Project #2, double bivy for my wife and I to use in the tipi...
I basically took the LytW8 design that's floating around and stretched it out for 2 people. The bottom is 1.1 silnylon and the top is 1.1 uncoated nylon. I used a #3 coil zipper and 1 oz no-see-um fro Bear Paw Wilderness Designs.
My final dimensions:
Top nylon strip: 9”
Body length: 75”
One thing I tried on this thing that worked well was terminating the zipper at each end with a strip of nylon. Probably a waste of time on a bivy but I want to terminate the seam on my next tipi like this (since that turned in to a debacle). First I sewed a tube out of ripstop making sure that no raw edges were showing, then I sewed the tube on to the end of the zipper. It makes a great zipper stop and it can be incorporated easily into seams. Here's a pic...
The dimensions are pretty roomy, the bivy fits us well with our golite quilts. I don't think I would make it any smaller because I like lots of room and don't mind a little extra weight but if someone wanted to I'm sure they could trim the dimensions quite a bit and still have it usable.
Many thanks to the pioneers of the LytW8 design and John at Bear Paw for the materials and info!