Who's talking about epoxy?? what I understood was that we were discussing gel coating of a "polyester" FRP catamaran, nothing to do with epoxy, vynalester, or phenolic resins, acrylics, eurathanes, propolins, ethylines or any other of the vast array of so called "plastics" Mind you if you want to get really technical and "stuff up" some one who asked for simple advice for a non "professional" on the way to repair his cat by diverging, then yes. certain substances mixed with resin or gel coat DO have an effect on their gel times over straight resin and or gel cvoat, ie if aluminum tri hydrate is added, as a filler, or as a fire retardent then the effect on gel times is radically different, also if you add a product called "sealite" (a trade name) which is actually powdered "marble", (used for pour moulded vanity tops etc,) to have a finished effect undetectable by the general public from actual marble when done well, also changes the gel time ratios. But that is not relevent to any thing that was wanted on this original posting, simply why did his attempts at repair to the bottoms of his hulls fail and help in how to rectify the problem, Not a complete discourse on the FRP industry.