I was lucky today and found the site where I got those 2 photos from.
Here is the story that goes with the photos. copied without permission and will be deleted next week.http://www.shf.org.au/SpecEv/Hammock.html
A hammock you can sleep in with a straight spine!
Do you like the idea of a hammock for the stable ride it gives on a rolling ship, but don't like sleeping bent in a curve?
This design of hammock is based on the principle of a suspension bridge - the suspension wires (hammock ropes) are curved, supporting a straight roadway (the part where you sleep). If the hammock is tensioned correctly, it allows you to sleep on your back, side or front, with a straight spine. Hardly traditional, but very comfortable.
I chose the length below simply because 1900 mm was the width of the cloth I could buy, and it was long enough for me. To make a longer hammock, I suggest drawing out this curve full size, then extending the curve to the extra length in both directions. Use a bendy piece of wood to draw smooth curves. You will need extra width in proportion – I would not make the middle any narrower than this. I used an unproofed cotton canvas, for greater comfort on hot nights. A synthetic cloth would be stronger and more mildew resistant.
Cut your piece of cloth to the size below (or bigger). Note that this is not the finished size, as all edges must be hemmed. Note also that there is more curve in the side at the head end, A, to support the greater weight of the upper body.
Cut the triangular corner reinforcing pieces from the side offcuts and sew them on (I used a domestic sewing machine for all except the edge roping, with no problems).
Fold a pleat 150 mm long into the centre of the head end, A, with the pleat 25 mm wide at the edge of the material, and sew flat:-
Hem all sides with a 15mm hem (no wider, or you will have trouble on the inside curves)
Make up the rope bridle as shown below (I used 12 mm Silva rope), hand sewn along the curved edges with doubled sewing twine, using a needle and palm, in the same way as a bolt rope is sewn onto a sail. This is quite fast to do.
Sew the rope especially strongly to the corners.
Add an outside pocket or two for your torch, water bottle etc.
Fit two 750 mm wooden spreaders (longer in proportion if you have increased the size), rig the hammock and adjust the tension until your spine is quite straight (if you sag in the middle, increase the tension; if you droop at the ends, decrease). It looks odd when empty, but is great when you are in it. Enjoy!
1. Put a net or similar across the head end so your pillow can't fall out.
2. Put a bit less curve in the sides if you like a tight, high hammock, or more curve if you prefer a soft, low hammock.
Bosun, James Craig