type B ship. /" Theref Therefore ore in in an even eventt of floo floodin ding g of a com compar partme tment# nt# oil oil from from carg cargo o tank tank of of Ty Type ( vessel vessel will will run out causing decrease in displacement and increase in freeboard# whereas in case of type B ship# the sea water will enter the cargo space resulting in increase in draught and reduction in freeboard.
tate the general requirement requirement for a )@P + vessel to be given the same )4+?L4R freeboard as )@P 4 vessel of the same length. ( type B vessel can be given the same T(B%$(G freeboard as Type ( vessel of same length if the following criteria are satisfied: (ny Type B84 ships of over !44 mtrs long +Type B!44" satisfying the following conditions at summer draught: a" 'rov 'rovid ided ed wit with h stee steell hatc hatch h cov cover erss whi which ch are are wea weath ther er tig tight ht.. b" (ccess to the engine room room from deck protected by house. house. c" 'rovi 'rovide ded d with with ope open n rail railss for for 24 24 of of the the len lengt gth h of of the the vess vessel el and and not not bulw bulwar ark. k. d" The weathe weatherr deck deck must must be fitt fitted ed with with a prote protecte cted d raise raised d catwa catwalk lk or or under under deck deck ways ways to to allow allow safe safe access for the crew. e" Shall Shall rema remain in aflo afloat at afte afterr flood flooding ing of any any two two fore fore and aft ad6ace ad6acent nt comp compart artmen mentt with with an an assum assumed ed permeability of 92 at summer summer draught
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)! 1ebruary )4!2
/dentify the additional corrections required when converting +4/C R+>4R& to 4/G1& R+>4R&, e0plaining the reason for each correction. Depth correction: The standard freeboard freeboard depth of a ship under under the Gules > $ M !2 If the freeboard depth is more than $ M !2# then the freeboard is increased If the freeboard depth is less than $ M !2# the freeboard may be decreased provided that the superstructure is at least 84 of length amidship position or trunk over entire length of the vessel. "orrection for position of dec% line: 1reeboard must be capable of vertical measurement. If the vessel is having a rounded gunwale# then the freeboard must be corrected by the vertical difference between the actual position position of the deck line line and the correct position. position. !uperstructure correction: correction: 1reeboard will be reduced if: a" The The ship ship is with with suff suffic icie ient nt stan standa dard rd heig height ht supe supers rstr truc uctu ture re +0G" +0G" b" Eas sufficient water water tight trunking to a minimum height and width. This reduction will vary according to the length of the superstructure = trunk as a percentage of the vessel’s length. If the superstructure or trunk is of less than the standard height = breadth then the correction will be reduced proportionally. If it is not of sufficient height or length or width then no reduction in freeboard. !heer correction: $oad line regulations assume a standard sheer for the vessel. If the vessel has a greater sheer than standard# the basic freeboard is decreased. If the vessel has a lesser sheer than the standard# the basic freeboard is increased. If the vessel’s amidships superstructure is less than !4 length# then there is reduction in freeboard. &owheight correction:
The load line rules contains a formula for calculating the minimum bow height based on the vessel’s length and block coefficient. If the bow height is les than the calculated height# freeboard is increased. !u//er ,reeboard : (ssigned only upon 0wners request F only increase in freeboard. ,reeboards /ay also be increased at the owners request or where there are no openings or cargo port holes below the freeboard deck
orrections are then applied to the (ssigned Summer 1reeboard in order to determine the Tropical# @inter# 1resh @ater and Tropical 1resh water freeboards.
