From: damouth@wrc.xerox.com (David E. Damouth)
Subject: Re: Neophyte tent groundsheet question
Reply-To: damouth@wrc.xerox.com
Organization: Xerox Webster Research Center
Date: Wed, 7 Oct 1992 15:43:15 GMT

Marc says: >Me, I don't like wet sleeping bags, and I like to pack a dry tent,
>so I have a three ply floor - Plastic drop cloth outside, tent floor,
>plastic drop cloth inside.  The outside cloth is a 2 mil cheap
>piece of plastic that I use primarily as a vapor barrier, and
>doesn't weigh much at all.
>

This reasoning for the outside cloth completely escapes me.  Instead of
packing a tent with the outside of the floor damp, you instead pack a
dry tent and a wet piece of plastic.  The damp plastic plus the dry
tent has got to weigh more (and be bulkier, and take longer to pack)
than simply packing the tent with a damp bottom.

As we've discovered in previous exchanges, the inside vs. outside
groundcloth issue is a religious war, with more emotion and dogma than
data and reason in some of the postings.  There are also regional
climate and soil type differences which folks sometimes forget to
mention in their brief answers.  The original questioner didn't include
an address  - so we don't know what his tenting environment really is.

I camp mostly in rainy, wooded country (northeast US and Canada).  The
soil is likely to be damp from previous rain, and the liklihood of rain
during a several day trip is high.  The tent is likely to be pitched on
soil, not bare rock, and I take reasonable, but not obsessive,
precautions to clear away sharp twigs, loose rocks, etc, mostly for my
own comfort, but also to protect the tent.  It's not always possible to
pick a site with good drainage away from the tent.  Sometimes,
particularly on the Canadian Shield, the only flat
non-pointy-rock-covered site is the bottom of a little hollow among the
trees and boulders, where rainwater has washed soil into the hollow to
make a flat "flood plain".  A hard rain will result in water under the
tent on such a site. But for the same reason, such a site often is very
comfortable - covered deeply with leaf mold or pine needles.

I always use a sheet of plastic inside the tent - a 2 or 3 mil cheap
drop cloth, cut about six inches bigger than the tent floor all the way
around, and thus lapped up the side of the tent six inches or so.  I've
never had water in the tent, except for condensation from inadequate
ventilation in humid weather.  I used this technique for many years
with an old tent with a worn-out floor, which had visible pinholes and
flaking of the coating.  The plastic always protected me.  I still do
the same thing with my new tent.

The inside plastic also helps keep condensation out of the sleeping
bags, if the plastic laps up the tent side as far as the coated floor
material.  The uncoated tent sides stay dry, but the inside of the
coated floor can get quite wet in humid or cold weather, both because
it doesn't breathe and because it is on or close to the cool ground.
The sleeping bag can easily rest against the side of the tent, near the
floor (or directly on the floor, since it may be bigger than the pad or
may shift off the pad) and will wick moisture from the side or bottom.
The sheet of plastic, insulated by a small air gap from the coated
material, stays dry on the side toward the sleeping bag.

As others have pointed out, an outside ground cloth always presents the
risk of funneling water under the tent, and won't help at all if water
is actually flowing downhill toward the tent.  It made sense back in
the days when we always dug a big trench around the tent.

An inside drop cloth also makes it real easy to get rid of the crud
that inevitably comes into the tent on clothing and feet.  Just pull
out the plastic, give it a shake, and the accumulated dirt and leaves
are gone.

Cliff Jacobson, in his wilderness camping book, makes the argument that
more wear and tear on the tent floor comes from equipment and feet
abrading the inside than from rocks abrading the outside, and therefore
that an inside cloth provides more protection than an outside one.

IMHO, if you are tenting on bare granite in dry conditions, then an
external ground cloth makes sense. Otherwise, you get more value from
an inside cloth.  And as MARC says, if you are really obsessive about
protecting the tent *and* staying dry, and you don't mind carrying
extra weight, then you put ground cloths *both* inside and outside.
---
/Dave
David E. Damouth
Xerox Webster Research Center, Rochester NY.
damouth@wrc.xerox.com
voice: 716-422-3186
fax: 716-265-7133


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