Air Bed Puzzle?

[woodbloke]

On our recent trip to Switzerland, we camped for a couple of days at Lukerbad in the Alps, at an altitude of 1438m. On one of the nights we had a bit of a storm with driving rain and high winds... then during the night the temperature dropped to what I assume was well below zero. To show you just how cold it got, here's a pic of the campsite in the morning:

The clear blobs on the Landy bonnet are not water, but solid blocks of ice. The rain must have frozen the instant it hit a horizontal surface, me in the background doing brekky (rosti and baked beans with lots of tea). We had been sleeping on standard air beds like this but were both absolutely freezing in the night, as the air beds didn't warm up and we could feel body heat being drained away thru' the sleeping bag....the underside of my carcass was gradually getting colder and colder and it wasn't until I put some towels on top of the air bed that I started to get a bit warmer. So here's the question.....if the air beds are full of air (naturally enough) which is an excellent insulator, why were we both so cold? I've been trying to puzzle it out for the last few days. As soon as we got to a warmer site the air beds were fine. Can anyone please shed a bit of light on this one. Many thanks - Rob

 

[Paul Chapman]

Surely the answer is to get a double size air bed and get the wife to warm up your side before you get in

Running out the door before Alyson reads this....

Paul

 

[spadge]

Hi

Air is only a good insulator if it is trapped to prevent it moving and transfering heat.
Airbeds are poor insulators because the big spaces inside allow convection currents. So your body warms the air next to it which is then cooled by the ground and so on and so on. They are not meant to insulate you only to provide some comfort.
You can buy Thermarests which are airbeds that contain a closed cell foam. This stops any convection current and helps minimise heatloss but IIRC the thickest ones you can get are only about 50mm thick and they are fairly expensive.
As you already have the airbed buy some closed cell foam camping mats and use these underneath the airbed. That way you get insulation from the mat and comfort from the bed. Job done.

Cheers

Grahame

 

[mudman]

Small air cavities are good insulators, but large ones are not as convection currents can start up taking the nice warm air away from your body and replacing it with nasty cold air.

Blast, beaten to it. That'll teach me to answer the phone.

 

[woodbloke]

Hi

Air is only a good insulator if it is trapped to prevent it moving and transfering heat.
Airbeds are poor insulators because the big spaces inside allow convection currents. So your body warms the air next to it which is then cooled by the ground and so on and so on. They are not meant to insulate you only to provide some comfort.
You can buy Thermarests which are airbeds that contain a closed cell foam. This stops any convection current and helps minimise heatloss but IIRC the thickest ones you can get are only about 50mm thick and they are fairly expensive.
As you already have the airbed buy some closed cell foam camping mats and use these underneath the airbed. That way you get insulation from the mat and comfort from the bed. Job done.

Cheers

Grahame

Ahhh, that explains it, many thanks. Our airbeds were in fact on top of camp cots like this so were well off the ground, but we were still freezing . Will be getting some decent Thermarest mattresses for next years expedition and we'll put them on top of a camping mat as well.

Paul - never mind SWIMBO to warm me up, I had a few tots of hooch that night to try to warm up.....didn't make any bl*&%y difference - Rob

 

[Adam]

[Will be getting some decent Thermarest mattresses for next years expedition and we'll put them on top of a camping mat as well.

My experience is I'd rather have a 40mm thermarest either for temperature, or general comfort over a air mattress any day. Well worth the investment.

Adam

 

[mr]

Paul - never mind SWIMBO to warm me up, I had a few tots of hooch that night to try to warm up.....didn't make any bl*&%y difference - Rob

Did your sergeant never tell you not to take booze on exercises? Unfortunately despite the "warming burn" the hooch only has the effect of flushing the skin with warm blood which then cools down rapidly and can lead to hypothermia. So it does you no favours at all really.

Cheers Mike

 

[Harbo]

Rob - air bed on top of a cot - what decadence - suprised you did not roll off ?? :lol: :lol: :lol:

Last time I went camping we used straw palliasses - very snug!

Rod

 

[woodbloke]

Rob - air bed on top of a cot - what decadence - suprised you did not roll off ?? :lol: :lol: :lol:

Last time I went camping we used straw palliasses - very snug!

Rod

Did once - Rob

 

[RogerM]

[Will be getting some decent Thermarest mattresses for next years expedition and we'll put them on top of a camping mat as well.

My experience is I'd rather have a 40mm thermarest either for temperature, or general comfort over a air mattress any day. Well worth the investment.

Adam

SWMBO and I returned to camping last year and bought a pair of Thermarest Luxury Camp mattresses to use in Yellowstone and Mt Rainier National Parks in what turned out to be freezing conditions. After my memories of cold nights 30 years ago on conventional airbeds these Thermarests are the absolute "Dogs Doobries"! We decided to get the best money can buy on the basis that even the best ones only cost the same as one night in a hotel, and if we didn't get on with them we could flog them on Ebay. They come in various thicknesses from 2cm to 6.3 cms - so the 6.3 cm one it was! There is a version called the "dreamtime" but these are just the 6.3 cm Luxury Camps with an additional layer of foam and a fleecy cover rather than a genuinely thicker mattress.

They are self inflating so no pumping up is involved - just unroll them and leave them for 10 mins and they're ready to use. I would never go back to a conventional airbed after using these. Expect to pay about £85 online - you may find them cheaper if you look around tho'.

link

HTH

 

[woodbloke]

Got a couple of 4 season Thermarests today from Blacks, didn't realize that you need to store them flat and inflated under the bed...were advised by the guys in the shop that this is the right way to store them for an extended period. They also said that using the Thermarests on top of a foam carrymat was a better than to use them directly onto the groundsheet of the tent. We also got some silk inner liners for our sleeping bags so we should be quite toasty next holiday in the mountains - Rob