900 cubic inch per ounce goose down

D

DancesWithKnives

Joined
Apr 21, 2001
Messages
1,385
Back in the 1970s I bought a state-of-the-art bag that was supposedly the only one around to feature 700 cu. in./oz. fill power goose down. Around the early 90s I got a custom Feathered Friends expedition overbag with 800 cu. in./oz. down. Lots of commentators doubted you could really get down that fine, but eventually several manufacturers made it fairly common. Now Marmot has their Helium 15 degree bag out in 900 cu. in./oz. down with a lighter fabric and zipper. Total weight is "down" (no pun intended) from 2 lbs to 1 lb 13 oz. Check it out at www.rei.com . [I tried to create a link but couldn't get it to work. Sorry.]

I am 6 ft. and about 240 lbs, and last year's regular size Helium fit me fairly well (surprisingly). The folks at Feathered Friends and the other bag companies have their work cut out for them!
 
DWK, Thanks for the quick rundown of down's increasing loft & the heads-up on the bag. Over the years, down processing has gotten cleaner with less feather material getting through the screening process, yielding puffier filling material. But I wonder if those "cubic inches of down per ounce" ratings aren't calculated at the request of over-aggressive outdoor gear marketing types by engineers laid off from the EPA's "miles per gallon" rating team. ;) I mean, if goose down is so expansive (now up to 900 cu in/oz) how come Canadian Geese aren't the size of Buicks??? :confused: :D

Marmot bag page: http://www.rei.com/online/store/Pro...productId=47637959&parent_category_rn=4500514
 
RokJok,

Like you, I'm usually skeptical. And I admit that I have not yet handled the 2003 model. However, despite being a long-time fan of Feathered Friends' fine work, I must acknowledge that the 2002 Marmot Helium really impressed me. Large enough for a Fat Boy, very good loft, nice hood, etc. I hope Feathered Friends fires a return shot!

What I REALLY wish is that I could actually get by with that 12 oz. corrugated space blanket bag that cost $30 or so!
 
There are 2 numbers that may be much more important than the raw cubic inches per ounce as it leaves the factory. First, what is the loft after being compressed for 3 months or 3 years and then fluffed for 30 minutes if you are lucky? Second, how thick is it under you when you are laying on a ground cloth on frozen ground? It will never re-fluff like it was originally, and when it is compressed under you the insulating value is comparatively pitiful.

OK, humor me a moment.. Any way to make a mini-cot or hammock for INSIDE the bag so that the loft under you is not compressed except for the feet of the cot/hammock frame? This would be a royal pain in actual practice but would massively increase the R value of the bag. I guess if you were sleeping in a "regular" hammock the support rope at the foot could be run through the little opening at the base of the zipper (if the zipper goes all the way down on this bag) and the bag would be zipped around the hammock and the person. Has anyone ever tried this?
 
Grommit, you think like an engineer, not that that's a bad thing. ;)

The cot idea would bear some analysis of thermal dynamics, balancing the conservation of the bottom down's insulative value vs the amount of heat needed to heat the increased air mass around your body. Jerry over at Wiggys.com talks about how you want as close to zero distance between your skin and your sleeping bag inner surface as possible to minimize moving air currents carrying heat away from your body (convective thermal loss). Wiggy designs his bags so that the inner liner drapes right on your body as much as possible to minimize convective heat loss. So the cot idea wouldn't be good on that basis due to introducing a layer of air around your body, at least on the bottom, that could move around and carry away heat. With zero body-to-bag distance, any heat you lose is through the surface contact of your body with the bag lining (conductive thermal loss). The heat lost conductively goes into the insulative layer of your bag, which is designed to stop its migration away from the source. That keeps warm the air next to the bag's inner lining and your body which is in contact with that lining.

I suppose you could make a grid of little curtains (like baffles) hanging under the cot to reduce air current movement. I think a 12 ounce closed cell foam pad would be lighter than the cot, but a lot more mundane to thinks about. ;) I suppose an "ultra-cot" would be made of 2" diameter sealed titanium tubing with 1/100" wall thickness filled with helium to "lift" you a bit and reduce the impact of the cot's feet on the lower sleeping bag. (Sorry, short sleep last night & I'm getting a little punchy about now. :yawn: )

Wrapping yourself and a hammock inside a sleeping bag is a very interesting idea. I think the limiting factor will be the sturdiness of your bag's construction and insuring that it has a double-slider zipper.

I've seen info on a sleeping bag with an integrated foam pad (or foam pad pocket maybe?), but can't remember the manufacturer. Isn't there a company making a mixed-filling sleeping bag with goose down filling on top, fiberfill on the bottom, and an unsewn/unquilted top fabric layer to minimize wind/rain penetration?? :confused: I seem to remember seeing an ad for it in a magazine, but I'm old enough to question my recollective abilities. Theoretically it would be a good idea.
 
