Quilt shell tricks

[R]

Has anyone tried any of the following?

1. Sewn a quilt or bag on the bias?  The hope is that it will be a bit stretchy, more comfortable and leave less dead air around you.  Montbell does this w/ their super stretch line of sleeping bags.  They also use elastic thread, but I’m not interested in that.  I’m skeptical on this.  If anything, it seems like a good way to end up w/ cold spots.
2. Added a single layer of fabric around the back of a quilt, closing it like a sleeping bag?  I’ve never used a quilt clipped to the pad, and I question how well it seals out cold air around freezing or below, especially for an active sleeper.  I’m thinking a back panel could work well for a contoured back hole like a Katabatic quilt.  Maybe use just one or two snaps/velcro to hold the edges together down the center.
3. Made a hybrid DCF/breathable quilt?  Basically, make the quilt from 0.34 DCF, then add a 12″ – 15″ wide strip down the middle of breathable fabric.  The idea is to realize the weight savings of DCF, but avoid a full vapor barrier.  I don’t want to end up w/ a puffy full of condensation when I get up.  A short test indoors w/ a sheet of plastic inside a down bag says this might work.  Potential weight savings are 1oz – 2oz compared to a 0.67osy breathable fabric.

 

[Ken Thompson]

2. Like Big Agnes bags, kinda

3. Yes. There is a thread on that here somewhere. Tim at EE made one custom year’s ago.

[James Marco]

Actually I have had a Super Stretch #0 for eight to ten years, before the Super Spirals. No problems with the thread. This was a concern when I purchased it and their support assured me that it would last at least 20 years.

Yeah, like Ken said, Big Agnes did this. They used two layers of fabric that you slipped the pad into…no insulation, otherwise. It worked, but they never used a high FP down and all the extra fabric made them heavy for their temp range.

Yeah, several people tried working with cuben(DCF) on bags. Mostly they were failures because they never dried quickly enough. Usually, my bag simply stays dry after I am in it for an hour or so. My body heat tends to dry it out. Of course, I also add my own insensible perspiration to the system. When I get out of the bag, and quit adding moisture, the bag will usually dry out within 15-30min, due to residual heat trapped by the down. With cuben covering 2/3 of the bag, you will loose this, I think. It will take about an hour, in sunlight to dry out. But, this is only my best guess. If you are camping in desert (dry) conditions, it might work fine. If you are camping in a rain forest, no down will ever dry out. Conditions usually trump novel designs, but good thinking…

[R]

Ken,

2.  Sorta.  More like this: https://backpackinglight.com/forums/topic/90198/

3.  You mean this one?  https://backpackinglight.com/forums/topic/21198/  Close, but not quite.  The breathable strip was just on the outside to aid lofting; the inside was all Cuben – full vapor barrier.

[R]

James,

1. Was the stretch primarily from the elastic thread?  Or did you notice positive effects from the bias cut?

3. I don’t quite follow the moisture/drying problem. Are you describing full cuben quilts?  You also refer to your own quilt – can you describe that?

To clarify my proposed design, both the outer shell and inner liner will be DCF everywhere except a stripe down the middle where both outer shell and inner liner will be breathable.  So the only place significant body moisture will enter the quilt is through the breathable inner liner at the top/center of the quilt, which is the same place it can leave the quilt, via the breathable outer shell.  Are you suggesting the needle holes from sewing baffles allows enough moisture in to the down to be a concern?  Can you point me at any related threads?

[Nick Smolinske]

1. I have a Montbell Down Hugger and I like it a lot. In fact I was just thinking about trying to sew a more comfortable quilt using that design feature. As for what provides the stretch? I’d say the bias cut and the stretch stitching are both required. But rather than mess around with elastic thread I’ll just sew the baffles on with a slight zig-zag stitch. I suppose the baffles should be made out of noseeum cut on the bias as well, although to complicate things I would probably sew karo baffles so who knows?
2. I’ve never tried this, although I agree with you that attaching the quilt to the pad isn’t the way to go. Too much dead space, at least if you’re a side sleeper like me.
3. I don’t think this is a good idea. For one it will be clammy, for two it will be disposable. I took apart some 2-year-old Zpacks bags (heavily used) to harvest the down from them, and the mylar on the 0.34oz cuben baffles had mostly disintegrated. At least a quarter of the down was trapped in the dyneema fibers. Given the marginal weight savings, I think a DCF quilt isn’t worth the reduction in lifespan.

