Bonasa wrote:
This is my first shot at a fiberglass repair and it didn't go quite as
smoothly as it showed in the book. I'm stumped about what to do next and
hope someone on this group has either done the same thing or can tell me how
to fix this.

I had two good size holes in a 22' sailboat to patch. The holes are shaped
long and narrrow, cracks in the hull that I cut out and laid in epoxy resin
and fiberglass. I followed the instructions in the book by Don Casey on Deck
and Hull Repair. I worked from the inside, grinding a 12:1 bevel and laying
down increasingly larger patches of epoxy resin soaked fiberglass.

The part I screwed up is the plastic I had laid up against the hull for the
first coat of gelcoat was not reinforced well enough. When I was squeezing
the patches to get the air bubbles out I pushed too hard. Taking off the
backing the fiberglass has set up perfectly except I pushed it so some of
the fiberglass now bulges beyond the exterior of the hull itself. Naturally
the gelcoat I had applied before laying down the fiberglass just fell out.
By the way I talked to the technicians at West Systems who assured me that
the polyester resin would stick to the epoxy patch.

Now I'm not sure what to do. My first impulse is to sand (scuff) the
fiberglass down past the hull and lay on gelcoat, then sand the gelcoat
flush with the hull. Would this work or am I just ruining the patch job? I'd
rather not use paint so any suggestions that would allow me to use gelcoat
(I've already got it) would be appreciated. Thank you in advance for any
help!

If the glass and not just the resin has protruded, sanding it down will
compromize the strength of the repair, since you'll be cutting through
the glass. I hate to say it, but your best bet is probably to grind it
all out and start over. Another option would be to grind it down on the
outside and add more reinforcement on the inside. Without seeing the
sitution, it's hard to say whether that's a viable approach.

As West Systems told you, epoxy and gelcoat ARE compatible, within
certain limits. Epoxy will adhere just fine to fully cured gelcoat,
provided that the surface is clean and (preferably) sanded lightly to
give it some "tooth". Gelcoat will adhere to epoxy given the same
conditions (fully cured, clean, sanded epoxy). I've done this numerous
times on repairs that could only be accomplished from the outside.