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)! 1ebruary )4!2
&escribe the general provisions of the current Passenger hip Construction Rules governing the ability of a Class / Passenger vessel to withstand flooding flooding due to damage, and the stability in the final condition. General Re0uire/ents: !" 3argi 3argin n line line is is the the water water line line and and must must be atle atleast ast D8mm D8mm below below the the upper upper surfa surface ce of of the the bulkh bulkhead ead deck. )" 1loo 1looda dabl blee len lengt gth h dep depen ends ds upon upon the the per perme meab abil ilit ity y of of the the comp compar artm tmen ent. t. (a% 'ermeability for cargo and store spaces > 84 (b% 3achinery spaces > 2 'assenger spaces > 92 (c% *" The The vess vessel el shou should ld rem remai ain n aflo afloat at in in the the even eventt of dama damage ge to to any any com compa partm rtmen ent. t. /" 1actor 1actor of sub subdi divis vision ion +to determ determine ine ma7 ma7 spaci spacing ng betw between een transv transvers ersee bulkh bulkhead ead"" varie variess inver inversel sely y with the ship’s length# length# the number of passenger and the proportion of under water space used f or passenger = crew and machinery machinery space. 2" -reate -reaterr degr degree ee of subdi subdivis vision ion +or small small factor factor of subd subdivi ivisio sion" n" must must be be prov provide ided d when when (a% The vessel is long (b% The number of passengers is large (c% 3uch space below the waterline is used for passenger = crew accommodation and=or machinery space. 8" 'ermit 'ermitted ted length length betwee between n bulkh bulkhead ead > 1looda 1loodable ble length length 7 1actor 1actor of subdi subdivis vision ion..
1ssu/ed da/age: !" Aertical e7 e7tent is fro from ke keel to to deck )" Tran Transv sver erse se e7te e7tent nt must ust be be )4 )4 of the the Bea Beam m of of the the vess vessel el.. *" $ong ongitu itudinal inal e7te e7ten nt of dam damage age must be: !! mtrs between bulkhead +0G" *m P * of the length of the vessel
1ssu/ed ,looding: The vessel must be able to withstand the flooding of the following number of compartments +final waterline at# or below margin line" !" 1actor of subdivision more than 4.2 TE; any one compartment )" 1act 1acto or of subd ubdiv iviisio sion betw etween een 4.2 and and 4.** .** TE TE; (ny (ny ) ad6a ad6ace cen nt com compartm artmen ents ts *" 1actor of subdivision 4.** or less TE; (ny * ad6acent compartments Re0uired !tability after after ,looding:
In the final stage# after any equali&ation +G0SS 1$005I;-" measures# the vessel must comply with the following condition: !" )"
*"
Gesidual -3 atleast 24mm. 1inal heel not to e7ceed: D degs with one compartment flooding flooding +0G" !) degs if two or more compartment is flooded. 'osi 'ositi tive ve resi residu dual al -< curv curvee wit with h a ran range ge of at leas leastt !2 !2 deg degss
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)! 1ebruary )4!2
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(rea (rea unde underr res resid idua uall -< -< cur curve ve to be at leas leastt 4.4 4.4!2 !2 mr up up to: to: ither )) degs F for one compartment flooding flooding +0G" )D degs F for two compartment compartment flooding +0G" (ngle of progressive flooding ?f @EIEAG IS $(ST
2"
3a7i 3a7im mum resi residu dual al righ righti ting ng leve leverr to to be be at at lea least st eith either er:: a" !4 cms +0G" b" Eeeling moment P 4.4/ m @EIEAG IS -G(T -G(TG G 5isplacement
8" The The he heelin eling g mom momen entts to to be be cal calcu cula latted from rom: rowding of all all passengers towards towards one side side +0G" $aunching of fully loaded loaded davit launch survival survival craft# +0G" @ind pressure @EIEAG IS BI--ST
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)! 1ebruary )4!2
7ith reference to the current Passenger hip Construction and urvey Regulations (a%
0plain the e0tent of hull flooding assumed when calculating the ship9s ability to survive hull damage.
In order to arrive at the minimum required stability for the 'assenger vessel after suffering flooding of compartment# the following two factors are taken into consideration: !" )"
(ssumed 1looding (ssumed damage.
