One thing I had yet to test was how my Hennessy Hyperlite Hammock would perform in very cold temperatures. In warm summer months the hammock is a great way to sleep. Because you're off the ground there's no thermal conduction between you and the warm Earth, and through conductive means (wind) your body heat rapidly dissipates. For these same reasons, sleeping in a hammock in the winter makes for some potentially frigid sleeps.
I've heard great things about using Hennessy's Super Shelter to sleep warmly, but for pack weight reasons I've elected to simply put my RidgeRest SOLite pad under my 25° down sleeping bag (Halo from REI). (The SOLite pad is covered with Mylar on one side, which reflects some of my radiated heat back to me. I think I will carry this regular length pad even in warm weather in the event I find myself sleeping in a shelter.)
This has been a strange winter here in the eastern half of the U.S. in that the temperatures have been quite mild and snowfall practically nonexistent. So last night I when a cold front rolled down from Canada, I took a short hike down to the creek running through campus to spend the night in the frigid temperatures. It was a valid test for the most extreme AT conditions. When I set up the hammock at 9 pm there was a light wind and the ambient temperature was in the upper 20's. At midnight, the temperature was 23°F, but by now the wind was blowing at 15 mph making the wind chill 8°F. By 4:00 in the morning, it had dropped to 18°F (but the 20 mph winds created a bitter equivalent 1°F wind chill). When I awoke at 6:00 the temperature had dropped even further to 16°F, the 9 mph winds making it feel like 9°F. For most of the night light snow or freezing rain fell, with the relative humidity at 85%.
Obviously I survived the experience and was actually fairly warm for most of the night. I wore my mid-weight Smart Wool long underwear, a pair of Darn Tough wool socks, and a synthetic balaclava. Except for my feet, which are always cold, I slept warmly unless I rolled off the SOLite pad causing cold to creep up and into my bag.
At 3 or 4 in the morning I was forced out of my warm cocoon because nature was calling in a big way! (Why is it that the urination duration is indirectly proportional to the ambient temperature?) After returning to the shelter of my hammock, it was evident that my 25° down bag wasn't able to keep up with the falling temps even though I now wore my thin fleece jacket. Luckily I had my brother's vapor barrier liner (VBL) in the hammock with me, ready to be tested. My brother, Kyle, has been educating me on the benefits of VBLs when the mercury plummets. He sent me the one he used on his bike ride across Japan and encouraged me to carry it on my AT hike. The VBL is a waterproof sleeping bag liner that traps both body heat and moisture, thereby significantly improving the insulation rating of any bag. It is only useful in cold - not cool - temps because otherwise you'd wake up drenched in sweat.
Just two days ago I told Kyle of my plans to test my sleep systems, including his VBL, but that I doubted I'd take the VBL with me on my thru-hike. After all, my down sleeping bag and SOLite pad was all I needed, right? At 4 in the morning, I promptly changed my mind and wriggled my way into Kyle's nylon liner. After that, I slept warmly and soundly. No cold spots, no cold feet, no tossing and turning. Just a great sleep. The VBL is definitely coming with me on my thru-hike, at least through spring in the southern mountains and again in the Whites of New Hampshire, where weather can change on a dime and snow in August is not uncommon.
My comfort level took a nosedive at 6 am when I had to exit the hammock and break camp. I knew I was in trouble when I reached down under my hammock and grabbed my boots. I tried pulling them up but they were frozen to the ground. I pulled harder and large patches of earth came up with each shoe, having frozen to their soles.
Despite being given a nice pair of gloves and a mitten shell by another three of my brothers (Gy, Joey and Douglas), I needed full use of my fingertips to untie the hammock knots and therefore had to remove the gloves. Within minutes my fingers were numb and in pain. I was so cold that I didn't bother to untie the tent stakes from the rain fly, opting instead to roll up the metal stakes inside the fly. Under normal conditions I would never take a shortcut like that and risk damaging the expensive tarp, but my hands were in serious pain and I was desperate to break camp and get moving to warm up.
(Kyle had also given me a pair of neoprene gloves that can expose the fingertips, but they were too warm to hike with and took a long time to dry once soaked with sweat so I was thinking that these might not accompany me on the trek. However, in light of my severe discomfort at the campsite, I am leaning toward bringing them along as a pair of camp gloves until I am through the Smokies.)
Next, I need to experiment with my lightweight Salomon boots in some deep snow, which we may not see in this crazy winter we're experiencing!
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