World's Lightest Bug Bivy – 3.4 oz

Looks pretty well done.   Explain again why did you decide to go full no-see-um floor instead of having a different fabric as a floor/groundsheet?   Is this just always part of a modular system that can include a  second bivy?

+1 to everything that A D said.  Inquiring minds would like to know about the latter.

Nice and light Monte. As my first MYOG project I’m planning something similar with a waterproof floor. To include a waterproof fabric on the floor of your design without adding weight one could use 0.51 oz/yd2 Cuben – wonder if it would hold up OK if always using a groundsheet like polycro. Alternatively, how about using 1 oz/yd2 Cuben or 1.07 (finished oz/yr2) MEMBRANE silpoly PU4000 for the floor? These two options would add little weight, probably still under 5 oz. total. I’m leaning toward the 1.07 silpoly PU4000 for my bivi floor.

I made the bivy with a net floor to allow for drainage. If it’s rains I simply pull away the polycro from underneath. That way water doesn’t pool up. The MB waterproof sleeping bag cover keeps me dry. Don’t need the weight and hassle of a full coverage tarp. Can be set up faster and requires a smaller footprint. You could also go without any tarp at all, but a little head coverage is always nice.

I place a Ridgerest ccf pad under the bivy and WPB to keep them from lying in water. Even though the bag cover is waterproof, it will eventually wet out. Of course the pad also provides cushioning to sleep on.  I also have the option of pitching my 52″ square cuben mini-tarp (2.2 oz) overhead  to cover the upper torso instead of the heavier Dog Tarp.

These gear items allow me to get XUL.  With the WPB cover I don’t need as warm (and heavy) sleeping bag/quilt. The system is good as an FKT/ adventure race setup, but gives you the option of going without a hot bivy when it’s not raining, yet you still have 100% bug protection.

Yea Lester, I’d personaliy go with the Ripstopbytheroll PU4000 HH silpoly if I wanted a waterproof floor. I’d think a .51 cuben floor would probably hold up for awhile with a polycro sheet underneath, but as you know the cuben doesn’t handle abrasion very well.

Cool stuff. Years ago I built something similar:

Here’s a link with pic.

Since you mentioned using it  on hot nights  with  just the netting, I wanted to caution about my experience with such a design. As a fellow Floridian, I’m sure you can relate to the aggressiveness of mosquitoes which will bite through netting against skin with reckless abandon. Best to have it lifted off one’s lower body if attempting to use without quilt or other protective barrier. At least in my experience anyway.

Thanks for the link Matt. Please tell me more about the bug bivy such as dimensions, weight, closure, etc. In the pic with the dog, is that a WPB inside or a sleeping bag/quilt? Maybe a bag liner?

I hear you about the skeeters biting through the netting, but I would usually be clothed except for the face, neck, hands and possibly arms. With the pullout tied up (like in the pics) the face and neck don’t touch the noseeum. Might need a little deet for the arms though.

This bivy has long since been cannibalized and the mesh used on other iterations such as this cuben fiber floored bug bivy design used on the AT in 2013. So, sorry to say no dimensions to share, but a bit snug for sure. That’s a quilt in the picture. I can’t remember the type of opening, but will say I’m a big fan of the top zipper pictured in the link above: much easier in and out for a lanky person…