Fiberglass is a very versatile material for molding custom auto interior components. It can be sculpted to any shape, and molded or finished in any color or design you choose. Fiberglass is typically used to mold custom speaker enclosures for upgraded car sound systems, but it can also be used to make backseat center consoles, video monitor enclosures or even custom-shaped backseats.
Remove any interior components, carpeting, etc. that will be replaced with the fiberglass structure. Measure the dimensions of the space where you will install the fiberglass piece, making note of any unmovable structures the fiberglass must accommodate (e.g. wheel wells).
Draw the dimensions of the fiberglass piece onto the foam block. Also draw in the outlines of any general contours you'd like the piece to have.
Rough out the shape on the foam block, using a large knife such as a box cutter. Then use a smaller knife to sculpt any detailed shapes you'd like on the finished piece.
Trace the shapes of any openings you will need in the fiberglass piece (for speakers, control panels, cup holders, etc.) onto the foam. Carve indentations into the foam that are at least as deep as the element you'll be installing into the finished piece.
Place the sculpted mold in place in the car to check for fit. Remember that the final fiberglass shape will be 1/8 to 1/4 wider than the foam model. Make any adjustments necessary.
Prepare the foam mold by spraying it with clear acrylic sealer and allowing it to dry. Then apply a liberal coat of wax mold release, using a cloth to smooth the wax and buff it to a sheen. Finally, use a cloth to apply a coat of liquid mold release.
Mix the two-part epoxy according to the manufacturer's directions. Using a paint roller and pan, apply a coat of epoxy to the foam model. Do not apply epoxy to areas that will not be fiberglassed. Allow the epoxy to completely cure, as per the manufacturer's instructions.
Mix another batch of two-part epoxy in a clean bucket. Dip pieces of fiberglass batting into the epoxy and spread them on the model, trying to keep all of the batting running in the same direction. Do not place batting over openings that will hold installed components. Using a paint roller and pan, apply another layer of epoxy over the batting. Allow the epoxy to cure.
Place additional layers of batting over the first, following the same procedure, until the fiberglass is as thick as you want it to be.
Apply a smooth layer of fiberglass-filled putty over the top of the fiberglass shape, using a putty knife. Mix fiberglass colorant into this putty, if desired, before puttying. Allow putty to cure according to the manufacturer's directions.
Sand the top layer of the shape smooth, and buff with a portable buffer. Remove the fiberglass from the foam model.
