Compression Sack ?

4:18 p.m. on December 11, 2009 (EST)
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I've been wondering about something and thought I'd ask your thoughts. How does a compression sack effect the loft of a down bag. I know that you need to shake and fluff your bag out after removing it from the sack but will the compression eventually cause a bag to loose it's loft? I'm talking about just useing the compression sack for carrying in the pack on the trail.

Gary C.

8:51 p.m. on December 11, 2009 (EST)
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Yes, a compression sack will eventually affect the loft of a down bag. The reason is that keeping the bag tightly compressed or doing repeated compressions will eventually put permanent bends or even break the down plumules. But if you store the bag in a loose storage bag, or better, spread out on a shelf, you can slow the loss of loft. Actually, down is pretty durable. I have an Eddie Bauer Karakoram expedition bag (rated at -40 degrees when new, back in the days when Eddie Bauer was the leading expedition sleeping bag, parka, and down pant supplier in North America) that I bought in 1960. It is probably about a -20F bag these days, but I don't use it for winter camping anymore. That's almost 50 years of use, the first 20 being pretty heavy usage.

The effect of a compression sack on synthetics is significantly greater than for down, for some reason. Primaloft does not seem to suffer anywhere near as much as other synthetics, though it does lose loft faster than down.

9:01 p.m. on December 11, 2009 (EST)
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Okay, so is it acceptable to compress for the duration of the trip, as long as you hang or lay the bag out during storage. I understand compression has a negative effect over time. But is compression for the trip standard procedure, or is a standard stuff sack what you would recommend for a down bag?

Thanks

12:53 a.m. on December 13, 2009 (EST)
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Thanks' for the repys guys.

I've been carrying a 20 degree down bag and just packing it in the bottom compartment on my pack. I recently bought a Marmot +5 down bag and it's a pretty tight fit so I thought that a compression sack might make things a little easier and less worry about catching it in the zipper. I may go ahead and try a compression sack and see if I like it any better. The +20 bag is fine for 90% of my Sierra trips so the new bag won't spend much time compressed.

11:56 a.m. on December 13, 2009 (EST)
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When I pack my Golite Featherlight 20 degree bag during camping trips I use a compression sack that makes it about the size of a soccer ball. I sleep in it at home now and its always fully lofted on my bed. But anyway after about 5 years of camping 6 months of the year I have noticed very little loft lost from compression.

2:12 p.m. on December 13, 2009 (EST)
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I used a WM down bag for about 150 days and thought it would have lost some loft from the daily compression at the bottom of my pack. After i washed it it was so lofty i couldn't put it back in it's stuff sack. OTOH i forgot it compressed for 2 months and it was never the same, i had to retire it. Lesson learned!

5:38 p.m. on December 13, 2009 (EST)
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I never use a compression sack for any gear,to hard on it.When storing anything i always hang it up or keep it in a large cotton bag.All my old down gear,some 35+ years old,still works great.

12:30 p.m. on December 14, 2009 (EST)
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Many down bags now come with compression sacks instead of stuff sacks. My latest REI bag did. They are well within design specs for down bags. Like Bill S said, down is pretty durable. I like it that newer bags come with the large cotton storage sack -- my first few bags did not. This sure makes it easier to store it properly when not in use.

1:19 p.m. on December 14, 2009 (EST)
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Okay, so is it acceptable to compress for the duration of the trip, as long as you hang or lay the bag out during storage. I understand compression has a negative effect over time. But is compression for the trip standard procedure, or is a standard stuff sack what you would recommend for a down bag?

Thanks

Depends on the trip. If you have to get everything into a limited space, then you have to use a compression sack, no other choice. An example is many of the month-long expeditions I go on. To get the gear to the trailhead, you have to stay within the airlines' size limits. Sometimes you have to get it into the bush pilot's plane. Maybe you and your 3 buddies are trying to cram yourselves and gear into a Smart car (well, maybe not that small, but 30-40 years ago we crammed 4 people and gear into VWs). Then on the trail, you have to carry it all (maybe putting some in a sled). In that case, you do what you have to do.

However, if you do not have a tight space limitation, then a more roomy stuff sack is the desirable way to go.

1:25 p.m. on December 14, 2009 (EST)
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..... After i washed it it was so lofty i couldn't put it back in it's stuff sack. ...

That's an excellent point! Sleeping bags and filled parkas do have to be washed every so often. Washing them (with the right kind of soap, designed for washing such items, in the right kind of machine or by hand) will restore a lot of loft. This is especially true of synthetic bags. I do think 150 days is going a bit too long, though.

To emphasize - right kind of soap and right kind of machine. Do not use just any old soap and do not use your typical home washing machine. Follow the manufacturer's directions.

And, as a number here have posted, store the bag laid out flat or in a very large cotton or mesh sack (large enough so there is not compression and you do not have to stuff it in).

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