When I said cot, I was talking itty bitty cot. If the sleeping bag loft is supposed to be 1.7 inches, the cot bottom surface would be 1.7 inches off of a flat surface to both minimize the compression of the insulation (ever worn insulated gloves that stretched tight over the knuckles? Brr. Any compressed insulation is no longer a good insulator.) and eliminate introduced dead air space that would increase the surface area to mass ratio or enclosed volume at all.

Another way to avoid compression would be to have the insulation in individual pressurized pockets so that it can not compress, bu tthat would introduce the conduction of the pocket walls and make packing a real bear.......

The bag and hammock idea would need a bag with internal strech bungies or something to keep the lower part from sagging down, like they do the waist of ski jackets or something to again limit the enclosing of more volume than necessary. The weight would be held by the hammock just like if you and the bag were on the hammock, but the bag is around it as well. Does not seem like that strong a bag would be necessary, but a central rope port in the toe and hood would be needed.

by and large, just using the antigravs would simplify the whole process.....
 
My Feathered Friends Expedition Overbag has no insulation on the bottom. It has a pocket designed to take a full-length Thermarest pad. You could probably even jam a thin blue foam pad under the Thermarest in the pocket. It is cut large enough to put a snug 5 degree bag inside it so that you get roughly a -40 combo.

In moderate weather I use the overbag alone. Although there is a little extra airspace, it is extremely roomy and comfortable. However, as RokJok points out, the extra airspace would be a problem in colder weather (I've had it down to 20 degrees, but that's about the limit). The problem is that it weighs 3 lbs and the Marmot weighs 1 lb 13 oz. Not a problem for most applications but the ultra-light crowd wouldn't like the extra 1 lb 3 oz.
 
Grommit,

I just discovered that some others share your thinking on placing the insulation below the sleeping surface. Check out www.speerhammocks.com . Their peapod sleeping bag system apparently wraps around one of their hammocks, along the lines you suggested. I haven't checked it out very carefully, but thought I would bring it to your attention.
 
Fellas, I think I have fallen way behind in the sleeping bag department. It's time to get educated. All this stuff makes my head turn.

Can someone give a good ultralight recommendation?

Here's a few numbers to help out:

6' tall
245 lbs.
Large build, but no pot belly
I move around a lot when sleeping
I rarely ever get "cold" and most bags end up unzipped all the way by morning light...


Thanks!

Dan
 
Pendentive,

Your dimensions are not far from mine. However, when I roll around at night in a smaller mummy bag, I usually turn WITH the bag, rather than inside it. The 2002 Marmot Helium was big enough to accomodate me and allow me to comfortably turn/bend/etc. with the bag. If you are looking for a larger bag that is roomy enough to move around inside, the Feathered Friends expedition overbag with sleeping pad pocket (that I mentioned above) will do the trick. If you go to www.featheredfriends.com , they also list a couple other extremely light bags with generous dimensions. I have not personally tried them so I can't say how they fit. They aren't quite as light as the Marmot but they should be roomier and really well made.
 
Pendentive.. Two words... Western Mountaineering

And don't ever store a down bag compressed...
 
Isn't that one of the great things about the Wiggy's bags, that they can store compressed for years without hardly compromising the re-lofting capability? That and the fact that they do not collect water and ice over a few days which seriously diminishes the down's loft advantage. Of course, this may just be Wiggy's advertising propoganda. Anyone with actual comparative experience in sub-frost sleeping in down? does it actually collect ice?
 
I've slept in down bags a lot when the temperature was 10-30 degrees F. I've never had a problem with ice crystals building up in the down. However, I've read about that happening to McKinley/Himalayan climbers. Perhaps the difference is that during the day I experienced above-freezing temperatures about half of the time. I usually air my bag out in the morning (before packing) and in the early evening (right after setting my tent). That may be allowing any moisture to evaporate, whereas it probably wouldn't if the temperature never got above frigid McKinley/Himalayan temps. I don't really know.
 
Grommit,

After 300 something bag nights and many of those in sub freezing as well as outdoor under tarp or under clear sky...as opposed to tenting... I can tell you ... It depends on your set up:)

You may collect a bunch of frozen condensation in a subfreezing tent or even in a snow pit but mine has always been external never in the down. Down, as any other insulator (without the use of a VBL) will have condensation after you sleep in it. It is in the care of your gear that you will get it dried.

Wiggys IMO are way overhyped.. They weigh a freakin ton for the temp range claimed. They have real scratchy liners. They are pretty uncompressible and way overpriced. Like I said IMO.

-Sam.

Oh that reminds me Grommit... You should really look at the Stephensons or Exped DAMs. (Down Filled Air Mattresses). They would meet many of the criteria you were looking for.
 
You must log in or register to reply here.
Back
Top