FIBERGLASS BODY BUILDING AND “COPY” TECHNIQUES
By David Tlollmann
FIBERGLASS BODY BUILDING AND “COPY” TECHNIQUES
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Materials and Working Techniques Selection of fiberglass and resin.
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How to Make Mock-Up and Molds Mock-up based on the original metal body Parting flanges and substructures
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Moldless Sandwich Method Build a body without a mold
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How to Copy The Original Car Body Mold the original body without ruining the paint work.
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How to Copy The Body Kits
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Finishing and Painting Fiberglass
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Materials and Working Techniques Fiberglass Fiberglass, as the name implies, is a material composed of glass fibers. These fibers are impregnated and embedded in a hardened resin. When in its molten state, glass is drawn out into tiny fibers (filaments) that are only a few ten-thousandths of an inch in diameter and anywhere from 10 to 12 in. in length. A group of filaments can be twisted to form a strand, then strands can be twisted into yarn, and finally this yam is then woven into a fiberglass cloth. Uke other textile fibers, they can be woven into different materials, such as glass cloth, glass matting, and woven glass. The glass fibers are also available in powder form (used primarily in fiberglass filler) and in very tiny short lengths called chopped glass.
The fiberglass is coated with methacrylic chromic chloride complex. This chrome coating makes fiberglass look shiny and what this coating really does is to help the resin to wet-out better for an improved bond. Fiberglass without the chrome coating can lose its bonding strength with resin in a short period of time. While selecting fiberglass materials consult with the supplier. Most fiberglass manufacturers should provide technical data that shows exactly what the material is for and the coating involved, the recommended resin to use.
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The type of weave for cloth or roving determines the strength of the final products. The most common types of fiberglass used in kit car body are cloth, roving, matte, and chopped strand. The first three are applied using hand lay-up, and the chopped strand is sprayed with choppergun (this method is commonly used in mass production of fiberglass products). Chopper gun method can spray strand of fiberglass and resin very quickly. In general, a fiberglass product made with a chopper gun is not as strong as a hand lay-up.
Fig.l Uni-directional rovings - a loose weave with a greater number running oneway - to give greater strength in that direction
Fig.2 Glass fibre cloth - a tight weave of glass fibre which provides extra strength 3
Essentially, for low (or even single) production kit car body making we need to choose hand lay-up method. The choice of fiberglass cloth should be .010 to .015 inched thick, and with a medium open weave for good resin penetration.
Resin Resin is a type of plastic. There are many different types of resins, such as the polyesters, the epoxies, the ureas, the acrylics and the phenolics. For kit cars, polyester is resin of choice. Resins of polyester are a heavy liquid, weighing about nine pounds per gallon and ranging in viscosity between water thin and molasses thick (measured from 100 eps to 70,000 eps). For kit cars use resin with thickness around 700 eps is recommended. At this thickness, the resin flows well and can thoroughly wet fiberglass cloth. When thicker resin is desirable to work on vertical or overhead applications, a thickening material- Thixotropic powder can be added. Polyester resin harden into different levels of flexibility, from very rigid to very flexible, and the more flexible type of resins can resist crack and impact better. A modestly rigid polyester is recommended for its being easy to work with and good sdffness.
Resin cures or harden as a binder with fiberglass filaments as the core strength material. For resin to harden, it must have a catalyst added and then heated to 200 F. for approximately two hours. However, if the heat is not added, the combination of resin and catalyst can last for several days before the catalyst begins to 4
cause internal heat and subsequent hardening. This chemical heat, called exothermic, will turn the liquid into a solid form. Exothermic heat cures the resin just as the external heat will, but at a much slower rate- far too slow for the kit car body building. Since a big heating oven is not possible, and long natural curing time is not acceptable, an accelerator is added. This accelerator serves to boost the catalyst causing the exothermic heat to intensify. The resin will harden much faster in a large mass (due to the exothermic heat involved) than when spread thin. Therefore resin must be mixed in relatively small batches to avoid unnecessary waste. The most common resin/catalyst/accelerator formula calls for about 2 % catalyst and accelerator by weight.
