I have finished my Ύ length winter under quilt. The dimensions are 53x41x3. There are eight chambers. The baffles are 2 high but I over stuffed it with 8.07 ounces of 800 fill power down from Stormcrow, http://www.hammockgear.com/ . The shell is 1.1 calendared, breathable, olive green nylon ripstop and the baffles are 0.9 ounce noseeum netting, both from Scott, http://www.backwoodsdaydreamer.com/ . The suspension is a combination of 1/8 and 3/32 nylon shock cord, with cord locks all from http://www.owfinc.com/ and 1.75mm Zing-It from http://www.reddenmarine.com/ . Gutterman Sew-All 100% polyester thread was used throughout, matching green of course. The finished weight of quilt with suspension is 15.7 ounces, (14.0 without suspension).
Below are a few pictures taken along the way (just to prove it happened).
The whole quilt is not a rectangle. It is a parallelogram, which you can see in the 1st & 2nd pictures. Imagine the finished quilt as a rectangle, then slide one long side up 6. Now figure out the equivalent measurement for your actual cut width, so that the angle at the corner is the same on all your cut pieces (remember the top & bottom fabric of the quilt are different sizes). THIS IS CRITICAL: Make sure to figure out which diagonal you lay on! You want the long diagonal to go in that direction! This parallelogram allows a smaller quilt to match the coverage of a larger quilt more efficiently.
The material was cut to allow 2 seams all around to provide enough for the channels where the shock cord will go. Also, my finished quilts always end up 5% smaller than my design calculations. (Same principle as the missing sock in the dryer). So I design the quilt to be 5% bigger than what I want for the finished product. The cut sizes along the edges are as follows:
Side next to hammock; 46 x 58.25 this allows for 2 seams all around. This piece will lay flat against the hammock bottom, pulled there by the suspension.
Side away from hammock; 56 x 62.25 this allows for 2 seams all around plus 2 more for the baffle height. The reason for the additional 2 is to match the baffle height. Since the inner fabric is pulled tight against the hammock bottom, this outer layer needs to provide all the 2 height at both side edges and at the head & foot ends (whereas in a top quilt the edge height would probably be shared by both the top & bottom fabrics).
Netting; 54.25 x 2.5 (7 required) this allows two 1/4 seams to attach netting to top & bottom fabrics.
As a personal preference, I stop my baffles before the edge of the cut fabric so I don't have to deal with the netting in the edge seams and shock cord channels.
This is how I deal, with the fact that head & foot edges are different length and yet, have to be sewn together. My 'next to hammock' baffle spacing is 5.25 while the 'outer' baffle spacing is 6. Before sewing anything, I first mark the lines for the baffles. Then, I make two marks in the seam allowance area 3/4 apart, centered in what will be the baffle chamber. Next, I pinch the fabric together in the seam allowance and sew along the two lines, which removes the extra 3/4 (per chamber) from the edge of the outer fabric. Then, I mark two lines 2 apart, at each end of the foot & head (but inside the side edge seam allowances) and pinch & sew those together to account for the extra 2 of 'outer' material for the quilt height. Now, the edge length of the 'inner' and 'outer' fabric is exactly the same at the head & foot of the quilt. Look at the 3rd picture below for the picture of the finished product.
The 'outer' fabric edge is 4 longer than the 'next to hammock' edge, also, due to the extra 2 at each end for the quilt height. I mark two lines 2 apart, at each end of the foot & head (but inside the head & foot seam allowances) and pinch & sew those together to account for the extra 2 of 'outer' material for the quilt height. Now, the edge length of the 'inner' and 'outer' fabric is exactly the same at the two side edges of the quilt.
I have found (the hard way) that these channel seams can quickly get out of hand, probably due to my amateur sewing skills. But, I have discovered a way that keeps them under control for me. Note in the 4th picture that I sew a line just inside the edge of the fabric and another at the 2 seam allowance line that I had marked. Now this edge won't go wild on me while I fold, tuck and sew the shock cord channel, which will be the next step.
I sewed 3 of the 4 channels, then filled the chambers with down (1 ounce per chamber in this case). The 4th picture is from a previous summer quilt I made but shows my PVC pipe device I made to facilitate the filling process.
Once the down is in, I sew the last end closed and make the shock cord channel on that end. I then cut 4 feet of 1/8 nylon shock cord for the two side edges and attach 4 feet of 1.75mm Zing-it to the two ends using an Albright knot. Then I put a cord lock toggle 3 off the center of the Zing-it. Remember that the quilt is a parallelogram, 6 off of rectangular. By placing the toggle 3 off center, I have 6 more Zing-it on one side of the toggle than the other. Therefore, the pulling force on the quilt edges matches the quilt shape. Finally, I put 3 feet of 3/32 shock cord in the head & foot channels with a tiny cord lock on each end. All the detail for the suspension can be see in the next to last photo.
Voila! Finished! See the last photo. Now all I have left to do, is go hang!