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  1. #1
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    Difference in loft of different fill powers

    I am just getting into the whole Hammock thing in the last year. During that time I ordered my first set of quilts 20 degree 800 fill power. Now I have added a set of 40° 850 fill power quilts. There does seem to be a difference in the loft between the two different fill powers. Maybe it is just that with the 850 you do not get the “thin spots “where are you have to shift your down around a little bit. I just think it is interesting.I do not know if I would pay the extra for the 900 fill power down but it would be interesting to actually be able to compare.
    Last edited by Longwinters; 02-23-2021 at 13:32.

  2. #2
    cougarmeat's Avatar
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    Longwinters, in the section for donating members, there’s a sub-forum on Ultralight gear where I asked about 850 fill vs 950. I was advised that, if a lighter TQ/UQ was the goal, I’d get more result by paying attention to fabric choices; 10D vs 15D for example. There were some posts that preferred 850 over 950. They acknowledged that though 950 was initially lighter, in some circumstances it seemed to loose it’s loft quicker. Note that in colder weather, without a chance to “air out” - like a foggy, cold, wet, 3 or 4 day camping trip - condensation will can build up. Warmer, summer days - probably not a concern.
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  3. #3
    Senior Member Cruiser51's Avatar
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    The term "Fill Power" means how many cubic inches a single ounce, of down, will fill. So it takes more of the 800 FP down for a given volume, than the 850 FP.

    So the only real observable difference between 2 quilts, same construction, filled with different power down would likely be to actually weigh them ( I don't believe you would be able to observe/see any discernible difference between 800 and 850). The lighter of the 2 will be the 850 and the difference in weight is what you are actually paying the premium for.

    Whether the quilt uses 800 or 850 should not impact it's actual performance or what it "looks like" ... you may see difference in quilts with different ratings, but that has nothing to do with the FP of the down used IMO.


    Brian

  4. #4
    New Member Sherlock's Avatar
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    There’s a few variables here that can affect things.
    1. The general rule on loft (meaning the measurable depth/thickness of the baffle) is 1/2” for every 10F, starting with 1” for 50F, 1-1/2” for 40F, etc.
    2. The amount/weight of down needed to fill that space will decrease as the fp goes up, because the higher fp can expand and insulate a greater area than a lower fill power by weight.
    3. Even though there is a standard amount that fills that area, companies will often over fill that area 20-30% above that amount to help with shifting, wear and tear, and insulative loss due to moisture.
    There isn’t an industry standard for all of this, so each of these variables could impact the overall loft and the placement of the down in the quilt, and ultimately your comfort through the night.

  5. #5
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    There is a feeling of loft difference in my experiance. Lower fp feels much stiffer (for lack of a better term) compared to 900+. Higher fp sometimes feels like there's nothing in there, esp in summer quilts.
    As you get into the 40 degree and lighter stuff, this softness of the down makes it seem like it's not lofting as much. It is of course, but it does not feel like it to the hand.
    Above 40 degree ratings down starts to loose its edge over synthetics. This is in part due to how little insulation is in a 50 quilt, there just isnt enough down to provide coverage in the high fp down.

  6. #6
    Senior Member Cruiser51's Avatar
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    Quote Originally Posted by chapinb View Post
    There is a feeling of loft difference in my experiance. Lower fp feels much stiffer (for lack of a better term) compared to 900+. Higher fp sometimes feels like there's nothing in there, esp in summer quilts.
    As you get into the 40 degree and lighter stuff, this softness of the down makes it seem like it's not lofting as much. It is of course, but it does not feel like it to the hand.
    Above 40 degree ratings down starts to loose its edge over synthetics. This is in part due to how little insulation is in a 50 quilt, there just isnt enough down to provide coverage in the high fp down.

    The original poster set the tone comparing 800 to 850 down .... IMO that would nearly impossible to distinguish any differences between two quilts using those materials and made to the same temperature ratings. Once you start spreading that the FP difference out a bit, there will be tell tale signs, but not with a 50 FP delta.

