Originally Posted by FatOldGuy
Well I would not make a resin tank. I was thinking of a two part mold. I would coat the inside of the mold with layers of fiberglass. Or make a wire frame and cover it in fiberglass. That is how I make speaker boxes for cars.
The resin castings I do are mostly to make custom car models.
Come to think of it the wire model may not be a bad idea.
I made epoxy resin RC boat hulls by carving the shape from foam, epoxying it up, and the melting the foam out with MEK or acetone. Messy but not to hard to do and got a great result. Use EPOXY resin instead of fiberglass for gas tanks. (Might consider lining it with fuel resistant coating too)