View Full Version : new cut, dual differential
i have tested a prototype with differential fabric on the long side, at 2" per.
so now, the top layer on a Freeze is not only 6" wider than the bottom across the width of the uq, but also it is now 2" longer, along the length.
i have noticed this does two things.. first, it forces the uq into a very slight curve, about how you would lay in your hammock.
second, it allows more loft in the baffles, with almost no noticable compression of the down*
im considering offering this as standard or as an option with the quilts containing overfill. id like to see what the customer thinks as well. let me hear your thoughts!
*down has been tested to show that even with a 50% compression, it retains the same warmth.
jackleberry
01-18-2011, 22:01
This is the way I've made my (currently only half-filled, awaiting more down) DIY underquilt, loosely based on Shevy77's description. Due to some measurement errors, I ended up with a few inches more differential and less baffle than I had intended. The length differential is 5-6 inches. The result is very puffy looking. I won't be able to tell how well it fits until I snag some more (vintage) down.
...the top layer on a Freeze is not only 6" wider than the bottom across the width of the uq, but also it is now 2" longer, along the length.
This makes perfect sense to me, and is how I made my down underquilts.
*down has been tested to show that even with a 50% compression, it retains the same warmth.
This is a very comforting statement. Where did you find out about it?
Jerry
jackleberry
01-18-2011, 22:16
This makes perfect sense to me, and is how I made my down underquilts.
This is a very comforting statement. Where did you find out about it?
Jerry
I think the quote is from some testing done for the military... I can't seem to find a reference to the results... IIRC the real meaning is that you can overstuff by 100% before you start to loose insulation effectiveness, not that you can compress a quilt 50% and still have the same warmth as you would uncompressed.
I think the quote is from some testing done for the military... I can't seem to find a reference to the results... IIRC the real meaning is that you can overstuff by 100% before you start to loose insulation effectiveness, not that you can compress a quilt 50% and still have the same warmth as you would uncompressed.
i do believe that the statement said just that... you can squish down to 50% of its full loft before it loses thermal efficiency...
and, i cannot find that reference either but i do remember this: it was posted at BPL by our very own Jack Teir.
I wonder if Jacks' remember that info..
jackleberry
01-19-2011, 14:54
i do believe that the statement said just that... you can squish down to 50% of its full loft before it loses thermal efficiency...
and, i cannot find that reference either but i do remember this: it was posted at BPL by our very own Jack Teir.
I wonder if Jacks' remember that info..
Well, given that some fairly extensive searching on the matter turns up nothing in the way of references (not even in the form of marketting claims by the big sleeping bag manufacturers), I would say that this statement currently has the status of myth.
The way you interpret the statement would appear to violate the principle of loft, which would allow one to make a bag/quilt twice as warm for a given loft value by stuffing it with 200% as much down as would normally be required given the fill-power.
I personally believe that most of the claims people make about the added warmth of overstuffing are a result of A) psyhological factors B) increased down pressure resulting in decreased lofting time [most bags recommend 3-4 hours to reach full loft!] and C) crude volumetric calculations made my manufacturers resulting in UNDERSTUFF being the standard, with the added "overstuff" merely bringing the quilt closer to the correct fill level.
thats good stuff, Jackleberry..
but regardless of mythical status and what not, the new dual differential cut of the te-wa's allows for fuller loft, making the compression of said loft less a concern.
end result: warmer quilt :cool:
jackleberry
01-19-2011, 15:24
thats good stuff, Jackleberry..
but regardless of mythical status and what not, the new dual differential cut of the te-wa's allows for fuller loft, making the compression of said loft less a concern.
end result: warmer quilt :cool:
I've been thinking about that too... Since the baffles run lengthwise, it would seem that any restriction at the ends would cause the down to migrate toward the middle--resulting in less loft at the ends, but also less down (so the down would not really be compressed a lot locally, but instead compressed a little throughout the entire baffle. It's possible that a tapered thickness like this might be somewhat desirable as the parts of your body (or just empty space in the hammock) being covered by these sections of quilt may require less insulation (if, for instance, it happens to overlap the coverage of the footbox of your topquilt). In this case the down would be better used insulating the users core (which is, I think, the basic design principle behind the fractional length underquilts).