Room temperature has an effect on curing time, with the time speeding up on a hot day, and slowing down on a cold day. When a bucket of pure resin is mixed with catalyst and accelerator at the 2 % basis, it will start to set in about 40 mins. and cure completely in two hours at 70 F. Using this as a reference, the builder can vary his formula to suit his particular conditions.
The strongest combination of resin and fiberglass is about less than 50 % resin by weight. The resin used in lay-up is air-inhibited because it never fully cures in the presence of air. It stays tacky to the touch and it is desirable when you are laminating several layers of fiberglass. A finishing resin which is not air-inhibited is required for the final layer coat to seal off the air. The waxy surface of the
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finish resin can be wiped clean with acetone, or it can be sanded if additional fiberglassing is needed. For small repair job, you can buy a resin that works as a finish also as a laminating. Big job like a whole body using the two-step system yields the best result.
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How to Make Mock-Up and Molds « Mock-up I
f a special fiberglass body is desired, it can be made up from a
mold. This procedure is rather expensive and time consuming, but is useful when more than one body is to be made.
Fig.3 Chassis is set un wuudcn planks
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Fig.4 This buck is made of wood.
Mock-Up bases on original metal body - There must be some kind of basis for the mold, and this becomes the mock-up ( something with a shape of desired). In many cases, original metal bodies are usually used. The metal is straightened to perfect condition, or it is possible to modify the contours with plaster and bondo. This Mock-up is usually used to make female molds and these female molds then make the final body. If the mock-up is used as the male mold, the final body will be slightly larger and have rough outer body finish that requires a lot of surface preparation.
Make Female molds from Mock-Up - Make sure there is no dents or deep scratches on the mock-up, Prime the surface with a polyester primer surfacer. Note: Do not sue lacquer-based primers because the resin will melt lacquer materials. Sand the primed
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grit paper. Wax the surface with mold release wax (such as Part-All and Meguiar’s). Note: Regular car wax won’t work! Follow the instruction for the release wax you buy. Wax three to six times and make sure no spot is missed.
Next, spray on two or three very light coats of PVA (poly vinyle acetate) over the wax area. This will ensure the mold not to stick to the part we want to make. Spray two or three heave coats of gel coat onto the mock-up. Gel coat is a smooth, paint like material which will form the smooth inside of the mold and become the surface of the female mold we want to make.
Now, lay-up the first pre-cut pieces of the three-quarter-ounce mat over the resin-coated surface. This first layer is the cosmetic layer, which must be smooth and thoroughly free of bubbles. Use roller to roll the bubbles out. Lay-up second and third layers using one-and -a-half-ounce mat. Total of three layers is strong enough for a mold that is intended for use only a few times ( Note: a production mold which will be used to make 50 or more copies should be about a quarter to half-inch thick).
Reinforce the fiberglass with wood frame (see Stiffen the fiberglass ...). This reinforcement serves two major purposes: 1) The mold won’t distort over time. 2) This framework will serve as a solid base, which will prevent the mold from rolling around while you are working with it.
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Use sharp putty knife and wooden wedges to help in removing the mold. Now, you have completed the female mold!
Make Bodies - Making the fiberglass body will follow nearly the same procedure in lay-up as in making the mold. Wax the mold with parting agent. Spray two or three heavy coats of gel coat onto the mock-up. About one ounce of gel coat is required to cover one square foot area. The fiberglass fabric to be used in the body or parts lay-up will be an open square weave, of about 8 ounces per square foot. Laminating with layers of cloth alone would produce a rather flexible body. Most kit car bodies are made of one layer of cloth, one or two layer of matte (2 ounce per square foot), and a final layer of cloth. In this sandwich, the cloth provides the strength and the matte serves as bulk.
Fig.5 The sequence of lamination in a fiberglass body
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Parting Flanges - A full body will not normally pull form a muck-up. Parting flanges are places so that the mold can be taken apart and removed from the initial mock-up. Parting flanges made of plywood or metal must be made to fit the mock-up precisely, before each section of female mold is fiberglassed in place.