1ssu/ed ,looding The number of compartments involved in the assumed flooding conditions are based upon the 1actor of subdivision. subdivision. $esser the factor of subdivision# subdivision# lesser the 'ermissible length of the compartment and hence more the number of compartments taken into consideration for assumed flooding. Eowever at any instant not more than * compartments are assumed to be in flooded condition. The vessel must be able to withstand the flooding of the following number of compartments +final waterline at# or below margin line" !" 1actor of subdivision more than 4.2 TE; any one compartment )" 1act 1acto or of subd ubdiv iviisio sion betw etween een 4.2 and and 4.** .** TE TE; (ny (ny ) ad6a ad6ace cen nt com compartm artmen ents ts *" 1actor of subdivision 4.** or less TE; (ny * ad6acent compartments 1ssu/ed da/age: 1ssu/ed da/age: /" Aertical e7 e7tent is fro from ke keel to to deck 2" Tran Transv sver erse se e7te e7tent nt must ust be be )4 )4 of the the Bea Beam m of of the the vess vessel el.. 8" $ong ongitu itudinal inal e7te e7ten nt of dam damage age must be: !! mtrs between bulkhead +0G" *m P * of the length of the vessel
If the damage of lesser e7tent than indicated above would result in a more severe condition regarding heel and -3 loss# such damage shall be assumed for the purpose of the calculation.
(c%
>utlin >utlinee the the addi additio tional nal factor factorss ta!e ta!enn into into acco accoun untt to dete determi rmine ne the the permissible length of compartments in ships built after "HH5.
'ermissible length of the compartment having its centre at a point in the length if the ship means the product of the floodable floodable length at that point point and the factor of sub division division of the ship. ship. 'ermissible length > 1loodable length 7 1actor of Subdivision. The features of the ship that are considered in determining the length for the purpose of subdivision calculation includes: !" Block coefficient of the vessel )" 1reeboard ratio *" Sheer Gatio
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)! 1ebruary )4!2
/" 2" 8" D"
ompartment permeability $ength of the vessel ;umber of of passengers. The propo proporti rtion on of the underw underwate aterr spac spacee used used for passen passenger gerss = crew crew and and machin machinery ery space space
The permissible length between the compartments is reduced +due to decrease in the 1actor of sub division" when !" The le length of th the ship is more )" 3ore num numb ber of of pa passengers are ca carri rried *" 3uch 3uch of of the the space space below below the the wate waterli rline ne is used used for for passen passenge ger=c r=crew rew accom accommo modat dation ion and or machinery space.
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&escribe toc!holm agreement with reference to the stability requirement of Passenger Ro3Ro vessels. #urpose of !toc%hol/ !toc%hol/ agree/ent: !" $ays $ays down down the the sta stabi bili lity ty requ requir irem emen entt for for 'as 'asse seng nger er GoG GoGo o ves vesse sel. l. )" (gre (greem emen entt con concl clud uded ed afte afterr the the disa disast ster er of sto stoni niaa *" Sign Signed ed betw betwee een n nin ninee nor north ther ern n ur urop opea ean n sta state tess in in !99 !998. 8. /" These upgrades S0$(S 94 94 standards. 2" Takes Takes into into accou account nt the the eff effect ect of wate waterr accum accumula ulatio tion n on the vehicl vehiclee deck deck afte afterr damag damagee # maki making ng the ship safer in heavy seas. 8" (pplie (ppliess to all 'assen 'assenger ger GoGo GoGo vess vessels els operat operating ing on sche schedul duled ed int intern ernati ationa onall voya voyages ges betwee between n or from designated ports in northern urope irrespective of 1lag. Re0uire/ents by the 1gree/ent: 1gree/ent: !" 