That said, the most feasible way to do your DCF quilt would be to make that middle section totally separated from the others (by using cuben baffles). That way your moisture won’t end up in the rest of the quilt, only in the breathable part. You’d need to also add some breathable ports across the other baffles so air can enter and escape when packing the quilt.

[R]

Ok, after much digging through BPL threads:

2.  I guess I’m making a ‘top bag’, as in a sleeping bag that has no insulation on the back; or these are ‘wings’ I’m adding to a quilt.  Examples in Cuben here, and here.  I think I’m a thumbs up on this feature, but I’m still curious to hear from any one that’s actually used them.

3.   At the start of this year, Steve Evans said his 0.33osy Cuben quilt is still going strong 8 years later.  Note, he listed 0.33osy, not 0.34.  Guess I’ll try to figure out if the laminates are a different material.  Here, some one suggested exactly what I am.  Tim Marshal (of Enlightened Equipment) ixnayed the notion for fear moisture would fill the whole quilt.  Partitioning the breathable segment w/ DCF baffles would address this.  Not sure if Tim’s other point about channeling too much moisture in one place is a real concern or not.  I suppose I could use synthetic fill in that area, but the weight of that defeats the whole purpose of DCF in the first place.  Even a layer of 2.5osy Apex on top of down would eat the weight advantage.  Although it would mean most of the down is wrapped in waterproof DCF.  And of course, if most of the quilt is laminate, no opportunity for item 1, the bias cut.

[Jerry Adams]

I do something like #2, except it’s more like a bivy

[R]

Jerry,

Can you elaborate, or post a photo?

[Jerry Adams]

I will do that some time.  I just made a new version which I’ll try out and take some pictures of then post.

[James Marco]

1. Was the stretch primarily from the elastic thread? Or did you notice positive effects from the bias cut?
Both, I believe. For any fairly successful design, balance is always built in. It appears that everything was pulled fairly firmly when it was sewn. Then allowed to relax, and was filled. So, using it as a bag, it usually means a fairly snug fit with no added air space. Using it as a quilt, at say 32F/0C, it is plenty warm but allows some cover to be thrown clear for comfort. Did I mention it was actually a 10F bag?

??Where’s two??

3. I don’t quite follow the moisture/drying problem. Are you describing full cuben quilts? You also refer to your own quilt – can you describe that?
I don’t have a cuben quilt for exactly this reason. For the 2oz of potential savings, I would rather be able to dry it easier, which *any* cuben/DCF will inhibit.

To clarify my proposed design, both the outer shell and inner liner will be DCF everywhere except a stripe down the middle where both outer shell and inner liner will be breathable. So the only place significant body moisture will enter the quilt is through the breathable inner liner at the top/center of the quilt, which is the same place it can leave the quilt, via the breathable outer shell. Are you suggesting the needle holes from sewing baffles allows enough moisture in to the down to be a concern? Can you point me at any related threads?
Assuming a full cuben/DCF quilt with only needle holes, yes. Moisture can enter as you sleep and the bag is warm. Warm air holds a lot more moisture than cool air. In the morning after you get out (up to 15min-30min the bag will be at ambient,) but it no longer has the ability to vent the moisture it picked up. Soo, it will condense slightly inside. As the number of nights progress, it gets worse. You can think of this as water vapour being sucked into the down and staying in the down. Even with synthetics, this will happen, but will be less noticeable at first. Since this is actually statistically based, You can roughly equate the drying time needed for a full standard shell as the starting point. Adding partial cuben/DCF will increase the drying time to infinity as the amount of cuben/DCF used is increased (as a function of percentage of the surface covered.) I cannot tell if this is linear, exponential or some other curve. But because you are covering the down and the air exchange is through down that has already been partially dried and resisting it (remember the convection example?) I am guessing it is exponential… The more it drys, the harder it is to dry. It could well be hyperbolic or similar, though.

Going with a completely sealed bag/quilt is impossible for any light weight backpacker. Why? Because you cannot compress the air out of it to hike…it is sealed. It would be like hiking around with a blown up air pad all the time. High volume, means a bigger pack. A bigger pack means more weight. Carrying 3 pounds of ping pong balls would take a LOT more pack than carrying around 3 pounds of compressed sleep gear. Follow? BTW, smaller is usually lighter for any piece of gear, not just for compressible ones.

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