    Brian

  7. #7
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    I can't remember where I read it and haven't verified it but a 50% increase in fill power equates to a 100% increase in insulation for a given weight. Down being a natural product there's variation in it and what is stated as being 800fp could be anywhere from 776 to 824. Some manufacturers/suppliers always round down, others just go to the nearest 50.

    There isn't just fill power to consider, there's also down to feather ratio. It's all but impossible for the down to be plucked without some feathers being included and the feathers don't have anywhere near the same insulating properties as down. While the relationship between fill power and down/feather ratio isn't linear you are unlikely to get 600fp with a 95/5 ratio or 900fp with a 80/20 ratio. It's the feathers that you notice when pressing against the material since they have quills, the "stiffness" noted above. It's also feathers that escape rather than down as the quills push through the material. It's unlikely that you'll find pure 100% down, which may not be desirable anyway, it's quite likely that the feathers provide some form of structure to the mix and help protect the down.

    That down/feather ratio also means that lower fill powers tend to require heavier shell materials to prevent "down" escaping whereas the higher fill powers can use lighter materials like 10d and 7d. I've three down jackets, one with 1000fp, one with 900fp and one with 750fp (all European fp ratings so add 50 for US ratings). They've all got different shell materials, that on the 1000fp, 10d I think, drapes and molds itself to you whereas the 750fp jacket just sort of hangs. I had the option with the 900fp of getting the same material as on the 1000fp but I went for a slightly heavier shell just for durability. Of course a material that is close fitting or clinging can feel clammy so there's a balance point.

    Given the same shell material and fill to a given rating I'm not sure I'd be able to tell the difference between two fill powers less than 100-150 apart. I "feel" like there's more difference between 600 & 700 than between 800 & 900 if that makes sense. Might just be imagination on my part.
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  8. #8
    Senior Member cmoulder's Avatar
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    I haven't delved deeply (quite shallow-ly, in fact) into the methodology for determining fill power but from the little I've seen it starts getting quite subjective and murky above 800fp and certainly in the 950-1000fp range. IIRC the most extreme claim I've ever heard is something like 1200fp for Eider down. (Kinda cool that it's a duck laying claim to the fluffiest down.)

    From a practical standpoint, my EE 30deg TQ with 7D/950fp weighs 400g on the nose and smooshes down incredibly small. And it's actually warm at 30°F. Not all that many years ago such specs were 'dark side of the moon' stuff.
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  9. #9
    ObdewlaX's Avatar
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    Interesting thread. I'm about to get rid of a couple of sleeping bags that I've had from my tent/tarp days, one being a Western Mountaineering Antelope bag. It's an older, high end bag and I was interested in finding out what fill power down was used when it was in production, so I emailed their customer support. Here's the reply I rec'd:

    It’s sort of a roundabout answer. Depending on when you got your bag, we probably called it 700+ or something like that, but it’s actually the same down. The way fill power is measured has changed and become a little more meticulous over the past 50 or so years and the numbers that it achieves are gradually getting higher and higher, but so far as I’m aware, geese haven’t meaningfully changed in that time. When we started making bags, the process of measurement was to leave the down in a box overnight and check it out in the morning, but now it’s this whole process of tumbling and blowing up the down to get the absolute maximum loft possible.

    I saw that North Face is putting out a jacket with 1000fp down now, they must have some pretty sweet geese.

    More food for thought... 😬
    Last edited by ObdewlaX; 05-29-2021 at 10:35.

  10. #10
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    I have a jacket and HG Econ quilts with 800FP. I also have a HG 950 and a 1000 jacket. A couple-few down clusters have come out of the 800's and they're small-ish. Like, the size of my ring finger tip.
    The 950 and 1000 have had a down cluster or 2 try to make their way out (i was able to pull all of them back in successfully) but the down clusters were HUGE. One of the 1000's was like a chicken nugget size, and still had enough in the jacket to pull it back in.

    Although its hard to feel the difference between 800 and 950, visually the size difference of clusters is easily noticeable. My new 950 40* HG burrow looks transparent but is toasty warm.

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