Message-Id: <199805111837.OAA29859@mail.gwi.net>
From: "Ron Franklin" <oldhaven@mail.biddeford.com>
To: baidarka@lists.intelenet.net
Date: Mon, 11 May 1998 14:36:03 -0500
Subject: Re: [baidarka] saggy skins
> From: Ben Collman <collmanb@jsd.k12.ak.us>
> Subject: Re:saggy skins
>
> I made a query a couple of months ago about sagging skins and got one
> response. I would appreciate replies from anybody else with any insights.
>
> I'm building a West Greenland skin boat. Three friends have finished
> theirs. In each of the first two cases (the 3rd hasn't had time yet) the
> skins were initially tight. After painting, they stayed tight until they
> were moved outdoors, at which time a LOT of slack appeared in the skins.
>
> We are using heavy nylon skin from Dyson, and painting it with neoprene and
> hypalon. Can anybody - the more responses the better - offer me any
> insights into what is happening and how I can avoid it? I am at the point
> of painting my boat now, and want to avoid the same problem.
>
> Thanks in advance.
>
> Ben Collman
I've had reasonably good results by using an electric iron to shrink the
skin after it is sewn on at a fairly comfortable tension, not going to
great pains to get out all the slack . The nylon comes from GBD in what is
called a greige state, meaning it has not been heat set. ( At least in my
experience, and I would assume it hasn't changed over the years.) This is
similar to the heat shrink dacron used on airplanes. Also, Nylon becomes
slack when it absorbs moisture, and will shrink when it dries again.
Additionally the heat used to heat shrink it complicates things in getting
the tension right. The skin will vary in tension with moisture no matter
what, at least in my experience. The best you can do is get it in a good
mid range. Mine, using the heavy skin, seems to be a bit tight when dry
and sitting in the sun but looks fine in the water.
The technique I like is to use the iron with a wet towel between it and the
skin. The water turns to steam and pretty much prevents the temperature
varying much over 212 degrees F. It also puts water in the nylon and so it
shrinks to the moisture laden tension rather than the dry tension. If you
overheat the skin it will start to sag like most plastic at melting temps,
but in the 180 to 220 range it tightens the skin pretty well. I go over
the whole thing for one quick pass, then work carefully with any problem
areas. It's tempting to keep doing it over and over since it is so
satisfying to see the wrinkles go away, but restraint is a good idea. As
the skin dries it will shrink more, and you may see some hollows develop,
but they should be no big deal, and will go away when you get in the water
for the first time and overturn in your exuberance.
Works for me, but results will vary with individuals who are more or less
picky than I about getting things just right when sewing the skin. I
figure if you use it much it will look like hell in a few years anyway.
BTW, the wet towel and iron trick works well for bending thin wood strips
over a form. Sort of a portable steam box. Soak the strips for a while
then lay them one at a time against the form, put a wet cloth on them and
create steam with a hot electric iron. You can feel the wood release as
the steam is driven into it.
Ron Franklin
Bowdoin, Maine, USA