> I have access to a bunch of scrap polystyrene foam at work. (Brand
> names Dow Blue Board and OC Pink Board) I was wondering if it would
> be compatible with epoxy. I would like to shape paddle blades with
> it, mount the foam to my paddle shaft and then 'glass the whole shooting
> match.

This I'd like to see. Let us know how it works out, and send some pictures of the results. ( good or bad!)

> Has anyone tried this? Does epoxy "eat" foams?

I have heard of people building surfboards this way. and I saw an article on making model airplane parts using this technique. It works for some people, and should work for you. Why not try a small sample? Wrap a block of foam in a few square inches of thin fiberglass and brush on some resin.

> I'm also considering making forms with foam and then applying
> a release agent and trying to lay up fiberglass whitewater boatss.

Unless you can get an extremely smooth finish on your machined foam your mold will be rough. That could lead to problems. Were you perhaps thinking of lining the foam with a layer of fiberglass, and then sanding and polishing the fiberglass facing to a smooth finish? That would probably work, but check your costs. It might be cheaper, easier and faster to make a female mold from pine strips. Or, use your foam to make a ``plug'' a boat, or solid block in the shape of a boat, which you can use as a form for making a mold. You layup the 'glass on the plug to make a substantial, reinforced fiberglass mold, which can be polished and prepared for production.

Solid fiberglass boats might be heavier than wood-cored (plywood or cedar strip) models.

Happy experimenting. Paul Jacobson