Feather question

7:25 a.m. on October 21, 2006 (EDT)
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I'm considering my choices for a sleeping bag. I am aware of all of the benefits/disadvantages of both down and synthetic fillers so I'm not asking for any of that type of information. What I am wanting opinions on is down leakage.

I have used your "Gear Reviews" as a starting point for bag selection, and some, not all, of the down bag reviews mention feathers that never end. I have a down parka and only see a few feathers once in a while, but then, I never fold it up and compress it.

Is this a common problem with most down bags, does it indicate a less well made bag when it leaks forever, and does it eventually lead to temperature rating reduction from the original estimates?

Alfred E. Neuman (aka Blackbeard)
What, me worry?

7:34 a.m. on October 21, 2006 (EDT)
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Oh yeah...

Can anyone explain the broad variation in how some reviews indicate the temperature ratings are so out of kilter? Are some of these bags' ratings just hype, or is it mostly individual dynamics, like metabolism, and under padding, etc.?

Blackbeard
(peeking out of my hole)

10:02 a.m. on October 21, 2006 (EDT)
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Ok, Alfred (wonder how many of the younger generation remember who Alfred E. Neuman is, and how he originated?) -

First the temperature question - There is no industry standard for rating the temperature comfort zone for sleeping bags. The crude way is to just measure the loft of the bag (actually pretty good when you calibrate it for yourself). But this does not take into account whether the bag is "sewn through", or one of the various construction methods - box, V-channel, offset, etc etc etc.

Some companies have used instrumented dummies (I think REI does this). Some just send people into the field (I recently tested a bag as part of a group of folks this way). Problem is, again, how do you control for personal factors, fatigue, recent meal, variations in the pad underneath, in a tent (what kind of tent - mesh, single wall, double wall...), wind and breeze, humidity, etc etc. Some have people sleep in a controlled room.

There has been an ongoing effort in the industry to standardize, but this hasn't reached any kind of conclusion.

Lots of companies use guidelines that were published by the US Army 60 or 70 years ago (during or just after WWII). The way the data for that were obtained is now considered highly suspect for reliability.

Bottom line is that some companies are very conservative in their ratings, and very consistent (Feathered Friends, Western Mountaineering). Some are very optimistic (most of the mass market bags). The rest fall in between, with the quality manufacturers being close to the conservative end.

So the simple answer is - there is no standard, and companies publicize whatever number sells the most bags.

Down leakage later.

11:12 a.m. on October 21, 2006 (EDT)
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Sleeping bag temperature ratings

The young man with the Black Beard asked:
"Can anyone explain the broad variation in how some reviews indicate the temperature ratings are so out of kilter? Are some of these bags' ratings just hype, or is it mostly individual dynamics, like metabolism, and under padding, etc.?"

Besides the longer comments,

1. some of the ratings are "optimistic", or in harsher terms, hype. This is true of most of the mass market bags.

2. many of the ratings are based on measuring the loft and using the old USArmy tables, which basically are for survival wearing your combat gear in the bag. They do not account for bag construction - sewn through or not, zipper baffle, neck baffle, tighter-fitting (warmer) vs looser fitting (cooler, with rectangular bags being much less warm for the loft), mummy vs other shapes (the hood keeps warmth in, rectangular has open top which leaks lots of heat).

2a. some of the ratings assume sleeping in a tent, some assume sleeping with nothing on, some assume sleeping with clothes appropriate to the conditions (little for warm weather bags, long johns for cold weather bags), some make assumptions about the thickness of sleeping pad (thicker for colder conditions, so more underneath insulation) - again no consistency from company to company, no industry standards.

3. There is no standard for testing warmth of bags, although within a given company's range of bags, the relative ratings are ok (Company A's 0 deg bag will be warmer than their 30 deg bag, but Company B's 0 deg bag may be warmer or cooler than Company A's 0 deg bag).

4. Individual variations, both person to person and for a given person's current condition, make a big difference - fatigue (more fatigued generally means colder), recent food intake (food eaten just before getting in the bag generally means warmer), exercise (doing a bit of exercise just before getting in the sack generally means warmer), clothes worn in the bag (some people sleep in the buff, some in their long johns, are the clothes damp from sweat or from being out in the rain or snow).

11:20 a.m. on October 21, 2006 (EDT)
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Feathers

All down bags leak some feathers. Higher quality bags use more "downproof" materials and leak fewer feathers. But they also use higher-loft down, which has lots more tiny plumules, which tend to get through the fabrics more readily. Still, the top end bags from Feathered Friends and Western Mountaineering leak less than Generic Sporting Goods bags.

