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11552Re: Layering?

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  • André Corterier
    Dec 1, 2005
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      Careful with the term "dead air space". Dead air space is "dead" (as
      in: the air does not move around in it enough to effect convective
      heat loss) only when the volume of air is small. Hence, down
      insulation with its many, many individual fibers creates many *very
      small* individual spaces of air (this is slightly simplistic, but
      will do). I am not sure at what volume of uninterrupted air
      convection starts, but am rather sure that a cubic inch is more than
      enough. That's why garden variety air mats don't insulate at all
      well. So the "extra" space you have in your sleeping bag likely
      isn't "dead" air space but extra space you a) need to warm up and b)
      contributes to convective heat loss.

      So my money would be on keeping the liner in the bag in order to
      reduce "live" air space.

      Of course, if you're doing this close to home and the forecast is for
      two similar nights in a row, I'd suggest you try it out both ways and
      see for yourself which is better.

      Finally, if the "liner" is large enough to accommodate both the pad
      and the bag (without pressing down on the bag's loft) it must be
      huge. Probably better to have a liner for the inside of the bag (you
      don't want anything to press down on your bag from above).


      --- In hammockcamping@yahoogroups.com, PennyBright <GreenSoul@g...>
      > I'm gearing up for my first test of winter hammocking, and was
      > on adding a fleece liner bag I have to my system.
      > Any idea if it would be more efficient insulation wise to use the
      > inside my bag , or around it on the outside? I'm thinking that
      inside it
      > would reduce my dead air space (my bag is a little large for me),
      > outside it would protect the warmth in the loft from being stripped
      away as
      > easily.
      > Also, if I used it outside the bag, I think I might be able to
      slide the
      > blue pad into it..... I'm not sure, I'm going to test that later
      today. I'm
      > not sure if there would be any value in that or not.
      > Anna
      > --
      > http://long_trails.blogspot.com/
      > [Non-text portions of this message have been removed]
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