WPB Bivy-design ?s

Some thoughts:

1. Create a mockup using a cheap builder's tarp. A full-size fake is the only real way to check for usability!

2. Consider looking in an army surplus store. You might find a wpb bivvy or bivvy tent that's ripe for hacking. I picked up a full goretex tent bivy for under $50. It's huge and weighs a little under 3lbs. BUT slicing it up and adding a PU or silnylon floor would get that down below 2lb.

3. Many wpb army bivvy bags are big enough to use as a tent anyway and putting a base onto one would get the weight down.

4, I sliced ad resewed an army bivy bag down to 600g for 100% wpb leaving a generous 300g for tarp, poles and pegs in your weight limit.

I've always like the concept of a simple WPB bivy. You might take a look at Miles Gear for some inspiration and thoughts on sizing: http://milesgear.com/

I wanted a bivy for the exact same use. My first shot at it turned out like this.

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=51690

I am refining the design for a second make of it that is looking about like this right now. I am still thinking about it.

Army surplus- I hadn't thought to look there, as I already have the materials. Any online surplus sources to recommend?

Milesgear- Interesting site, gave me a good idea of workable dimensions. I had thought about making a full tyvek bivy just to make my rich hilleberg-toting friends feel like pansies. I still might.

M90 bivy- would you use that bivy as a standalone shelter? I would feel awfully vulnerable with nothing but m90 overhead, but then again I live in the PNW. Even in summer a good 24hr deluge is common.

Jeremy,

I made a bivy very similar to that in 2003. My vestibule is larger though…just large enough that I have cooked under it while still inside the bivy during rain. I have stake-out loops at both corners of the top and a pull-out loop right above my head for more head room. The head end and side opening are fully screened. I'm an active sleeper so did not include stake-out loops on the foot end. That way, my lower body has the freedom to curl up, ie, the lower half of the bivy is allowed to move with my body.

The floor and vestibule are 1.1oz sil-nylon and the top some kind of heavy WPB…I believe Outdoor Wilderness Fabric told me Gore-Tex.

The vestibule can be staked to the ground in nasty weather yet the head area remains lifted for ample breathing room.

I used this bivy tons in all kinds of weather and really liked it. I quit using it due to not having enough foot room when I switched over to NeoAir. I was also wanting something lighter as it weighs 18oz. I'm guessing with the use of cuben for the floor and vestibule as well as a lighter WPB top, I could get it down to the 13-14oz range. But, it's a bit more of a project than I want to tackle now…plus, I have been enjoying the extra space of my modified Hexamid.

Anyhoo, just thought I'd share my experience with ya. Have fun with it!