Mole, wasn't that thing in one of the Apprentice episodes last year??
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.JPG) Fearnmore Which One? this?
or this?
Don't know as I haven't got a TV But I have got this: which is similar to the cocoon I've finally finished my home-made quilt. Here's a few snaps for those who are interested. weight - just under 750g I should be happy to 4degC, some US types reckon they go frosty with this level of insulation.
Also, it fits well over/around my PD400, so making it good for very cold weather, if a little heavy
head:
footbox (zipped and velcro)
foot - unzipped
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 I've been down to about minus 15 in a minus 4 Combi bag with a good down jacket and thermal leggings and an Exped downmat. I don't get what's so 'unconventional' about the idea of boosting a bag with clothes? If you're at home in bed and it's cold you'd put some PJs on. What's the difference?
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The Raku thingie, Mole.
Don't have a TV either but watched it on the 'puter!!
In one episode they had to sell fancy new gadgets and one of the 'novelty' articles looked exactly like the Raku, but yellow. Can't remember if it was last year or the year before, but I'm positive it was the very same thing. I thought it was daft but if I recall right there was this wily female contestants who sold loads to a gullible shop keeper in the Midlands by giving him the sweet eye and won the episode.
It looks like a fluffy deep diver's suit, the Raku, not the wily female contestant...
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 fearnmore, more likely a Selk bag... but I didn't see it either
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 > as far as a quilt is concerned, you must be car camping or something. i've NEVER heard of anyone taking a quilt up a mountain  but hey, each to their own. Think of the 'quilt' being discussed here as simply an unrolled sleeping bag (like a traditional eiderdown). The logic is that you mat provides insulation from the ground (and, anyway, insulation under your body is compressed, so pretty ineffective at trapping warm air). A quilt can also be considered more versatile. Don't think of a cheap, heavy quilt you'd use on your bed at home. Think about a minimalist thing, using the highest performance down money can buy, in the lightest of enclosures (Quantum, Cuben, etc). If you want to see examples of such things, search for 'quilt' in the MYOG forums at BPL.
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JB. Yep, that rings a bell. That's a neat idea, innit. You can sleep on the go.
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Going back to the question of separate legs, arms etc. I think a full thermal analysis would be seriously tricky... but intuition seems to suggest that keeping limbs in thermal contact with eachother is helpful - it has the effect of reducing the exposed surface area at constant volume. Think of it this way. You're standing out in the cold with insufficient clothing to stay comfortably warm. What do you do by instinct? You bring your legs together and cross your arms over the body putting your hands under your armpits. If it got really bad you'd squat in a ball. All of which would reduce your exposed surface area and bring up your volume:area ratio. I'm not 100% sure you can extend this indefinitely, but I am fairly confident that it should be warmer to be in a bag than the same amount of insulation in clothing. If the clothing you wear is damp or constrictive then it could easily worsen your situation by increasing evaporative heat loss in the first case and reducing blood circulation in the second.
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Aye, John, I was joking about the neat idea of course. It's the same reason why mitts are warmer than gloves, isn't it.
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On my next winter trip I'm going to sleep bollock nekkid in my bag and see if I'm warmer 
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Actually I used to do that Sean when I used a heavy synthetic that could go in the wash once in a while. There's no explaining the idiocy of youth... but I was OK to -10C @ 5000m in Nepal...
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 Aye, John, I was joking about the neat idea of course. It's the same reason why mitts are warmer than gloves, isn't it. Is it? Or are they warmer because the mitts have a smaller surface area than the fingers of a glove. I agree that a bag which was narrow enough to make you keep your legs together while in it would have less surface area than 'trousers', but who would put up with such a restrictive bag? Edit for typing error.
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| Edited: 12/03/10 16:12 |
I'll let John The Scientist answer that...
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Was he one of the Apostles? 
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 I thought he was in the A-Team...
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I'm talking about Johannes of Bromley, the Man in the Space Poncho. 
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Frum,I can't speak with authority on this one. But consider this. You're wearing some nice warm trousers. Which is warmer - standing legs apart or legs together? I’d say there was a significant warmth advantage of having your legs together which happens naturally if you’re on your side in a sleeping bag and isn’t far from the truth lying on your back. I’ve managed to bivvy in fairly cold temperatures – January in Northern India - without a sleeping bag in the past using a down jacket for my body and wrapping a thin blanket around my legs a couple of times inside an army goretex bag. This had the effect of keeping my legs together during the night and I can’t say it was cosy exactly but didn’t get cold enough to stop me sleeping. I reckon night time temps were around +5C. I do have chunky thighs which might help!
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| Edited: 12/03/10 16:18 |
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I don't dispute that the 'legs together' effect helps keep you warm, and agree that a bag narrow enough to make you do so would be warmest. I was suggesting that the width of a normal, comfortable sleeping bag gives a greater surface area and more internal dead air space which offset this advantage. The result of the trouser-legged-bag would be about as warm as the conventional bag while you sleep, and more convenient to wear while sitting in the tent cooking, etc. I'll try and modify a bag some time to test these theories.
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 What about those bags that have elasticated sections around the legs, are they warmer than the same spec bag without the elastic bits? Mountain equipment make them I think.
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