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#204834 - 09/23/20 03:00 PM Sleeping Bag Compressed Volume
Louie Offline
newbie

Registered: 09/23/20
Posts: 3
Loc: California
I am looking for a new bag for winter camping, have been looking at these 2:

https://www.rei.com/product/164851/mountain-hardwear-bishop-pass-0-sleeping-bag-mens

https://www.rei.com/product/147279/big-agnes-anvil-horn-0-sleeping-bag-mens

I am leaning towards the first one, Mountain Hardwear. My only question is it specifies a compressed volume of 10.8L while the Big Agnes specifies 3.94. Since both bags are 0 degree, use the same fill, and are roughly the same weight, how do you explain the vast difference in compressed volume.

Also how does compressed volume relate to stuff sack size? The Big Agnes has a stuff sack that is 5x larger than the compressed size, which I guess means the stuff sack does not compress the bag as much as it could. However the Mountain Hardwear bag has a stuff sack that is smaller than the compressed volume, which to me would mean the bag could not fit in it's own stuff sack.

Is compressed volume a mostly meaningless number?

Thanks for the input guys.

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#204853 - 09/29/20 11:43 AM Re: Sleeping Bag Compressed Volume [Re: Louie]
BZH Offline
member

Registered: 01/26/11
Posts: 1050
Loc: Madison, AL
The BA bag is a smidgen smaller because it is a quilt and has no backside insulation, but that certainly doesn't account for the differences in compressed volume.

I am guessing it has to do with the size compression sack they give you. Down is really able to compress quite a bit. I would be shocked if you could only compress that MH bag down to 10 L.

The question is do you want to spend the time getting the sleeping bag into the tiny little bag they give you. I personally don't mind doing that. But I can also see potential customers getting frustrated with not being able to get the bag back into its sack.

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#204854 - 09/29/20 03:43 PM Re: Sleeping Bag Compressed Volume [Re: Louie]
aimless Online   content
Moderator

Registered: 02/05/03
Posts: 3139
Loc: Portland, OR
Is compressed volume a mostly meaningless number?


It depends on how you think about the question. Because many UL backpackers try to get away with the smallest possible pack size in order to save weight, they compress their sleeping bag until it is as hard and dense as a baseball (although bigger grin).

But, as far as a manufacturer's published number for "compressed volume" goes, there are zero standards for how to measure this, therefore no way to know what that number really means compared to another sleeping bag maker's number. In that case, yes, it is meaningless.

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#204859 - 09/30/20 10:36 PM Re: Sleeping Bag Compressed Volume [Re: BZH]
Louie Offline
newbie

Registered: 09/23/20
Posts: 3
Loc: California
Originally Posted By BZH
I am guessing it has to do with the size compression sack they give you.


That is what I thought, except the BA bag has a stuff sack that is 4-5 time larger than it's "compressed volume". Anyway I think you guys confirmed my suspicion that these bags probably can be compressed roughly the same amount and the compressed volume figure is more or less meaningless.

I am about 1/2 inch taller than BA's regular's max size of 70 inches so I was probably going with the MH regular's 72 inches, which should fit me nice. Was just thrown off by it's large compressed volume.

Oh and I don't usually use a stuff sack, just stuff it loose in my pack.

Thanks for the input.

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#204864 - 10/05/20 02:57 PM Re: Sleeping Bag Compressed Volume [Re: BZH]
Louie Offline
newbie

Registered: 09/23/20
Posts: 3
Loc: California
Originally Posted By BZH
The BA bag is a smidgen smaller because it is a quilt and has no backside insulation....


Where did you read this? I am not seeing it.

I always figured that a sleeping bag prevents heat loss above you, while the pad you are on prevents heat loss below. That is, the crushed down insulating in the bag you are lying on doesn't do very much.

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#204865 - 10/06/20 09:52 PM Re: Sleeping Bag Compressed Volume [Re: Louie]
Rick_D Online   content
member

Registered: 01/06/02
Posts: 2912
Loc: NorCal
Some head-scratching differences among the listed specs lead me to believe they're not measured using the same methods. In short, I'd take the compressed volumes with a grain of salt because it could be as simple as that is the volume of the supplied stuff sack. One is not 2x the volume of the other.

Coincidentally, the last bag I bought is from Mountain Hardware, which came with a compression stuff sack, so what volume value do you derive from that?

I don't believe that BA bag is a quilt--it's not stated as such--but it does have a mattress capture system, which is a nice feature I think. It's also far roomier if that is a consideration--the MH bag looks very snug. Efficient so long as you don't move a lot during the night.

Cheers,
_________________________
--Rick

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#204873 - 10/12/20 02:04 PM Re: Sleeping Bag Compressed Volume [Re: Louie]
BZH Offline
member

Registered: 01/26/11
Posts: 1050
Loc: Madison, AL
Originally Posted By Louie
Originally Posted By BZH
The BA bag is a smidgen smaller because it is a quilt and has no backside insulation....


Where did you read this? I am not seeing it.

I always figured that a sleeping bag prevents heat loss above you, while the pad you are on prevents heat loss below. That is, the crushed down insulating in the bag you are lying on doesn't do very much.


Go to the link in the OP and look at the 5th picture at REI. It shows how the bag is designed to be incorporated with a sleeping pad.

And... yes I agree the bottom insulation on a traditional sleeping bag is dead weight you are carrying. Currently I only buy quilts (when I need a new bag... which isn't very often). My personal favorites for performance at a great price are from enlightened equipment.

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