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sseaman
11-01-2010, 08:16
I have a 35 degree REI bag, and a 40 degree REI bag, I did a trial run a few weeks ago in the upper 30's with the 35 degree bag, and stayed warm, with the my underquilt in place. I am getting ready for a weekend trip and the forecast is for mid 20's. The 40 degree bag is 3/4 zip, so I am thinking of using it as an over quilt.

Any thoughts?

sr1355
11-01-2010, 08:31
I'd be interested to hear how it goes for you. I have a zero bag and a 25* bag that I'm thinking of figuring a way out to NEST together to use your term... I'm wondering if you might get some insulation compression in the footbox with a 3/4 zip over the other bag....

Knotty
11-01-2010, 08:36
It can be hard to deal with two bags in a hammock but you do what you have to. The benefit isn't always as great as you might expect because the outer bag can compress the inner.

There's a great article on the subject out there but I can't remember where. Maybe someone has a link.

fourdog
11-01-2010, 08:46
The key to using two bags, is one is over sized from the other and then you do not have the compressin.

Also a lot of the sythinitics do not compresses as easly as others and or down.

Wiggy bags are a good example of that and always remember loft =
warmth.

Just because a mfg says there rating don't mean its true. If you don't have the loft you don't have insulation.

fourdog

tjm
11-01-2010, 10:22
IMO, when nesting two bags in a hammock, you should consider the bags as your TQ only.


This is my experience nesting two sleeping bags while using sleeping pads in a tent.

When I first started, I bought a BA Encampment model sleeping bag because it fit my budget and I liked the insulation on top and pad on the bottom BA system.

The bag was rated for 15*F but only worked to ~25-30*F for me. I think the semi-mummy cut caused me to have too much dead air space.

Later I bought my son a MARMOT sawtooth down 15*F bag. That bag has worked very well for him and I have used it comfortably to 15*F with a light wool base layer.

Fortunately, the down bag fits into the syn bag very nicely with ample room for the down to expand. I have used the nested combo down to 0*F with a base layer, down vest and wool hat and was toasty.

The insulation of a quilt or sleeping bag is primarily related to its thickness [loft].

US Army Quartermaster insulation table
temp ... sleeping ....... light work ..... heavy work
40F .........1.5" ................. .8"................. .20"
20F .........2.0" .............. 1.0" ................. .27"
. 0F .........2.5" .............. 1.3" ................. .35"
-20F ....... 3.0" .............. 1.6" .................. .40"
-40F ....... 3.5" .............. 1.9" .................. .48"
-60F ....... 4.0" .............. 2.1" .................. .52"

Remember, in a hammock, you need this above you and below under you.

sir_n0thing
11-01-2010, 12:12
Be careful when nesting a down bag inside of another bag. Even if the outter bag is larger, the weight of the outter can still compress the inner.
I've been playing with using a light 50° synthetic bag as a liner inside of various other bags. Waiting for cold weather to test the results. :-)

wisenber
11-01-2010, 19:25
Mountaineers have been using overbags for years. Usually the outer bag is more water repellent and over-sized. This keeps outside moisture from your down and adds more insulation. Simply nesting normal bags will probably keep you warmer than a single bag, but not as warm as the combined rating of both bags due to compression. It's an awful lot more bulk without the proportionate benefit.

..and I'd hate to try 0° F with only 2.5" of loft. I'm guessing that Quartermaster was figuring on a lot of worn clothing underneath all of that.

LyttleBryan
11-02-2010, 07:44
many companies will label their bags "over bags" if they are actually intended to be nested. Big Agnes makes some descent over bags, specifically Yampa and Lost Dog.

if you have a bag that full unzips you can open it and lay it over your bag as a quilt. That works too.

tjm
11-02-2010, 08:24
..and I'd hate to try 0° F with only 2.5" of loft. I'm guessing that Quartermaster was figuring on a lot of worn clothing underneath all of that.

