Subject: Re: baidarka Re:Polyurethane
From: James Mitchell (mariner@seanet.com)
Date: Fri Dec 15 2000 - 00:14:42 EST
I am not so sure it is water absorption. My hulls all do it to a greater or
lesser extent in the cold weather. This is the "loose skin" phenom I was
talking about with Raven. Actually, I think it helps stability by creating
scallops between the stringers. If I have done the proper job of heat
shrinking my hulls just before coating, and if I have coated in the morning
so that the coolness of the night isn't in operation while the coating is
setting, I get much better luck with skin tightness.
I don't know if the Empire coating that I am using (2 part poly) performs
differently on this characteristic than does the Zar, or any of the other
coatings. I am pretty sure that the coating does a good job of limiting the
expansion, as it is so watertight. Incidentally, I have been unable to work
the shipping problem on this stuff for lack of time. Need to get the hazmat
sheets, talk to a shipper. If anyone has solved this, I'd be interested.
----- Original Message -----
From: "Bill Low" <billow@capecod.net>
To: <baidarka@lists.intelenet.net>
Sent: Thursday, December 14, 2000 10:44 AM
Subject: Re: baidarka Re:Polyurethane
> Hi Mark
>
> Well you have the corn cob effect as a little girl said of one of my early
> boats. Many people have had this with nylon. I have not been able to pin
it
> down except that nylon will absorb quite a bit of water and in doing so
will
> stretch and get baggy. I tried everything to get rid of it. I even coated
> the entire inside of the skin to stop any water movement. Didn't work. I
> have tried other polyurethanes with the same result. Some have had good
> results with heat steaming the nylon before coating. I never tried it
after
> coating but that might work.
> The result was that I changed to polyester skin. No problem of any kind
with
> that because it won't absorb water. I wish I had some magic bullet but as
I
> said it is a somewhat common problem. I don't think that the ZAR is the
> problem, I think it is how you prep the nylon with heat before coating.
But
> I gave up on nylon for many additional reasons also and moved to polyester
> so I don't know for sure.
>
> Bill
>
> ----- Original Message -----
> From: "Mark Starr" <marks@mystic.org>
> To: <baidarka@lists.intelenet.net>
> Sent: Thursday, December 14, 2000 3:39 PM
> Subject: Re: baidarka Re:Polyurethane
>
>
> > Dear Bill,
> > I had written to you before about polyurethanes for nylon skin boats,
and
> > tried the Zar exterior oil based satin polyurethane on the boat I just
> > completed (3 coats, applied inside a heated finishing room). After
using
> > the boat a few times, and having left it with a little water in it out
in
> > my unheated barn, the skin buckled up over the entire hull (it was drum
> > tight up till then). After bringing it onto a glassed-in porch, the
skin
> > has shrunk back to its tight state. I am assuming that the urethane is
> > waterproof, but vapor permeable. Has this been your experience with
this
> > Zar product, or did I somehow mess up the process? I can go back to the
> > Duratuff, but it is quite expensive, and I would like to find something
> > easier to get as well. Thanks for any light you may be able to shed on
> > the problem, and happy paddling!
> > Sincerely,
> > Mark Starr
> >
> >
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> >
>
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