I have found that if the stiffer polyester resin is used on epoxy resin
and there is flexing of the material, the polyester resin will crack and
pull loose. I have installed several grunch plates on ABS canoes and
epoxy resin is what comes with the kits. I have made my own strips from
kevlar and the only problem that I have is when I hit rocks over a long
period of time, I have to re-apply material to the spot that gets the
most wear. My Sunburst II is 12 years old and has done many a
whiterwater trip in Tennessee and I have had to repair my front grunch
plate twice.

I have repaired several fiberglass canoes over the years and I have
found that epoxy resin does the best job for repairs. If the repair is
very large then I will use the resin that the boat is made of so as to
maintain the rigidity that was originally there.

Lynn



Brian Nystrom wrote:
Lynn Tegrity wrote:

Polyester resin cannot be used on a boat using Epoxy resin. Epoxy
resin cures and stays flexible. Polyester resin cures and becomes much
stiffer. The resin that you buy at a auto supply house will be
polyester risen.


This is not exactly true. Polyester products such as gelcoat can be
applied successfully over fully cured epoxy that has been cleaned to
remove any amine blush. I do this all the time on repairs and have never
had any adhesion problems.

IMO, epoxy should be used for repairs and other bonding applications,
since it creates a stronger bond than polyester resin will. For
sacrificial layers such as keel strips, either will work, but epoxy is
more abrasion resistant.