If you're looking to design and build new body parts for your auto, fiberglass can be the simplest way to do it. When fiberglass parts are built right, using multiple layers of the glass sheets coated in laminate resin, they are sturdy replacements to their steel counterparts. Fiberglass can be used to construct new body panels or bumpers, enclosures for things like subwoofer speakers, or stylish spoilers for mounting on the hood or trunk.
Measure the area on the vehicle where the part will be attached. Take down the dimensions of the auto's stock bumpers, fenders, hood and trunk. Even if you're not replacing an actual body part, you still need these measurements for parts you'll mount onto the car, like side panels or a spoiler.
Design the body part's look, shape and dimensions. Draw and sketch out your designs on paper. Convert these drawings to visual 3D animation if you have animation software on your computer. Write down the exact dimensions and measurements, making sure they fit with the auto measurements you took earlier.
Create a mold for the body parts out of urethane foam. Cut the large foam blocks into the body part's shape. To help get the mold to its correct size, make the cut bigger than is should be and whittle or sand it down to the shape the fiberglass will be placed on.
Wrap aluminum foil all around the mold, making sure it's wrapped tightly. You can spray adhesive onto the foam so the foil will stick. Apply non-stick cooking spray to the foil's outside so the fiberglass won't stick.
Lay a sheet of fiberglass over the outside of the mold if you're making an actual body part. For a part you're mounting onto another part, cover the entire mold in fiberglass. Apply a coat of laminate resin to the fiberglass sheet and wait for it to dry.
Remove the fiberglass from the mold if it's not completely wrapped around it. Use extreme caution when removing it, as one fiberglass sheet by itself is very fragile.
Reinforce the body part with more fiberglass sheets, applying more laminate resin to the surface and laying another sheet onto it. For a part where you removed the mold, apply the extra fiberglass to the part's inside, adding as many sheets as you think is needed. For a part where the mold is completely wrapped, add a couple of more sheets along the entire outer surface.
Smooth out each fiberglass sheet as you apply it to make sure there are no air bubbles. A hand roller will help you do this.
Paint and detail the body part once it's finished. Apply primer to the entire surface before the actual paint itself, then apply multiple coats of the paint in even, level strokes. Once the paint is dry, the part is ready to be attached to the auto.
