I have a polyester/ glass laminated part (gelcoat on one side) and I
need to repair a hole in it. In the past, Ive sanded the
glass/polyester, cleaned it up with acetone and then used west epoxy and
"boat tape" glass. The polyester part is about 4 years old.

This works reasonably well but the bond doesnt seem as good as the
original polyster glass to glass laminations or if I were bonding epoxy
to epoxy.

Any suggestions on a really strong way to fix holes in polyester
laminated structures or improvements on what Im already doing would be
appreciated.

Regards,

wh

hypothecated on driving over rocks, you would do better to study
the charts.

Well, I did GET the hole by "driving" over a big rock land sailing... I was
hoping the rock might take the damage next time.

When I patched a 3" thru hull hole on my 3/8" thick HR28 hull,
all polyester glass, I used a 'feathered' polyglass patch and
could not see it after it was done. I cannot imagine the bond
failing, I tried to dig at it with an awl, etc. There is no way
I would not use epoxy to repair polyester, because from then on
you would need to cover it with epoxy. It would complicate even
bottom painting. Grind out all the epoxy, rough sand, clean with
acetone and restore it to like new with like material.

Don't think about it too much. Do it like the pros do. Feather
the edges inside and out, and learn how to mix and glop
polyglass.

If you are worried to the point of doing engineering studies
hypothecated on driving over rocks, you would do better to study
the charts.

Opinions, opinions, ever'body gots opinions.

Terry K

Walt wrote:

I have a polyester/ glass laminated part (gelcoat on one side) and I
need to repair a hole in it. In the past, Ive sanded the
glass/polyester, cleaned it up with acetone and then used west epoxy and
"boat tape" glass. The polyester part is about 4 years old.

This works reasonably well but the bond doesnt seem as good as the
original polyster glass to glass laminations or if I were bonding epoxy
to epoxy.

Any suggestions on a really strong way to fix holes in polyester
laminated structures or improvements on what Im already doing would be
appreciated.

Regards,

wh

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Walt ) writes:

hypothecated on driving over rocks, you would do better to study
the charts.

Well, I did GET the hole by "driving" over a big rock land sailing... I was
hoping the rock might take the damage next time.


perhaps if you glass the rock the boat will slide over.

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Best bond is with epoxy, rock or hull.

Ron

Ron Thornton ) writes:
Best bond is with epoxy, rock or hull.

not if "best" is "the lowest cost bond which satisfies the requirement".

to prove the hypotheisis that epoxy is the best resin to glass a rock so a
boat will glide over it you have to perfrom a controlled experiment with
sufficient replications to be statistically significant. my money would be
the polyester as the lowest cost bond which would meet the requirement.



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Ron Thornton ) writes:
William,

What part of "best bond" didn't you understand or are you just trying to
start an argument.

its an old argument. "best" is not "best" when it costs more than needed
to do the job. there are lots of ways of saying it, like using a cannon
to kill a fly.

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William,

There is no argument in the context of this thread. Walt already has
done the repair with epoxy so cost is not a consideration. He seemed to
be asking if polyester would be better. I say no way.

Epoxy is best because its bonding abilities are well documented compared
to polyester. To prove that polyester is good enough for coating a rock
(or any one time repair) requires a guess or some testing. Neither
approach is worth the risk of using an inferior materal because of the
cost difference between E and P for the normal repair jobs we discuss
here.

Ron

(Ron Thornton) wrote in message ...
William,

There is no argument in the context of this thread. Walt already has
done the repair with epoxy so cost is not a consideration. He seemed to
be asking if polyester would be better. I say no way.

Epoxy is best because its bonding abilities are well documented compared
to polyester. To prove that polyester is good enough for coating a rock
(or any one time repair) requires a guess or some testing. Neither
approach is worth the risk of using an inferior materal because of the
cost difference between E and P for the normal repair jobs we discuss
here.

Ron

Ron,... Hey, I wuz just having a little fun with William when I
mentioned the rock, and btw, I have done the tests and you might be
surprised at the result... a lot has to do with the color of the
rock!...
Sorry, I did not mean to start a fuss.
Scotty, going back to my rocks...

"best" is not "best" when it costs more than needed
to do the job

Yea, that was my protocol in early years of boat ownership. Now, if
the materials cost isn't significant compared to the labor and hassle
effort, I always buy the "best" stuff at whatever I'm trying to do,
which would be bond strength if fixing hull holes. Also go for
user-friendly; epoxy doesn't give off fumes when polimerizing. Now,
if i needed a hundred gallons of resin for a job, I'd look close at
whether polyester resin would suffice.