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which pad for 20 F
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George L Privett
(gprivett)

Locale: Whitehorse, Yukon, Canada
- 35 C with 7XL Exped Down Mat on 01/02/2009 20:35:12 MST Print View

It seems like it has been around minus 30 C for weeks, and I have been reluctant to go winter hiking and camping except for a couple of day hikes on snowshoes. Cabin fever was starting to rear its head. It was -35 this afternoon and I decided on the spur of the moment to test some gear.

Clothing: (not my regular hiking gear) light wool long johns, cotton polyester pants, cotton t-shirt, polyester pullover, breathable shell, fleece vest, poly insulated inner, leather 'street boots' with thin insulation and thin wool dress sock.

Pad: 7XL Exped down mat

Sleeping bag: 30 year old down rectangular Mount Whitney bag, lots of miles, 4.25 lbs total. No tags with specs - just some nylon tape covering holes.

Location: outside deck with poly-tarp shed to keep out snow.

Test 1
1. I took a fully inflated Exped outside in the cold. In a couple of minutes the air in the Exped seemed to shrink by half and it sounded and felt like waxed paper. I added more air with the pump/bag by rolling the bag shut rather than pressing it on the floor. It was not 'hard' full.
2. Covered it with the sleeping bag in quilt fashion.
3. Lay on the mat under the quilt for a few minutes - felt a bit cool but not cold. Could probably slept if tired.

Test 2
1. Put a 16" x 50" foil bubble wrap down centre of mat. (It is used to wrap hot water tanks and pipes. Put a cheap sleeping bag with 1/2" polyfill lined with a mylar space blanket under the down sleeping bag.
2. Lay down for about 30 minutes - didn't feel cool, even with the jacket unzipped. Would have stayed longer but had to pick up some folks downtown.

Conclusion: I would probably feel confident winter camping in a tent or tarp at -25 C with a 7XL Exped and a down sleeping bag. I would probably take take an extra foil bubble wrap or thick foam pad as a precaution. It might make sense to take a pulk or toboggan for the additional weight and bulk.

George - Whitehorse, Yukon

Michael Cheifetz
(mike_hefetz) - MLife

Locale: Israel
Prolite4S +maybe GG thinlight1/8" on 01/03/2009 10:51:20 MST Print View

Jay,
FWIW i have slept with ease @ around 20F with Prolite4S and feet on rucksack. this was inside doublewalled tent (TN Laser) so no wind. I used a custom Nunatak alpinist (extra fill) so was REALLY toasty.
i can relate to your question since i am also looking at hikes where temps will hover around the 32F range but MIGHT get to 20F or so. and would sleep without a second thought with prolite4 and your bag (assuming of course you have tent and balaclava and such.
I am now converting to tarp+bivi for shorter trips and plan to use 40F bag+ MB UL jacket and pants+cocoon 90 balaclava (might also try my yet to be ordered MLD XP 2.5oz/syd) In these circumstances i will probabaly take GG torsolight and GG thinlight 1/8" for feet
YMMV
Mike

Greg Mihalik
(greg23) - M

Locale: Colorado
Re: - 35 C with 7XL Exped Down Mat on 01/03/2009 11:16:12 MST Print View

George,
You said -
"I took a fully inflated Exped outside in the cold. In a couple of minutes the air in the Exped seemed to shrink by half and it sounded and felt like waxed paper. I added more air with the pump/bag by rolling the bag shut rather than pressing it on the floor. It was not 'hard' full."

No experience here with -35C, but inflating a mattress just to the point of "no contact" between body and ground seems to keep things warmer. It will look about 1/2 full.

Perhaps not as much loss out the now shorter sides?
Maybe a more restrictive convection path to the ground?

Definitely more comfortable to lay on than a "firm" mattress.

Michael Cheifetz
(mike_hefetz) - MLife

Locale: Israel
cool air=less volume on 01/04/2009 04:28:23 MST Print View

George and Greg,
I assume you are all aware of the fact that air as it cools also contracts in volume (approx lineraly) so your account is very reasonable - you inflated with warmer air and then it cooled off and the pad shrunk!
For that reason i always inflate my thrmarest way before i have to sleep and let it cool down and then inflate a bit more if i want...the worst thing is inflating with (in case if the Thermarest) your warm breath right before you go to sleep and then wake up at 2AM to a really thinned out mat!

BTW - a bit off thread - have any of you had real trouble with inflatables and frost inside - i.e. if you inflate with breath and then it freezes inside? I havent any trouble for temps around 20F or so but i guess thats because not cold enough and my body warmed it up.
Is there any other inflation trick w/o using breath?
Mike