Too high of expectations from DAM’s?

I was using an Exped Downmat 7ul recently in about 10-15f and I found it a bit chilly under my hips, putting my sit pad under it sorted it out.

I was a bit surprised to be honest, I think I noticed he cold more so when I was on my side as I was putting a lot weight on that area.

So you generally slept well and warm at sub 0F temps and you're disappointed with the performance of your gear?

I'm confused as to what more there is to expect. More than likely the icing over was just from pressure by sleeping on it. If you press snow it ices up (hence glaciers).

> I could still see some shine off the snow which would be ice.
Perfectly normal. After all, there is SOME heat flow down through any mat, so a little bit of melting and reforming must be expected.

> I also felt last night some cooler areas on my pad, but after staying still for a
> bit, that area/tube warmed up.
Also normal, but a bit cunning.
Since your hips put the highest pressure on the mat, that is where your mat is thinnest. So that is where you get the most heat flow downwards and the most melting at first. Ah, but after a while the snow under your hips gives away a bit, creating a somewhat contoured bed in the snow. That makes a depression under your hips, so the mat ends up pressing over a wider area, so it is no longer quite as thin just there. So it slowly gets warmer there.
Yes, quite normal. We often find we sleep better on snow than on hard ground or rock.

Cheers

I muck around with my Exped 9 DAM when uninflated and inflated to see if I can try make sure the down is evenly distributed and thus properly insulating. Can anyone provide insight as to how the down is contained in the baffles and what, if anything can be done to keep the DAM working properly?

BPL has an article testing insulated mattresses (probably by Roger C.) The R value of the insulation increases the more you inflate the mattress. This also makes it less comfortable for me, but is a way to stay a bit warmer in the cold.

The Exped 9 appears to have a continuous piece of open cell foam across each end of the air mattress. This should stop any migration of the down between tubes. I store mine inflated in the closet and flip it top to bottom every now and again to keep the loft up. If you fill the mattress about half way and slap your hand on it here and there it will fluff the down and distribute it.

I also have a $7 wally mart fish tank air pump that I use to blow air through it for a few days after a trip.

btw- I was out last week at about +5F and my battery powered Micro burst was kind of reluctant to inflate the Exped. Any body else had this problem? The material gets a bit stiff at lower temps though. I wasn't sure if this was typical or I just needed new lithium batteries. Might help to massage the pad a bit to take the stiffness out but I didn't have the patience and just blew it up old school. Might just make this SOP?

Mine has been perfectly reliable but I wouldn't use any DAM without at least a torso length piece of CC foam for back up.

Dustin, just asking for others' experiences, don't know if the mattress was over rated.

Roger, thank you for the informative answer and some of my thoughts too, really appreciate that.

The CA group I have done many winter and summer trips the last 9 years, we've never discussed mattresses much if at all, but then, not everyone goes out in these temps. Our group without me has done sub-zero trips, mine have all been solo trips, relying on my old snowmobile to get me back in there, usually in the Perazzo Meadow area off of Hwy 89, north of Truckee, CA. The snowmobile was sold a week ago, so I'm on my own power now. This would be my 3rd or 4th solo trip in sub-zero temps. Don't think that snowmobile at 35-50mph isn't cold!

Duane

"btw- I was out last week at about +5F and my battery powered Micro burst was kind of reluctant to inflate the Exped. Any body else had this problem? The material gets a bit stiff at lower temps though. I wasn't sure if this was typical or I just needed new lithium batteries. Might help to massage the pad a bit to take the stiffness out but I didn't have the patience and just blew it up old school. Might just make this SOP?"

Batteries generate power from a chemical reaction. As the temperature drops the reaction in the battery slows down and the power output drops. Next time try putting the battery in your pocket to warm it up before using the pump.

I've noticed the same thing. One trip on the snow, it was good but then the very next snow trip, an extra pad was needed, Hmm, weird cuz the first trip was much colder. I have a sneaking suspicion that the down shifts within the tubes, especially when inflating/deflating. No proof – tho when I open the valve at home the foot end has a little extra puff and the body area feels empty. I will say that two pads (blue topped ridgerest + downmat 7) was plenty warm.

Thanks Surf, I'll try that next time. A marginal battery combined with cold temps may have been the problem. A fresh battery and some backyard testing is in order.
Also here's some battery data I found:

Percent Service
Temperature *C Lithium* Alkaline
40 100 100
20 100 100
0 100 60
-20 85 20
-40 60 5

*Lithium Iron Disulfide
Ah sorry, I have no idea how to fix the formatting.

I've used this pad at least once as the sole pad on snow before and been fine. But I'm also older, so I think that can be factored in. In the AM, my camera took a couple pics then said to replace the battery. Well, I had taken enough of my Radius 43 and MSR GK so I was fine. I wanted a few more pics, so I stuck in down in my shorts, took a few more pics later, all was well.:) In my early days of snow camping, I did not have the proper gear, so I combined a couple summer pads and did fine, the dog sleeping on a few beer flats I packed in for her.(Dobie)
Duane

I noticed bottom chill in the torso region at about -10F with UL7. I added a prolite torso pad and was fine to -25F.