Ogri, here's the plan; (you may want a pen and paper to sketch this as you read)
Part 1:
1) 1x single duvet (circa 1350mm x 2000mm) trimmed down to 1000mm x 2000mm.
2) Lie it out flat on the floor and measure along one short side from the corner marking it with a pen at 200mm, 300mm, 700mm, & 800mm.
3) Do the same at the opposite end of the duvet.
4) Measure along one long side from the corner marking it with a pen at 400mm, 600mm, 1400mm & 1600mm.
5) Do the same on the opposite side.
6) You should now have duvet with markings on all four sides.
7) Using a pen and straight edge do a "dot-to-dot" job between these points;
i) Short side 300mm mark to adjacent long side 400mm mark.
ii) Short side 200mm mark to adjacent long side 600mm mark.
8) Now cut along these lines, chopping the corner of the duvet off.
9) Ok, so you've roughly rounded off the corner of the duvet. Now do the same for the other corners. Using a sewing machine you will need to seal the cut edges.
Part2:
1) 1x 2250mm x 2250mm square of tight woven cotton.
2) Lie it out flat, then find the mid point on the top and bottom edge and measure 550mm to the left and right away from these points, marking the points with a pen.
3) Now fold the sheet between these marked points, giving you an overlapping envelope.
4) Using a sewing machine, sew a seam 25mm in from, and parallel to the folds top to bottom.
5) Again using the sewing machine, hem the two short ends (about 10-15mm should do it), then fold these in on themselves (effectively reducing the sheets length) and sew this at the edge effectively making a tube with sealed ends. Repeat for the other end.
6) Cut one of the sealed ends of each tube (at the corner of the sheet), and shove 1050mm of shock cord up the tube. Youll need to force it though the stitching of the first (lengthwise) set of tubes you made. Again repeat for the other end.
7) Using the sewing machine, sew over the end of the shock cord (only the last 10-15mm) at the sealed end of the short length tube so that it cant come out again.
8) Now add one of those plastic spring toggle things on the loose end of each shock cord.
9) Ok, so now turn the whole thing over so you are looking at the other (back) side of the cloth.
10) Now to fit the shock cords to the long sides of the envelope.
11) Cut a small hole at each end of the original cloth tubes (long lengths), just inward of the width wise tube seam, and push a 2500mm length of shock cord right through the tube and out through a corresponding hole at the other end of the tube.
12) Repeat for the other side and attach more of those plastic spring toggle things on the loose end of each shock cord.
All thats left to do now is dye the cloth of you want to, then waterproof it with Nickwax. When its dry, fit the trimmed duvet into the envelope and hang it under your hammock. My only concerns are that a bed sheet may not have a tight enough weave, so you may want to use artists painting canvas, or something similar.
If you want to change the tog rating, fettle a different duvet to shape. Simple!
Chris
..if you'll show me yours.
