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[pct-l] Tyvek bivi-sack



Dude-

You had the process half right. Per the expert on vapor barriers, Jack
Stephenson, you sleep naked in your VB bag [Jack thinks you should hike
naked but that's another story] and get up at 3AM to wipe yourself down with
a towel. Per Jack, just mop up the puddles. Whats the problem? Jack argues
that sleeping this way will reduce you loss of body water at night resulting
in less dehydration and/or water scrounging.

TOM

PS: I think Jack makes great tents but otherwise has bats in his belfry

-----Original Message-----
From: dude [mailto:dude@fastmail.ca]
Sent: Thursday, October 17, 2002 5:37 PM
To: pct-l@mailman.backcountry.net
Subject: RE: [pct-l] Tyvek bivi-sack


--
I think Tom is right.  I used a vapor barier bag as a bivy bag on my
last ultralight JMT trail run (total gear and food 6 lbs).  It just
doesn't work as well because the bag keeps the body's mpisture in
and your sleeping bag will get soaked.  I could not believe it.  I
woke up at 3am with puddles in my barrier bag!!

you need a fabric that will breathe for a bivy bag.



> I would use a vapor barrier INSIDE the bag if I was going to use a
> barrier outside the bag. Otherwise human sweat will collapse the
> bag in no time. This is the problem with Gortex as an external
> fabric for Sleeping Bags. It doesn't let the moisture from the
> sleeping body OUT.
>
> Make a vapor barrier from sil-nylon that encloses the body. This
> will prevent sensible sweat from entering the bag. Actually, it
> will reduce sensible sweat because the sil-nylon enclosure's
> humidity will come into equilibrum with the body's skin.
>
> Tom
> PS: Monte, please check with Greg or me. It will save you lots of
> time trying out your inane ideas.
>
> -----Original Message-----
> From: Montedodge@aol.com [mailto:Montedodge@aol.com]
> Sent: Thursday, October 17, 2002 2:42 PM
> To: pct-l@mailman.backcountry.net
> Subject: [pct-l] Tyvek bivi-sack
>
>
> --
> [ Picked text/plain from multipart/alternative ]
> My new winter project!! I want to see if a tyvek bivi-sack will
> fly. ( As in
> work) Has anyone dabbled with making a bivi-sack out of this stuff
> and how is
> it as far as moister?? I will be taking my down bag down the yukon
> next summer and will keep it in a dry bag all day paddling, but a
> few weeks of solid rain could make it a bit "iffy" when in use at
> night.  Tyvek should add
> a few degrees of warm as well as long as I don't get wet from the
> inside out!!! Thanks, Jethro Tull
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