Re: Fiberglass Gas Tanks
I'm very interested to see how your fiberglass tank project goes. Been looking at doing the same thing myself - I even made a styrofoam hotwire cutter to make smoother styrofoam cuts, but then I got swamped and I haven't had enough time lately even to try it out.
I'd like to use polyester resin for my tank instead of epoxy resin, because of budget limitations. I did some reading online, and I found a couple of problems with polyester resin for this application: 1) polyester resin will dissolve a styrofoam mold, and 2) gasoline with added ethanol will eventually dissolve a polyester resin gastank.
Solutions that I was considering, other than using epoxy: 1) wrap the styrofoam mold in saran wrap and mist with WD40 (as a mold releaser) to protect it from the polyester, and 2) coat the inside of the finished tank with KBS Gold tank sealer (not Kreem tank sealer, b/c Kreem's website says that it doesn't bond to fiberglass) to protect it from the gasoline.
This is all just from information I gathered online, though - the only real-world fiberglassing experience I have was helping my buddy fix a model once...