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30F Bag Comparisons--which to buy? (with spreadsheet!)
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rick .
(overheadview) - F

Locale: NYC
Re: Re: "I'm Your Density." on 03/10/2014 22:49:55 MDT Print View

Thats interesting, and I had read (and apparently forgot) that post in infamous 18950.

I have a follow-up? Why isn't every bag "overstuffed"? Ie discount the FP to increase down density.

Its just shorter baffles if you maintain fillweight.

If the EN testing would come out warmer just by increasing density (overstuff) why is it an add option and not standard practice?

That's what I don't get. I imagine a lot of it is the higher density prevents loft sagging and fills nooks/crannies better.

I'm fully accepting I'm way out of my depth on this one! Just curious about all this, since I sew my own.

Michael L
(mpl_35) - MLife

Locale: The Palouse
Re: Great feedback on 03/10/2014 23:08:50 MDT Print View

David,

I can confirm katabatic as top quality. I purchased my wife a quilt from there back when they were new and cheap-er. Top quality. Much more loft than my similarly rated nanatuk. Her 30 degree quilt is as lofty as her 15 degree bag.

James Marco
(jamesdmarco) - MLife

Locale: Finger Lakes
Re: Re: Re: "I'm Your Density." on 03/11/2014 06:29:00 MDT Print View

"I have a follow-up? Why isn't every bag "overstuffed"? Ie discount the FP to increase down density."
There are too many variables to consider when you try to market this. If you stuck with exact fillpower, you end up with a bag/quilt that is too lean. Here, I would cite the Jacks or Better quilts of a couple years ago. Techically, they were filled with a minimum fill weight allowing maximum "fluffing" or expansion of the feathers. The quilt would develop cold spots over the course of the night, especially for active sleepers. This was fairly well documented a couple years ago. The solution was a couple ounces of overfill. At the current cost of down, this means 10-20 dollars in down. Not something a manufacturor is willing to add without cause. It just costs more to manufacturer.

Adding 2x the fill would about raise the cost of materials by $50-80 in a typical covering. And really have no effect other than to insure good performance if the down is degraded through moisture, dirt, lack of care, etc. It just adds weight, making the bag look like it is a lot heavier than it needs to be. Would you select a 30f bag that weighed 23oz or one that weighed 33oz? By the same token that 2.5x the ammount of down does not really hurt performance, it really doesn't help, other than insurance. It WOULD potentially help if provided more room to loft. It would then be a different bag! I believe the discussion of the article decided 10-15% overstuffing was adequate for most uses.

While down heat retention is mostly due to convectional disruption, larger pockets are less efficient than smaller pockets. This is generally why higher fill downs are better than lower fill downs, there is more branches per plume. However, each branch looses "stiffness". So with higher fill downs, moisture, dirt and body oils degrade it faster than the stiffer lower fill downs. 750FP downs are more consistent over a night than 900fill downs for this reason, in the real world of camping.

Increased density will generally increase heat loss thru conduction. So, increasing the amount of down in a covering might also increase heat loss. I believe this was noted by Mr Nisley and was it was decided that a max of 2.5 was a maximum. Note that sleeping on the bag is a special case. Especially applicable to and around the edges as the down goes from highly compressed to maximum uncompressed, or, rougly 30-40% of a bag. Under you, the feathers still provide fair to good insulation.

One of the worst things that can happen with a bag is cold spots. For example, at 30F sleeping under a 0f bag with your feet hanging out. Your feet get cold and your entire perception is of getting cold. Even though your torso is more than warm enough. This is rather extreme, but just to make a point. This is where "clinginess" or "stickiness" of down plumes comes into play. Eider down only has a loft of 750-800. Yet the perception of the warmth it provides is roughly equivalent to 900-950fp goose down. The difference is the stickiness of the down plumes. The plumes have more barbs on them allowing them to lock together better, forming a more even coating over the entire surface. Expensive as hell, it is considered superior to goose down even at it's lower loft. Cold spots are a big reason that overstuffing works as well as it does, filling in gaps, and edges. 'Corse, a bag will cost between 5000 and 7000 USD.