I agree. The loft from actual sleeping bags is a lot more. The Army was probably using very fit young men and not really concerned with whether nor not they were comfortable.

beep
11-02-2010, 09:17
IMO, when nesting two bags in a hammock, you should consider the bags as your TQ only.


This is my experience nesting two sleeping bags while using sleeping pads in a tent.

When I first started, I bought a BA Encampment model sleeping bag because it fit my budget and I liked the insulation on top and pad on the bottom BA system.

The bag was rated for 15*F but only worked to ~25-30*F for me. I think the semi-mummy cut caused me to have too much dead air space.

Later I bought my son a MARMOT sawtooth down 15*F bag. That bag has worked very well for him and I have used it comfortably to 15*F with a light wool base layer.

Fortunately, the down bag fits into the syn bag very nicely with ample room for the down to expand. I have used the nested combo down to 0*F with a base layer, down vest and wool hat and was toasty.

The insulation of a quilt or sleeping bag is primarily related to its thickness [loft].

US Army Quartermaster insulation table
temp ... sleeping ....... light work ..... heavy work
40F .........1.5" ................. .8"................. .20"
20F .........2.0" .............. 1.0" ................. .27"
. 0F .........2.5" .............. 1.3" ................. .35"
-20F ....... 3.0" .............. 1.6" .................. .40"
-40F ....... 3.5" .............. 1.9" .................. .48"
-60F ....... 4.0" .............. 2.1" .................. .52"

Remember, in a hammock, you need this above you and below under you.

FWIW, Western Mountaineering rates a 5" loft bag (2.5" per side) at 20-25 degrees F. depending on bag shape (mummy=20 degree; semi-rectangular=25 degree). I've found their ratings to be accurate (for me).

Wags
11-03-2010, 23:05
someone either here, or backpackinglight actually did a comparison of this. basically what temp you could expect to get to if you combined A with B

Bradley
11-04-2010, 00:19
I have a 35 degree REI bag, and a 40 degree REI bag, I did a trial run a few weeks ago in the upper 30's with the 35 degree bag, and stayed warm, with the my underquilt in place. I am getting ready for a weekend trip and the forecast is for mid 20's. The 40 degree bag is 3/4 zip, so I am thinking of using it as an over quilt.

Any thoughts?


I'd be interested to hear how it goes for you. I have a zero bag and a 25* bag that I'm thinking of figuring a way out to NEST together to use your term... I'm wondering if you might get some insulation compression in the footbox with a 3/4 zip over the other bag....

I post on this subject a while back,
If your interested, This is what happened (http://www.hammockforums.net/forum/showpost.php?p=276935&postcount=25) when I put 2 bags together for an entire winter down to -40
This is an actual run, this was not a drill. Night after night full on winter.

sseaman
11-09-2010, 10:54
So this test went very well for me. The temps dropped to about 25 over night, and I stayed comfortable if not too warm. My tarp wasn't positioned the best so I had a little wind hitting my feet. I slept on a car sunshade, which did not go well as I woke up in the morning wet, but atleast I wasn't cold. We had sleet off and on through the night which made it really feel like winter camping.

Festus Hagen
11-09-2010, 11:35
Glad it went well for you. My only experience with nesting bags thus far was with a 30 bag and a 45 bag, both rectangles on the ground (with a pad). I was expecting temps to bottom out at 10F or maybe 0 at the worst, well we saw -17F on the coldest night. I fricken froze. I seriously don't think I slept at all that night, for fear of not waking back up. When I packed up my tent I found a man-shaped section of ice in the snow where I was sleeping... nice.

I may try this again with an EMS Boreal (synth mummy 0 bag) using a Eureka Casper 15F synth mummy bag inside. I think it would go a little better :)

sseaman
11-09-2010, 13:40
The only part of my bags that overlapped was at the foot end maybe 18" and the rest of the second bag was just layed on top. This also kept it from sliding around.