5emand 5emandss that that a vess vessel el sati satisfi sfies es with with the the requi requirem rement ent of S0$( S0$(S S 94 with with a consta constant nt heig height ht of water on deck. )" The The heig height ht of wat water er on on vehi vehicl clee dec deck k is base based d on on a /.4 /.4 mtr mtr sig signi nifi fica cant nt wave wave.. *" The he height of of wa water sh should be be 4.2mtrs if the residual freeboard at the damage opening is 4.* mtrs or less 4.4 mtrs if the residual freeboard at the damage opening is ).4 mtrs or more /" Inte Interm rmed edia iate te valu values es can can be be det determ ermin ined ed by line linear ar inte interp rpol olat atio ion n
&escribe the stability problems associated with a conventional Ro3Ro ferry. The stability of vehicle ferries poses particular problems due to the following: ,ree !urface ffect: a" Becaus Becausee the the vehi vehicle cle deck deck usua usually lly e7tend e7tendss over over the length length and breadt breadth h of of the the vess vessel el withou withoutt restriction# this type of vessel is especially vulnerable to the effects of free surface b" Such vessel may rapidly lose lose all stability and and capsi&e if the vehicle deck becomes flooded. c" auses of of su such fl flooding in include 5amage to bow or stern door at sea Bow or stern door left open at sea Bow or stern door open and unattended during loading = discharging operations. $oss of watertight integrity due to collision with another vessel or rocks. $oss of water tight integrity due to shift of a vehicle in heavy seas. %se of water curtains +coupled with inadequate drainage" 3nade0uate !tability !tability 3nfor/ation due to: a" Speed of turnaround in port. b" $ack of detailed information information about cargo units units and disposition disposition 4ther factors: a" Eigh ,,- of of ca cargo units on on vehicle de deck b" Aulnerability Aulnerability of GoGo units units to shifting in bad bad weather. c" Eigh windage area of GoGo vessels.
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7hat precautionary precautionary measures must be adopted to improve stability of Ro3Ro ferries a" b" c" d" e" f" c"
(utom (utomati aticc draug draught ht gaug gauges es at at the the stem stem and and ster stern n with with remo remote te reado readout ut shou should ld ensu ensure re that that floodi flooding ng of the vehicle deck in port is avoided. ( loading loading computer must must be available to the ship’s ship’s officer in port port for rapid calculation of stability before the vessel sails. sails. Indica Indicator tor lights lights must must be be prov provide ided d on on the the brid bridge ge to to show show when when shell shell=lo =load ading ing doors doors are open open = closed. Eeavy Eeavy GoG GoGo o carg cargo o units units must must be weighe weighed d asho ashore re and and the the infor informat mation ion provi provided ded to ship ship’s ’s office officers. rs. Such units must be secured by chains to the deck before departure. Incr Increa ease sed d drai draina nage ge requ requir irem emen ents ts for for veh vehic icle le deck decks. s. Stockh Stockholm olm agreem agreement ent provid provides es enhanc enhanced ed stabi stabilit lity y requ require ireme ment nt for for GoGo GoGo passen passenger ger ferrie ferriess with with 24 cms of water on vehicle deck. 'rov 'rovis isio ion n of of some some for form m of of sub subd div ivis isio ion n on on the the vehi vehicl clee dec deck. k.