Fig.6 Parting fringes made of plywood need to be fit to the mock-up
Add Substructure - More bulk can make fiberglass body more rigid. The extra laminations are add to areas need to stiffen the body. Metal pieces or wood can be laminated to fiberglass to reinforce the stress concentrated areas. Laying fiberglass over a length of pvc pipe or garden hose to the inner face of body works
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or honeycomb can be used under a hood, doors and a deck lid as core material with fiberglass overlaid to form sandwich structure. The sandwich makes body panels strong and light and also serves as good sound insulation. These substructure should be added while the body is still in female mold. Fiberglass can not be bolted directly without a attached substructure because the bolt will crush the small area around that bolt. To allow the stress to spread in large area. ( see fig....)
Fig7 Fiberglass panel is stiffened with wood, foam or extra lamination
Gluing the fiberglass - RSP is a urethane adhesive, it is mix 1:1 and will set in about three minutes, it glues two materials together with or without pressure. This glue has the viscosity like water, but it can be made into a paste by adding filler (sawdust, cement, etc.). Follow the instruction by the manufacturer. RSP should be available in your local fiberglass or plastic suppliers.
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Moldless Sandwich Method For making only one body with the least amount of material and time, fiberglass is directly lay-up on a mock-up made of foam which will be crushed and removed after the fiberglass body is cured. The foam mock-up is consisted of layers of crossecdonal foam templates glued together ( 1 to 2 inches thick) to create the desired body shape. The foam mock-up is carved and sanded to form smooth contours. When the shape is satisfactory, a coat of plaster is applied over the foam in order to form the final smooth surface. This mockup will not be used in producing female mold, instead it’s used as a disposable male mold. As a male mold, it does not produce the outside surface of the final body, therefore it does not need to be filled and sanded to achieve the perfect surface. Since this is a disposable mold, there is no need to use release wax on the mock-up There is no need to consider how the final body will pull from the mock-up because the foam mock-up will be crushed and removed. However, the outer surface of the final body will tend to have rough outer body finish that requires a lot of surface preparation.
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Step One - Trace the outside line on tracing paper with a centerline, and cut off foam board using the paper as templates. The body contour can be a totally new design or can be taken from a small model, enlarged to one-one scale.
Step Two - A mock-up is created by gluing these foam contours together with all centerlines aligned on one straight line.
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Step Three - The foam mock-up is carved and sanded to form smooth contours. Fill the dents and fix the shapes with plaster as necessary.
Step Four - Lay-up fiberglass with one layer of cloth, one or two layer of matte, and a final layer of cloth. Spray a thick coat of gel coat on the final layer.
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Step Five - After the fiberglass is cured, crush the remove the foam mock-up underneath. Sand off remaining foam and plaster on the inside surface. Add substructures as needed and coat the inside surface with finish resin.
Step Six - Mount the fiberglass body on the chassis. Cut off doors, hood, windows and etc. Mount doors and hood with hinges. Prepare the surface for final finish.
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How to Copy The Original Car Body Use an original car as a mock-up without ruining its paint job. Few years ago, in many cities, for about $300 to $400 a day you can rent a Ferrari or a Lambourghini of your dream. While many rented the dream cars for the thrill of once in the life time, many borrowed the original cars to make body copies. Nowadays, it’s much harder to find a place to rent those exotic cars. Anyway, if you can get hold of one you like and want to make a female mold out of it, you will find the female mold making method described previously impossible. Obviously, you need to preserve the car in its original shape (so you can return the car as if nothing has happened to it). In this method, paper and white glue are used to substitute fiberglass and resin to make the female mold.
Fig.9 Paper and glue are used to make female mold
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Wax the entire car including glasses with mold release wax (such as Part-All and Meguiar’s). Note: Regular car wax won’t work! Follow the instruction for the release wax you buy. Do not use gel coat. Lay-up the pre-cut pieces of paper (newspaper, cotton paper or any paper that contains a lot of fiber and able to be soaked in water easily). Paper glue such as the white glue need to be diluted with water so it can be applied with a brush. Laminate the paper and glue to a thickness of about a quarter of a inch.
After the paper mold becomes really dry, which may take a few days, reinforce the paper mold with two layers of fiberglass and add wood frames. Release the mold from the original body. Now you have completed the paper female mold.
The inside surface of paper female mold is not as smooth nor as strong as gel coated fiberglass mold. Therefore it can only be used once to produce a mock-up. This mock-up will again produce the fiberglass female mold, and which makes the final body.
