Differential cut between layers of synthetic insulation?

[warbonnetguy]

yes, it's the same reason a sheet of fabric can compress the insulation, the farther out it is from the inner shell of the uq the larger it needs to be, so if you're using several sheets of insul that have decent loft, each successive layer is being bent over a larger curve and should be larger so as not to compress what's below.

i laid the uq flat and looped each new layer on by stepping the perimeter in a little each time. this put wrinkles/loosness in the interior of the layer, but when it's installed under an occupied hammock, that would go away (unless you stepped it in too much)

[warbonnetguy]

are you going to cut the triangles out of your insulation as well?

[Merganser]

are you going to cut the triangles out of your insulation as well?

That's the plan, then I would loop them closed like in the KAQ how to. The darts take up about 50% of the difference between rectangular and the shape of the hammock (I took a series of girth measurements to determine the darts). Gathering on the ends will take care of the rest.

My rational for 50% was that I didn't want to build too much curvature in the UQ (avoid a gap under my butt). I'd get it close and then let the suspension take care of the snugging it up.

In the very middle of the UQ I think the form is very close to the curvature of the hammock. Elsewhere there would be at least some gathering to take tension off the insulation. I would think this would mitigate compression pretty effectively.

[Merganser]

Well I finally managed to finish this project off. Things went reasonably as planned.

I cut the inner shell using my pattern (same one I made the form from) and sewed the darts. I laid it out on the from and started with insulation.
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I cut the first layer a couple inches wider than the inner shell and draped it over the form. I lined long edges parallel to the edges of the form, gathered and cut out the darts, just using the form as a guide rather than try to calculate everything. I sewed the darts together with heavy duty thread. I repeated this process for the second layer of insulation.
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Once I was done with the darts I trimmed the insulation to the size of the form. I kept the scissors parallel to the floor the whole time.

For the outer shell I decided to measure it using the inner shell and insulation laid out on the form. I measured at the widest point. (I also did the math on this, interesting the numbers were nearly idetntical) I did the same for the length. I cut a rectangle for the outer shell using these dimension and the lined my pattern up on it to make the darts. I made each dart the same, extending them to the edge and shifting the patter a little to each side to so the so the extra width was divided equally. When I had it all cut out I sewed up the darts.
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I decided to use grosgrain ribbon along the long edge so I could draw it tight without stretching the nylon/insulation. I cut the grosgrain to length with a loop and a pair of cord locks at each end. I also attached a loop and strip of grosgrain where my tie outs would be.
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With the addition of the grosgrain I decided that it would be too much to try to sew that all together with the insulation so I just sewed up the shell layers and the grosgrain. The fabric for the outer shell of course was longer than the grosgrain and the inner shell. I put about 5/8-3/4in of it in a couple pleats on each end and the rest (about the same amount) in a pleat where the tie outs were. I found that if I suspended the grosgrain under some tension it was a lot easier to pin it up.
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I decided to just hem the ends and top stitch them later. I attached a reinforcement and center loop, with cord locks on each end. I also sewed split tube to the inside shell on each end for gathering.

I hand stitched the insulation to the shell. The grosgrain provided nice reinforcement for this. On the ends I wound up going through the inner shell becuase I hadn't given myself much to work with. Next time I will leave more of a seam allowance and create a rolled hem on the ends to sew the insulation to. The insulation is a lot stronger than I expected.
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I turned it right side out and laid it back on the form. I pinned up the ends and top stitched them together. The excess fabric was taken up by pleats at the darts and rolling the grosgrain out and sewing flat across it.

I made 5 rows of quilting loops with some nylon yarn. I chose spacing so that the space on the long edges would be about half of the spacing in the field. I made marked (with pins) the center row (lengthwise) first and the divided it across. The I marked the rows along the long edge. The final two rows I centered between the middle row and the edge row on each side. After I had them all marked in quilted away.
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Turned out nice. Fits under the hammock with no air gaps that I can detect. You can really feel it reflecting back the warmth.
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[GrizzlyAdams]

very nice! I especially like the use of that form you had for draping the fabric / insulation over. That would be great assist to me when making such a quilt because I find it is a lot easier to think in 3D when I can see in 3D also.

Grizz

[Peter_pan]

Just my opinion, I disagree. The JRB Nest & I have experienced cold spots due to either a too tight or too loose situation. With the diff cut MW have yet to experience cold spots. Differential cuts vs std cut (JRB MW3 vs. Nest) of same weight are warmer.

Koaloha05, et al,

Well a differential cut helps.... But dual differentials are better.... However, the real key is body contouring radial baffles to eliminating compression...And that is why the Mt Washington excells.

Pan

[Merganser]

very nice! I especially like the use of that form you had for draping the fabric / insulation over. That would be great assist to me when making such a quilt because I find it is a lot easier to think in 3D when I can see in 3D also.
Grizz

Thanks Grizz. I don't think I'd have gotten a decent result without the form. My shell probably would have been OK because the math I did do wound up coming out the same as the real world (imagine that) but I doubt I would have gotten the insulation layers quite right.

[TinaLouise]

your quilt looks fantastic!!

what weight climashield did you use and is it one layer or did you sandwitch together more than one?

Have you weighted the finished quilt? And what do you think the temp ranges are going to be? this looks like a warm uq!!

Great idea in using the cardboard to make a form to drape your fabric over. When I was sewing one of my uq's I stacked a group of books up to make some sort of form so I could see the quilt curved. Didn't work out so well. If I ever make another, I'll diffinately think of your cardboard creation.
TinaLouise

[Merganser]

your quilt looks fantastic!!

Thanks.

what weight climashield did you use and is it one layer or did you sandwitch together more than one?

It's "combat" 3.7oz/yd, .9in. I used two layers.

Have you weighted the finished quilt? And what do you think the temp ranges are going to be? this looks like a warm uq!!

Without the shock cord on the ends it was 28oz. The total CLO is 5.8, if you believe some of the charts that should get you to 20def F. I don't believe the charts but I expect it will get me into the upper 30s anyway. It'll be a while before I'll be able to prove that.

Great idea in using the cardboard to make a form to drape your fabric over.

There is no way this project would have turned out as well as it did with out the form. Especially anything to do with the insulation. I used it for everything, right down to the quilting.

[jaydweight]

What are the measurements for your pattern? This is a really sweet idea and I want to as soon as I get some materials.