New camping cot!

[ppine]

Re: New camping cot!

Coyote,
The total depth is about 5 inches. With all of that stuff under there the thermarest doesn't need much air. Otherwise it starts to feel perched like you could roll off.
Hunting in Nevada is high, especially for deer and elk up around 7,000-10,000 feet or more. By October it is usually between zero and 15-20degrees above at night. Sometimes it is colder.

[tplife]

Re: New camping cot!

Stopping the heat loss from a cot is pretty easy - something you cannot do with a big air mattress: Replace all the open space underneath with cellular material like pine needles, foam rubber, packing peanuts or similar filling. This allows a barrier that replaces the heat exchanger under the cot with something more like the mattress in a typical RV. Of course, you aren't likely to carry thick foam blocks or bags of packing peanuts along on your trip, so I'll just leave it at that.

[Old Time Camper]

Re: New camping cot!

One of the things you might want to watch out for is the feet on a cot can wear holes in your tent floor. I used to use tennis ball on the feet but my dog is always trying to get at them.
I found these furniture sliders and they are the perfect size for a cot. They are Waxman Reusable sliders 3" in a pack of 16 on Amazon for $11.26. I need 9 for my queen size cot, and the dog can have his tennis ball back!

[tplife]

Re: New camping cot!

Actually, in general solids conduct heat better than liquids, which conduct heat better than gases.

http://www.engineeringtoolbox.com/th...ity-d_429.html

Thermal conductivity:

Air, atmosphere (gas) 0.024
Water 0.58
Aluminum 205

But, ground is a really crappy solid when when it comes to thermal conductivity (probably because of the tiny pockets of trapped air. It's usually a better thermal conductor than air, but worse than water, unless the ground is saturated with water.

Snow (temp < 0oC) 0.05 - 0.25
Soil, with organic matter 0.15 - 2
Soil, saturated 0.6 - 4

The reason the ground is warmer than a cot or an air mattress (if you lack sufficient insulation) is that you have a prayer of eventually warming up a little bit of the ground beneath you. With open air circulation under you, there is no prayer because you are trying to warm up an infinite amount of air. Also, due to warming by the sun and thermal mass of the ground is usually warmer than the cold night air.

As a practical matter, I'm usually so warm when I'm camping that I wake up sweating in the middle of the night.... and that's on an air mattress with a synthetic sleeping bag under me, down bag on top. My mistake is that I love being in a furnace when I lie down to go to bed, but that's just too much insulation in the middle of the night. I've started taking a featherlight 40 degree Marmot Atom down bag and just using that as my top layer.

With my DreamTime setup, I think I could sleep on the polar ice cap and not be cold. Dreamtime with a 2.5 inch self-inflating mattress. Both layers of a synthetic bag on top of that. All of it in a washable rectangular fleece bag. Talk about comfy. I think it's better than my bed....

Nice try, but most solids are non-metallic and are very poor conductors. Metal is a good conductor and an exception, but no one camps on a metal plate. Liquid is a good conductor but gravity gets in the way. Gases are only good insulators if you stop the convection, thus the self-inflating sleeping pad when on solid ground. Gas is trapped in the pad and below the pad is only the ground, a poor conductor. Elevate your pad onto a tubular air mattress or cot with open air and convection becomes very rapid to achieve equilibrium, and you wake up wondering why you didn't sleep better.

[hwc1954]

Re: New camping cot!

I included the thermal conductivity numbers for soil and water logged soil above. Both are poor conductors, but better than air.

The convection in a self-inflating foam filled mattress is stopped by the foam inside the mattress. The convection inside the mattress isn't going to be more or less, regardless of what it is sitting on -- although, obviously, you need more insulation from your pad on a colder surface.

I'm not too worried about being cold from my mattress. The Dreamtime by itself is R = 9, which is among the best insulation of any commercially available sleeping pad. I'm adding the insulation of a both layers of a "15 degree" synthetic bag and 2 layers of 200-wt fleece to the DreamTime. I expect that will be sufficient down to around freezing, which is when I pull the plug on camping. If, by chance, I were to be cold, I guess I could always slide everything off the cot onto the floor of the tent, with a 1/2 inch layer of closed cell foam on top of the ground added to everything else.