Interesting bit of trivia - I have a copy of a study report from the Army labs on the best fill for Arctic bags. Turns out that the best fill is not pure down plumules, but a mix of feathers with the plumules. And the type of feathers? Turns out it is chicken feathers! The big problem that made the chicken feather mix unacceptable is that when wet, chicken feathers have a horrendous stench. They tried to de-odorize the feathers, but were never successful. For some reason, mixes with duck or goose feathers did not work out as well.

12:08 p.m. on October 21, 2006 (EDT)
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Re: Feathers

Quote:
Ok, Alfred (wonder how many of the younger generation remember who Alfred E. Neuman is, and how he originated?) -

Yes, I wondered about this part also - not so much remembered, but ever knew this guy. I can also remember that he is the one who started the world-wide protest "Down with Pay Toilets". You think anyone in that younger generation knew you use to have to pay to .....

I have seen duck down, but never chicken down.

I am taking this part about the type of feathers as a known industry fact, and that a leaky bag may be of a lesser quality to some degree, as manufacturers could avoid a lot of the excessive leakage with proper materials/binding etc.

How about the leakage contributing to effectiveness? Will this leakage over years lessen the "real" rating? Obviously, this only affects bags that are kept a very long time, but if I like something, I use it forever.

Can you tell I have a lot of engineering in me?

Just plain ole Steve this time.

1:42 p.m. on October 21, 2006 (EDT)
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Re: Feathers

Steve asked "How about the leakage contributing to effectiveness? Will this leakage over years lessen the "real" rating? Obviously, this only affects bags that are kept a very long time, but if I like something, I use it forever."

Good question. I don't know the answer, but a guess is that there is no, or very little, short term effect. I do know that my Eddie Bauer Karakoram bag was originally rated at -40F (it had extra fill), but now feels more like -20F or so (comparison is to my Feathered Friends -40F bag). The Karakoram has lost down over the years (got it in about 1960, for an exorbitantly outrageous for the time $55, a huge amount for a kid in college - but the tuition at that super expensive college was $500/year at the time, and now charges $15,000/year). Anyway, my experience with that bag suggests that the answer is that over a 45 year time frame, the bag has lost some effectiveness, due at least in part to losing down, plus maybe losing loft thanks to my storing it stuffed between trips for a number of years (not much room in a shared college dorm room).

9:49 a.m. on December 5, 2006 (EST)
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Re: Feathers - my two cents worth

Well - consider this "suitable for framing or wrapping fish" (as we're on a Mad magazine trend here) - your down bag will suffer the most loss of insulation from the normal breakdown of the down clusters - these are fairly fragile things - they get crushed when you pack the bag, they get crushed under your body weight when you sleep in the bag -they accumulate dirt and body oils, which doesn't allow them to "fluff up" all that well over time. When you're on an extended winter trip, they'll suffer a loss of loft just because of the moisture you convey to the bag (I've read that on Arctic expeditions your sleeping system can gain 20KG in weight over a couple month period ...). The amount of down and feathers that "sneaks out" has far less impact (unless, naturally, you manage to rip a good sized hole in the shell - no crampons in the tent please!).

temperature ratings - very personal thing - I sleep "hot" - so I can be quite comfortable in -20 weather in a bag rated for 0 - assuming that I've got a nice thick foam pad under me and my tarp is staked down tight so there's no heat loss from the wind (convection). My wife sleeps "cold" - she'd likely need a -40 bag to be comfortable on a -20 night (but I know there's no way in heck I'm going to convince her to head to the mountains in January). If you have to err, err on the conservative (warmer) side - diet, exhaustion, hydration, weather, a hot drink (no alcohol) before bed, will all impact how "warm" you'll sleep -I'd rather have to open for a bit of ventilation than lay there wearing every article of clothing I've got shivering in a sleeping bag for a very long winter night -

As I said at the start - take it for what it is - an opinion - suitable for framing or wrapping fish -

4:36 p.m. on December 10, 2006 (EST)
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The Army chose a mixture of "chicken feathers" and "water fowl plumage" as the general stuffing agent of a huge number of sleeping bags with thin, pretty much water resistant, cotton shells. I had one such bag called a US Mtn Regular. It was wonderful.... warm and soft and a cotton liner is more comfortable to your skin than a nylon liner. The waterfowl feathers were for warmth and the stiffer chicken feathers were to generate loft. Now theres a thought - Loft does not equal Fill Expansion. It was a concept, it worked.
Jim S

October 22, 2014
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