Planning a Serenity type bivy

How many sq.yd. of material are you using for the sidewalls? The weight difference between netting and the cuben .5 is less than an ounce and probably negated by the increased amount of thread for extra seams. Now if you used 0.33 oz cuben that may provide a half ounce savings even with the extra seam weight penalty.

You could also use a 7/10d fabric for a minor savings in weight versus insect netting and still maintain some breathability.

The one on the left should be more than enough netting.

My car camping dome tent has only two small net patches with a rainfly to cover them, and I've never had condensation issues.

Remember that the cuben won't breathe. You could replace it with M50 or similar (Nobul) to maintain a more breathable inner – and cut the cost. Use the cuben where wind blown rain is a potential problem.

The design on the left will have plenty of netting, so I wouldn't worry about condensation. However, like some others said, it makes more sense from a money-saving standpoint to use something like M50 instead of the cuben. As long as it is out of the direct rain, it will repel splashes just as effectively, while still having some breathability.

Thanks for all the input, yes, the left one is probably what I will go with for netting.

As for fabric, I have 0.5oz cuben for the walls already (left over from the tarp), but I also got to thinking when Dustan mentioned using 0.33oz cuben. Except for where I want to sew a zipper at the door (use 0.5oz), I think I will go with the 0.33oz as I have a couple of yards. 1oz cuben will be the floor.

Still don't know how I will sew a neat curved zipper on the cuben. Thinking, thinking…

Steve

Thought about this a bit more; decided on the path of durability (0.5oz walls and 1oz cuben for floor). M50 is 21.4g/m^2, so it isn't lighter than any of the cubens I'm consering for the walls.

How about this for ventilation? Is there enough? The strip of netting would be 40cm wide total alone the entire length of the tarp.

I'm also considering having it match the cant. curve from the tarp it will go under, and maybe have the corner seams be cant. curves also. I find my SS seems to sag in the front, even with staked out corners.

Thanks for your feed back!
Steve

This current version you have is almost exactly the design I came up with a few months ago. Was hoping to get a company started and produce it, oh well…

I think that is plenty ventilation. I would say for simplicities sake though, get rid of the triangles. Just have a rectangular piece of cuben coming up from the tub floor, and a rectangular piece of netting on top.

Hint! Think "rain fly" not "tarp". With the cuban side walls, you only need to protect that small section of netting on the top, this will save you several yards of redundent material and weight! Just give the rainfly a generous overhang and you will not have to worry about weather or bugs, or condensation.
You might be on your way to one of the lightest shelters produced, according to my calculations. Remember I wanted to produce a similar design…

I do have an idea to make this even lighter, but I'm gonna keep that to myself for the moment…

Please keep us updated! Since I never was able to get things going I never was able to see the real world version of my vision. I would love to see the real world weight! I hope you are making a .5 cuben rainfly? This should be a crazy light shelter.