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Re: [at-l] Bivy Sacks/Tarps (more...)

At 04:45 PM 1/17/97 PST, James P. Lynch wrote:
>Lot of great posts on bivy sacks and tarps.  Question: do the bivy sacks, in
>folks' experience, have a strong enough bottom, waterproof layer to (1) keep
>out water and (2) hold up well and not develop tears, leaks, etc.

Can't say, but there is a difference in the fabric used in different
models.  For example, the Integral Designs Unishelter that I have on order
uses a 4.8 oz/sq yard oxford fabric with a 3/4 oz coating of urathane for
the floor.  The OR bivys use a 1.7 oz/sq yard fabric with their "Hydroseal"
coating.  This is one of the reasons that the OR advanced bivy is 9-15 oz
lighter than the Integral Designs Unishelter (depending on the Unishelter
model).  Also, I suspect that camp location makes a big difference (e.g.
soft duff vs. sharp stones).

By the way, the folks at Integral Designs will make a Unishelter with a
lighter floor (e.g. 1.9 oz coated ripstop), but claim that in their
experience the lighter fabric is "less durable and more prone to puncturing
by rocks and other sharp objects."

I have a friend who uses the OR Advanced Bivy and a small tarp for camping
in all seasons, and who says if she did the AT again she would use her
bivy/tarp combo (she used a tent on her thru-hike).

By the way, there were a lot of things I liked about the OR design, and I
came very close to buying one.  They also make a "Deluxe" model with one
hoop, and a "Standard" model with no hoop at all (note: if you are over 6',
you may find the "deluxe" and "standard" models too short).  The lightest
weight approach would be to use a hoopless bivy as a sleeping bag cover
along with a small tarp.  Integral Designs makes simpler, lighter, bivy
sacks as well.

One possibility might be to go with the lighter floor and a groundsheet.  I
chose not to out of concern that the goundsheet would funnel water under
the bivy where it would be trapped and forced through the floor under
pressure.  This is the same reason it is important to keep the edges of a
tent groundsheet from sticking out from underneath the tent.

Another suggestion for weight shaving with the lighter floor (credit to
Evan Jones (I think) at Integral Designs for this one) was to use the small
tarp as a ground sheet in dry weather (for abrasion), and as a fly in wet
weather (for extra living space).  I suspect that you'd run through a few
tarps that way, but they are a lot cheaper than bivy sacks!

In the end, though, I ordered the Unishelter over the OR Advanced bivy
because I thought it would prove more livable (for me) on a long trip.  I
went with the standard (heavier) floor, because I didn't feel like I knew
enough to go around changing their design.

Happy Hiking!

-- Jim (not as experienced as I'd like) Mayer
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