First hang went O.K. but

[Biker Eagle]

SIL and I went backpacking this weekend to the Sipsey Wilderness and took our new ENO's. I was skeptical but got a great nights sleep as did my SIL. We went to the same spot in Jan & it was in the mid 20's. I had my Thermarest NeoAir therm plus my Thermarest 35 degree down blanket and was cozy...on the ground. Fast forward to this weekend and I woke at 4am with my shoulders, arms, and hands cold. The low temp was 40 degrees. WTH did I do wrong? By the way the Thermarest pad kept my backside warm.

[BillyBob58]

So you were using your pad for back insulation in the hammock? If so, how wide is the pad? Pads need to be wider in a hammock. Or your shoulders will compress your bag into the side of the hammock causing cold spots.

[Biker Eagle]

I think the pad is 24" wide and the hammock is a doublenest. Would wearing my down sweater have made a difference? (Left it at home, not cold enough, ha!)

[DanglingModifier]

You would have been warmer with a down sweater, but quite likely not enough to be comfortable. Trade the down for a wool one and it would make a much bigger difference. A down sweater is going to behave a lot like a sleeping bag. Compression from the hammock and your body weight will dramatically reduce it's warmth. Your top was warm from the blanket because it wasn't compressed where it lies on top of you. Your back was warm because of the pad. Your sides, and arms (and butt if you're a side sleeper) had some compressed blanket against them with cold hammock fabric directly against it, and compressed down can't overcome the convective heat loss from the hammock fabric. Compressed down = compromised down.

Next time bring a wider pad or a good wool layer for your torso and arms. Look up "segmented pad extender" on the site here for more ways to extend a pad to supply more coverage. Alternatively, buy or make an underquilt which will wrap more around you from underneath and give better shoulder coverage.