[pct-l] Re: Gear Tradeoff -- Tents versus Sleeping Bags

[Brett Tucker" <blisterfree@earthlink.net (Brett Tucker)]

Well, Tom. Looks like Ron Moak is back, and I like what he's been saying
lately. So I'll just have to defer your offer onto him. :)

Actually, I don't know that I agree with the physics you're employing with
regard to moisture and temperature within the shelter and bag
micro-environment. If the shelter micro is high humidity, then the bag micro
is gonna be likewise. What we need is a temperature gradient, in order to
drive moisture away from us before it condenses into heat-sapping liquid.
That gradient is likely to be higher under a tarp than inside a tent,
because the tarp user is not able to heat the shelter's micro-environment as
efficiently. So, bag warm + shelter cool = moisture transfer away from
person and out through bag. At least, this is the physics as I understand
it, mostly from what I've learned about waterproof-breathable fabrics. These
work best in cold humid weather, as opposed to warm humid weather, again
because of the temperature gradient idea. That said, if the temps will be
below freezing for extended periods, then both tarp and tent users might be
inclined to use a VB to avoid the frozen-insulation syndrome.

As for the idea of a quilt ventilating better than a bag, not necessarily.
The quilt's (or a bag used like a quilt) main advantage is its weight
savings, due to its elimination of a bottom layer. To perform correctly, a
quilt still must cover the person, and this only permits about the same
degree of ventilation that we would find in a fully-enclosed bag. A more
influential factor might be the amount of insulation in the quilt or bag,
the shell material's porosity, and whether or not it employs a DWR or
membrane of some sort. All of these things, as you know, affect
breathability, and sometimes they can cause more harm than good. Like, I
wouldn't use a down bag that had a W/B covering, unless I were also using a
VB, since otherwise the bag might became a condensation sandwich. Ideally, I
want the most breathability I can get from a quilt or bag, while at the same
time being able to keep its exterior free of weather and external
condensation. Again, a properly-pitched tarp often handles the job
wonderfully - IT is the "DWR."

I am willing to bet the Stephenson is a very good tent in terms of
ventilation. Right now, I can't confirm what you're saying, although someday
I hope to. But in 3-season conditions, a tarp vs. Stephenson's best would be
an interesting challenge indeed. In the dead of winter, forget it. Give me a
tent. Tarps do have their limitations in very cold weather, or when it's
snowing with spindrift, or the wind is blowing at whole gales. Not that they
suffer structurally under these conditions. Again, it comes down to the
performance of the micro-environment.

Sometime I'll come up with a list of various weather scenarios, and explain
which shelter I would choose for each. Often you would see the tarp listed.
But a tent would be on the list, too. And not only in winter. Actually, I'll
be leaving for the Appalachian Trail in a few days, and what kind of shelter
am I taking? Why, one of Fallingwater's specials - a silnylon tent. I'll
tell you why when I get back. :)

- blisterfree


From: "Reynolds, WT" <reynolds@iLAN.com>
To: "'Brett Tucker'" <blisterfree@earthlink.net>,
   Pacific Crest Trail
<pct-l@mailman.backcountry.net>
Cc: Bighummel@aol.com
Subject: RE: [pct-l] Re: Gear Tradeoff -- Tents versus Sleeping Bags
Date: Wed, 25 Sep 2002 14:17:15 -0700

Well, Brett I challenge.

I say I can ride out cold, moisture and any combination thereof, in my
Stephenson than you can in any tarp, no matter how well pitched. In fact I
say that there is NO comparison

You see anyone doing high peak assaults using tarps? No ! But Stephensons?
yep!

For typical PCT cold and wet storm conditions I say that I will be able to
use my bag like a quilt when you are trussed up like a mummy because the
inside of the tent is 10-15 degrees warmer [and, yes, higher humidity] so my
body moisture will vent directly to the air not thru the bag. Finally, I say
that the venting system deployed by Jack Stephenson is superior to a tarp.
Jack, in fact, advises people to NOT OPEN the windows because it will
disturb the carefully designed air flow characteristics.

That being said, I experienced one of those cold pockets while sleeping out.
The temp hit 24. My Feathered Friends Rock Wren II was warm enough, but just
so. It was a wet cold-very uncomfortable.

Tom