gel coat and fiberglas

[Robb Newman]

We've got a fiberglas dingy that we put some gouges last summer. Two of them in particular go all the way through the gel coat, and the fiberglas is exposed. The fiberglas strength is in no way compromised - the gouge does not extend into the fiberglas. My initial thougth is that I can simply add gel coat to cover the gouge, then sand it smooth. However, as I read the instructions on my can of Seafit white gel coat (model 34803, a two part gel coat), it says in bold capital letters: "GEL COAT SHOULD NOT BE APPLIED OVER AN EPOXY." Here's my question: fiberglas is just glass fibers in a matrix of epoxy, so if I put gel coat in the gouge, it will be in contact with the epoxy of the fiberglas, right? What happens if you do install gel coat over epoxy? Should I put something else in the gouge first, and then gel coat over that? Or is the epoxy used to make fiberglas a different sort of material from the epoxy that the gel coat instructions refer to? Or, since it is just on my dingy, should I quit worrying and just fill the gouge with gel coat?Thanks!

 

[Been there]

Most likely, your dinghy is NOT epoxy

Fiberglass is a generic term for a laminate of glass cloth layers set in a resin. Epoxy is NOT another term for resin, but names a particular chemical category of resins.The most common (and least expensive) resin is polyester. 99% of all fiberglass boats afloat are made with polyester resin. Vinylester resin is more expensive, but has the advantage that it is less permeable to water. Some boat builders have started using it in the outer laminates, to reduce blistering. Epoxy resin is even more expensive, less permeable, mechanically stronger, and creates strong secondary bonds. The latter is the reason it is used when adding to the glasswork of an existing boat. Polyester resin does not bond well to a polyester laminate that has already set. Epoxy is commonly used by home builders.If your dinghy was a production boat, almost certainly it was made with polyester resin, NOT epoxy. On the other hand, it is quite likely that any repairs to it have been made with epoxy resin.

 

[Bill Colombo]

Gel Coat and Epoxy

I agree with "Been There" that your dinghy is most likely not built using epoxy resin. Epoxy matrix construction usually has an epoxy top coat. If so it would not need gel coat at all. I would suggest testing a small scratch first to check the adhesion. You might also try getting in touch with the manufacturer to make sure.Good Luck! Bill C., Doyle SFGood L