View Full Version : Making a bivy

09-14-2017, 16:40
Hi I would like to know if you can make a bivy only using Cuben fibre? Will there be to much condensation from making a bivy with cuben fibre as both the top and the bottom pieces. Should I be using a breathable top layer and if so what fabric do you recommend? Thanks

09-14-2017, 17:16
do not make the top and bottom out of cuben. Use something like M50 or M90 or similar materials for the top, plus some netting for the area above your shoulders. see www.ripstopbytheroll.com and www.thru_hiker.com

09-14-2017, 18:15
Thanks I also found that borah gear uses Argon67 for their top. But I think that m50 from thru-hiker is the lightest. So far all I've made is a mock up to test the size and I've made the mesh shoulder part for the actual bivy.

09-14-2017, 18:16
Cuben really has minimal advantages in a bivy.

Because you will want something under it that negates potential wt savings

30d silnylon is best bottom, 1.3 oz/yd

0.74 cuben, with ul groundsheet if some type will be 1+, as will 1.1 cuben

Potential savings is about 0.5 oz, but need groundsheet, and whole thing is less durable

If you use a 1/8 " ccf pad as groundsheet and part of sleep system, yiu can realize the 1 oz groundsheet savings too. Here it make sense somewhat.

Of couse, some use that groundsheet multipurpose
Rain skirt, etc
In which case several oz are saved there too. Now the cubens rockin

Just Bill
09-14-2017, 19:21
What do you mean by bivy?
Most people- including some of the answers shared here- mean a splash bivy to use under a minimal tarp.

M50 and Membrane 10 (from ripstop by the roll) are basically the same fabric. Argon (from Dutch) is a distant third IMO, but many love it.
Those are all DWR coated fabrics- not WP, but breathable.
Think windshell- not rain coat.

If you want a true bivy- probably the most reasonable option right now is the WPB from Kyle- https://ripstopbytheroll.com/collections/waterproof-breathable-laminate-composite-fabric/products/1-4-oz-10d-waterproof-breathable

He's got that coated Robic .7 for the floor but I agree that a Membrane Sil or other floor works pretty well. Cuben doesn't pack that smooth either. A poly cro ground sheet backs things up pretty nicely too.

Honestly though the only bivy I've ever had any luck with is a design of my own with a small vented foot box and a vented head. I tied out the foot to a tree and just used a found stick to prop up the head.
Fully sealed up in WPB you'll still wet it out- especially on the AT. Maybe out west on a cooler night you could pull off a WPB unvented- but doubt it.

Just Bill
09-14-2017, 19:28
PS- If you don't care much for how it looks.

If you seam the floor to the top with a basic single roll hem seam- you don't need to seam seal it and while it's a day's work- it's possible to rip that seam and swap in a new floor easy enough.
Sil-Membrane will hold up for a season with no ground sheet- you just have to be prepared to swap it out... but if you think ahead on the sewing you can re-use the very expensive WPB top and sacrifice the floor each season.

The other thought- these days most of us are on an Air pad... that is several inches think. So unless you are literally sleeping in a puddle you don't need quite the bomber floor you used to.

Just Bill
09-14-2017, 19:30

That's about the lightest serviceable floor I know of.

Though Rockywoods supposedly has something similar I haven't seen or used it.

Just Bill
09-14-2017, 19:33
That's the membrane sil-poly.

If you do a vented design- you can build a full bivy out of it- and it packs exceptionally small for what it is. So long as you don't pitch it drum tight it holds up pretty well. There were some complaints at Hammock Forums but some of that is trying to pitch UL fabric drum tight... that much tension and it doesn't take much to mess it up. I have a hammock tarp that is pitched with no stakes that had held up well over 200 nights with only a few minor pin holes.