a really stupid question

I’m a fair-weathern paddler.

I never camp in the snow (not since I retirted from the Air Force that is).

And although I have paddled a SoT in December, this is Southern Arizona which means… maybe 40 degrees air temp.

So, after one Autumn camping trip, I found my old 50-d bag didn’t work in 40-d weather…

So I bought a lighter, 30-d bag that packs better.

I’m also planning t obuy a duplicate so I can zip them together to make a double bag. you know why.

Now i’m going kayak camping in minnesota end of next month and am wondering…

Here is the STUPID question…

If I shove one 30-d bag into another 30-d bag, what does that do to the temp-rating?

Turn it into a 60-d bag because I’ve compressd the fill or change it to a 20-d bag because i have twice the insulation???

Since my only experience with low-temp bags was military ones, I never thought about this.

Increases the insulation generally.

– Last Updated: Aug-31-09 2:36 PM EST –

Using a sleeping bag within another will increase the insulation. The less compression that occurs to the insulating material, the better it will work.

Note that the temperature ratings aren't that accurate.

Note that a single bag designed for the same temperature rating might be lighter than two used together.

2 bags
I’ve used an over bag or a bag liner to increase the temp rating of my bag. It works but sometimes it can be a pain if you toss and turn, just imagine trying to unzip two zippers that don’t like up anymore.

Stuffing two bags will compress one and it will probably feel pretty confining. Can you unzip one and use it as a blanket on top of the one you’re in? The insulation you sleep on gets compressed and doesn’t do much good anyway.

The more coats you wear the warmer.

The more socks you wear the warmer.

The more insulation in your roof the warmer.

The thicker the sleeping bag the warmer.

the rates are a ball park. and never leave a bag in the compression bags when not in use. clean and fluff them yearly to remove oily skin residue that flattens the fibers minimizing dead air space.

Suggestions for N MN in Oct

– Last Updated: Aug-31-09 3:34 PM EST –

If your 30 degree bag zips together with one of your lighter bags here's my suggestion. Get full length and maybe even insulated sleeping pads to keep the ground cold from transmitting to you; put the lighter bag down on top of the pads, the heavier one up to loft on top. If it's one of those very clear, calm, frost on the pumkins kind of nights, plan on wearing your polyprop long underwear, dry socks, and your thin wool voyageur toque (to keep your head warm). If its really cold, be sure to take along an additional micro fleece top and bottom layer to put on, or a fleece blanket to cover over the 30 degree bag. I think you will find the polyprop long underwear and the wool toque as being the most effective to stay warm, rather than putting one bag inside another.

it will make it warmer, but remember, the rating on the bag is not the temp that you will be comfortable at, it’s the temp that the bag is still “safe” to use in. I generally add about 10deg to get the comfortable temp.

You might also try

– Last Updated: Aug-31-09 9:23 PM EST –

a lightweight bag liner. Cabelas has some that cost less than $30.00. They increase the bag's warmth, plus you can use them by themselves in the summertime.

Speaking of old military bags... If you can find one in an old surplus shop or online, I'd recommend the wool bag liner they used to make for the older mummy bags. I still have one from my old Civil Air Patrol days in VT and it's been worth its weight in gold.

bag inside bag
I’ve done this before. On a winter climbing trip in the Adirondacks i put one 20 degree bag inside another 20 degree bag. The thermometer bottomed out that night at -30 degrees. I had the two bags inside a bivy sack and i was wearing my down jacket. I was able to sleep pretty comfortably but i wouldn’t say i was toasty. But it worked.

So i think you’ll be fine with the double bag thing. Just try it at home first to see how it goes. It’s just a lot of zipping, especially if you have to pee at night. And you won’t have much room inside the bag, but that only makes it more thermally efficient.

Are we on the right track?
You said: “I’m also planning t obuy a duplicate so I can zip them together to make a double bag. you know why.”

In my neck of the woods, when you talk about zipping together two sleeping bags (you know why), it means you are going to have company in there with you. This gets me to thinking . . . How long ago was it the wife and I began sleeping in our bags not zipped together? (I think it began when the kids came.) Now, I think we have not gone back because one of us (I won’t say who) gets up to pee too much.

you will have to test
I don’t think there is any to know for sure until you try. Also watch the temps in MN as it was 15-d cooler in July when we were there then was forcasted. It was a cold couple of nights.

I’ve never had a problem
with my 20 degree bag and a silk liner bag in sub-freezing temps.

2nd the liner idea

bag liner
Those inexpensive fleece sleeping bags make good liners as well.

I also recommend Ridge Rest sleeping pads. I used one in Norway (about 150 miles north of the Arctic Circle) and didn’t have any problems.

Can I come home with you?!?!?!
I’ve been trying to move to AZ for 3 years. Do you care to help a fellow paddler move to the best place on earth?

cell 570 352 8806 Dennis

Not a stupid question
Actually a very good one.

Zip the two together, double the size
and add a willing partner of your make and model. 96.8 + 96.8 = 193.6 degrees / Add friction and you will toasty warm

30 + 30 = 60