Hi,

I'm doing some repairs to my Catalina 36, which is made from polyester
resin/glass over wood (like most "fibreglass" boats). Should I stick with poly
resin, or go with epoxy? I know epoxy is "better", but I'm concerned that it
wouldn't stick well to the existing poly, and that the (poly?) gelcoat won't
stick to it.

Suggestions?

Lloyd Sumpter
"Far Cove" Catalina 36

Secondary bonds with polyester are not strong. Sand thoroughly and use epoxy.

Whoever's compiling the FAQ, add this one.

Lloyd Sumpter wrote:

Hi,

I'm doing some repairs to my Catalina 36, which is made from polyester
resin/glass over wood (like most "fibreglass" boats). Should I stick with poly
resin, or go with epoxy? I know epoxy is "better", but I'm concerned that it
wouldn't stick well to the existing poly, and that the (poly?) gelcoat won't
stick to it.

Suggestions?

Lloyd Sumpter
"Far Cove" Catalina 36

Well the problem lies in the fact that the polyester gelcoat would not stick to
the epoxy.

You will have to use poly. I won't stick as well, but will have to do.

Rich

On Sun, 28 Dec 2003 20:09:18 +0000, Toolowd wrote:

Well the problem lies in the fact that the polyester gelcoat would not stick to
the epoxy.

You will have to use poly. I won't stick as well, but will have to do.

Rich

Yeah, that's it exactly.

The boat BUILDERs that I ask this question invariably recommend epoxy. The boat
REPAIRers I ask usually say "use the same material that's the If it's poly,
use poly..."

Building a boat from scratch: epoxy, no question. Repairs on FRP/gelcoat? Jury's
still out...

Lloyd

Don't use gelcoat. LPU paints weather better and are easier to work with than
gelcoat.

Toolowd wrote:

Well the problem lies in the fact that the polyester gelcoat would not stick to
the epoxy.

You will have to use poly. I won't stick as well, but will have to do.

Rich

Use geloat over epoxy if you care to do so. You just have to do a lighg
sand on the epoxy so there is some tooth there. You have to do the same
with polyester or vinylester, because the cohesive bond with gelcoat
(which is also polyester) is poor (lust like any other polyester).
The only advantage to a gelcoat finish on a repair is that it is
relatively good for a color match and as it is applied thinker than any
paint, it can be wet sanded to fair the surface.
If you were planning to paint anyway, blow off the gelcoat job.
Matt Colie

Jim Conlin wrote:
Don't use gelcoat. LPU paints weather better and are easier to work with than
gelcoat.

Toolowd wrote:


Well the problem lies in the fact that the polyester gelcoat would not stick to
the epoxy.

You will have to use poly. I won't stick as well, but will have to do.

Rich

Toolowd wrote:

Well the problem lies in the fact that the polyester gelcoat would not stick to
the epoxy.


True in most cases, but System Three make an epoxy formulated
specifically to go under polyester. I've used it many times and never
had a failed bond.

Look at their SB112 epoxy resin.

http://www.systemthree.com

Definitely use epoxy for the repairs.

Brian Cleverly

You will have to use poly. I won't stick as well, but will have to do.

Rich

I watched a video on boat repair recently in which polyester and gelcoat
were used to repair a crack in a polyester boat below the waterline. The
inside of the hull was sanded down and 2 layers of mat applied. Then
the finish on the outside was sanded, then some putty filler followed by
gelcoat were put on with lots of sanding with different grits at each stage.

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Toolowd wrote:
Well the problem lies in the fact that the polyester gelcoat would not stick to
the epoxy.

You will have to use poly. I won't stick as well, but will have to do.

Gelcoat is purely cosmetic and I'm far more concerned with the strength
of the underlying repair, so epoxy gets the nod for that. I've applied
gelcoat over epoxy repairs and it works fine as long as you sand the
epoxy surface.

--
Regards

Brian

On Mon, 29 Dec 2003 03:58:11 +0000, William R. Watt wrote:

I watched a video on boat repair recently in which polyester and gelcoat were
used to repair a crack in a polyester boat below the waterline. The inside of
the hull was sanded down and 2 layers of mat applied. Then the finish on the
outside was sanded, then some putty filler followed by gelcoat were put on with
lots of sanding with different grits at each stage.


Yup - that's the way I was taught.

Lloyd