7oz Tyvek bivy sack for $45

[Andrew F]

Here are some pics of a Tyvek bivy sack that I made based off of an old post by Mateusz (which can be found here: Old thread):

Stuff sack made with Tyvek scraps

Bottom of zipper detail

Top of zipper detail

Final weight including the stuff sack is 7.15 oz. I used Tyvek 1443R (the variety used for clothing, 1.25 oz/sq yard) for the entire bivy. Making the bottom out of the more-waterproof Homewrap would probably have added approximately 1.5 oz. However, I regularly use a waterproof padded ground sheet from Suluk46 so I was not too worried about water getting through the floor. I used a #3 YKK locking zipper from Thru-hiker which added about 0.75 oz to the overall weight.

All seams were taped with Tyvek tape cut in half to 1" wide, with the exception of the zipper, which was sewn in with a single straight stitch through 2 layers of Tyvek into the zipper. The Tyvek tape is really strong and with 1/2" on either side, taped both inside and out, the seam is stronger than the material. This also has the advantage of not requiring any seam sealing.

I experimented with some scrap to see what the strongest option for sewing was, and as expected, the fewer holes there were in the Tyvek, the stronger the stitch. So I used a single straight stitch with the longest stitch that my machine could do. This works pretty well, and while it isn't as strong as the tape, I'm not worried about ripping the zipper out any time soon.

I do not have a hood drawstring right now, but I will probably add one as shown in the instructions and Mateusz's pics. The hood is a bit floppy without it.

Overall I am quite happy with how it turned out. It remains to be seen how breathable it is. Some research showed that people have been quite happy with it and haven't had any issues with condensation. It certainly feels quite warm, much warmer than a layer of Momentum 90 would be. I will report back once I try it out a few nights. The total cost was about $45 ($30 for the Tyvek, and $15 for the smallest roll of Tyvek tape, which I used about 1% of) and approximately 5 hours of labor including research.

Instructions: http://translate.google.com/translate?hl=en&sl=sv&tl=en&u=http://www.andersj.se/overdraget1.htm

Pattern: http://www.andersj.se/overdrag1/overdrag1.pdf
(I modified this to have a side zip, and changed the height from 15 to 22 cm to accomodate my NeoAir.)

Andrew

[Curtis B.]

That's very, very cool! I've avoided making my own bivy but you've just shown me how it might not be so scary! Nicely done!

[Brian UL]

Bravo! the best MYOG Ive seen on here in a long time.

[Eric Johnson]

Love it – any one have links to purchase materials?

[Andrew F]

I tried this out in Ventana Wilderness this weekend. It worked great! The material adds a significant amount of warmth, much more so than a thin layer of nylon. I experienced no condensation. Overnight low was 32F and I was comfortable in my Summerlite which I usually get pretty cold in around 36-38F.

I got the Tyvek material from Amazon for around $4/yard. It was really easy to work with, and for the sewing challenged such as myself being able to tape it makes it a piece of cake to make things out of. You don't have to worry about seam allowances, or finishing any ends of the fabric, since it isn't woven and doesn't unravel.

Andrew

[Tom Peterson]

I agree with both Curtis and Brian – a great project and simple enough to not be scary. I'd never even thought about buying Tevyk from Amazon – great idea.

[Adam Klags]

Any ideas as to where to buy this version of tyvek for cheap? About how much did you use and need overall?

[mister jarvey]

Any updates about the performance/ durability of the tyvex bivy sack?

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