I tested out a new sleeping setup last night in Western Massachusetts, up in the Berkshires. We camped overnight at Windsor Lake in North Adams, and the temperature dropped below zero. Windchill may have breached -10ºF. I hope someone can compare my results to their own and benefit. Please ask if you have any questions, even if it's "Why the hell don't you use an underquilt?!"
Hennessy Hammock Ultralight A-Sym Backpacking Hammock
Tyvek Kite-Making Sheet Liner
Thermarest Z-Lite Sol Torso Length
Outer- EMS Solstice 20º Synthetic
Inner- MH Ultralamina 32º Synthetic
C.A.M.P. Men's ED Slim Down Sweater
Smartwool Midweight Baselayer
Baffin Down Booties w/ thick socks
MH Mesa Backpacking Pants
OR Windstopper Peruvian hat
First off, the sleep setup was very, very close to warm, but not quite warm. I fell asleep about 10:30 PM and awoke from the cold at 5:30 AM, so I got 6-7 hours of continuous sleep. That is the mark of a good sleep setup in my mind, even if I'm uncomfortable once I wake up. I felt my stomach in the morning and my core was as warm as a furnace. Still, the discomfort could have been prevented, which I'll go into below.
I also learned that no matter how bad I want to, my 40L backpack is not big enough for my winter setup. It technically fits everything easily, with room to spare, but that constitutes compressing both sleeping bags. I will be using a bigger bag in the future. That was not fun to do in the morning with cold hands. I also did not enjoy untying the knots on my hammock with freezing fingers, but I got it done in the same amount of time that I usually do.
Wind under the hammock was, as I predicted, negated a lot by the Tyvek sheet. It was big enough to wrap up the sides of my sleeping bag on both sides, and it stayed in place all night. It also made shifting my pad around inside the hammock during the night much easier. I was a huge fan of this sheet, and while I am concerned about durability it looked fine in the morning.
1) Warmer hat
2) Swapping the Thermarest Z-Lite Sol for a Thermarest NeoAir X-Therm Torso. I was reluctant to use a NeoAir since I was so satisfied with my Z-lite, but it really is a necessity and with a hammock, I'm unlikely to puncture it.
I didn't know they made a Torso X-Therm! I was unhappy with the full length All-Season I had because if my feet hang mid-calf I can't sleep. If they hang mid-thigh I have no issues. I was looking at the NeoAir X-Lite Torso (the yellow one), and the R-rating was only a bit higher than my foam pad... did I really want to spend $130 for 3.2 R-value versus 2.6? No. But will I pay $150 for 5.7 R-value? Hell yes! I had been meaning to pick up another all-season and this is perfect for my needs.
3) Swapping my MH 32º Ultralamina for a MH 45º Ultralamina. My body wasn't cold, except my back from the insufficient pad. I will save a little weight here and get a bag that will be more suited to the Spring/Summer trips I have planned, and continue using the EMS Solstice 20º combined with this as a liner for warmth.
Overall, it's a good system. It seems sketchy using so little insulation with a hammock, but I can sleep through anything and I am glad for the leg elevation. I am a believer in Tyvek, and if I rip it, it was only $7. I will be using this setup, with the mentioned changes, this coming weekend on Mount Moosilauke, NH. I'm guiding a 3-day student trip.