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Bonded Cuben down quilt
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Colin Krusor
(ckrusor) - M

Locale: Northwest US
Bonded Cuben down quilt on 06/10/2011 22:26:24 MDT Print View

This quilt is my first and it’s not quite finished. I’m not sure when I’ll get time to attend to the last details, so I thought I’d go ahead and post about it.

Given that my girlfriend and I are both slender and not particularly tall, this double quilt is huge (74” wide x 80” long). I chose these dimensions because I plan to attach tabs to the top that can be used to suspend it a little under the tarp (like a low net-tent), to make a little quilt-tent for warm nights. In total it weighs 29.6 oz, of which 23 oz is a mixture of 750 and 800 fill power down, some of which I dyed brown as an experiment a while ago. The total weight of the shell is about 6.6 ounces, which makes the down/shell material weight ratio 3.48. The loft averages about three inches. The baffle walls are 2.75” high and spaced three inches apart. It packs down to about the size of a gallon jug.

The shell is mostly 0.33 oz cuben. It is completely bonded, so, insofar as the cuben itself is waterproof (not strictly true), the quilt is waterproof. In the center of the quilt, though, on the top side only, is a fabric patch analogous to the “skunk stripe” on the historic cuben quilt made by Tim Marshall for Steve Evans. The fabric patch is an oval 3 ½ feet wide and 4 feet long.

The fabric I used for the patch is polyester ripstop kite fabric. It originally weighed 0.98 oz/yard on my scale. It had a melamine coating and is pretty heavily calendared. I used a chemical bath to strip off the coating and dissolve the surface of the fibers a tiny bit. It now weighs about 0.71 oz/yard, and it still seems very strong and down-proof. I don’t recommend trying this. The M50 fabric, from Thruhiker, would be a much simpler alternative if it still existed (and it has a DWR for the same weight).

I think a fabric patch for drying out the down is a good idea for sewn cuben quilts, but for a bonded cuben quilt like this one I guess one could argue it either way, because the patch itself is really the only way for water to get in. I decided to try the patch idea more or less arbitrarily. I chose the dimensions and placement of the fabric patch to minimize the risk of the fabric being wetted by rain splatter or contact with condensation on the tarp.

The baffle walls are made of 0.29 oz/yard nonwoven nylon. This material is very similar to nonwoven polypropylene (like agricultural “floating row cover”), but it’s nylon 6,6 (which has about twice the tensile strength of PP). This was sewn to 1/2” wide strips of 0.33 oz cuben, and the cuben strips were bonded with 3M 4693H plastic-bonding contact cement to the shell material (but sewn to the fabric patch). I tried Hysol U09lv at first, but using the two-part adhesive was far too time consuming for fifty-six 76” bond lines (354 feet of glueing). I’m glad I used the contact cement instead. I used an irrigation syringe with a very fine tip to put a hair-like thread of glue on the shell material and then immediately pressed down the strips sewn to the baffle gauze. When I tested the bonds later, I actually found that the bonds made with the contact cement have better peel strength than the early bonds I made with the Hysol, and I popped a couple of stitches in the nylon/cuben strip seam without causing the cuben/cuben contact cement bond to budge. I think others have also reported finding that contact cements have good peel strength on cuben (maybe Steve or Lawson?).

Anyway, I’m glad that I was able to establish for myself that a cuben quilt shell can be made by bonding alone without any weight penalty or apparent loss in strength compared to sewing. I always wondered about that. I’ll post updates when I get around to adding under-pad cordage loops and suspension tethers for making a little quilt-tent. Any feedback is welcome.




Edited by ckrusor on 06/10/2011 23:22:36 MDT.

Javan Dempsey

Locale: The-Stateless-Society
nice on 06/10/2011 22:43:40 MDT Print View

Very nice work Colin.

Having done a fair bit of experimenting with this myself I largely concur with your findings, although I definitely would go so far as to say its equal in strength to a traditional quilt with sewn baffles. Contact cement is certainly the only suitable adhesive I've found for this app however, due to its sticky standy nature allowing much more forgiveness in peel. I would certainly keep this thing away from tight stuff sacks however, since you could definitely pull a baffle apart from what I've seen.

Still, its absolutely functional for the application. I've had a WIP bonded cuben underquilt, half finished for a while myself.

Kudos on a cool and well executed project!

Dustin Short
(upalachango) - MLife
Re: nice on 06/11/2011 17:04:50 MDT Print View

Since you bonded the cuben and there are no sew holes, had you not put in the ripstop patch, how would air get into and out of the quilt? I'm sure this would greatly affect both compressibility and lofting of the quilt after packing. So your whim probably turned out to be fortuitous.

Had you sewn it, the needle holes may be enough for air to get in, but with the bonding I have images of trying to pack a giant balloon that bursts in a cloud a down!

Colin Krusor
(ckrusor) - M

Locale: Northwest US
quilt on 06/11/2011 21:16:26 MDT Print View

Javan, thanks for the advice. I'll do as you suggest and make the stuff sack a bit oversized.

Dustin, Tim Marshall makes some of his cuben quilts by bonding the baffles (karo baffles) to the shell, then sewing the edges to close the shell. He adds a tube-like open-ended cuben sack to the foot end of the quilt, and air is forced in by filling the tube with air and rolling it into the quilt. When packing it away, the air escapes through this inflation vent and the side stitching. If I had decided not to use a big fabric patch, I would have come up with some air-trafficking plan like Tim's.

Dustin Short
(upalachango) - MLife
Re: quilt on 06/11/2011 23:16:05 MDT Print View

Ah, interesting solution. I figured there would have to be some way to allow air in and out. Didn't know anyone was making all cuben quilts yet. Looks like Tim has a pretty unique solution that sounds effective.

Good to hear you would have used something similar. As it is, it's a great quilt. Kudos on the workmanship!

Adam Kilpatrick
(oysters) - MLife

Locale: South Australia
Re: Bonded Cuben down quilt on 07/02/2014 17:45:42 MDT Print View

Hi Colin

wondering three years on, how your bonded baffles have held up? I like how you've done them.


Colin Krusor
(ckrusor) - M

Locale: Northwest US
Quilt on 07/04/2014 09:43:10 MDT Print View

Hi Adam,

On the whole, the quilt has held up well. My wife and I have used it quite a bit (maybe 30-35 times). I would change a few things, if I was doing it over again. The 0.29oz nonwoven nylon baffle material turned out to be a bit too fragile. Stuffing and unstuffing unavoidably pulls a bit on the baffle material, and the material has torn in some places. Because this material is nonwoven, it tears "plastically"; some of the fibers break and it stretches out. So, the quilt now has some bulgy parts. If I did it again I would use 4 momme silk, which is the next lightest option (0.45 oz) and significantly stronger. The bonding all seems to be solid.

I never did find time to attach suspension points. I made the quilt extra large because I imagined stringing it up inside the shelter so it hovered just above us, like an insulated inner-tent, on warmer nights. I imagined that this would offer more comfort than having the cuben against our skin and trying to vent by sticking our legs out. I still think it might be an interesting feature for a large quilt.

This quilt turned out very warm, and we haven't used it at all this year because we got tired of getting sweaty under it. The vapor barrier shell narrows the comfort range, and even in temperatures that seem on target, it is difficult to avoid clamminess. We had a double quilt made with Nobul1 fabric and water resistant down by Zpacks, and that's all we use now. It's much more comfortable in most conditions. I've heard similar things from some (not all) other users of cuben quilts (and also cuben down pants and jackets). It seems like a good idea, but it isn't much fun in practice.