Mike,

Fortunately, you got about 99% good information. Gelcoat is polyester
resin with color in it (actuate, but somewhat simplistic description).
It does not bond well to unprepared epoxy, but it (like any polyester)
doesn't bond particularly well to unprepared polyester either. This
least you with two choices - 1. sand the epoxy before appying the
gelcoat (unless you are real good, you probably will anyway) or - 2.
apply a coat of vinyl ester resin to the epoxy to be a primer for the
gelcoat. I often end up doing both.

Get and use epoxy for the repair. Get the pump set so you don't have to
worry about mix-measurement. Get the good stuff and everytime you have
think about what it is coating - think about what a boat yard would be
charging you.

Good luck

Matt Colie

Bonasa wrote:
Hi,

Once again I need to draw on the wisdom of this group hoping for an
explanation or clarification. I posted earlier regarding the repair of an
impact hole in a fiberglass sailboat hull. I'm using the Don Casey boook
"Sailboat Hull & Deck Repair" and have run into conflicting/confusing
information.

In the book, he states that epoxy resin should always be used for repair
because it creates a stronger bond than polyester resin. He then goes on to
state that the only time not to use epoxy is when using polyester gelcoat.
Okay, so far so good.

Then in the section titled "Impact Damage" which is what I'm following, the
first step in the actual repair is to lay up a piece of acrylic on the
outside of the hull and apply a 20 mil coat of gelcoat from the interior up
against the acrylic, then start laying up the fiberglass layers on top of
the gelcoat.

This is a large repair (4' long by approx 4 " h) and strength is the primary
importance to me, so it would seem epoxy is what I would want to use. But
following those directions I have to use polyester resin to have the
fiberglass adhere to the first gelcoat layer. Is there something I can use
to substitute for the gelcoat that will allow me to use epoxy? Any
suggestions? Is there some kind of paint that will have a thick enough
consistency to use on a nearly vertical surface? Using epoxy resin for the
strength is more important to me than what the finish looks like, it'll be
underwater so the cosmetic aspect doesn't matter much to me.

Thank you for any help and suggestions on how to handle this part. Also, one
person requested I keep posting the progress of this disaste....I meqan
project. I'm putting together a web site of sorts to show the progress.
www.geocities.com/lokisdad1026 if you're interested. I have little time and
no knowledge of web page design so don't expect much but maybe it'll help
someone so I'll do the best I can there.

Mike