Re: Compatibility of Epoxy and Poly
Actually the Glen-L Epoxy manual I have says that it is not really a problem and that all of their tests say go for it. However, they recommend that the Poly surface be roughed up and that they do NOT specifically recommend it as the weld is, like wood, stronger than the Poly. Their concern is that if is used structurally the Poly layers may separate and that there would be a failure of the weaker portions of the Fiberglass system . . . Here's what it says . . .
(*) NOTE: Epoxy will stick with great tenacity to properly prepared fiberglass laminates or structures (such as existing boat hulls) made from polyester resin. However, one should not count only on the epoxy in this instance where the bonded component will be subjected to stress. The reason is that the epoxy will be so strong that a failure may occur in the actual fiberglass laminate itself (as opposed to the polyester/epoxy bond interface) resulting in damage to the laminate and/or get coat. Such junctions should be mechanically fastened as well whenever possible. Fiberglass surfaces should be prepared by thorough sanding to remove any gloss, paint, dirt, oil, or grease, and left with a roughened resin surface (take care NOT to cut into the actual fiberglass reinforcement).
"http://www.glen-l.com/supplies/pxman-use.html"
