Date: Fri, 26 Apr 1996 09:30:46 -0700 (PDT)
From: George Dyson <rowlf.cc.wwu.edu!gdyson@imagelan.com>
To: baidarka@imagelan.com
Subject: Re: Copy of: Pin-holes (& Redwood)
In-Reply-To: <960425181034_76250.453_CHK68-1@CompuServe.COM>
Message-Id: <Pine.ULT.3.91.960426092900.20589A-100000@rowlf.cc.wwu.edu>
Pinholes! Copies of pinholes! Those self-replicating buggers.... you
spend years eradicating them from kayak skins, and then they start
showing up in your mailbox!
Here's what I know. These pinholes are distinct from outgassing, which
may leave small blisters that are cosmetic, with almost any
solvent-carried coating on any kind of skin. These only infect one
species of skin, the 26-oz double-weave nylon, and only using hypalon
paint. A neoprene primer coat (or intermediate coat) is a sure cure. The
cause (or at least the position of the pinholes) can be traced to a
real, mechanical problem, I believe. If you examine the 3-dimensional
weave of that cloth, you find that because it is really 2 layers of cloth
that are interwoven, there is a pattern of intersections formed by one
thread dropping down to the other layer every so often, these ponts (and
the resulting pinholes) arrayed on about a 5mm grid. If the coating
begins to build on the fabric without filling this cavity, it becomes
self-perpetuating, i.e., you can paint over it many times and each time
the paint traps a tiny bubble, leaving the pinhole to resurface and
torment you again. Neoprene always fills the cavity (being more
tenacious) whereas Hypalon (chlorosulfonated polyethylene) usually does
but *sometimes* doesn't. Can't figure out why--seems independent of how
thick, how thin, how hot, how cold, rising or falling temperature, how
long between coats, whether you are in a good or a bad mood.
On a happier note: Redwood was one of the preferred materials for
baidarka parts (and paddles). Referred to by Veniaminov, 1840, among
others, as "Chaga" or "California cedar." Originally from drift logs that
were washed out to sea from the Humboldt river, etc, taking a long time
to get to the Aleutians, but none the worse for it when they arrived.
George B. Dyson gdyson@cc.wwu.edu
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