Inspired by other members' DIY bridge hammocks and tents, I have had an idea for a very light-weight hammock suitable for Hong Kong winter or North American Fall weather.
Rationale: To me a bridge hammock is essentially a replacement for a sleeping mat. Therefore, whereas a hammock is a suspended tent, we could have a suspended bivi-bag. There is the added advantage that I could pack a bed-roll and bivi on the ground if I turned up at an untried camp site and found it devoid of trees. The best part is that the bottom of the sleeping bag is uncompressed and you get the full loft effect.
Design: My idea above is intended to make use of a minimum of materials and be easy and quick to construct. Essentially, you take a standard sleeping bag (plus bivi if you want) and using a sewing machine, stitch in a series of buttonholes along the side on the bottom side near the zip. If you have a bivi as well, the holes should approximately match up.
Next, cut and hem a sheet of breathable rip-stop material to the approximate shape of the item below. The caternary cut outs between the attachment points are not fundamentally necessary. This sheet should be tapered to fit the inside of the sleeping bag and the attachment points should match up nicely.
Next, make an attachment sleeve cap for your hiking poles. This should fit over the ends of the pole and there should be a tab so they can be tied one to the other like mittens and hold on the ends of the poles.
Next, either attach webbing straps or cord from the poles to the attachment points of the support sheet and caps through the buttonholes, or instead use a sewn and hemmed sheet panel cut in a catenary curve to replace the straps. The attachment should be removable ideally to facilitate cleaning.
The Result: Once the assembled system is hung, you can get in onto the support sheet and zip yourself in or just lay the top cover over depending on the weather. You can also use a sleeping bag liner, which would go around you like normal and you would lay in it over the suspension sheet. The suspension sheet and straps would weigh less than, and pack smaller than ,a sleeping mat.
Let me know your thoughts. All I need to do now is get hold of a sleeping bag to test it out on.