Quote:
Originally Posted by RobertSmalls
Coroplast can be bent. You can score it with a razor blade and make bends. But there really is no easy way to make round features.
I've been carving pink polystyrene insulation foam to make single-use molds for fiberglass + epoxy resin. Polyester resin eats styrofoam. Fiberglass works great for me. It should be possible to make professional-looking parts with it, but I've mostly stopped short of doing that. You can get a smooth finish and paint it with automotive paint, but mine is somewhat wavy.
I haven't used foam core board, but I'm sure it would be easy to lay up a sheet of fiberglass over it to make a more durable part that holds its shape well.
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An idea that may be useful to you comes from Alex Strojnik, designer of the S-2 homebuilt sailplane.
Wanting to avoid all that sanding and filling of wing skins normally needed to make them smooth enough for laminar flow, Strojnik did fiberglass layups on flat sheets of new plexiglass on a table, so the smoothness of the plexi was imparted on the resin.
He waited until the resin cured to rubbery consistency, but not yet fully hardened, then peeled the skin section off the plexi and draped it over his wing panel, leading edge up, and used vacuum to suck and hold the still-curing but rubbery layup against the wing foam. It fully hardened in that shape, yet was still as smooth as the plexiglass upon which it had been laid at the outset. Sanding and filling was limited to narrow strips at the joints of skin panels, eliminating ~95% of that tedious chore. And, since sanding may mean sanding through the fibers which are the strength of the panel, his panels had no risk of compromised strength, since the fiberglass was not touched.
So, I'm wondering if Strojnik's partial-cure trick might work on compound 3 dimensional curves in addition to simple 2 dimensional curves like his wings.