Re: [bolger] Polyester vs Epoxy??
Most builders will accept the hysteria of the "experts" and NEVER us poly
and ALWAYS use epoxy. However I think there are more considerations to be
made. If there is a process to ensure a better bond to wood with poly,
then, why not. because some of the early hull glassing done with poly was
not as successful, the boating community has accepted the stronger bonding
epoxy as the standard bearer. However, many poly jobs are still going strong
after much abuse. I think that the poor experiences were the result of a
poor job. Then, there is the reasoning that poly is NOT waterproof. That is
relatively true so, why not use a barrier paint over it? Dynamite Payson, a
man of no little experience, uses poly to wrap his hulls. Yes, many of them
are dry sailed and not subject to the constant pressure of full time
submersion but he would not be cavalier with his construction when it means
so much to his reputation and subsequent livelihood. Some people reserve
epoxy for the gluing only and don't even glass the hull at all. Maybe epoxy
below the waterline is a safe compromise.
For my money, If I were to construct a plywood hull on a large hole in the
water, in which I was to sail the briney deep, I might epoxy -encapsulate
with fiberglas the hull below the WL and epoxy above. OR I might just use a
good house paint above. I would rather be on the water at a cost I could
live with rather than become a curator of a museum piece anyway.
and ALWAYS use epoxy. However I think there are more considerations to be
made. If there is a process to ensure a better bond to wood with poly,
then, why not. because some of the early hull glassing done with poly was
not as successful, the boating community has accepted the stronger bonding
epoxy as the standard bearer. However, many poly jobs are still going strong
after much abuse. I think that the poor experiences were the result of a
poor job. Then, there is the reasoning that poly is NOT waterproof. That is
relatively true so, why not use a barrier paint over it? Dynamite Payson, a
man of no little experience, uses poly to wrap his hulls. Yes, many of them
are dry sailed and not subject to the constant pressure of full time
submersion but he would not be cavalier with his construction when it means
so much to his reputation and subsequent livelihood. Some people reserve
epoxy for the gluing only and don't even glass the hull at all. Maybe epoxy
below the waterline is a safe compromise.
For my money, If I were to construct a plywood hull on a large hole in the
water, in which I was to sail the briney deep, I might epoxy -encapsulate
with fiberglas the hull below the WL and epoxy above. OR I might just use a
good house paint above. I would rather be on the water at a cost I could
live with rather than become a curator of a museum piece anyway.
----- Original Message -----
From: <daniel.curnutte@...>
To: <bolger@egroups.com>
Sent: Friday, April 28, 2000 9:25 AM
Subject: [bolger] Polyester vs Epoxy??
>
>
> I know there has been a lot of discussion on this subject already..
but....
> Polyester is just so cheap compared to Epoxy, so I am tempted... One of
the
> possible solutions could be the suggestion I received from a company in
England
> which is a distributor for GRP materials.. I quote...
> "G4 Sealer Varnish
> A moisture curing single part polyurethane varnish. Withstands
temperatures up
> to 200c with good chemical resistance. Cures to translucent amber
colour...
>
> G4 is probably the best primer for ensuring a good bond between Polyester
resin
> and materials such as metal, wood and concrete. It is recommended by
several
> leading manufacturers of Polyester resins for that purpose. On a clean
bare
> substrate brush on the G4, as soon as it becomes finger-tacky but within 4
hours
> apply the Polyester resin and Glassfibre laminate."
>
> Has anybody out there tried this method?? Just to compare, I calculate
> sheathing my hull and decks will cost me under $200US in Polyester resin
(plus
> cloth) but Epoxy will cost around $800USW (plus cloth)...
>
>
>
>
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>
>
>I know there has been a lot of discussion on this subject already.. but....hours
>Polyester is just so cheap compared to Epoxy, so I am tempted... One of the
>possible solutions could be the suggestion I received from a company in England
>which is a distributor for GRP materials.. I quote...
>"G4 Sealer Varnish
>A moisture curing single part polyurethane varnish. Withstands temperatures up
>to 200c with good chemical resistance. Cures to translucent amber colour...
>
>G4 is probably the best primer for ensuring a good bond between Polyester resin
>and materials such as metal, wood and concrete. It is recommended by several
>leading manufacturers of Polyester resins for that purpose. On a clean bare
>substrate brush on the G4, as soon as it becomes finger-tacky but within 4
>apply the Polyester resin and Glassfibre laminate."Polyurethane varnishes are common enough, in New Zealand at least. However
when exposed to sunlight the polyurethane breaks down and flakes off. That
would not be a problem if it is covered with paint or something.
I wonder if dacron cloth could be wetted with polyurethane varnish much as
glass cloth is wetted with epoxy. Has anybody tried this?
Roger Dewhurst.