&iscuss the stability problem problem associated with the the design and operation operation of a conventional >il Rig supply vessel. The stability of the 0ffshore supply vessel poses particular problem due to the following: 5oading and*or Discharging Discharging cargo at sea: sea: a" (ffect (ffectss the the vertic vertical# al# transv transvers ersee and and longi longitud tudina inall pos positi ition on of the - of of the the vessel vessel.. b" This is of particular particular relevance since cargo operations operations may be taking place place as the vessel is rolling rolling and pitching in a seaway. c" The cargo cargo is is often often in liq liquid uid form form +wate +water# r# fuel# fuel# mud mud etc" etc" which which will will result result in virt virtual ual loss loss of stabil stability ity due to 1S during the cargo handling operation. cessive !tern Tri/ Tri/ a" 0ccu 0ccurs rs thro throug ugh h long longit itud udin inal al dist distri ribu buti tion on of load loaded ed weig weight ht.. b" It may occur during an ill advised advised discharge discharge = load# or when working with cables=anchors. cables=anchors. c" ons onsid ider erab able le ster stern n tri trim m dev devel elop opss dur durin ing g the these se stag stages es.. d" This This may may caus causee the the work working ing deck deck to to beco become me awas awash h there thereby by reduci reducing ng the water water plan planee area area and critically reducing the vessel’s stability. -ater entrap/ent The working deck is often used to carr y drill supplies# machinery# machinery# and pipes etc.# some of which have been found to retail large large amount of water due due to seas on the after deck. (n allowance allowance for such volume of water entrapped must be made in the stability calculation. ,ree Tri/ 1ree trim affects the -< curve of the vessel. a" There There is is a redu reducti ction on in in the the stabi stabilit lity y after after the the angle angle of of deck deck edge edge immers immersion ion due to vess vessel el trim trimmin ming g by stern due to rolling. rolling. b" This is caused by the the after deck becoming awash and reducing the waterplane waterplane area when the vessel is heeled in a seaway. !tabiliser Tan% Tan% 3any vessels are fitted with flume stabili&er tanks
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These can be counter productive in some sea conditions for e7ample when working cargo or working cables overside. This is because a heeling arm is produced which results in water in the stabili&er tank moving to the low side in passive flume tanks thereby increasing the list. 1urther more they will generate a significant 1S which will reduce the vessel’s stability stability and should be allowed for.
7hat are the recommended measures to improve i mprove stability of the >ffshore supply vessels. a" b" c" d" e" f" g" h" i" 6" k" l" m" n"
5ischarge fr from to top of of st stow fi first. onsider the use of ballast ballast to counteract any negative negative effects on stability stability or loading or or discharging. @hen @hen balla ballasti sting ng at at sea sea to count countera eract ct rem remova ovall of cargo cargo## due due accou account nt shou should ld be be taken taken of the the adve adverse rse initial effect of free surface on the vessel’s stability. If nec neces essa sary ry rem remov ovee a suf suffi fici cien entt qua quant ntit ity y of of high highes estt dec deck k carg cargo o firs first. t. 3ini 3inimi mise se fre freee sur surfac faces es by kee keepi ping ng the the numb number er of of slac slack k tan tanks ks to to a min minim imum um.. @hen @hen liqu liquid id carg cargo o is is bein being g disc dischar harged ged## due due accou account nt shoul should d be taken taken of of the the 1S 1S on the the vesse vessel’ l’ss stability. $oad=d $oad=disc ischar harge ge in such such an orde orderr so as to to main maintai tain n adequ adequate ate trim trim and and = or or freeb freeboar oard d at all times. times. @hen @hen stow stowing ing deck deck carg cargo# o# adeq adequa uate te arra arrange ngeme ments nts for draina drainage ge shou should ld be made made betwee between n stow stowage age racks to the freeing ports. ons onsid ider erat atio ion n shou should ld be give given n to to the the use use of pipe pipe plug plugs. s. (llowance should be made in stability calculations calculations for the entrapment entrapment of water. In the the calcu calculat lation ion of of the the vesse vessel’ l’ss stat statica icall stabi stabilit lity y curve curve## use use ,; tabl tables es that that have have been been Korr Korrect ected ed for 1ree TrimL @hen @hen stab stabili ili&er &er tanks tanks are in use# use# the the free free surfac surfacee effe effects cts should should be take taken n into into accoun accountt in in stab stabili ility ty calculations. The means means of dum dumpin ping g the the cont content entss of of such such tank tankss in an eme emerge rgency ncy shoul should d be tested tested.. @here @here port port and starbo starboard ard cargo cargo or serv service ice tanks tanks are are cros crosss conne connecte cted d such such conn connect ection ionss shoul should d be closed at sea.
