: This is a little bit off subject, but I'll ask anyway. I don't think I'll
: have enough MAS epoxy to do the fill coats on my yak, but I have enough to
: do all the fiberglassing. I have a supply of WEST that I can use, not a
: lot, but at least half a gallon. Is it OK to use WEST as a filler if I
: wait a while and scrub, then sand very lightly to create a mech bond? I
: have a while to think about it, but thought I would ask. If need be, I can
: buy more MAS epoxy.

Generally speaking, once a coat of epoxy resin, or polyester resin, has completely cured it is now a solid piece of plastic. If you scrub off anything that may have settled on the surface-- be it byproducts from the polymerization reaction, wax, mold release agents or droppings from the birds nesting in the rafters over your work area-- you should have a reasonably inert surface to work with. Sanding to give the surface some "tooth" should make it possible to glue to it, or cover the surface with an application of epoxy resin.

If you need to fill the weave in your glass, the texture may cause you problems. You are going to have a hard time sanding the first layer smooth, or cleaning off any accumulated scum. Perhaps you might want to just glass and fill the weave on a small area with one brand, and then use the other brand for glassing a different area. You could do the left half with one resin. Let it harden and then sand a tapered edge so you could feather, or overlap the glass from glassing the right side, which you would do with your other brand.

It would not be my preferred way of doing things, but working in this manner might be a way to use the materials you have with the least problems.

Hope this helps

PGJ