Jul 16, 2012 at 11:24 pm #1292070
@drongobirdLocale: San Francisco Bay Area
Jim and I have been using down double top-quilt for 25+ years. The first two were hacked rectangular sleeping bags. The one we currently use is a 10 year old custom Nunatak back-country blanket which I tweaked. I'm ready to build a new one that incorporates a few improvements, including lighter shell fabric.
I've got enough experience using double quilts to know what dimensions and features I want. I've done enough sewing to think I can do this without creating a total disaster, but not so much skill that I'm not nervous :)
I've been reading old threads about making quilts, and have gleaned a lot of useful information. Now I'd like advice. For reference, we sleep in a traditional double-walled tent in night-time temps ranging from 25 to 55.
First question… After reading all the threads I could find on fabric options, I'm planning to use M50 for the shell and Nobull (aka 8D, EightD) for the liner, as recommended by Aaron Sorensen in a recent thread. Is there a compelling reason to use a different combo? I fear that I may have missed threads discussing advantages and disadvantages.
Second question… I'm considering making the baffles run along the length instead of the width. The overall bag will be ~70" wide (tapering at the bottom) and ~77" long (plus foot-box and pleated neck flap); so there's not a big difference in the chamber length if I run the baffles in the non-standard direction. It occurs to me since width is so much shorter than length on a single-bag, the chamber size is smaller with horizontal baffles, and therefore down is more controlled by horizontal baffles. But a double-bag is not so dissimilar in the dimensions.
I think there might be two advantages to length-wise baffles, but I may be completely wrong, and I'd hate to find out after all the cost and labor of building the bag. First possible advantage is that there's not as much vertical relief along a chamber that runs head-to-toe as there is in a chamber that runs from floor over the body and down to the floor on the opposing side, so possibly less shifting of the down during the night. Second possible advantage is that it would make it very easy to build baffles for a differential cut, where the shell is a greater circumference than the liner. However, I'm not sure that a differential cut would actually be that useful in a top-quilt in the same way it is in a mummy bag. Eager to hear opinions.
Third question… I haven't seen MYOG designs that use trapezoidal chamber shape, and wonder if there would be an advantage.
That would add an ever so tiny bit more baffle material, but those two sites imply it gives a better result. It shouldn't be any more difficult to make it with trapezoidal chambers, so if it gives a higher quality result I can't think of a downside. Thoughts?
Thanks very much,
amyl.smugmug.comJul 17, 2012 at 6:47 am #1895389
@retiredjerryLocale: Oregon and Washington
The next time I do down, I'm going to do this:
One piece of fabric on the top (black). Another, wider piece of fabric on the bottom (red).
8D (Nobull) (I'm glad you've been keeping up on that) is not totally down-proof. Expect some leakage.
Verticle baffles are fine, but maybe you're overly worried about down shifting sideways. If you put enough down in, it should be okay. If you put as little down as possible to make it the lightest, then you'll have down shifting.Jul 18, 2012 at 9:58 am #1895687
@vickrhinesLocale: Central Texas
1. M50 downproofness: Thruhiker says it works with 900cu in down. That's because high count down has few quills to punch through. Any quills that sneak past the sorting process will poke through the M50. This isn't a problem for me. I just snip the protruding pointy ends off and poke the rest back inside. They won't come through again. Don't pull them through; there is always more stuff clinging to them and you will open up a larger hole.
2. I understand your logic regarding longitudinal baffles. Never tried them myself. Differential cut is easy to achieve with cross-sectional baffles if you use a good, ultralight noseeum net which does not need to be hemmes. Down shift is rarely a problem if you have enough loaded. Use noseeum net in any case because it gets coated with down thereby preventing the baffle from acting as a conduit for drafts.
3. Trapezoidal or slant baffle construction was promoted for years by Hollubar based on a pencil and paper analysis that was flawed. Theoretically the slant baffles would allow the most uniform loft. It doesn't work like that in real life. Conventional square baffles work just as well.
4. You probably know this already, but if you fold the shell fabric along each baffle line and stitch a narrow (1/8 or 3/16) hem, you can then stitch the baffles to the hems and no stitching will show on the outside.Jul 18, 2012 at 10:29 am #1895701
@drongobirdLocale: San Francisco Bay Area
Thanks Vick for the info about trapezoidal baffles.
"4. You probably know this already, but if you fold the shell fabric along each baffle line and stitch a narrow (1/8 or 3/16) hem, you can then stitch the baffles to the hems and no stitching will show on the outside."
I've mocked up what you're describing – does it look right? I've not seen this method on sleeping bags I've owned. Is there a functional advantage, or is it aesthetic? I'll be using Nanoseeum for the baffles, should I hem the Nanoseeum first, or can sew it on with raw edges?Jul 20, 2012 at 11:06 am #1896226
@oroambulantLocale: San Francisco
Big advantage of the double stitched baffle seam is there are no threads to snag. Disadvantage is weight. If you have baffles every 5" and 1/2" seam, that's 20% more fabric.
Have you considered karo-step? More work to sew, but a LOT easier to stuff down. You don't have to weigh down, just stuff it.
I used a 4'x4" mailer tube that I snaked into the far corner of the quilt through 5" of unsewn seam. I taped the quilt to the tube. I opened a hole in the down's plastic bag and slipped it over the tube and my hand. With my hand inside the plastic, I grab the down and shove it into the tube. Occasionally I rammed it with a broomstick. I kept a vacuum going with noseeum over the upholstery attachment to grab loose down. I also used the vacuum to pull every last bit of down out of the plastic bag. It took me all of 30 minutes, and no down floating around the house.
I think it would be a royal pain to weigh and stuff individual baffles. I still haven't figured out a sane method (I'll be sewing a down jacket next and that has separate compartments).
The karo-step also works great in the field for moving down where you want it.
Congrats on taking the plunge. I look forward to hearing of your experience!
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