On the other hand, snow has a much higher specific heat than earth or rock (and most other things), and even at higher temperature, will suck up heat much faster than even significantly colder rock. You can demonstrate this simply. Put an ice-cube size rock in the freezer overnight. Next day, hold the rock in one hand and an ice cube in the other for a while, or drop each in a glass of water and feel the difference.
Thats why we use ice in our drinks instead of, say, chilled marbles, and why melting snow is such a lousy (if necessary) source of water.
For thermal qualities, give me dry rock, gravel or sand over snow any time. Frozen soil is somewhere in between.
ice doesn't "suck the heat" from the glass, it melts faster because it is warmer than the rock, which will probably form ice on its outside when droppped into water. But none of that simulates sleeping on an insulated pad.
Holding an ice cube and a cold rock in thin neoprene gloves for half an hour is what you want to do after that night in the freezer, and do that in a place that is as cold as that freezer. Now you have a fair test that simulates what happens under your ground pad and tent floor when it's really cold.
Bit of a late addition here Im afraid Melting Ice or Snow is an example of an endothermic reaction, which draws energy from the environment in the process of the reaction this may be why the Ice cube feels colder. It is incorrect to say the ice is warmer if they are both at the same temperature. clearly. Also we need to take into account "the latent heat of conversion" IE the ice at zero degrees Celsius (or there abouts) draws energy from the environment to become water at zero degrees Celsius ( or there abouts) the energy has not raised the temperature in this part of the reaction,it has broken the extra hydrogen bonds formed in the open lattice structure of ice compared to water
Probably irrelevant in regards to the overall discussion.
broke down and bought an Exped Downmat UL7. Still don't have it, but looking at a cold climate trip in fall, I wasn't going to bring two foam pads, and a single isn't really that comfy nor warm. So I went all luxury with the latest and lightest winter pad.
Will report back how it works in the Sierra after I return in October. I was looking at the Neoair Xtherm as well, but I couldn't find it at a decent price, plus some reviews mention that it is quite a noisy pad. The Exped UL pump design is pretty genious for their new models and saves weight, while keeping moisture out of the pad.
[quote=Fishmonger] The Exped UL pump design is pretty genious for their new models and saves weight, while keeping moisture out of the pad. [/quote]
Thats pretty ingenious... you know it had to have been invented by some poor trek leader trying to take care of a sick team member who brought a blow up sleeping pad to 12000'. "What (gasp blow) are you trying... (gasp blow)... to do (gasp blow)... kill me (gasp blow)?"
I splurged on the battery powered model at 2.3 oz for when I backpack with my wife and need to inflate 2 NeoAirs. I have an abundance of hot air (gasp blow) so I can inflate one (gasp blow) without passing out (gasp blow) but the second one (gasp blow) makes me so light headed I become an air traffic control hazard (gasp blow) and I prefer to have my wife save her breath for more important things (blow gasp ). :)
received the Exped UL7 yesterday. The first inflation took 5 rounds with the "shnozzle bag," but really was as easy as suggested in the video. Deflation takes a while if you want to get it back into the rather tight stuff sack. Sure wished they had added half an inch of extra room.
I have the Long/Wide version because all others are too short for me, and it is definitley the widest pad I ever had. Also very comfy at over 2" thick. To keep the weight down the fabric is rather thin, though - it comes with four repair patches and glue, and I am packing an extra patch of Tyvek to put under it to avoid having to read the rather lengthy patching instructions it comes with :grin:
I'll take it on the trail for a late season Muir Trail in about 3 weeks - short days and long nights in fall, so it'll get ample use.
> [color:#000099][i]Deflation takes a while if you want to get it back into the rather tight stuff sack.[/i][/color]
I found deflation of the self-inflating Thermarests with the internal insulating foam padding was a problem. Then I learned to suck the air out by using my mouth and inhaling the air out of the pad.
I could sure shrink the pads down so they'd fit into the stuff sack. The padding inside was so compressed that after I put the pad into the sack, I'd open the valve and allow it to re-inflate a little to better fill the sack.
One guy warned me of lung problems from this, but I never experienced any.
[quote=Fishmonger]Deflation takes a while if you want to get it back into the rather tight stuff sack. [/quote]
I find this:
with Thermorest and others with foam, I release the valve, then immediately start rolling it up, pressing on it with my knees and weight to squeeze out all the air
different technique with the light weight ones (like NeoAir)- I find it better to release the valve, then lay down on it with it flat for a while until it stops hissing. Why? It lets so much air out of it that I can then fold with only a little hand squeezing, then easily put into the stuff bag . (I could have tried that with the Thermorest self-inflating but never did)