Make Mock-Up From Paper Mold - Prime the inside surface with a polyester primer surfacer. Note: Do not sue lacquer-based primers because the resin will melt lacquer materials. Wax the surface with mold release wax (such as Part-All and Meguiar’s). Note: Regular car wax won’t work! Follow the instruction for the release wax you buy. Spray two or three heave coats of gel coat onto the mock-up. Gel coat is a smooth, paint like material which will form the smooth
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inside of the mold and become the surface of the female mold we want to make.
Now, lay-up the first pre-cut pieces of the three-quarter-ounce mat over the resin-coated surface. This first layer is the cosmetic layer, which must be smooth and thoroughly free of bubbles. Use roller to roll the bubbles out. Lay-up second and third layers using one-and -a-half-ounce mat. Total of three layers is strong enough for a mold that is intended for use only once or a few times. The mock-up made from paper mold require a complete surface preparation before it can be used to make female mold.
Make Female Molds from Mock-Up - Make sure there is no dents or deep scratches on the mock-up, Prime the surface with a polyester primer surfacer. Sand the primed surface with 400-grit paper. Wax the surface with mold release wax (such as Part-All and Meguiar’s). Wax three to six times and make sure no spot is missed. Next, spray on two or three very light coats of PVA (poly vinyle acetate) over the wax area. This will ensure the mold not to stick to the part we want to make. Spray two or three heave coats of gel coat onto the mock-up. Gel coat is a smooth, paint like material which will form the smooth inside of the mold and become the surface of the female mold we want to make.
Now, lay-up the first pre-cut pieces of the three-quarter-ounce mat over the resin-coated surface. This first layer is the cosmetic
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layer, which must be smooth and thoroughly free of bubbles. Use roller to roll the bubbles out. Lay-up second and third layers using one-and -a-half-ounce mat. Total of three layers is strong enough for a mold that is intended for use only a few times. ( Note: a production mold which will be used to make 50 or more copies should be about a quarter to half-inch thick) Reinforce the fiberglass with wood frame (see Stiffen the fiberglass ...). This reinforcement serves two major purposes: 1) The mold won’t distort over time. 2) This framework will serve as a solid base, which will prevent the mold from rolling around while you are working with it.
Use sharp putty knife and wooden wedges to help in removing the mold. Now, you have completed the female mold!
Make Bodies - Making the fiberglass body will follow nearly the same procedure in lay-up as in making the mold. Wax the mold with parting agent. Spray two or three heave coats of gel coat onto the mock-up. About one ounce of gel coat is required to cover one square foot area. The fiberglass fabric to be used in the body or parts lay-up will be an open square weave, of about 8 ounces per square foot. Laminating with layers of cloth alone would produce a rather flexible body. Most kit car bodies are made of one layer of cloth, one or two layer of matte (2 ounce per square foot), and a final layer of cloth. In this sandwich, the cloth provides the strength and the matte serves as bulk.
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How to Copy The Body Kits
The body kits you purchase may be one large piece or several pieces. They are usually not rigid enough to make accurate female molds. Therefore these body or body pieces need to be pre-mounted on the car chassis.
Fig. 10 F-40 body kits pre-mount to a chassis
Once the mock-up is set up, apply release-wax on the gel cost surface. Wax three to six times and make sure no spot is missed. Wax three to six times and make sure no spot is missed. Spray two or three heave coats of gel coat onto the mock-up. Gel coat is a smooth, paint like material which will form the smooth inside of the mold and become the surface of the female mold we wan i to make.
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Now, lay-up the first pre-cut pieces of the three-quarter-ounce mat over the resin-coated surface. Tins first- layer is Lhe cosmetic layer, which must be smooth and thoroughly free of bubbles. Use roller to roll the bubbles out. Lay-up second and third layers using one-and -a-half-ounce mat. Total of three layers is strong enough for a mold that is intended for use only a few times. ( Note: a production mold which will be used to make 50 or more copies should be about a quarter to half-inch thick)
Reinforce the fiberglass with wood frame (see Stiffen the fiberglass ...). This reinforcement serves two major purposes: 1) The mold won’t distort over time. 2) This framework will serve as a solid base, which will prevent the mold from rolling around while you are working with it.
Use sharp putty knife and wooden wedges to help in removing the mold. Now, you have completed the female mold!
