Re: [Paddlewise] Poncho as Storm Cage

From: Dave Kruger <kdruger_at_pacifier.com>
Date: Tue, 12 Jun 2007 00:46:50 -0700
Joseph Pylka wrote:
>> Does anyone know if one side or the other should face out on Tyvek?
>> [snip] I wonder about layering it under a breathable fabric as well.
>> It probably doesn't work as good as Goretex, but it seems like a cheap
>> way to make some gear. Paul M

> It's not a breathable material but rather a vapor barrier.  That is what
> it is ordinarily sold as.

I've heard Tyvek described as a "vapor barrier" before, but I think that is 
very misleading language.  Check out Wikipedia's piece on it, in which you 
will find:  "Water vapor can pass through Tyvek, but not liquid water."  It 
is more properly a _liquid_ barrier, inasmuch as it passes water vapor, but 
not water liquid.  The Wiki citation: http://en.wikipedia.org/wiki/Tyvek

And, here's the language the manufacturer uses to describe its properties: 
  "This unique balance of properties, which cannot be found in any other 
material, makes Tyvek. lightweight yet strong; __vapor-permeable__, yet 
water-, chemical-,  puncture-, tear- and abrasion-resistant."  Source: 
http://www.tyvek.com/whatistyvek.htm

As far as its use for clothing:  it does not last; it does not withstand 
repeated flexing nearly as well as materials designed for clothing.  IIRC, 
its vapor transmission rate is much lower than Goretex.  Finally, it makes 
no difference which side faces the liquid water, AFAIK.  I believe you see 
it on houses with the logo out just because "that's the way we have always 
done it."

-- 
Dave Kruger
Astoria, OR
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Received on Tue Jun 12 2007 - 00:46:54 PDT

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