Fiberglass Ice Chest and Generator Box Project

Now that you mention it, the enamel paint did just de-laminate from the surface and did not become a fluid sticky mess as it does when you apply a thinner or other solvents to enamel. I'd bet between the poor adhesion the paint had on the slick PVC surface and the fact of the PVC being somewhat impervious (which wouldn't allow the gasses to properly escape during the initial curing process (as they would on something like a wood substrate) it caused the enamel to fall off. Or maybe the actulal PVC itself reacted poorly to the gasses from the polyester and cause the de-lamination...

 

It sounds like the mold will come apart easily if the part doesn't stick to it.

Yes, that doesn't sound like a good test for finding out what will work in a mold.
In your test, did you prepare the pvc for the paint? Did you try it on a more acceptable base, like plywood or something? Did you let the paint dry well and then wax it 3-4 times? Apply any pva? Actually, I don't think even polyester resin sticks that well to pvc, it seems easy to peel off.

I always liked spray can paint or 1 part auto enamel for plugs. You could work up the surface with easily sanded and faired materials, and then the final paint appearance was what the mold or part would be like when laminated.

Trying to get a decent finish on a female (concave) surface is very difficult. You might put in a lot of time trying to do it and end up having to sand and fair and recoat the outside anyway. That's where flexibility of appearance concerns can save you an awful amount of toil and trouble.

 

Yes the PVC was primed with Bullseye sealer primer then top coated with enamel. NO I didnt try in any other areas as I was not thinking of that at the time and I just so happened to only apply it to the PVC trim area (at the top of the lip). Reason being, is that area is the top of the lip which is not part of the mold that I will be laying to and i didnt want to do risk messing up the mold surface. Hind sight I should have prepped an area on the outside of the mold to test on... which I might go back an do that. Yes, I gave the enamel 24 hrs of cure time then applied 6 coats of Meguiars Mold release wax (think its the Meguiars Mold release wax 8 2.0). I did not use any PVA as I didnt have it handy to buy locally (that I know of) and didnt have the patience to wait on ordering. Also I read that the PVA was necessary with the right amount of release wax which is why i applied the extra layers or wax.

I figured I would definately have to do some finish work on the gelcoat after pulling from the mold so I am got it as smooth as possible by spending a lot of time faring and sanding between coats.

 

Next time, do yourself a favor and build your mold with melamine, Kleen clay, and packaging tape, sprayed lightly with PVA. The molds can be built to be disassembled to strip, so acute angles, in turned lips, internal ridges etc are all possibilities. Plastic trim pieces from Lowe’s help a lot.
Quick, simple, and though it does leave you some sanding, at least it’s not inside of a female mold.
I build custom fish boxes, seat bases, storage cabinets, even some furniture this way, and can usually turn out a part in three days, if I can get it built and gel coated in a day.