Sleeping System Rather Than a Sleeping Bag?

Dear Editor:

I have followed with interest the recent article and letters concerning the finer points of modern sleeping bag design. Without in the least devaluing these efforts, I feel your readers should be aware of a divergent and revolutionary line of research. Myself and my associates are at this preliminary stage by no means certain we are not following a blind alley; still, there is always the possibility other groups have engaged in similar projects and all of us could benefit from an interchange of ideas.

In short, the problem is one of conserving the heat produced by the human body for the sake of keeping that body warm during the hours of sleep. Leaving aside for the moment the matter of long-wave radiation, certainly the conventional sleeping bag has been the best solution to that part of the problem relevant to heat-loss by conduction. However, the columns of your journal have spotlighted the horns of the current dilemma: insulating material must be light and compressible; when it is compressible it loses insulation value.

Research

Is there, then, any alternative to the present attempt to provide, in the mountains, something simulating a “cozy bed at home?”

Possibly so. Because of patent regulations I cannot identify the school nor the project, but one of our club members, a “cold weather” specialist, recently spent some months in the narrow area of “body heat loss by member.” Certain of the project findings were so startling that our club, last year, undertook to particularize for mountaineers. With a small membership and only private funds we have but outlined the potential, but are encouraged to continue.

It has been found (and long suspected by mountaineers) that at least 65% of the heat-loss from the human body (assuming normal clothing) occurs in the extremities—hands, feet, head. For reasons having to do with circulatory structure, the small of the back is another region of exceptional heat-loss.

It has, moreover, been found that under normal circumstances (proper food, no injuries, etc.) the heat-production of the human body is, on the average, 30% greater than necessary to maintain body temperature. By far the major vent of this excess heat is expiration.

Our research has been to find if this waste heat from respiration could be directed to the regions of major heat-loss. If a practical method can be devised to capture most of this waste heat, and channel it properly, then the over-insulation technique of the sleeping bag can be dispensed with.

The major difficulty in containing expired heat is the water vapor content. Experiments with various filters continue, and here we could most particularly benefit from the research of others.

 

Insulation

In any event, let me briefly summarize the present “sleeping system.” First of all, we continue a compromise by using more insulation for the extremities: a double-balaclava helmet of fine-woven wool for the head; elbow-length double-mittens of fine-woven wool; knee-length double-socks of fine woven wool; a six-inch square double “patch” for the small of the back.

War Surplus Masks

Second, over the rest of the body, we assume normal climbing apparel: trousers, shirt.

The key to our “system” (as distinguished from a “bag”) is the re-cycle of body warmth. In our admittedly crude experiment we have been using a nose-and-mouth masks (war-surplus ether masks, in fact.) A fairly complex valve sits outside the mask which allows normal inspiration of outside air, but diverts all expired air into the filter, and thence by tubing to the hands, the feet and the small of the back. (With the present outfit ordinary leakage between mask and face more than suffices—with the double helmet—to warm the head.)

The “in-out” valve is home-made, expensive, and not by any means perfected. For the filter we have been using—to repeat—many things. The best yet found is plain calcium oxide ground to a particle-size of .00000000000001 inch diameter. We know only one source for the product, and since their entire output goes into missile research, and is quite horribly expensive, we are seeking some other dehydrant. For purposes of comparison, with this compound we found seven ounces sufficient for a night’s sleep; moreover, the “wet” product regains 85% of pristine efficiency after only five to seven minutes in a pan over the flame of a 69-L Primus.

For the tubing, we’ve been using an extremely light polyethylene product of one-half inch diameter and no wall-thickness to speak of.

Weight

For the “warming sacks,” however, we’ve been using a moderately loose weave of cotton-nylon, since otherwise the sleeping climber would simply be puffing into a balloon.

Our “sleeping system”—extremity-helmet-mittens-and socks; mask, valve, filter, tubing and “warming sacks”—weighs one pound twelve ounces, though this varies from system to system. The expense is far greater than that of the finest sleeping bag—now.

Nor have all the kinks been worked out of the system, such as valve failures, filter-clogging, tubing leaks, etc.

But during the last summer and winter, when the equipment did not break down, our members have spent comfortable nights when the temperature was low and the winds were high, all over the Cascades.

Suggestions Wanted

It will be many years before the climber can depend upon a “sleeping system” rather than a sleeping bag. And most of our tests have been made in the realm of comfort rather than survival. That is, we have been seeking a way to avoid triggering the “shiver-mechanism” of the human body, the main destroyer of sleep. At present, we press no claims at all for the “system” in survival situations.

For the latter, we are presently postulating, in addition to the “system,” a blanket of thin plastic, preferably dark-colored, if the sleeper is not within a tent or under a tarp.

These investigations and preliminary conclusions are presented tentatively, hoping and expecting that your readers will assist our future research by comments, suggestions or criticisms.

H. Hawthorne Manning, Pres.
Cougar Mountaineers
Issaquah, Washington

 

The July 1959 Cover

Cover photo by Niles Werner.

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Feature image: A G7 Alpine Shelter, with two G7 Pod inflatable portaledges inside, in the Waddington Range, British Columbia, Canada. The image was featured in the article, “Behind the Curtain” by Corey Buhay in SJ 321. / Photo: Nic Vissers