Bag Layering???

Almost forgot…My winter pad is a NeoAir All Season LW and I'll be in my Notch.

TA
-Mark

I stack bags as my winter system. it's much more economical for me than buying a -20º bag, which is what I need if I want to go deep-winter.

I use a 15º Mountain hardwear Ultralamina with a 45º Ultralamina inside of it, but I sleep warm. I have been to 15º so far this winter and have not needed both yet. So, I would probably take these two to -15º without hesitation, even lower with a coat and some down booties.

I would supplement the 15º with your 55º for Colorado, but given their deep freeze recently you may want to use the 30 instead depending on whether you find yourself cold or not. Because of the efficiency of the insulation, a puffy jacket should be part of your sleep system with any combination.

The 15º + 55º + Jacket would be my choice.

I know nothing about Schoeller Dryskin, though- someone else will have to comment on that. Judging by the advertising on it, I might even be inclined to use the Dryskin + 15º + Jacket if I was using a tent.

Hey Max…I sleep reasonably warm as well.

I have had my Pinnacle down to 15-16deg with just light merino or poly baselayers, wool socks, and wool beanie. I will have my EB Downlight, my Ether, and a lightweight polartec hoody (grid/powerstretch hybrid) with me as well.

The arctic cold snap is supposed to move off by Tuesday and return to 30deg days and teen nights.

I'd love to take nothing extra, or just the liner…but…I will probably bring all (3) extras and decide at the TH.

-Mark

If you do a search here on BPL, you'll find there is an equation someone posted that will tell you what temperature you can bring your two bags down to.

If memory serves me, it's something like this…one bag 55F and the other 30F

30 – (70-55/2) = 22.5F

Not exactly the savings one might expect. I remember keying into the thread because I wanted to get my 35F bag down to 20F.

There are obviously other factors. What type of pad you're on, what type of clothes you wear, etc.

Edited: Here is the thread I alluded to above:

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=78887

If the two bags don't compress, it should theoretically just be additive

the 30 degree bag will give you (92 – 30) = 62 degrees of temperature difference (skin temperature is about 92)

55 bag will give you (92 – 55) = 37 degrees

together you'll get 99 degrees of temperature difference so it should be good down to (92 – 99) = -7 degrees

except that the surface area will get bigger as the loft increases – let's say the loft of the 30 degrees is 2 inches. Then the outer circumference will increase 12 inches. If your average circumference is 36 inches, and it increases by 12, that's 33%, so you'll only get 66% from the 55 degree bag = 25 degrees, so together it'll be (92 – 62 – 25) = 5 degrees.

So the formula would be:
temperature rating of warmer bag – 2/3 * (92 – rating of thinner bag)

But all of that is B.S. – if there isn't enough room, the outer bag will compress the inner bag so you won't get this much – figure the second bag might give you 10 or 20 F reduction but you really have to test it in the real world

I'll have to search the internet to see if a calculation for this can be confirmed. I find it difficult to believe that adding a 55F bag to a 30F can yield a 5F bag. That makes no sense to me.

I went to WM's website and added the down fill ounces for a 40F bag to a 30F bag. It was less than the down fill ounces for one of their 5F bag. There would be even less fill with a 55F bag than a 40F that I used to compare.

I agree, that's just theoretical

If you add a second bag it will almost certainly compress the inner bag or both bags, so it just depends on how much they compress so there is no formula

But, if the outer bag is big enough, it should be 5 F. You could have a quilt and lay it over, but then heat will leak around the edges some

Can you effectively layer your Pinnacle without impeding on the loft of the bag?

An adequately lofted EN rated 15F down bag on its own should be warmer than a compressed down bag stuffed inside a 55F summer weight bag.

I would start refining your supplemental clothing choices, carefully consider camp selection on your trip, and shore up pad insulation by adding a CCF pad.

Thanx for the follow-ups guys…I'm gonna check the girth of these extra bags tonight, and see how the fit is (or isn't) over the Pinnacle.

I think I will most likely end up with the Pinnacle, the Dryskin liner, and my supplemental clothes.

I will have my 30deg bag with me in the car for rest stop snoozing, so I'll have some back up if conditions change before we get to the TH.

TA
-Mark

Hey Guys…Figured I would follow this up, just for info/stats sake…

I used the Pinnacle inside the Nanowave and compression didn't seem to be an issue, as far as I can tell.

The low was -5 deg and I was completely comfortable wearing 200w merino top and bottoms, thick wool socks, and a Powerstretch beanie. In fact, I had to pull the hood away several times during the night.

FWIW.

-Mark