As far as loft sagging, yes. This happens. Overstuffing does help to alleviate this. But under what conditions do you propose to test it? Air pressure, mosture content, what fabric weight, and so on. No, the only feasable way is to just measure a bag, then let the user decide if it warm enough. The EN ratings usually give a WIDE spread, just don't expect them to keep you warm (forgive me) unless you are a dummy.

rick .
(overheadview) - F

Locale: NYC
Re: Re: Re: Re: "I'm Your Density." on 03/11/2014 07:48:57 MDT Print View

James,

I think I wasn't quite clear in my question, I'm saying:

maintain fillweight, and
use shorter baffles, to hit the "overstuff" mark.

Not just stuffing more down in, which is the typical process now (and sounds like it was/is needed in underfilled bags). More down obviously weighs more, that has the issues you bring up.

I guess I'm asking why aren't bags just stuffed to the optimum amount? and what is that amount? haha. Sounds like some small fraction less than labtested FP. Different manufacturers have different theories? Surely they test and refine these things.

Because the shell weight stays (nominally) constant, you'd think that you could optimize temp vs. weight if you got the density just exactly right.

>But under what conditions do you propose to test it? Air pressure, mosture content, >what fabric weight, and so on. No, the only feasable way is to just measure a bag, >then let the user decide if it warm enough.

Just give me all of the data points, and I'll draw conclusions from that (in parallel to the EN tests). I don't work for ASTM, so I don't know/care how, but there are reasonable ways to control variables on this. The reports I've read over the years on the EN ratings give me the conclusion its far from a perfect tool, so more data can't hurt here. And few cottage quilts are EN tested, some mainstream bags aren't either.

As it is now loft is seemingly rounded to the nearest quarter/half inch, if given. That is sort of all I was asking. Someone wrote above that the baffle height, along with other info, would be enough, that'd be a great start. That's easy to include on a spec list.

I work in architecture, its common to see every spec and dimension and inner workings of say a window assembly, and understand and compare pros/cons of the components, then choose one that fits the particular need. So I tend towards expecting info in that way, not trusting an industry standard test. More, accurate, data can't hurt on a spec list (except it shows who is lying where!)

James Marco
(jamesdmarco) - MLife

Locale: Finger Lakes
Re: Re: Re: Re: Re: "I'm Your Density." on 03/11/2014 08:47:03 MDT Print View

Just give me all of the data points, and I'll draw conclusions from that (in parallel to the EN tests). I don't work for ASTM, so I don't know/care how, but there are reasonable ways to control variables on this. The reports I've read over the years on the EN ratings give me the conclusion its far from a perfect tool, so more data can't hurt here. And few cottage quilts are EN tested, some mainstream bags aren't either.

Well, I don't know. Too much data can result in too fine of a resolution in the result. For just humidity, there is data needed every 15 minutes to measure the amount of himidity in/around the down. Then we can look at the area you are camping in. Above tree line, below tree line, near a stream or lake, in a vally, on a ridge, below a ridge, in a field, under a tree, and so on. Then we can look at the region we camp in, pehaps in relation to the overall average conditions for rain, temperature, etc that effect himidity, whitch in turn effect water vopour in the bag. Finaly we have just the general climatactic conditions, be it tropical, temperate, arctic, or whatever. All this, and probably the perspiration rate between sexes, size of individuals, and more, effect the overall dampness of a bag. And for any one individual, it would still not be correct because there is a wide variation in the overall ideal sleep conditions between individuals. Yes, you can certainly drop these on a spreadsheet, plot a chart of three variable data points simultaneosly. Without engineering training, you cannot integrate more. N-Dimensional data analysis (one form of linear algebra) is not apparent nor seems to make sense to most. Better to use the fuzzy data of an EN test and simply give a wide range...it makes more sense to most people.

rick .
(overheadview) - F

Locale: NYC
Re: Re: Re: Re: Re: Re: "I'm Your Density." on 03/11/2014 12:36:37 MDT Print View

James,

What?

