Hi there.
I have a small (14 foot) grp boat which needs some repair work done to the
hull and cuddy.
My question is which type of resin should I use for the repair - epoxy or
polyester resin?
I have a feeling epoxy is best for marine applications but just want to
check.
Please advise
Thanks
Davy M.

"David Murray" wrote in message
. uk...
Hi there.
I have a small (14 foot) grp boat which needs some repair work done
to the
hull and cuddy.
My question is which type of resin should I use for the repair -
epoxy or
polyester resin?
I have a feeling epoxy is best for marine applications but just want
to
check.
Please advise
Thanks
Davy M

Polyester is for bathtubs.

Lew

wrote

I thought polyester was for really cheap, tacky clothing?

That too.

Lew

"David Murray" wrote in message
. uk...
Hi there.
I have a small (14 foot) grp boat which needs some repair work done to the
hull and cuddy.
My question is which type of resin should I use for the repair - epoxy or
polyester resin?
I have a feeling epoxy is best for marine applications but just want to
check.
Either is fine for fabrication, but polyester won't stick very well, so it
is not a good choice for repairs.

On Wed, 12 Sep 2007 20:57:28 GMT, "David Murray"
wrote stuff
and I replied:

!st question: what sort of reapairs; fillin or gap bridging? Are you
glassing or only patching?

Polyester builds well, when mated with the glass mat (CSM...chopped
strand mat) that has the right impregnation (binder) to accept it. It
works into woven glass quite well. It does not __stick_ worth crap
(not even to a blanket)....or to old poly/glass

Be aware that epoxy is not happy with the glass mat that is used with
Poly; it does not not react with the binder that is for ployester. I
am a bit out of date, but check even for woven glass. Some were sized
with biner IIRC

Hi there.
I have a small (14 foot) grp boat which needs some repair work done to the
hull and cuddy.
My question is which type of resin should I use for the repair - epoxy or
polyester resin?
I have a feeling epoxy is best for marine applications but just want to
check.
Please advise
Thanks
Davy M.


Human bevaviour: Bestiality with a brain

Thanks for your advise folks - I guess it's epoxy then.

Davy M.

On Sep 13, 3:16 pm, "David Murray" wrote:
Thanks for your advise folks - I guess it's epoxy then.

Davy M.

Yeah, and if you use any glass cloth, mat, etc, make sure it is for
use with Epoxy, not Poly, or Vynel, etc.

On Sep 12, 4:57 pm, "David Murray" wrote:
Hi there.
I have a small (14 foot) grp boat which needs some repair work done to the
hull and cuddy.
My question is which type of resin should I use for the repair - epoxy or
polyester resin?
I have a feeling epoxy is best for marine applications but just want to
check.
Please advise
Thanks
Davy M.

Polyester will do fine. I was looking at some 20-year old Abacores
this summer at a sailing club I used to belong to when the boats were
new. These are club boats used in training and racing so they get a
lot of abuse. The polyester repairs are all holding up fine.

Unless you buy epoxy in 55 gal drums and can get it cheap. In small
lots it's still pretty expensive. about twice the cost of polyester
around here. Or if you already have some epoxy on hand you want to use
up.

Polyester is more brittle and less adhesive but it's good on a ridgid
surface which is clean and pourous, which old sanded polyester is.

Epoxy is a great waterproof glue, and the cured resin is stronger and
more flexible than polyester. Also epoxy molecules are similar to the
cellualr structure of wood so it cures right into the wood for
excellent bonding.

Polyester is easier to mix and more forgiving. If you don't mix in
enough hardener you can mix up more and spread it on and the hardener
will migrate into the uncured resin. Epoxy has to be mixed right the
first time. Some people develop an allergy to the hardener used in
epoxy and have to stop using it. Epoxy can go on over polyester, but
polyester can't go on over epoxy, so once you switch to epoxy you
can't go back to polyester where you've made repairs.

Finally, most of what you read in this newsgoup about polyester is
boatbuilder myth perpetrated in the past by sellers of epoxy desperate
to find some excuse for people to buy the more expensive resin, and
when it first came on the market is was more expensive than it is now.
It was a hard sell as anything but a great strong waterproof
adhesive.

I only use epoxy when I have to, and use polyester wherever I can.
But I do not, nor have I ever, worn a polyester leisure suit. That's
just going too far.

Wm Watt wrote:


Polyester will do fine. I was looking at some 20-year old Abacores
this summer at a sailing club I used to belong to when the boats were
new. These are club boats used in training and racing so they get a
lot of abuse. The polyester repairs are all holding up fine.

Unless you buy epoxy in 55 gal drums and can get it cheap. In small
lots it's still pretty expensive. about twice the cost of polyester
around here. Or if you already have some epoxy on hand you want to use
up.

Polyester is more brittle and less adhesive but it's good on a ridgid
surface which is clean and pourous, which old sanded polyester is.

Epoxy is a great waterproof glue, and the cured resin is stronger and
more flexible than polyester. Also epoxy molecules are similar to the
cellualr structure of wood so it cures right into the wood for
excellent bonding.

Polyester is easier to mix and more forgiving. If you don't mix in
enough hardener you can mix up more and spread it on and the hardener
will migrate into the uncured resin. Epoxy has to be mixed right the
first time. Some people develop an allergy to the hardener used in
epoxy and have to stop using it. Epoxy can go on over polyester, but
polyester can't go on over epoxy, so once you switch to epoxy you
can't go back to polyester where you've made repairs.

Finally, most of what you read in this newsgoup about polyester is
boatbuilder myth perpetrated in the past by sellers of epoxy desperate
to find some excuse for people to buy the more expensive resin, and
when it first came on the market is was more expensive than it is now.
It was a hard sell as anything but a great strong waterproof
adhesive.

I only use epoxy when I have to, and use polyester wherever I can.
But I do not, nor have I ever, worn a polyester leisure suit. That's
just going too far.



For what it's worth, I strongly disagree about the merits of polyester
mentioned here.

Great for initial build, but getting a secondary bond of eny strength
at all is problematic.

Epoxy for ALL secondayr work.

My .02
For what it's worth/

Richard

"cavelamb himself" wrote:

For what it's worth, I strongly disagree about the merits of
polyester
mentioned here.

Great for initial build, but getting a secondary bond of eny
strength
at all is problematic.

Epoxy for ALL secondayr work.

My .02
For what it's worth/


SFWIW, my observation has been that if it isn't the lowest cost crap
in the market, Watt doesn't use it.

Performance of the materials is not a criteria.

Lew