Bivy Material

[reh1966]

I am looking at making 2 of the Six Moon Design Meteor Bivy's, one for my son and the other for myself. I will also carry a tarp large enough to cover the both of us in inclement weather. Most of our trips are in the Virginia area but we have been known to go year round. Here are my questions.

-The design calls for the top of the bivy to be waterproof breathable material. I am assuming that this is to help reduce condensation on the inside but would that really be a problem since the upper head area is mosquito net?

- Would it be OK to make the top lower half out of the same material as the bottom? I found some nylon material in the clearance bin at Wally World. If that is really a bad idea what type of material should I get?

Thanks for the input.

reh1966

[Whistler]

-I think you might better off with a water-resistant fabric on the top. Something that has a strong durable water repellant [DWR] coating that will shed mist and the occasional sidesplash. Pertex Quantum and Nextec Epic are great choices that are also quite light. The advantage of these fabrics is that they will be much more breathable, and be able to let moisture out. Even the best waterproof-breathable fabrics can still be a bit humid.

A hiker/sewer named AYCE also has a good selection of high-quality DWR fabrics over at www.thru-hiker.com (http://www.thru-hiker.com). Rockywood, Quest, Seattle Fabrics, and Outdoor Wilderness Fabrics are also commonly used fabric retailers. They all have websites you can check out.

-I would not use the same material for both top and bottom. Top: needs to block wind, shed light precipitation, and also breath well and let sweat/moisture out. Bottom: needs to be impermeable to ground moisture. A good choice for bottom material would be siliconized nylon, aka silnylon. A fabric weight of 1.3 or 1.7oz/yd2 would be a good durable start for the bottom sheet, and still much lighter than comparable urethane-coated nylon.

Have fun with the project.
-Mark

[NoKnees]

I think that if you made the bivy with non-breathable fabric from the waist down you would have some condensation problems. A few times while tarp camping in storms I stuck the foot of my sleeping bag in the plastic bag I use to line my pack and I had some condensation during the night, Of course it was better than getting the sleeping bag soaked in the blowing rain.

For the bottom 1.1oz/yd silnylon is a good choice Light and waterproof.

If I were to make a bivy I would opt for 1.7 oz/yd epic if you could find some. Mountain laurel Designs makes a pair of very light bivys from this material. Thru-hiker is out of the 1.7 oz/yd epic and I don't know another source. Epic at 2.4 oz/yd is availible from OWF. It should work fine just a little heavier

I had thought that Microporous Polypropylene ( like O2 rainshield or frogg togg material) would be a good choice. Its the most breathable water proof material I know of and seems quite light. Does anyone know of a source for this as a roll good?

NoKnees