MYOG bivy bag
4 June 2010

I’ll update this article until the bivy is finished. There won’t be any follow-ups.

My next trip will provide me with a lot of wind and mosquitoes. As I’m tarp camping I need something against these two quilt-sleeper enemies :) To make it short, I need a bivy. After 3 of these prototypes:

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I got to the final pattern:

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It is designed to fit a side sleeper of size ~1.75cm, a 300g down(6cm loft) quilt and a prolite(2.5cm). It has got a total length of 1.90cm and a mid body(below shoulder, elbow)/shoulder width of 70cm/65cm. The bottom is silnylon and the top is pertex quantum and nanoseeum. The estimated weight( size² * weight of material + zipper ) is 205g including a 38g zipper of which I’m not sure if I’ll use it. I first cut out the silnylon according to my pattern. There’s no secret, but I marked all edges of the pattern with a pen.

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The result:

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Then I sewed the edges of the silnylon together in order to get the designed cube.

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I used double seams to secure the edges.

At the head area I appended two loops to tie out the bivy:

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The next step was to sew the noseeum and quantum together.

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Now for the interesting stuff, the zipper. I first secured the edge of the quantum with needles to the side of the zipper. Then I turned it around to double the quantum and secured it with yarn.

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After sewing the zipper I sewed the two pieces of quantum/noseeum together (the zipper was not full length). I started sewing 2cm away from the ends of the zipper. I sewed the 2cm’s by hand to ensure that it is midge-proof :) The final step was to sew the top piece to the bottom piece, this was done with one simple seem and one insurance seem before the first one(so 4 layers of fabric were secured).

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The sad thing is, when I finally took this bivy out to test it, I got a lot of condensation were the silnylon was. In fact it was so much that my sleeping bag was completely wet on its sides. The quantum was no problem and worked fine. I now make a second bivy consisting of quantum only with the same pattern. The final weight of the old bivy was 200g without lines, 217 with elastic lines. The new bivy will weight(estimated again) 178g. I’m really looking forward to it, because it offers full bug protection and I can turn and toss in it. It also offers wind protection :)