[Paddlewise] water, solar still

All the messages about water bags, urine, etc. brought to mind this old
trick for scavenging water in a real survival situation, much better than
drinking your urine. 

You can make a solar still to get fresh, distilled water with nothing more
than a plastic bag and a few rocks and a hole in the ground, plus vegetable
matter or some other source of water. I realized that if you had to, you
could turn your kayak into a solar still (or three, using the fore and aft
compartments) if there wasn't a good place to dig a hole, or if you needed
to move it around to stay in the sun.

The vegetable matter goes in the hole, inside the plastic bag. Water
evaporates and is distilled onto the inside upper surface of the plastic.
The top of the bag is made into a tentlike surface where water condenses and
drips to the low point of the plastic. Two ways I have seen suggested for
constructing this low point: 

1. (this is the one you'd use for a kayak adaptation, using your spray skirt
to hold the plastic bag over the cockpit, filling the cockpit with leaves or
even seawater) Put a rock in the middle of the plastic cover so it becomes
the low point of the plastic, and a cup inside the hole to catch the drops
of distilled water that fall from the plastic under the rock. 

2. If the bag is big enough, make a trench or moat around the hole and use a
stick to make the bag stand up like a tent. Hold the outer edge of plastic
at the moat using rocks. Water will roll down to the outer edge and into the
trench. Drink only the water that is in the trench around the outside. You
should make it at an angle, so any water in the trench flows down to a
single drinking basin, which is where you'd put your seal for easy access.

clear plastic works better than opaque plastic for a solar still. You'll
also collect more water if a portion of the plastic is shaded or otherwise
passively cooled, making a condenser. For example, a stick covered with
leaves will both cool the plastic locally to attract water and create a flow
path for the drops to follow.

The water will have some flavors, since you'll also be distilling a few
esters and alcohols from the plant material, but if you are careful to keep
organic matter out of the cup and the condensing surfaces, the only bacteria
or salt in the water will come from your hands or the air. It would be more
appealing than pee, and better for you.
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