Given the complexity involved, I think it would probably be quite difficult to put a number on what influence the edge design (tapered, ballooned, or box-end) might have on the overall temperature rating as perceived by the user. However, with the price of goose down being what it is, there is a compelling incentive to optimize its use...
true that.
at the gathered ends of my quilt, it differs on lay, hammock design, and user size.
near the knee end, my pad overlaps the quilt. at the head end, im wearing a blackrock or similar hat. so, yes i think its nice that the quilt may shift down towards the core. i find my feet need much less insulation than my torso. thanks for your insights!
do you have pictures of this said prototype? b/c if you don't, i don't believe you...
posted to the gallery last week. hint: ITS SILVER
btw, as Jackleberry describes on loft - this photo was taken just seconds after hanging this uq, so loft is not nearly full yet. actually, i filled this quilt by hand and it never really got a chance to break up the clumps and whatnot.
i see it and it looks nice. i like that silver
warbonnetguy
01-20-2011, 13:02
The way you interpret the statement would appear to violate the principle of loft, which would allow one to make a bag/quilt twice as warm for a given loft value by stuffing it with 200% as much down as would normally be required given the fill-power.
zero overstuff would technically be very understuffed by a customer's standpoint, but that's important when you're talking about zero overstuff compared 50% compressed.
what is the "correct" fill level? that's a matter of preference. i garantee everyone uses some kind of overstuff anyway (weather or not you think it's enough). an oz of down takes up like 1500 cubic inches or something, so you could take a standard quilt, remove a good portion of the down, and you could still get it to loft fully.
So if your quilt is sparsely filled (read zero overstuff), and then you double that, it will be nice and plump and a heck of alot warmer, all without changing the loft.
when you talk about overstuffing by 100%, that doesn't mean doubling the fill in somebody's quilt, those are already somewhat "overstuffed" to begin with.
good call on doing the length differential mike, there is a definate curve from end to end even on a short quilt like the breeze or the yeti, certainly not as much as there is side to side, but some differential is still needed (imo)
NCPatrick
01-20-2011, 13:11
Ummm. I'm not finding a picture of this UQ. I'm very interested. Have you got any links to the pictures you may have posted?
Thanks!
...an oz of down takes up like 1500 cubic inches or something...
Brandon - I'm not sure I understand this statement. I thought the fill power rating determined how many cubic inches the down would fill.
For example:
1 ounce of 800 fill power down should fill 800 cubic inches.
1 ounce of 650 fill power down should fill 650 cubic inches.
And so forth.
That's how I have been figuring out how much down to put in my DIY quilts(before overstuff). Calculate the volume of a baffle, in cubic inches, divide by the fill power I'm using, equals how many ounces are needed for that baffle. It has worked well for me, so far. Do I have this wrong?
Jerry
Mike - sorry for dragging your thread off topic.
jackleberry
01-20-2011, 13:50
zero overstuff would technically be very understuffed by a customer's standpoint, but that's important when you're talking about zero overstuff compared 50% compressed.
what is the "correct" fill level? that's a matter of preference. i garantee everyone uses some kind of overstuff anyway (weather or not you think it's enough). an oz of down takes up like 1500 cubic inches or something, so you could take a standard quilt, remove a good portion of the down, and you could still get it to loft fully.
So if your quilt is sparsely filled (read zero overstuff), and then you double that, it will be nice and plump and a heck of alot warmer, all without changing the loft.
when you talk about overstuffing by 100%, that doesn't mean doubling the fill in somebody's quilt, those are already somewhat "overstuffed" to begin with.
good call on doing the length differential mike, there is a definate curve from end to end even on a short quilt like the breeze or the yeti, certainly not as much as there is side to side, but some differential is still needed (imo)
OK, let me attempt to clarify a little bit. Fill power is effectively a measurement of the expansive force 1oz of down exerts agains a known, calibrated force (a weight on top of the measuring apparatus [not sure what the standard value is here...]).
