fiberglass building techniques

FIBERGLASS BODY BUILDING

AND

“COPY” TECHNIQUES

By David Tlollmann

1

FIBERGLASS BODY BUILDINGAND

“COPY” TECHNIQUES

2 Materials and Working TechniquesSelection of fiberglass and resin.

7 How to Make Mock-Up and MoldsMock-up based on the original metal bodyParting flanges and substructures

13 Moldless Sandwich MethodBuild a body without a mold

17 How to Copy The Original Car BodyMold the original body without ruining the paint work.

21 How to Copy The Body Kits

23 Finishing and Painting Fiberglass

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.

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Fig.l Uni-directional rovings - a loose weave with a greaternumber running oneway - to give greater strength in thatdirection

Fig.2 Glass fibre cloth - a tight weave of glass fibre whichprovides extra strength

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

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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.

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Fig.3 Chassis is set un wuudcn planks

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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Fig.4 This buck is made of wood.

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.

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Fig.5 The sequence of lamination in a fiberglass body

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.

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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

Fig.6 Parting fringes made of plywood need to be fit to the mock-up

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....)

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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.

Fig7 Fiberglass panel is stiffened with wood, foam or extralamination

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 mock-

up 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.

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Step Two - A mock-up is created by gluing these foam contours

together with all centerlines aligned on one straight line.

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.

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Fig.9 Paper and glue are used to make female mold

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.



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want to make.






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.




want to make.



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for a mold that is intended for use only a few times. ( Note: a


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.



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.

20

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.

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.




wan i to make.

21

Fig. 10 F-40 body kits pre-mount to a chassis


mat over the resin-coated surface. Tins first- layer is Lhe cosmetic




for a mold that is intended for use only a few times. ( Note: a


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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Fig. 11 Finished one-piece fiberglass body

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.

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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.

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.

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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.

Spray Primer - Wipe the panel clean before spraying. For fiberglass

surfaces, a catalyzed primer with sealer is preferred. First, spot-

spray 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 120-

grit 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 220-

grit paper. This will quickly reveal the high spots because the guide-

coat 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 static-

resistant 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 2000-

grit. 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 741195Houston, TX 77274

First printed in 1995

Copyright by David Hollmann 1995

fiberglass building techniques

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