Differential cut for a non-down underquilt

[Country Roads]

Background to question: I am making a new, full-length underquilt for my home hammock using pretty much whatever materials I can find around the house: An old thin comforter for the inner shell, a piece of 1.1 nylon for the outer shell and a combination of a fleece throw and a single-layer piece of Insultex for the inner insulation. It will need to be comfy down to around 60 degrees.
It will measure about 45 inches wide and about 73 to 75 long. I may taper it near each end. Will most likely not use full shock cord channel. I think I have enough linelocs for the suspension from each corner.

How much, if any differential cut should I use? Compression of insulation is probably not much of an issue, but I do want a nice fit to my hammock.

thanks much, Country Roads in WV

[genixia]

A few different ways of thinking:

1. Stack all of the layers on top of each other and measure the total thickness. Plug that into catsplat as the baffle height and use the resulting fabric measurements for inner and outer fabrics. Average for the two inner layers.
2. Assuming insultex outside fleece - As above, but cut outer nylon and insultex the same size. They're both so thin and don't stretch much, you can probably treat them as one layer for dimensioning purposes.
3. Assuming insultex inside fleece. Concentrate on getting the dimensions of the insultex correct to hang outside the inner comforter. Cut the fleece the same size as the insultex and rely on its stretch. You'd have to cut the outer nylon larger to accomodate the layers still.

I don't know which of these approaches will work the best. The reality is that for a 60 degree quilt the thickness isn't going to be a major problem. The simple approach of declaring that an UQ is 270 degrees of the circle around you results in the outer layer being 3/4*2*pi*thickness larger than the inner layer, or about 4.5" for every inch of thickness. Get somewhere close to that and you should be good.

[nothermark]

FWIW A differential cut is always something of an issue. One either ends up with wrinkles in the inner layer or compressing the filling.

[BrianWillan]

Background to question: I am making a new, full-length underquilt for my home hammock using pretty much whatever materials I can find around the house: An old thin comforter for the inner shell, a piece of 1.1 nylon for the outer shell and a combination of a fleece throw and a single-layer piece of Insultex for the inner insulation. It will need to be comfy down to around 60 degrees.
It will measure about 45 inches wide and about 73 to 75 long. I may taper it near each end. Will most likely not use full shock cord channel. I think I have enough linelocs for the suspension from each corner.

Just for reference, many full time indoor hangers just use a 1 season (50F) underquilt for their insulation. The Jarbridge from Arrowhead Equipment will do the job for you just fine. It is reasonably priced, and goes on sale periodically and is made by one of the vendors here.

After making and modifying a DIY synthetic underquilt a couple of times, I decided that it was too much hassle and there wasn't much in the way of cost savings when you factor in time and aggravation. However that is another can of worms that gets discussed from time to time on the site.

Cheers

Brian

[Country Roads]

Thanks for all the info. I will give this a shot and let everyone know how it works out. Might even take pics, unless it turns out so bad I fear killing someone with laughter.