Zero overstuff, as you call it, is acheived in a quilt when the expansive pressure of the down fill just overcomes the compressive force of gravity and internal forces acting on the shell. Determining where this point is requires an accurate volumetric measurement of the shell, not a simple formula of X Y and Z of the quilt outline. The shell material and construction cannot be ignored... The required fill for a 1.9oz/yd nylon shell and a 0.9oz/yd shell MUST be different (even if only very slightly) because more expansive force is required to hold up 1.9oz/yd...
Physical modelling would be much easier here, and would basically replace the fill-power measurement stage and the virtual modelling... Just stuff the quilt, allow it to loft, and keep adding down until the outward pressure of the fill on the shell results in a full and puffy loft (but not necessarily one that springs back instantly when disturbed). The total weight of the quilt could then be measured and the shell weight subtracted thus giving a fairly accurate fill level for a given fill-power of down.
Adding a slight overstuff here will help maintain a consistent loft as the loft of the down degrades with humidity, etc. Adding extreme overstuff would decrease the lofting time and increase the resiliency... But it would also increase the weight... I have my doubts that it would do much to increase the warmth.
In short... I think that the practice of roughly calculating fill level based on fill power and dimensions of the quilt alone is insufficient to account for all the factors involved, resulting in understuffed quilts.
"..the top layer on a Freeze is not only 6" wider than the bottom across the width of the uq, but also it is now 2" longer, along the length..."
Seems to me that it would be the other way around?
Jim
warbonnetguy
01-20-2011, 17:12
OK, let me attempt to clarify a little bit. Fill power is effectively a measurement of the expansive force 1oz of down exerts agains a known, calibrated force (a weight on top of the measuring apparatus [not sure what the standard value is here...]).
Zero overstuff, as you call it, is acheived in a quilt when the expansive pressure of the down fill just overcomes the compressive force of gravity and internal forces acting on the shell. Determining where this point is requires an accurate volumetric measurement of the shell, not a simple formula of X Y and Z of the quilt outline. The shell material and construction cannot be ignored... The required fill for a 1.9oz/yd nylon shell and a 0.9oz/yd shell MUST be different (even if only very slightly) because more expansive force is required to hold up 1.9oz/yd...
Physical modelling would be much easier here, and would basically replace the fill-power measurement stage and the virtual modelling... Just stuff the quilt, allow it to loft, and keep adding down until the outward pressure of the fill on the shell results in a full and puffy loft (but not necessarily one that springs back instantly when disturbed). The total weight of the quilt could then be measured and the shell weight subtracted thus giving a fairly accurate fill level for a given fill-power of down.
Adding a slight overstuff here will help maintain a consistent loft as the loft of the down degrades with humidity, etc. Adding extreme overstuff would decrease the lofting time and increase the resiliency... But it would also increase the weight... I have my doubts that it would do much to increase the warmth.
In short... I think that the practice of roughly calculating fill level based on fill power and dimensions of the quilt alone is insufficient to account for all the factors involved, resulting in understuffed quilts.
well, if you want to get technical about it, consider this: we were discussing down not losing any insulating ability when compressed by 50%. that's "50% compressed" compared to "zero compressed". zero compressed nobody uses, and what you prefer is probably alot closer to 50% compressed than you think, possibly even more than 50%.
take for instance a rectangular quilt 86" x 48" x 2" , that's 8256 cu" of volume. totally uncompressed down takes up about 1500 cubic inches of space per oz (that's about what i recall when i measured it), so 8256 inches of volume divided by 1500 gives 5.5 oz for a fill weight strictly by the numbers for zero compression (or as close as you can get since there is a shell pressing on it like you say). it so happens that the jrb hudson river is exactly those dimensions, and although the jacks no longer list a fill weight (or a baffle height) in their specs, i bet money they're using at least 10oz of fill in that quilt, so compared to totally uncompressed down, they're down is technically close to half compression. (10oz or more fill compared to 5-6oz), and the same goes fro everybody else, some companies overstuff even more.
warbonnetguy
01-20-2011, 17:14
Brandon - I'm not sure I understand this statement. I thought the fill power rating determined how many cubic inches the down would fill.
