Combined bag temperature rating

**Grinder** · 11-30-2006, 08:21

I'd like to get some opinions on this.

When you combine two bags (one inside the other) how much does the combined temperature rating go down?

For instance is a 30 dereee bag inside a 30 degree bag equivalent to a 0 degree?

Specifically, I have the GG lightweight bag that was discussed on this list a month or so back (50 degree rating, I think) .I also have an Eddie Bauer Bag liner (a poly blanket with zipper). Then there is the poncho liner I just bought (I slept comfortably with just it last night.-- low of around 60 degrees)

What temp could I be comfy at with combos of those three items??

I'm still playing with gear to optimize overall bulk for a given temperature.

When I win the lottery, I'll buy down and be done with it, but until then--- the dance goes on.

Miles of Smiles
Tom

**Peter_pan** · 11-30-2006, 10:25

Lot depends on how well they go together... if one restricts the other from full loft then you won't get a lot of gain...

First estimate take the send bag reating subtract it from 70, devide that number by two and then subtract it from the first bag rate for a combined value ex

Two 40 degre bags... 70-40 =30 devided by 2 =15 subtracted from other bag 40-15=25 for a first cut estimate of the combined bags... it may actually be better but probably not worse, so this works as a good conservative estimator, IMHO.

Pan

**Grinder** · 11-30-2006, 10:42

Thanks Pan,

That's just what I was looking for.

I have a weekend outing in North Florida coming up. With my 50 degree bag and a baag liner I should be good to 40, which is around the worst case low. I'll have the poncho liner in reserve.

Tom

**stoikurt** · 11-30-2006, 15:16

Originally Posted by teblum

Thanks Pan,

That's just what I was looking for.

I have a weekend outing in North Florida coming up. With my 50 degree bag and a baag liner I should be good to 40, which is around the worst case low. I'll have the poncho liner in reserve.

Tom

Where in North Florida?

**Grinder** · 11-30-2006, 17:46

We were going to go camp on the beach in the big bend area. Possibly as for north/ west as Destin.

My buddy came by today to tell me the trip is off. He has a conflict.

I hate it when they do that!!

Tom

**FanaticFringer** · 11-30-2006, 18:00

Funny I was thinking earlier about what temp my 2 Guide Gear 50 degree bags would be rated together. I was guessing 30. It looks like it is closer to 40.

**stoikurt** · 12-01-2006, 09:03

Originally Posted by teblum

We were going to go camp on the beach in the big bend area. Possibly as for north/ west as Destin.

My buddy came by today to tell me the trip is off. He has a conflict.

I hate it when they do that!!

Tom

Sorry to hear that. It should be nice and cool here this weekend (in the low 40's) with the lowest temp (low 30's) expected Monday night. If you make it up this way let me know and maybe I could come by and meet you and check out your system.

WV · 02-21-2010, 00:38

Originally Posted by Peter_pan

Lot depends on how well they go together... if one restricts the other from full loft then you won't get a lot of gain...

First estimate take the send bag reating subtract it from 70, devide that number by two and then subtract it from the first bag rate for a combined value ex

Two 40 degre bags... 70-40 =30 devided by 2 =15 subtracted from other bag 40-15=25 for a first cut estimate of the combined bags... it may actually be better but probably not worse, so this works as a good conservative estimator, IMHO.

Pan

I found this in Articles; it's useful. However I had to read it 3 or 4 times to figure out what was being said because of the typos. I'm used to decoding ordinary posts, but I think articles could benefit from a little editing. It took me a while to recognize that "send" was "second". I think Pan's computer hiccuped and dropped two letters. The other misspelled words are easily recognizable. I think it should be clarified which bag is the first and which is the second. Which is inside the other, and why? If the bags have different ratings, you get different results if you change which one is "first" in the equation.
I'm guessing that with a rule of thumb like this there's much wisdom in Pan's caution in the first sentence.

**Peter_pan** · 02-21-2010, 09:05

Originally Posted by WV

I found this in Articles; it's useful. However I had to read it 3 or 4 times to figure out what was being said because of the typos. I'm used to decoding ordinary posts, but I think articles could benefit from a little editing. It took me a while to recognize that "send" was "second". I think Pan's computer hiccuped and dropped two letters. The other misspelled words are easily recognizable. I think it should be clarified which bag is the first and which is the second. Which is inside the other, and why? If the bags have different ratings, you get different results if you change which one is "first" in the equation.
I'm guessing that with a rule of thumb like this there's much wisdom in Pan's caution in the first sentence.

As, mods,

This article was originally a reply to a post that was moved to the article section on general merit... My edit button capabilty does not reach back that far... Would one of you please edit this article... Thanks.

Pan

WV · 02-21-2010, 11:11

Originally Posted by Peter_pan

As, mods,

This article was originally a reply to a post that was moved to the article section on general merit... My edit button capabilty does not reach back that far... Would one of you please edit this article... Thanks.

Pan

Mods,
I didn't see the thread this was taken from until I had composed my response to the article. The thread has lots of useful info, explained in more detail. It might be good to relabel the article's link to include "more info available" or somesuch, in addition to "discuss this article or suggest new entry".