Why Dart?

[Str1der]

Sorry to revive this old thread, but I had a question about darts. In a differential cut UQ, where the outside layer (away from the hammock) is wider and longer than the inside layer (next to the hammock), don't you need to dart the outside layer on teh sides and head/foot to take up they excess material so that the edges all line up, or am I missing something? The reason I ask is that a few of the posts above seem to call for darting the inner layer.

Thanks,

Norm

From much research and polling of the experts, I have learned the following: The outer layer will be wider than the inner, but you will actually dart both. Darting has nothing to do with a differential cut. The best way to explain it is that the darting forces the fabric to "cup" the underside of the hammock. It adds a third dimension to the material rather than simply having a flat sheet of fabric. It really helps to take a piece of paper and tape darts into it to visualize the effect.

Completely separate from that, you will also make the outer fabric wider. This provides the differential cut which prevents the insulation from being compressed. This is because the "arcs" of fabric for lack of a better term have to be larger as you get further away from the hammock. I do not possess drawing skills but maybe my crude illustration will help. In the image, darting draws both pieces of fabric up into arc shapes and the differential cut makes the outer shell large enough to not compress the insulation between the liner and the shell.

[normis1]

Thanks Aragorn - believe me, your drawing skills are better than mine!

The next question I have (of course there's a next question!) is how do you figure out how much to dart the inner layer, how to space the darts, etc.?

[ljcsov]

Hey guys,

If I am making a Prima Loft UQ, how much smaller do I make the top layer than the bottom layer in order to get the concave shape? Is it just a slight differential? Thanks...

I was planning on making the UQ at around 52" long. I was unsure as to what I was going to make the width!

I understand the darting conceptually, but I am not sure how to make them and sew them myself.

[normis1]

Hey Ljcsov - check out this post for a handy spreadsheet to calculate the size of bottom and top layers: http://www.hammockforums.net/forum/s...ad.php?t=38134.

Here's a good quick video on sewing darts, with bonus British accents: http://www.youtube.com/watch?v=E8TseXUFMLY

[Str1der]

Normis1 gave you the jackpot with that post from Meteor. I had created a remarkably similar spreadsheet on my own, so I was pleased to see that I there was a method to my madness after all.

If you want a simpler but still very effective process, use the following methodology:
1. Determine liner width (this is the nominal width for the finished quilt).
2. Determine number of baffles (usually 6-9). You want baffles that are 5-8" across at their widest point (darting will make them thinner near the ends).
3. Multiply your liner width times 7/6 to get your shell width. This 7/6 multiple comes from gear making lore and seems to hold up pretty well, although I think your quilt thickness and baffle type play a part. For instance, sewn thru baffles or very high loft will probably require a bit extra for the outer shell.
4. I determine the amount to dart by deciding how wide I want the inner liner to be at the head and foot ends (reduced from the middle width). Whatever the difference in width is, divide by the number of baffles and you know how much to take in per dart in the liner.
5. Multiply that number by the same 7/6 to get the amount to take in per dart for the outer shell.
6. Usually, the head end is wider than the foot (depending on quilt length and owner preference), so you may dart less on the foot end than the head end.

I'm not an expert though, so take all that with a heaping shovel-full of salt.

[ljcsov]

Mine is set up a little bit different. I am using primaloft so I won't need baffles or an inner layer, just an outer shell. I guess I should just make the top part (toward hammock) a little smaller than the bottom (away from hammock). I am not sure as to how much though

[Str1der]

All my research has been for down quilts, so I'm not sure how to proceed with Primalift. I think I read that some people actually dart the insulation itself, but I don't know which insulation that was. If it is a sheet material, I would assume that it shouldbe possible.

[PuckerFactor]

I just did each successive layer longer and wider like so:

             Width   Length
Inner Shell  48       78
6 Oz. PL     49       78
3 Oz. PL     52       80
Outer Shell  53       82

To get them all to line up, I just scrunched them accordingly. It was very unscientific. Came out very nicely. For the end channels, I used 1.9 ripstop instead of grosgrain, and it worked much better I think. It flexes and scrunches much easier than GG does.

PF

[ljcsov]

I just did each successive layer longer and wider like so:

             Width   Length
Inner Shell  48       78
6 Oz. PL     49       78
3 Oz. PL     52       80
Outer Shell  53       82

To get them all to line up, I just scrunched them accordingly. It was very unscientific. Came out very nicely. For the end channels, I used 1.9 ripstop instead of grosgrain, and it worked much better I think. It flexes and scrunches much easier than GG does.

PF

Thanks PuckerFactor aka Primaloft genie! I will use your fractional differentials to my designed set up.

[silentorpheus]

Another thing you can do, if you're just using one layer of insulation between an inner and outer shell is to make sort of a boxed construction (this works best for rectangular shaped quilts - but it could likely be adapted for shaped quilts as well).

Make your inner shell the size you want the quilt to be - that will be the side against the hammock. Figure out how much loft your synthetic insulation should have - lets say for example it's 1" loft/thickness climashield. Make your outer shell about twice the thickness of the loft bigger than the inner shell on each side. So if the inner shell is 48"x60" and the loft is 1", then the outer shell should be 50"x62". Once that's done, cut a square out of each corner of the outer shell, with it's sides the length of the loft measurement (in this example 1" - so a 1"x1" square). Stitch the inner sides of those square areas you just cut out together, and you create a sort of 3 dimensional tray (essentially a fabric version of the lid of a shoebox for those visual people) which is now the dimensions of the original inner shell, that's deep enough to allow the full loft of the insulation you've chosen. That gets sewn to one side of the inner shell, the insulation gets sewn to the other side of the inner shell, and when you turn it inside out you have a three dimensional quilt that is the thickness of your insulation.

It's a little confusing and convoluted to explain without pictures, but that's the general gist. Just another option when you're dealing with synthetic and not down. Not sure how you'd then dart this, but for a simple construction (think the AHE Jarbridge) quilt, this works well. It'll look like this:



Where n=the thickness of your insulation:
Inner Shell = x" wide by y" long
Outer Shell = (x+2n)" wide by (y+2n)" long