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  1. #1
    Senior Member JohnSawyer's Avatar
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    DIY Down UQ- how wide to baffle?

    Ok, I've been watching all the diy UQ's, I have material, down, and even cut the noseeum.

    My basic design is: 55"x42", 2" baffles, diff cut...

    I have 1.1oz bags of down. According to Meteor's spreadsheet, I can go 5.5" inner and 6.25 outer on the baffle spacing, that get's me to 1.1oz/tube.

    Then I started looking at everybody else's designs that had fewer baffles... since I'm stuck (again) in analysis paralysis I wanted some input from those that have done it:

    Forget the down bag size, how wide should I go on the baffles?

    John
    "Do or do not, there is no try." -- Yoda


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    I'm watching with interest. I'm considering a very similar DIY UQ.
    I don't follow the number of baffles.
    Were you considering 7-8 baffles and now considering less?
    Also what's your total oz and fill power of down?
    Finally, what temps are you shooting for?
    Sorry, all questions and no answers.

  3. #3
    Senior Member JohnSawyer's Avatar
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    Quote Originally Posted by wwk10 View Post
    I'm watching with interest. I'm considering a very similar DIY UQ.
    I don't follow the number of baffles.
    Were you considering 7-8 baffles and now considering less?
    Also what's your total oz and fill power of down?
    Finally, what temps are you shooting for?
    Sorry, all questions and no answers.
    I have 30 1.1oz bags of down from a frostline kit. Consensus is to calculate for 600fp. My thought was 8 baffles, but wasn't sure if that was too narrow or in the "just right" range...
    "Do or do not, there is no try." -- Yoda


  4. #4
    MAD777's Avatar
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    John, here's my way to calculate the relationship of baffle width to average thickness.
    I came up with this by measuring loft and baffle spacing on several high end down sleeping bags that I think "got it right." It's handy because it gives me a number to use, rather than pick a random spacing with each quilt. Here goes...

    Add 1" to the average thickness, then multiply that by 1.5. That's it.

    Mathematically;
    T = average thickness
    S = baffle spacing

    S = 1.5 * (T+1)

    In the case of an underquilt, that would be the average spacing between the inner and outer shell. The inner spacing would be less and the outer, more.

    To illustrate; a 1.5" average thickness would have 3.75" spacing
    and a 4" average thickness would have a 7.5" spacing.
    Mike
    "Life is a Project!"

  5. #5
    Senior Member JohnSawyer's Avatar
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    Thanks Mad!

    So, If I'm shooting for 2.5" avg thickness... (2.5+1) * 1.5 = 5.25 Cool.. That fits my pre-calculated design, or at least within .25"...

    If I reverse that, and go with S=5.5, we get ... um.. er.. plus that, move that over... uh... T=S/1.5 -1.. plug in 5.5 for S and T= 2.67 Perfect!

    I'm off to start marking up some fabric!
    "Do or do not, there is no try." -- Yoda


  6. #6
    Senior Member DemostiX's Avatar
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    Quote Originally Posted by MAD777 View Post
    John, here's my way to calculate the relationship of baffle width to average thickness.
    I came up with this by measuring loft and baffle spacing on several high end down sleeping bags that I think "got it right." It's handy because it gives me a number to use, rather than pick a random spacing with each quilt.
    Italics added.

    "Yes" to this approach.

    But, can I wonder if optimal chamber cross-section has changed, now, with higher-fill-power downs?

  7. #7
    Senior Member G.L.P.'s Avatar
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    also LxWxH/fill power
    i pretty much use 5 inch wide Chambers on every quilt but you can make them as wide as you want

    say your making a UQ 56x45 and want it 3 season so use 2" baffles
    rule of thumb has been 2" for 3 season and 3" for winter it's not set in stone but i found there pretty true in regards to temp ratings

    so 56x45x2/800 (fill power) = 6.3oz of down needed for the said airspace
    so with 20% overfill around 1.2oz so 7.5oz needed... all you need to do is add up the amount of chambers you made 5" wide at 45" would give you 9 so just divide your amount of down 7.5oz by the amount of chambers 9 ..7.5/9 = .83 or .8oz of down per chamber
    this is just another way to do it ...figured i would put it out there to give you another option
    It puts the Underquilt on it's hammock ... It does this whenever it gets cold

  8. #8
    Senior Member JohnSawyer's Avatar
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    Quote Originally Posted by G.L.P. View Post
    also LxWxH/fill power
    i pretty much use 5 inch wide Chambers on every quilt but you can make them as wide as you want

    say your making a UQ 56x45 and want it 3 season so use 2" baffles
    rule of thumb has been 2" for 3 season and 3" for winter it's not set in stone but i found there pretty true in regards to temp ratings

    so 56x45x2/800 (fill power) = 6.3oz of down needed for the said airspace
    so with 20% overfill around 1.2oz so 7.5oz needed... all you need to do is add up the amount of chambers you made 5" wide at 45" would give you 9 so just divide your amount of down 7.5oz by the amount of chambers 9 ..7.5/9 = .83 or .8oz of down per chamber
    this is just another way to do it ...figured i would put it out there to give you another option
    ACK!

    Back to analysis paralysis!

    Oh, wait.. the only thing here is you're assuming the quilt has rectangular tubes, but with the diff. cut the out fabric is more tube-like... I guess that's what the overstuff is for....

    Thanks!
    "Do or do not, there is no try." -- Yoda


  9. #9
    Senior Member G.L.P.'s Avatar
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    Quote Originally Posted by JohnSawyer View Post
    ACK!

    Back to analysis paralysis!

    Oh, wait.. the only thing here is you're assuming the quilt has rectangular tubes, but with the diff. cut the out fabric is more tube-like... I guess that's what the overstuff is for....

    Thanks!
    yeah the 20% will cover the Diff cut but i always add another oz for the diff cut but thats just me i only ever do a half inch for my diff cut never seen the need for more but some do it's all up to the maker and your needs
    but no matter how you do it the end results will be the same there are a few different ways to calculate everything thats just how i was told to do it so i just stuck with it and works out every time ... but like i said the end results are the same
    It puts the Underquilt on it's hammock ... It does this whenever it gets cold

  10. #10
    bloomgorge's Avatar
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    Quote Originally Posted by G.L.P. View Post
    also LxWxH/fill power
    i pretty much use 5 inch wide Chambers on every quilt but you can make them as wide as you want

    say your making a UQ 56x45 and want it 3 season so use 2" baffles
    rule of thumb has been 2" for 3 season and 3" for winter it's not set in stone but i found there pretty true in regards to temp ratings

    so 56x45x2/800 (fill power) = 6.3oz of down needed for the said airspace
    so with 20% overfill around 1.2oz so 7.5oz needed... all you need to do is add up the amount of chambers you made 5" wide at 45" would give you 9 so just divide your amount of down 7.5oz by the amount of chambers 9 ..7.5/9 = .83 or .8oz of down per chamber
    this is just another way to do it ...figured i would put it out there to give you another option
    +1 saves me with typing
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