I don't care about the humidity at which they test.

I want the loft, or failing that the baffle height. published accurately. That is all.

That's all the "data point" I was referring to.

I've never suggested doing anything to the EN test, keep publishing it as they do now, I don't care. I just wish they published simple dimensional specs of a bag, accurately. You are the one getting into how to test it, humidity, all that. As I say, its a distance. Control the variables and measure it. simply that.

Would that not help you decide which bag may be closer to a stated temp? (keep in mind I said a lot of quilts and some bags are not EN tested)

James Marco
(jamesdmarco) - MLife

Locale: Finger Lakes
Re: Re: Re: Re: Re: Re: Re: "I'm Your Density." on 03/11/2014 13:41:31 MDT Print View

No, I don't believe so. Loft is pretty independent of the baffle height except within a similar baffle distance. If the distance between two baffles is different then the average loft will be different, too. For example my bag usually bulges above the baffles about 3/4". Should I add more down, or less, or not change it? If the himidity on one day is 100% and the next day is 30% the amount of down will vary, regardless if the baffle height is the same. A half ounce in 10 ounces is 5% for a rough example. What is the effect of diagonal baffling as in the spiral bags, or horizontal baffles as in some others? More or less loft? If there is less loft, it may be just as warm anyway. Then we run into diagonal baffling schemes. They could be trapezoidal baffles, longer but not higher, generally closing up any cold spots better. Some bags have dual sewn through baffles. I really think that having the baffle height without the amount of distance between them, and, the type of baffling system gets a bit tedious to analyse. Maybe not for you and me, but defintly for most campers. It would just be confusing. Enter the OilCan Harry types of salesman to interpret the specs for the average camper...

Ozzy McKinney
(PorcupinePhobia) - F

Locale: PNW
cal30 on 03/11/2014 14:20:17 MDT Print View

I'll toss in the Sierra Designs Cal30. "Water Resistant" Down, killer hood, pretty light. Pricey, got mine on SNC though. I like it.

Brian Reyman
(breyman) - M

Locale: Rocky Mountains
New Montbell Bags on 03/14/2014 15:58:32 MDT Print View

Montbell just released their new line. The 900FP #2 looks worth considering:
http://www.montbell.us/special/products/downhugger900/

If I was looking for a 25-30 degree bag, it's the one I would buy for sure (even though it is pricey).

David Drake
(DavidDrake) - F - M

Locale: North Idaho
Bought an EE Enigma 30*--first impressions on 04/21/2014 08:08:38 MDT Print View

Received my 30* Enigma quilt yesterday--first impression confirms Enlightened Equipment's excellent reputation.

Ordered a regular length/regular width just before EE changed the Enigma sizing, and I'm glad I did. The "old" regular fit to 5' 10"--with the new sizing, I would have had to choose either small (fit to 5' 6") or regular (fit to 6'). This size is the perfect in-between for me (I'm 5'6") with just enough extra length to pull over my head.

Quality is excellent--while not factory-made in appearance, it is impeccably crafted. Nice details, including the gusset at the top of the sewn-in foot box, and the pad attachment system.

Weight is right on spec--15.3 oz on my scale vs. 15.5 oz listed.

Well done, Tim and Enlightened Equipment.

quilt
gusset
logo

edit: Moved to here from another post.

Edited by DavidDrake on 04/21/2014 08:11:29 MDT.

Tim Marshall
(MarshLaw303) - MLife

Locale: Minnesota
Re: Bought an EE Enigma 30*--first impressions on 04/21/2014 11:54:41 MDT Print View

David,

Very glad you like it.

As far as sizing goes the current short is the same length as what you got. Our Revelations have always fit with a roomy feel and now the Enigmas fit the same.

We didn't change the actual size of the quilts just the way we explan the fit.

-Tim