Gooday all
While birding at Round Hill NR recently I learnt two things. One, when crashing through and climbing under and over the endless thick mallee scrub with bruised shins, scratched face and collar scooping up endless handfuls of sticks into my shirt, just stop, back off and follow the wife, she always finds the easy way. Two, never ever believe a two hundred dollar sleeping bag rated at so-called -7 degrees will keep you warm even if you wear thick socks, long undies, trousers, T shirt, flanelette shirt, two jumpers, a scarf, beanie and wool gloves in the bag at the same time. We also had air matresses and extra blankets and quilts.
So, can someone please suggest a not too expensive but warm sleeping bag when temperatures are about and just below zero, or, how do others go about keeping warm in such conditions.
Thanks
Greg Little
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Oh nice Steve, remind me never to borrow your wetsuit. Gee, us Mexicans are choice aren’t we.
Tony
If you want to get into the physics (and split hairs) – you don’t actually want to get rid of the air. Air has very low thermal conductivity. The problem is heat conveyed by convection – currents in the air inside the mattress and heat conveyed by radiation through the air in the mattress. So what you actually want to get rid of is the currents in the air and the radiation through the air.
One way to do this is fill the air mattress with down. Air is trapped into tiny spaces where the viscosity of air at this scale stops currents. Radiation be intercepted by multiple layers of feathers and will also be much reduced. Both these mechanism also are important in keeping birds warm.
Conduction will actually be increased because although keratin thermal conductivity is low its still 10x higher than air. But despite the higher conduction the estimates I’ve seen have the rate of total heat loss 5-10x less after filling an air mattress with down. Of course you can use other materials like closed cell foam to similar effect but its impressive that down is still so widely used for insulation.
Andrew ===============================
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Hi Greg
Part of the issue is the rating system that is used. I can’t remember all of the details but some of the factors are the rating is based on men and their are different numbers for surviving and being comfortable. I think looking up One Planet website and check out the rating system-how it is arrived at and what it means could be the way to go. If that fails ask at a reputable backpacking/bushwalking store. I have one planet synthetic(vegan) which kept me warm at 4,600 metres in Nepal. Gary
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Hi Greg, my middle son has fixed the cold problem. He sleeps in a swag fitted with an electric blanket run from his 4×4 auxiliary battery via an inverter. Works beautifully.
Tony
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Thick gaiters can be good for crashing through rough vegetation.
Do you mean an inflatable air mattress? That could be the source of the trouble unless you put extra insulation between it and the sleeping bag.
Peter Shute
Hi Greg,
I’ve got two down bags made by Aussie company One Planet,available through Snowgum stores.I think they are brilliant,but do not come cheap.
David Richardson
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You want a mummy shaped down bag greg. It should have a baffle that runs along the inside of the zip to stop cold air seeping through. It should have a hood that you can close around your head. If you think you will be in wet conditions a lot, then you might want a bag with a semi-permeable outer. I have a mountain designs dryloft bag I bought 14 years ago for a Tassie trip [I remember having a damp bag on several trips in the past]. Dryloft bags are especially brilliant if you like to bivvy out or camp in snow caves.
Regards, Laurie.
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Hi Greg and Birding Aus’ers, I recommend the brand “ROCK” Empire series Polar bags. http://www.fixeclimbing.com/pdf/rock_empire.pdf I’ve used them on mountaineering expeditions where I’ve camped in snow and I’ve still stayed warm. I agree with you that a lot of expensive bags aren’t worth the money but if you talk to people who spend time in places like the Andes, Himalayas and polar regions, I think you’ll find Rock bags are recommended b a few of them. Cheers
Inger
Inger Vandyke
Professional Wildlife Photographer and Writer Expedition Leader – Heard Island Expedition (3 November – 7 December, 2011) Assistant Publicity Officer – Southern Oceans Seabird Study Association (SOSSA)Author – The Scrub Turkey Chronicles http://scrubturkeychronicles.blogspot.com/ Mob: 0402 286 437
http://www.ingervandyke.com http://www.ingervandyke.blogspot.com
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