For example:
1 ounce of 800 fill power down should fill 800 cubic inches.
1 ounce of 650 fill power down should fill 650 cubic inches.
And so forth.
That's how I have been figuring out how much down to put in my DIY quilts(before overstuff). Calculate the volume of a baffle, in cubic inches, divide by the fill power I'm using, equals how many ounces are needed for that baffle. It has worked well for me, so far. Do I have this wrong?
Jerry
Mike - sorry for dragging your thread off topic.
yeah, like he said, those fill power numbers are with a calibrated weight pushing down on it, it lofts alot higher when uncompressed. (sitting loose in a box for instance)
warbonnetguy
01-20-2011, 17:22
"..the top layer on a Freeze is not only 6" wider than the bottom across the width of the uq, but also it is now 2" longer, along the length..."
Seems to me that it would be the other way around?
Jim
no, the curve from side to side (width) is a much sharper curve so more differential is needed there
jackleberry
01-20-2011, 17:32
well, if you want to get technical about it, consider this: we were discussing down not losing any insulating ability when compressed by 50%. that's "50% compressed" compared to "zero compressed".
take for instance a rectangular quilt 86" x 48" x 2" , that's 8256 cu" of volume. totally uncompressed down takes up about 1500 cubic inches of space per oz (that's about what i recall when i measured it), so 8256 inches of volume divided by 1500 gives 5.5 oz for a fill weight strictly by the numbers. the jrb hudson river is exactly those dimensions, and although the jacks no longer list a fill weight (or a baffle height) in their specs, i bet money they're using at least 10oz of fill in that quilt, so compared to totally uncompressed down, they're down is technically close to half compression. (10oz or more fill compared to 5-6oz)
Oh, I see what you're saying. I should have been more careful in distinguishing between compression (what I would call pressurization) of the down by overstuffing and compression in one dimension of the quilt (which would reduce the loft) as in squeezed baffles. I'm quite sure that the quote I saw from the military study left this distinction out, which further invalidates any conclusions we might like draw from it without gettting a look at the full description of the experiment.
warbonnetguy
01-20-2011, 17:47
Wouldn't 50% compression by one means be equivalent to 50% compression by the other?
Taking an appropriate filled quilt and squishing it by 50%, would then result in more than 100% compression of the down (since it was already compressed to begin with). Are they talking about down being at 50% compression or a down filled item being at 50% compression? that would make a difference.
how do you measure the warmth of uncompressed down anyway, considering you'd have to put it into an item (i'd think), which would by it's nature compress it.
jackleberry
01-20-2011, 18:11
Wouldn't 50% compression by one means be equivalent to 50% compression by the other?
Taking an appropriate filled quilt and squishing it by 50%, would then result in more than 100% compression of the down (since it was already compressed to begin with). Are they talking about down being at 50% compression or a down filled item being at 50% compression? that would make a difference.
how do you measure the warmth of uncompressed down anyway, considering you'd have to put it into an item (i'd think), which would by it's nature compress it.
Eh. No more than your open box does. Actually all of this gets a little more complicated when you consider the fact that underquilts have the somewhat unique aspect of being used in a suspended arrangement. I would think that (with differential cut quilts anyway) this would result in a minimum of fabric pressure since gravity is working to spread the sides of the shell apart rather than squish them together. Might help one get away with less down per volume unit than a top quilt might need.
I still don't believe you can take a given quantity of down, poly fill etc and compress it into a smaller space and expect it not to loose insulating ability. Nor do I believe that you can stuff the hell out of a quilt and do anything more than make it heavier and more expensive (and a stiffer).
I imagine that the curve of insulating ability looks looks pretty steep approaching proper fill (where the down presses sufficiently against the shell to get good loft), then levels out and starts going DOWN after 200% fill. Slowly at first and then much more steeply as you eventually approach a solid mass which will be thermally conductive. At 200% fill (where the down could be said to be 'compressed' by 50%, depending on how you interpret that statement) there should be little loss of warmth, but no gain either. You would have something twice as heavy and expensive...
