It isn't as easy as you might think is it? Having a GRP car I thought it might be an idea to have a go, plus my youngest wants to make an airboat this year.
I picked on the tear drop panel that covers the wiper motor on the Mk3 to make a mould and used a wet lay up with polyester resin. A couple of problems with that, firstly getting the original panel out of the ruddy mould can be torturous , particularly if you only used wax as a release agent, secondly there were bubbles and folds in the fabric. Doing it all over again with some careful cutting of material yielded better results but still nothing II wanted to use.
Ok, plan B... spend some money. I bought some epoxy resin, tissue fibreglass sheet.... and a vacuum pump. I'd followed a few pumps on Ebay which had all gone for more than I was prepared to pay for an experiment. Freeads turned up an old British made laboratory pump capable of pulling a gnats gonad short of absolute vacuum for £25. With the pump comes more expense as you have to buy vacuum bagging, permeable membrane, peel ply, breathable wadding and double sided adhesive tape.
The next attempt which was my first go with vacuum consolidation which further showed up the problems with using the wax for release, the epoxy stuck like the proverbial to a blanket and some of the gelcoat ended up staying with the mould instead of on the original panel. Ok, enough of this, I'm trying to create something, not destroy what I've already got.
Luckily when the gel coat was removed form the mould the surface wasn't bad, not perfect but not bad. The next step is to use the mould to create a plug to form a final finish mould. This time I've used PVA release agent which worked far better and with only a little bit of wrestling the plug popped out of the mould. As I type this I'm taking a break from cleaning up the surface of the plug, hopefully I'll have some decent pics to put up soon.
Rich