12-ounce down… sleep thing

[Brad Groves]

Hi all-
I'm just about finished with a potentially androgenous down sleeping bag quilt. My target all along was a 12-ounce sleeping bag. As it stands right now I'm at 11.8 ounces, but I still have to stuff one baffle (about 0.6 ounces), add the zipper (0.5 ounces) and decide whether or not to add a draft tube (.75 ounce?).

I mocked up the pattern from a bedsheet and tried it on several times–it fit great! Then I made the real deal and stuffed it with down, and I gotta say it's a snug fit–and boy, Lynn, I was surprised by how much shorter it got!

The way I see it, I have a few options:

I could try using the thing as a quilt, eliminating the draft tube and zipper. But I do really prefer bags and find them overall warmer.

Just not use the draft tube?

To make it a little less constricting, I could add a hybridized draft tube/ expansion panel for the zipper. (Add maybe 2" in girth.)

Also, I would probably have this thing finished if I weren't being brain-dead about the zipper. Got the continuous zip from Thru-Hiker, and for all my futzing about I can't seem to get the slider started onto the zipper. Any suggestions?

Thanks for your thoughts!

[Jim Colten]

Brad,

I'd go for the quilt option faster than you can say it … but that's my hike and doesn't need to be yours.

Dropping the bag's draft tube might be OK for warmer temps, what's your target low temp for this thing?

Remembering geometry, circumference=pi*diameter … so a 2 inch expansion panel adds about 5/8 inch to the diameter … will that be enough to eliminate the too snug feeling? Only you can know that. Might want to try basting in plain fabric expansion panels of various widths to decide how much you'd want.

[Lance M]

Have you looked at AYCE's "Using Continuous Zipper?"
He includes a drawing along with the text.

Also Specialty Outdoors Zipper Tips
Text for starting a zipper pull is at the bottom.

[Brad Groves]

Ahh, specs- 30 degree, 4" two-sided loft. About 58" shoulder girth for the top 9 inches, then narrows to 32" foot girth for the last 16" of length.

Jim, good idea about trial fitting. I think I could fit in the bag if it zipped up, but snug enough that when I breath my rising chest would pull up my arms. I talked to AYCE today and he had some helpful ideas. I might sew in an accent color and make an expansion a design element.

The thing is, I really want the 12 ounces… which is what would compel me to make this a quilt. Actually, if I made it a quilt I could narrow the girth 4-5 inches up top, and I think the finished weight would be about 11.25 ounces. But the reality is that every time I used the thing I'd be missing the zipper. So the extra 2 ounces or so is probably worth it. But I'm still considering the option.

Thanks for the zipper links! I'll have to play with the zipper some more when I get home tonight.

Any more thoughts?

[Tim Marshall]

if you're still having issues with the zipper it is because it takes 3 hands. I am lucky enough to have evolved such an appendage though years of struggling with adding sliders, others just need to seek the aide of a trusted friend.

2 hands pull the zipper tape apart the third hand pulls the slider on.

-Tim

[Lynn Tramper]

If it were me, I would turn it into a top-bag by narrowing the width and adding some plain fabric to the bottom. This would allow you to have a zip, a draft tube AND still make your 12oz goal, while making the "bag" overall a bit wider…For reference, I think my WM PODS are 44inch at the shoulder, plus another 18 inch of bottom fabric, for a total girth of 62 inches. Plenty roomy, warm and light.

[Don Meredith]

Brad, do you have photos or are they on the way? I'm seriously considering a MYOG quilt / bag and it sounds like you're already well down the path I'd like to take. I hope you don't mind sharing details…

[Lance M]

Tim is right on about needing 3 hands to start a zipper.

Stills from video:

Windows Media Player Video

Quick Time Video

Hope the links work OK. Just learning XHTML.

[Brad Groves]

@ Tim- So all I've gotta do is drink some toxic goo and encourage an extra hand to sprout? Sweet!

