Fiberglass Question : Can I use clear-coated fiberglass part as fiberglass form?

Hi all. I have a (probably) dumb question.

I bought a fiberglass cafe racer style rear fender/seat combo, and it is too small. However, the OUTSIDE dimensions of the piece I bought are the INSIDE dimensions that I actually need. The fiberglass piece I bought has been sanded, painted and clear-coated. Can I put release agent on the existing piece, and use it as a form for making my own new fiberglass piece over the top of it, and then pop the old piece out?

Thanks for your help.

You should be fine with a bunch of coats of release wax built up on the surface. If you want to be sure the new layup doesn't adhere, you can cover it in packing tape or even painters tape.


Sent from my iPhone using DO THE TON

Thanks, I sort of thought the painters' tape + release agent would work, but wasn't sure.

I made a couple of seats and things already with epoxy and never used any release agent.I always use standard packaging tape (see trough,glossy surface) and cover the surface and directly epoxy on that...never had problems with release.

If you form over the top of the piece you will end up with a mould of the piece, not a fresh piece with new outer dimensions. Read up some on fibreglass moulding. You ideally want to make a plug the exact size and shape of the piece you want in a high gloss finish, fine coat with carnuba wax and polish, fine coat of pva and then lay up the mould (assuming it can be done in one piece). Then just pop the plug out, dress and polish the mould and then lay up the part you wish to make. The beauty is you can re use the mould a thousand times and make trillions of dollars selling cafe racer parts to hipsters...... It's that simple.