If you took a quilt at 100% fill and put enough weight on it to make it half as thick/lofty, I believe it would be considerably less warm simply because the volume of trapped air has been reduced and trapped air is the real insulator.
oh man, i may have to re-title the name of this thread..
anyway, the info is good. just as long as anyone can find it! :p
slowhike
01-20-2011, 21:22
"..the top layer on a Freeze is not only 6" wider than the bottom across the width of the uq, but also it is now 2" longer, along the length..."
Seems to me that it would be the other way around?
Jim
No, I understand what you're saying Jim. I thought the same thing when I read that.
Maybe they are calling the layer of the under quilt that is against the hammock the bottom???
I have been calling the top & bottom layers as you see them with the under quilt deployed on the hammock... the top is against the hammock & the bottom is facing the ground.
If that would be the case, the top would be smaller & the bottom would be larger (in both directions) for a differential cut under quilt. Right?
Here is a drawing I did & posted on the Hammock Camping Yahoo Group back in Nov of 2006, explaining the idea of the differential cut under quilt.
http://www.hammockforums.net/gallery/files/2/5/PB300117_thumb.jpg (http://www.hammockforums.net/gallery/showimage.php?i=197&c=member&imageuser=25)
The red layer (which I would call the top) is facing the hammock & the green layer (which I would call the bottom) is facing the ground.
No, I understand what you're saying Jim. I thought the same thing when I read that.
Maybe they are calling the layer of the under quilt that is against the hammock the bottom???
I have been calling the top & bottom layers as you see them with the under quilt deployed on the hammock... the top is against the hammock & the bottom is facing the ground.
If that would be the case, the top would be smaller & the bottom would be larger (in both directions) for a differential cut under quilt. Right?
Here is a drawing I did & posted on the Hammock Camping Yahoo Group back in Nov of 2006, explaining the idea of the differential cut under quilt.
http://www.hammockforums.net/gallery/files/2/5/PB300117_thumb.jpg (http://www.hammockforums.net/gallery/showimage.php?i=197&c=member&imageuser=25)
The red layer (which I would call the top) is facing the hammock & the green layer (which I would call the bottom) is facing the ground.
yes, that may be easier for others to visualize. when i say "top" im referring to the way the quilt would lay on the ground, flat side down, and lofted baffles side up. its my visualization of the UQ (such is a reference to my particular method of construction, mainly)guess i should have better used the terms "inside and outside"
slowhike
01-20-2011, 22:01
Thanks for the clarification. Some of us are easily confused:D
Keep up the good work!
I was able to film a very short "how to" for the Freeze. That is my standard, 3 season model. The model is Felecia and the hammock is a Blackbird.
enjoy!
pompkF7OHFU
That is my standard, 3 season model. The model is Felecia
hehe i just realized how this sounded.. she is my 4 season model. I wouldnt survive without her especially in the Winter. :boggle:
gunner76
01-30-2011, 20:19
Some of us are easily confused
I stay confused :D
Te-wa - Glad to see you offering a dual differential cut UQ. It's a concept that makes a lot of sense. Good luck with the new model.
guys/gals
how i forgot to mention... the new cut also comes with 8oz of standard fill, over the 7oz offered previously. so now there is a 1 oz increase in 800+ fill.
now you get 1/2 a pound of goose down while remaining UL - the freeze still comes in at 14oz
:boggle:
testing this newer cut of the outer shell yielded a standard fill Freeze to 18.5 degrees without hesitation. (now 8oz fill stock, no xtra charge)
I do have a chance for some more testing this weekend in the local mtns and hoping for colder weather!
using the old style shell on the Freeze I easily pushed 25 so this one which allows a little more down fill could go to 15... id like to find out.
Nice results. I need to get out and put my Freeze to the low temp test...
If you come a little farther north, you will get the lower temps you crave. ;)
Ive gotten settled into the new house well.. took 2 weeks to find a spot for everything, but the new workshop is running. also, the website is updated a lil' bit and i'll post a better video in the 'directions' area soon.
happy hanging, te-wa