Questions about down fill quantity

[Bob Chiang]

Hi all,

I hope you can help me with a current sewing project. I have questions about the amount of down fill to install in a baffled down parka.

I estimated the volumes of sub assemblies (not individual channels) based on the surface area, baffle height, and estimated extra loft between baffles. I then calculated the weight of down fill based on the volume plus 10% and fill power (800).  I then filled the sleeves with the calculated amount of down (1.5 ounces each). When I held and shook the channels vertically, I could get the down to settle, leaving a soft feeling volume at the top.  So I added enough to completely fill each channel. It turned out to be 0.5 ounces additional down weight over the calculated amount for the sleeves! This has resulted in a sort of firm feeling surface especially when the sleeves are rolled into their finished shape.  The inner liner lofts to push against my arm covered with just a base layer.  It will try to compress any insulating layer I wear.

I’d appreciate any comments and suggestions for how to qualitatively decide how much down to insert. I don’t have a commercial down jacket for reference, just a 40+ year old down sweater from a Frostline kit! Does it make sense to fill until I can’t get the down to settle and leave a loose density at the top of the channels?

Or is there some typical pressure the filled channels should support? E.g. one ounce over 16 square inches shouldn’t deflect more than 1/2″ ???

For info, I originally calculated a total fill weight of 8.7 ounces.  The shell weight is about 10 ounces and will rise slightly with lycra casings and elastic draw cords.  If I fill the body like I did the sleeves, the total fill will be about 12 ounces.

Thanks in advance,

Bob

[Michael B]

From what I have read, down settling in ways which is undesirable seems to indicate the baffles are incorrectly sized for the desired fill. All the reading I have done so far seems to indicate there is some magical ratio of baffle height to baffle width. I also have not made any down products yet, but from what I can tell many people have not properly sized their baffles and then end up having to overfill to make up for the down shifting, as you suggest. This ends up with, likely, a warmer garment, as there is more down and less dead air, but all a heavier (though debatably minor), less compressible (more of a bummer in my opinion), and more expensive (i am cheap so using extra down would matter to me).

I assume you sized your baffles by comparing to some other similarly designed mass market jacket?

I think if you like the result with the exception of the weight, then go with it. Is it a boxed baffle or simple sewn through? If sewn through, I might suggest that cutting the baffle with in half by doubling the number of baffles may help mitigate the down migration, but may result in a less warm jacket than you want.

this is obviously just the engineer in me trying to think of solutions, not speaking from experience, I look forward to hearing what you end up doing.

[Sam Farrington]

Since switched from synthetic to down long ago, have bought only one down bag, an early edition of the Montbell spiral wrap bags reviewed on BPL by Will Rietveld.  He mentioned in the review that the fill was just enough to achieve the bag shape; in other words, no extra stuffing.  This was the only concern based on the review, but was amazed when the bag never flattened at all.  It has been well treated, and has kept its full shape.  Most amazing was that it kept me much warmer and was much lighter than synthetics, around 20 0z compared to synthetics around 2 lbs.

Had an EMS duck down bag when started backpacking, and just moisture from the air reduced it to a useless rag, so never expected to go back to down.  Will did also mention that the DWR was the best.  No worries about the foot box rubbing the inner of a single wall tent.  That, <span style=”text-decoration: underline;”>I</span> cannot attest to, because have always used double wall.

So with with the highest fill power goose down, suggest that the down does not need to be stuffed tightly or anything like it.  Note also that the Montbell is not one of the newer DWR treated down bags.  Am a big fan of giving up while ahead.  And a big fan of Will’s also.

[Jerry Adams]

I calculate the volume of each baffle.  For example for 2 inch loft, 4 inch baffles, 1 foot long it’s 96 inch3.  Divide by the down power (850 inch3 / ounce or whatever).  For example 96 / 850 = 0.11 ounce.  Multiply by 1.3 (if you put in an extra 30% it keeps the baffles lofted better).  For example 0.14 ounces.  Weigh that much down for each baffle.

When I first put the down in, the baffles are not anywhere near fully lofted, all the down will be clumped in a few places.  Then, beat on the baffles to get the down evenly distributed.  If you hold it up to a light you can see where there isn’t enough down.  or feel it.  Then, the baffles will be completely filled with no empty places.

I suspect you put in a lot more down than you needed.  Maybe just use it as is.

[Michael B]

I have the hope that maybe a solution other than overfilling is possible. Otherwise it seems “overfill” is a misnomer, am I right?

[Ivo Vanmontfort]

Heated debate

https://backpackinglight.com/forums/topic/68798/

Overfill is OK

[Bob Chiang]

Hi all,

Thanks for the comments and reference- interesting reading.

Michael, this is a box baffled construction, design based roughly on pictures of commercial parkas.  I think you and Jerry are right that I probably put in more than optimum.  Jerry, I used the procedure you described, including beating/fluffing.  When I filled with my calculated amount I was able to condense the down by jiggling to create low density voids in the baffled columns.  It just didn’t seem right to allow that to happen, so I filled until the chambers were full even when jiggled.

When the sleeve panels are formed into their finished tube shape, they seem sort of stiff like maybe there’s too much down.  I’ve only put my hands on a box baffled parka once in a store years ago, and maybe it felt the same?  I think I will leave them as is, and say it’s to resist wind pressure ; )  Maybe quilts and sleeping bags can loft closer to the fill power of the down because they are closer to flat panels and aren’t designed to resist wind?

For some reason, when I filled the front panels with the calculated amount of down, they feel pretty full even when jiggled vertically.

thanks again,

[Amber]

After stuffing the chambers with the calculated amount of down, and getting it all evenly distributed, it might help to walk away for several hours, or even a full day, to allow the down to reach its maximum loft. Then you might be able to get a better idea whether or not more is actually needed. I just went through the same thing with a quilt, and it was hard to find the balance between adding enough to fill the chambers and adding too much, preventing it from lofting properly.

[Jerry Adams]

if you just do it by weight, and then beat at it a little to get the down evenly distributed, I have got all the baffles fully lofted.

you need a scale that has 0.01 ounce precision. ~$15 at amazon “jewelry scale”

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