Fig. 11 Finished one-piece fiberglass body
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Finishing and Painting Fiberglass After all the bodywork is complete, a sparkling paint job will make the difference between an ordinary-looking car and a prime show-stopper. A good paint job requires time consuming body preparation. The secret is in the body filler and sanding.
Grind Seams - A fiberglass body just came out of mold has a lot moid release seams on the surface. These seams must be removed by grinding with a soft pad and 9-inch round, 40 grit disc paper. The soft pad will conform to the rounded shapes and contours of the body. Do not grind through the gel coat, exposit the fiberglass strands.
Apply Filler- After all the seams are smoothed out, wipe off all the dust. Use body fillers for fiberglass body, such as Tack Free from Fiberglass Evercoat ( this gives better result than Bondo which is good for metal body). Apply filler with a plastic spreader over areas as needed. 23
File Filler - As the filler become harden and before it completely cures, file over the filler with a Surform blade (most pro bodyman use a 8- to 10-inch curved Surform blade). Rather than pouching the file, use it in a drawing or pulling fashion for greater control. Carefully level the entire area just filled with your hand to find the high spots and shave them down.
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Block Sanding - This sanding will assure you that the surface will be smooth as well as level. The desired effect is to crosshatch the entire surface of the filler until it is level. Different body panels require different tools. A rounded, convex surface requires a 6-inch block, while a half-round block is needed for a concave one. For flat panels use a long board, and all edges should be finished with a 6-inch block.
Hand Sanding - Use 40-grit paper lor initial sanding because it’s coarse and quickly removes high spots for better contouring of the panels. Then, repeat the process with 80-grit paper.
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Spray Primer - Wipe the panel clean before spraying. For fiberglass surfaces, a catalyzed primer with sealer is preferred. First, spotspray the filled areas, apply three coat s of primer to these sections. Allow time for flash-off between each coat. Flash-off is the time required for the thinner to dry, leaving the surface tack-free (not sticky to the touch). After completing this priming phase, allow the body to dry overnight. Continue block sanding the entire body until no shiny spots remain. Next, hand sand the entire body with 120grit in order to remove scratches left by the 80-grit paper. Wipe off dust and apply two to three coats of catalyzed primer over the entire body, allowing it to flash between applications. Again, allow it to dry overnight.
Spray Guide Coat - Of all the tricks used by professionals to achieve the perfect panel, the guide coat is probably the best. However, it requires patience and the desire to achieve a perfect panel. Guide coat is a light, speckled layer of primer. When the guide coat is dry, gently block the panel with a long-board fitted with 220grit paper. This will quickly reveal the high spots because the guidecoat is sanded away, leaving only the primer. Conversely, paint will remain in the low spots. Continue block sanding until all of the guide coat is removed. If any low spots remain, build them up with additional primer, putty or, if the low spot is excessive, filler. Repeat the guide-coat, sanding and filling processes until there are no high or low spots.
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Wet Sanding - Use 400-grit paper and wet sand with a block. Wet sanding makes the job easier, reducing the amount of dust, and achieves a more paintable surface. You may want to spray a staticresistant coating because fiberglass body tends to build up static electricity. Prior to spray the topcoat of paint, the body should be blown off in every little corner to remove all dust and primer residue. Then, carefully wipe the entire body with a damp, lint-free towel. Mask off all surface that will not be painted.
Paint - There are three type of paint; urethane, lacquer, and enamel. Lacquer is more forgiving but requires many coats. Enamel required fewer coats yet dries slowly. Urethane is the most scratch-resistant and durable, with a better gloss than enamel, but it is more toxic and costs more. While painting, start with a light base coat, and then add two or three heavier coats with an even, sweeping motion. Be sure to follow the manufacturer’s instructions on drying time between coats. After adding the color coats, you can immediately apply the clear coats. Allow the paint to cure prior to color-sanding and buffing. Wet-sand with 1000-grit, and then once more with 2000grit. For buffing, use a super heavy-duty rubbing compound with a wool pad, then use a micro-finishing compound with a final-finish pad. Shine the finish with a bit of glaze or wax, and you are done.
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FIBERBODY DESIGN, INC. P.O. Box 741195 Houston, TX 77274 First printed in 1995 Copyright by David Hollmann 1995
