407RE: Hammock Camping RE: Radiant Heat Reflectors
- Feb 2 4:45 PM
Thanks Ed. I think the two strongest sections of your book are the part on cold weather and building a hammock IMHO.
And again, I hope everyone doesn’t think I’m putting them down for using a heat reflector or thinking the reason that they are staying warm is radiant heat reflection. I’m just certain now more than ever that there isn’t the science to support that. BUT, people using them are staying warm. If that is true, then how? If we can figure that out, then maybe more efficient systems can be found to make it work.
AKA SGT Rock
From: Ed Speer [mailto:info@...]
Sent: Sunday, February 02, 2003 6:31 PM
Subject: Hammock Camping RE: Radiant Heat Reflectors
Good discussion on heat loss Ernest. I think we all agree that the major body heat loss is from conduction, convection, evaporation & respiration. So unless one has conquered these, it's pretty pointless to worry about radiant heat loss. I gather you feel that the warming benefit from reflective fabrics is due to their vapor-barrier properties, not their radiant properties; or at least the radiant advantages are overshadowed by the vapor-barrier advantages. A good point indeed. Maybe we like using the Aluminum-coated Mylar emergency blankets because they are so light weight--even lighter than plastic sheeting. However, I often use my plastic sheet ground cloth as a vapor barrier on the bottom outside of my hammock--does it work as well as the emergency blanket? Of course, I don't know--they both work well enough to keep using them!
I'd be interested in seeing dependable numbers on actual body heat loss by the various processes. I have found the following, but its' incomplete for our purposes:
"The human body at rest losses 76% of it's heat due to conduction, convection and radiation; the remaining 24% is lost through evaporation, insensible perspiration and respiration".
It would perhaps be useful if we knew exactly how much each process contributes. Then again, nature is never a constant--like you said, things like wind and humidity greatly change the rules. So maybe exact numbers are impossible to determine.
Thanks for your reasoned discussion...Ed
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