Posted on firstname.lastname@example.org on behalf of John Wiedenheft
In the April 97 issue of BackPacker magazine, there is a small article on survival sacks. These are basically big rectangular bags, waterproof and windproof, which you crawl into for shelter from the elements. The author of the article tested two versions, one by MPI, made out of an aluminized mylar (space blanket type) material, and the other by Coghlan's, made out of 3 mil polyethylene. Both were 3 feet wide by 7 feet long. The author tested both on numerous occasions, simply by crawling into them and attempting to spend the night comfortably under various conditions. I went down to the local building supply house (thanks for the tip Andy!) and found some yellow colored plastic bags, made from 2 mil polyethylene. They had this same size and even larger. (I wish I could find a clear version - then the bag could double as a transpiration still.)
It seems to me that a much improved variant on the survival sack would be to stuff it with leaves prior to crawling into it, like a debris hut. This would add lots of insulation to the sack, in effect creating a large waterproof sleeping bag. Debris huts always have lots of sticks and other stuff that can puncture plastic bags in them. The author of the article did test the bags for toughness by poking toothpicks through them and making 1 inch cuts in them to see if they would tear. The polyethylene bag was much more resistant to tearing, although it was heavier (9.5 oz.) and also a bigger package to carry (6 in x 6 in x 1 in).
Yesterday I stopped in at a marine emergency supplies store. They specialize in life rafts, flares, water desalinators, strobe beacons, and yes, they even had a solar still kit! On the clearance table there was a "Survival Bag", similar to the two just described, except that the material they were made out of was very tough, like those mailing envelopes that you can't tear open. This Survival Bag also had a hood with a draw string and a zipper to get in through, instead of just being open on the end. I asked them if they could get more of these, but they said no, this one was purchased as part of a life raft/survival package, the life raft had been damaged and they were selling this survival bag from out of the kit.
It is called the ThermoSafe Survival Bag, made by Nauteknik A/S. This company is located in Oslo Norway.