OK, so polyester resin is not optimal, I understand it isn't really waterproof and has other drawbacks. But can it be used to reduce cost? Epoxy is pretty spendy, normal "fiberglass" resin is pretty cheap.
My thought is about using the polyester for under layers, initial wood soak, between 3/8 ply layers, between transom layers, some above deck use, and using epoxy for all outer layers or where strength is needed.
I recently built new floor boards for an inflatable, had a lot of polyester resin around so I used that. Thinned with acetone it soaks into the plywood real well... cheap fix. of course, there is no strength needed, nor is a real waterproof situation needed, just a real good water resistance in this case. The thinned polyester soaks in a long way, so a deep gouge in the floor still will not readily allow water penetration. I have not had epoxy soak so deeply.
On a completely unrelated side note: I have a lot of this resin I need to use up. I was going to do my garage floor with epoxy, but I spilled some of the thinned polyester resin on the floor. It seems to show that putting polyester resin on the concrete floor will make for a very nice sweepable surface, oil resistant, and cheap! So I'm going to apply it to the entire floor and use my floor for a test bed. I can always rough it up and go over it with the originally intended floor epoxy in the future when I want to spend a lot more money.
