A hammock with integral insulation





January 2004:

I have been working on a hammock with integral insulation. My first two attempts with down have been unsuccessful. I went back to the drawing board a third time and had some success.

I bought 14 feet of 44 inch wide polyester from WalyWorld and a 3/8 bat of polyfill meant for a baby crib comforter. Total cost: $14.

I scavenged the webbing from another hammock.

I cut the material into a 4 foot and a ten foot length, sealing all raw edges with a hot knife.

I sewed a half inch single fold over hem along the long edges of the ten foot section , sewing with a zigzag stitch 2mm long and 2mm wide.

I took the 48x44 inch section and sewed three one-inch fold-overs on each side. At the 1/4, 1/2, and 3/4 distances along each side, I pinned an inch long overlap and then sewed a hem all the way around the piece of cloth with a standard stitch. The created a rectangular section, whose middle balloons out.

Next I sewed three sides of this pouch to the center four feet of the hammock with a zigzag stitch. The insulation covers the hammock from my shoulders to below my knees, with my head at either end. The zigzag stitch allows the hammock material to stretch without worrying about different stretch amounts that the polyester thread and the polyester cloth need to stretch. (The cloth seems to be about the same weight as 1.9 oz ripstop, except that it is more breathable.)

Then I inserted the insulation as a double thickness. Before sewing the fourth side shut, I used a needle and thread to quilt between the hammock and the ballooning shell a single loop every 6 inches or so, all the way to the edges. Finally I sewed the final edge shut.

Total cutting, sewing, quilting time was about 2 hours.

The secret to getting the insulation to puff out is to make a pocket with edges shortened with darts (fold- overs). Otherwise, the hammock stretches and the outside of the pocket crushes the insulation against my body. 

I slept in the hammock on 15 January for half the night. Outside temperature was 22 F. I was warm under my quilt. I was warmer when I put a Travelpod over the hammock.

Today I napped in the hammock, bounced around in it some, looked for any sign of material weakness from the sewing, and checked to make sure the insulation was staying puffed out. Everything seemed in order.

Weight of the hammock prototype and straps is 27 oz. This compares with my double bottom hammoc's weight of 20 oz. That equals the weight of the double bottom hammock plus the target pad. And I get nearly an inch of insulation instead of a quarter inch.

Near the end of January, I ordered some 1 inch thick PolarGuard II for a second prototype. I obtained some $2 a yard taffeta (about 2 oz) at a fabric store and used the inch PG2 to make a pocket 3x4 feet on the bottom of a 48 inch wide hammock.  Weight of the hammock, straps, and hammock tubes is 28 oz.  

I used this hammock for a 7 deg F test on  January 23.  To the hammock, I added a Target pad and the TravelPod.  This made spending the night quite comfortable.  For some unknown warmer temperature, the target pad should not be necessary.   More details as I get more information.  


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