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Thread: A strange night

  1. #1
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    A strange night

    So I am playing with an insulated bridge design and headed to bed last night to try it one more time before taking on version 2.
    It is insulated with one full layer of Apex 2.5, and one torso layer 22x48. I used a CFF pad in my bag under my feet. So 5.0 Apex under my torso, and 2.5 oz and CFF pad under my feet.

    I went to bed in a 10-15 year old 750 fill down bag originally rated at 15*. I wore a merino 1, Cap 3, and Montbell UL down top. Cap 4 hat and fleece baklava, no pants and darn tuff socks.

    Point being- it was around 25-30 when I went to bed, but dropped to 7 or so (9 when I woke up) with wind chills below zero. High tarp, no windsock. I'm not going to say I had toasty uninterrupted sleep, but I slept for decent stretches and rolled over from time to time.

    Why did this work?
    Thus far in my experimenting with Hammocks it seems like you need MORE insulation in you UQ, but I had at best 30-40* of insulation under me, and let's just call it 5* worth up top.

    What are the thoughts of you more experienced hangers?
    Granted it's one night, but it throws off my thoughts thus far in regard to sizing UQ's.
    Do others match top and bottom insulation evenly or have some of you found you don't need as much underneath?
    I've been thinking you need to go heavier under than over- but is the opposite true?

  2. #2
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    ALWAYS GET LOTS OF INSULATION UNDER YOU. People in the North country know that, whether it is your bed, your butt (bum-touch-sitter), get insulation Under your body.

    I insulate the part of me that is nearest the ground, cold air stays low (most of the time), hot air rises. I insulate under me, very light weight stuff on top, just enough to give some insulation. I have problems with anything that presses down on my feet or shoulders, hate the heck out of hats and socks. I use a light well made quilt over the top when the weather is cold, in arctic conditions I have a suitable down bag I use. I do not Hang in arctic conditions unlike some members (I admire their tenacious experiments), I do travel through areas where arctic conditions happen with great regularity, I have been stuck and forced to spend the night in such conditions, I was fine because I sort of knew what I was doing, I had suitable gear in the vehicle with me, warm clothing, lots of insulation under me and some over. Under is the key. Adjust the top as needed. A good foundation is the key to everything, your life, your marriage, your sleep and your dwelling.

  3. #3
    Senior Member WV's Avatar
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    There are so many variables. I think the sleeper's metabolism and the wind are the ones likely to vary the most. The two ways that I am most likely to feel cold are: (1) CBS from compression of bottom insulation and/or from convection in an air space inside the hammock under my knees, and (2) cold legs or shoulders from air infiltration or compression of bottom insulation at the sides. I try to design to prevent both, and the better the overall shape of my bottom insulation, the warmer it will be for a given thickness because the thickness is more uniform. For some reason I am more likely to overheat from too much insulation in the top layer than the bottom (even though it's usually easier to vent the top), and that's what makes me prefer more insulation underneath. With all the attention given to socks lately, I think they are still underrated (even by me). They address potential airflow problems above and below - and on the sides if they are pulled out so they don't contact the hammock.

    I'm impressed that you used lots of insulation for the top half of your body, but didn't wear pants. I conclude that your circulation is better than mine. Or maybe it was the baklava, though that sounds like a sticky fix.

  4. #4
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    Quote Originally Posted by WV View Post
    There are so many variables. I think the sleeper's metabolism and the wind are the ones likely to vary the most. The two ways that I am most likely to feel cold are: (1) CBS from compression of bottom insulation and/or from convection in an air space inside the hammock under my knees, and (2) cold legs or shoulders from air infiltration or compression of bottom insulation at the sides. I try to design to prevent both, and the better the overall shape of my bottom insulation, the warmer it will be for a given thickness because the thickness is more uniform. For some reason I am more likely to overheat from too much insulation in the top layer than the bottom (even though it's usually easier to vent the top), and that's what makes me prefer more insulation underneath. With all the attention given to socks lately, I think they are still underrated (even by me). They address potential airflow problems above and below - and on the sides if they are pulled out so they don't contact the hammock.

    I'm impressed that you used lots of insulation for the top half of your body, but didn't wear pants. I conclude that your circulation is better than mine. Or maybe it was the baklava, though that sounds like a sticky fix.
    I seem to have some mental spelling block regarding balaclava's and pastries.
    Hot from the oven though there could be some temporary benefit not yet explored

    I'm with you on the windsock mostly...- If using a windblocking fabric for your shell it seems of dubious benefit underneath. I can see some benefit up top, much like a bivy sack- but this can be accomplished with a tight tarp in my gram counting view. But overall the concept at least, reducing convective loss via wind- it needs to get addressed some how. My current bridge has a tight tarp that hangs low at the sides (not on last night) that seals the top like a bivy, and provides a wind break at the sides- more or less a sock I suppose but not connecting at the bottom or requiring another layer of weight.

    One thought- there may be a small layer of additional air trapped in my design that, much like a thermo pane window, adds some insulating value. I erred on the side of caution when sizing the shell layer and it has a bit of free space, but as it's sewn in, there is no gap for heat to escape at the perimeter.

    I am a warm sleeper- but not enough to combat such a wide gap...

    But personal mysteries of body and design aside, I mainly wanted to hear more about if I have "conventional hammock wisdom" correct- An UQ should be a bit warmer than your TQ? It seems that way, just curious if others have switched that formula around at all.

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