Date: Tue, 02 Mar 1999 19:48:24 +0100
From: Stefano Moretti <s.moretti@agora.stm.it>
To: baidarka@lists.intelenet.net
Subject: baidarka polyester resin and ply
Bill Leonhardt wrote:
>
>
> In Bram's discription of most of his plywood difficulties, it would
> appear
> that most of the problems arose from inadequately sealing the plywood,
>
> especially the edges. I didn't know that polyester would allow water
> to
> pass through, so it would appear that this would not be a good choice
> for
> sealing.
Polyester slowly lets vapor in, then this condenses into water. Then
with heat it eventually turns into vapor again. What you've got is a
pressure cooker, and delaminating poly-wood with a good chance for mold
(dry rot).
> It's definitely important to use
> plwood with a glue formulated for a marine envirnment.
This is only resorcinol, red glue, hot/pressure industrial process. Only
secondly epoxy (cfr Richard Jagels in Wooden Boat)
> In spite of Bram's difficulties with plywood, I think that it is still
> a
> better choice over solid wood.
Same here...
> So, it would seem the trick is to get marine grade plywood, with many
> plys
> (and, hopefully, a minimum of voids), seal it well and monitor the
> condition of the seal with time.
Plywood is a fantastic material, when good. Marine ply (BS certified)
has NO voids, is boil proof over more than 12 hours I believe. I ran my
own tests and often find untreated ply on the beaches, as flotsam. None
is delaminated. Make sure the the plywood quality is good, protect the
edges carefully, and have a good sleep over the next 25 years at least.
> Of course, you might consider plastice ribs ala Feathercraft.....
... and be prepared to put the extra weight on your back and to have
some plastic brittleness before the next 25 years.
> Stefano