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&iscuss the stability problems associated with the )owing vessels and precautionary precautionary measures to improve the stability of such vessels. a"
@here @here port port and starbo starboard ard cargo cargo or serv service ice tanks tanks are are cros crosss conne connecte cted d such such connec connectio tions ns shoul should d be closed at sea. b" Such forces will often result result in a large heeling heeling moment which causes the the vessel to heel over to a large angle thereby reducing the vessel’s dynamical stability. This is particularly the case when the towline is short and has low stretch characteristics. c" 0ther 0ther fact factors ors affect affecting ing the the stabi stabilit lity y inclu includes des the dynam dynamica icall force forcess durin during g the the towin towing g opera operatio tions ns induced +e.g.# a sudden surge in the propulsion unit" and changes in trim caused by the pull on the tow line. #I%&I'# ( stability problem particularly to conventional tugs is the phenomena called -irting This is a sideways pull on the tug by the tow line when the ship is pulling away from the tug# which is lying abeam to the direction of the pull. The resultant heeling may be so large to capsi&e the vessel.
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b" c"
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Aarious rious aspe aspects cts in the the tug’ tug’ss desi design gn are are usua usually lly inco incorpo rporat rated ed so so as to to reduc reducee the the effect effect of heeli heeling ng moment on the overall stability of the vessel These include giving the vessel a large beam = length ratio# increasing the freeboard# reducing the height of the towing point etc.# The use of long tow line line with good shock absorbing absorbing capabilities capabilities +high stretch" will will help to reduce sudden heeling moments caused by high peak forces in the towline. The The dang danger er of of girt girtin ing g can can be min minim imis ised ed by by the the use use of -0-0- rop ropee +als +also o know known n as -0B -0B or or BGI5$". This rope is used to hold the towline down at or near the stern of the tug which ensures that the tug is brought into line with the direction of the pull and a capsi&ing moment is avoided. Slow Slowin ing g dow down n the the larg largee ves vesse sell wil willl als also o red reduc ucee the the dang danger er of girt girtin ing. g. Such an action will also reduce the vessel’s bow bow wave and therefore the heeling moment on any tug as it takes a line under the bow.
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4 vessel9s vessel9s side compartment is flooded as a result of a collision. &escribe the counter measures measures that may be ta!en ta!en in the event of such flooding. There are a number of measures that can be taken in the case of damage and flooding# including: a" lose all water tight doors. b" %se of ship’s pumps to remove water from the the flooded compartment. c" Take Take meas measure uress to restri restrict ct ingr ingress ess of wate waterr +eg +eg other other vessel vessel to stay stay in plac placee init initial ially ly and and = or use use of of collision patch. d" ross ross floo floodi ding ng F ballas ballastin ting g the the other other side side of the the vess vessel el to to bring bring the ship ship uprig upright ht +mo +movem vement ent of weights may also be considered". e" Ballas Ballastin ting g aft aft also also as to to raise raise forwar forward d sect section ion of the the vessel vessel or move movemen mentt of weigh weightt to achiev achievee similar effect. @hen combined with cross flooding this may result in the damage area of the hull being raised above the the water line. f" Gemova Gemovall of weight weight## part particu icular larly ly from from the the upper upper parts parts of the vessel vessel +eg empty empty swimm swimming ing pool" pool" g" Tran Transs sshi hipm pmen entt of ite items ms of of dead deadwe weig ight ht to to othe otherr vess vessel elss may may also also be be cons consid ider ered ed.. h" Shor Shoree up up int inter erna nall lly y to prev preven entt los losss of of ad6 ad6ac acen entt com compa part rtme ment nt.. i" If all else fai fails consider beaching. 6" Throughout the above# above# reference should be made made to the stability data onboard onboard providing guidance guidance for such circumstances. k" In addi additio tion n the the S3S S3S shoul should d be brough broughtt into into oper operati ation. on. This This usua usually lly involv involves es info informi rming ng shi ship p owners of the situation and gaining access to advice from e7perts associated with lassification society and = or salvage association.
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