Wednesday, March 2, 2011

Using snow shelters for extra bonus warmth

Until Saturday night, I had never slept in a snow shelter before. I made it seven winters working at a winter camp for boy scouts and supervised the building of umpteen such structures, but had never spent the night in one. Necessity has a funny way of changing such things.

It all came to be because my sleeping system was woefully inadequate for the actual temperatures experienced.

I really have two sleep setups for cold (winter) weather: a -20F degree down bag and a 20F degree MYOG quilt that I put inside a 30F degree down bag. The former can be used in a tent, under a tarp, etc., while the latter is placed inside a bivy. I used this quilt and bag setup in Montana in 2009 and feel comfortable with it to take it down to single digits above zero when combined with insulated clothing.

This weekend, several forecasts said that the Sunday low was zero degrees, and the temp would rise into the low 30s later that day. Perfect testing for my setup in a controlled environment. And then the cold broke loose.

The weekend temperature plunge started Friday night continued into Saturday morning. It was -14F at sunrise on Saturday, and -9F when my crew left base camp a few hours later. I rarely put on my down coat before about 3 pm. This weekend, it was on by 12:45 pm - just a few minutes after getting to camp.

I assessed the situation - I needed to do something. At this pace, the temp would not get above zero during daylight. Once sunset hit, the temp would plummet 10 to 15 degrees until it bottomed out just before dawn the next morning. I did not want to shiver my way to dawn.

Even with wearing everything I had, I needed to get more insulation into my system. Snow was the only thing available. Inspiration hit. When I did the Hudson Bay Expedition in 2005, I bought Tom Brown's survival guide a few days into the trip and carried it with me. I paged through it in the evenings, making mental notes of interesting ideas.

Small is beautiful Brown advised. With that, I started to make a pile of snow. It was about 3.5 feet high and about six feet long. It rounded slightly at the top as most piles do, and angled off the back. I poked foot-long sticks into the sides for a guides later. And then I let it sit for a few hours. I was to make a quinzee, al beit slightly modified.

When the few hours passed, the snow had settled and digging began. With Brown's words in mind, I took a shovel and excavated a coffin-size tunnel out of my pile. I slid myself in to test: my feet were near the back and my shoulders were directly below the door. Perfect.

With that, I unfurled by bivy and in it went my two sleeping pads (full length and 3/4 Ridgerests). Then went my backpack (GG Vapor Trail) to its spot under my feet, the remainder of its contents sitting in the bivy. Sleeping bags were next: first the bag and then the quilt layered inside. The whole package slid neatly into my tunnel.

Nightfall came, and now came the test. I took off my boots (Steger Arctic mukluks) and changed into dry socks. I then removed the boot liners from the moosehide and canvas shells, and placed them on my feet. As always, the mukluks went into my compression sack (itself turned inside out) and into the bag. I slid into the bag, wearing everything I had with me except my damp socks and insulated mittens. I even put hot water in my camp-issued 16 oz Nalgene bottle and threw it in the bag. Up went by parka hood, and my bag hood went over that. There was minimal space between the top of my bivy and the roof of the tunnel, but my insulation was not compressed.

I have never slept so well in the winter as I did that night. As usual, I woke up to urinate twice (1 and 5:30 AM - right on schedule) but was never cold. My feet were sufficiently insulated, and my nose was never cold. Dawn came at 6:30 am and I rose with the sun. I would later learn that the temp bottomed out at -14F - an impressive 20 degrees colder than I had ever taken that sleep system before. I walked back to base camp comfortable and more knowledgeable than when I left just 24 hours before.

My bags paid the price for this knowledge, though. I did not use vapor barriers, and perspiration condensed in my bag, quilt and down parka. Moisture from my breath condensed on and in the shell of my bag in front of my face and collapsed and severely compromised the insulation there (Andrew Skurka faced a similar problem on his Icebox trek). If I had had to spend another night out, I would have needed to spend an hour or so drying my bag in the afternoon sun.

This was not a situation I intend to repeat, but it was inspirational and informative. I can't think of how I could have solved my problem any better, and I am for the wiser because of it. I do not intend to test this again, but its lessons will be used on many trips to come.


samh said...

You had no choice but to deal with the situation and not only were you successful but it proved educational.

George Carr said...

Great post Matt. Not to change topics but how long have you been using the Steger mukluks and what are your impressions? I've had my eye on them for a while now and am thinking of taking the plunge.