@Lynn- Top bag was a thought… I've always rolled with my bag, though, and I'm not sure if I'd get used to rolling in it. Also a zipper problem noted later.

@ Don- No pics yet. I'll put some up when finished, though.

@ Lance- Hmmm. Use a hand on each side of the zipper tape and my teeth on the zipper pull ;P

One detail I forgot to mention is that I prefer full-ish length center chest zips, which is how I designed this. If I converted it to a top bag I'd have to slice it down the middle, and I'm not sure I can stomach that.

I just might tape the thing together tonight and sleep out in it to see what it'd be like as a quilt. Just maybe…

I'm trying to figure out how to build a draft tube that extends loft to the "wrong" side of where the tube is sewn into the zipper. That part seems tricky.

[Tim Marshall]

if you can use it as a quilt you can make it a top bag. Just make the top wide enough so you can slither in and cinch it closed.

Maybe not preferable, but a way to save all the work you've done.

-Tim

[Brad Groves]

OK, so, it's done.

Centered zip, draft collar/extension, no draft tube. Functional finished length is really about 56 inches, although I cut fabric at 62 inches. I added the draft collar bit to try to bump up length to 58 inches. Works out all right for now. The zipper problem I was having was that I wasn't paying attention to the orientation of the double-pull (ie, pull tab on inside and outside of slide), and was trying to put the slide on the zipper upside down.

This is a hyper-super-mega-efficient cut. I mean, I think my Summerlite is a pretty roomy bag. This one is technically really too snug, given that it's tight enough in my (narrow-ish) hips to compress the insulation a little. Outside chest dimensions (all dimensions measured flat) 26 inches, hip 20 inches, foot 8.5 inches. My original plan was 59 inch chest girth, cut out of 60" fabric. But the fabric started out at 58.5 inches, then I lost some functional girth after stuffing with down. Original plan was 32 inch footbox; the original panel I cut was too large, then too small. The third attempt seems to be just right.

I think because of the hyper-efficient cut, this bag is HOT! I only used about 6 ounces of down (yeah, yeah, I know… that vest I did used 12!) but it lofts beautifully and I did calculate mass of down required for each baffle. (In case you're wondering, 5 inch baffle x 1.9 inch desired height x width, ie 32 inch. Take that number and divide by fill power of down.) I start getting warm pretty much as soon as I slip into the bag.

My original working calculations varied from an expected finished weight of 12.6 to 13.2 ounces. The finished weight is 14 ounces (yes, exactly 14, unless you want to get to thousandths of ounces). Shell fabric was about .08 to .09 osy high from spec, which was about .8 ounces. I also hadn't planned on adding the draft collar, which added .75 ounces. I did use a little less down than originally planned. I messed around trying to use it as a quilt yesterday because I could have kept the weight at about 12.5 ounces. But the footbox is so tight the bag automatically rolls over with you. Zipper was needed.

Thoughts: I off-centered the draft collar so there wouldn't be a gap right over my neck. I should have put the drawcord on edge closest to my head, instead of where the main bag ended. Next project will allow more girth and length (say an extra 3 inches added into planning figures for cut fabric?). I used baffles cut at 1.5 inches and sewn to a functional height of 1 inch, allowing an "extra" half-inch loft on each side; I believe in having the greatest density of down possible. I cut the footbox baffles a half-inch higher and stuffed accordingly; my feet get cold easily at night.

Bottom line, the bag is 2 ounces over goal, but only about .8 ounces over calculations. More importantly, my overfilled SummerLite weighs 20 ounces, this one weighs 14–I just cut 6 ounces from my pack, for a bag that's at least as warm!

[Brad Groves]

For those of you who like facts and more measurable data:

This photo doesn't represent just loft; it's a more vertically-oriented, constructed footbox to ensure that my toes don't poke up into the insulation too much. So there's definitely just some air in there!

[Don Meredith]

Very nice!

[Author]

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