open-footed bivy?

Posted by: 41253

open-footed bivy? - 03/14/15 07:06 PM

I've been playing around with some of the lighter clothing-style Tyvek I bought a while back, exploring some ideas for a lightweight, fair-weather bivy. The goal is to have something for short trips where rain isn't expected but isn't out of the question either. I folded a 5- by 9-foot piece length wise and glued a seam about five feet up. It weights 6 or 7 ounces and could almost certainly be trimmed some once I figure out what to do with the head area. I was about to seal the bottom but decided to hold off because I thought that it might be nice to be able to kick the foot-end open to regulate temperature and moisture.

I was dreading shimmying into the thing when I noticed that with the open bottom it's really easy to just slip it over my head while standing up. In the process I also noticed that it might make a decent tunic against rain or cold. I walked around the back yard holding up my "skirts" and with the open flap over my head until I found a place I liked and just sat down. At that point it's pretty easy to police the ground of sticks and rocks, take off my shoes, and lie down. I'm thinking that the foot end could either be left open (maybe with the top cut longer than the bottom to avoid rain rolling down the floor) or I could fold the end over and secure it with tape or snaps or something until I want to stand up again.

I've been considering a few options about some mechanism in the head area to keep the cloth off my face. One idea is to add some tie points that might go to a tree or sticks jammed in the ground. I tested that with an improvised Fletcher-style Visclamp using leaves and a hangman's knot. It worked OK but I'm afraid of tearing something if I move around too much. Another thing that looks promising is using some hoops with the ends jammed in the ground as a kind of frame to throw the flap over. I had recently trimmed some trees and had a lot of nice, bendable branches around but I'm sure that more suitable poles could be obtained if I decide to go this way.

I plan to take this thing out next time it rains and play some more. My question is, what do you all think about an open-footed bivy?
Posted by: PaHiker

Re: open-footed bivy? - 04/01/15 07:57 AM

Depends on where you're camping. I would never have thought about things like this until I was bpkng in Arizona where I read warnings about sleeping outside a tent, and the dangers of scorpions in the area.
Posted by: adamlogan

Re: open-footed bivy? - 04/04/15 02:30 AM

Why not make it cinch-able like a quilt? No matter what its going to require a bit of extra material if you want to do a fold or cinch etc.

You mentioned doing the top long, would that mean your feet would be on the ground? Or are you thinking about keeping it a really long bivy sack?

I would worry about rolling, I'm a side sleeper so I roll a lot personally. Are you planning to use stakes at all to keep the bivy sack stable? If not, I would be sure that your design is side agnostic.

I'm thinking of how I fold chip bags, but I think it would require more material to do the fold than you have or want, idk. I would not enjoy being worried about undoing the fold in the middle of the night, especially if there are scorpions and snakes about!

Could add a buttons or install grommets.
Posted by: 41253

Re: open-footed bivy? - 04/04/15 07:09 PM

I'm not worried about scorpions (or at least I wasn't -- thanks a lot PaHiker!) but I do worry about ticks. I was cowboy camping with just a plastic sheet in January in an area without established sites and very few level spots. All the spots I found late at night when I finally stopped looked as though the pine needle and leaf duff had been recently used as a bedding for large animals. I've never heard about problems with snakes approaching stationary people around here but deer ticks are a real concern.

My original thought for the foot was a rolled edge as you say with Velcro tabs or buttons but I may just seal the bottom up for simplicity and give up the "Gatewood Tunic" idea. If I just leave the bottom open it'll probably ride up in the night and I'll end up with my legs sticking out.

I've been waiting for a good rain since I put this thing together but the only rain we've had when I've been at home and available for this silliness has been a light drizzle. That afternoon I lay out in it for a half hour or so reading and it was fine. I set up an Outdoor Research bivy that a friend lent me and I tried that as well. I liked the extra space of mine and the ability to reconfigure the head material as an awning so that I could look out at the scenery or maybe even heat up a cup of coffee. With the OR bag when it's raining and there's no other protection overhead the only option is to zip it up and stare at blue nylon a few inches away. We'll see what happens in moderate wind and rain. Even if I stay bone dry inside it seems as though feeling the drops might get oppressive after a while.

I hadn't considered the effects of rolling around in the night. It's possible that I could bring the whole awning sheet in the head area down. Maybe when it's sleep time I just pull it over my head and curl up burrito style. It sounds as though some backyard testing it in order, but I'll probably just try it on an overnighter in a few weeks when it probably won't rain and see what happens. The plan I have in mind has me sleeping about a mile from a trail shelter so failure won't be too expensive.

The head area is still a work in progress. The material started out as a 9x5 foot piece of Tyvek and a 2x2 sheet of Polycro (or Polycryo ... whatever). I rolled and glued the bottom 5 feet and cut sideways at that point in either direction so that when layed out it looks like a "T" with the vertical bar 2 1/2 feet wide double-thickness and the horizontal bar 5 feet wide by 4 feet high single thickness. Then I glued a 2-foot by 2-foot piece of polycro to the bottom centered on the seam, where I'd cut the Tyvek horizontally, to extend the ground sheet from five to seven feet. This means that the contraption is not roll-agnostic. I lie down and drape floppy 5-foot by 4-foot head section over a few hooped branches that I stuck in the ground. As with a tarp, I can tug and fold into many configurations. I don't plan to stake it, just weigh bits down with my pack (used as a pillow) and maybe some rocks or something.
Posted by: adamlogan

Re: open-footed bivy? - 04/05/15 05:25 PM

Hope you'll post some pictures of your setup, it'd be great to see and understand better the ways you're using it.
Posted by: 41253

Re: open-footed bivy? - 04/12/15 02:28 PM

I tested it on a recent eastern Oklahoma Ouachita Trail overnight trip and it worked well ... under optimal conditions. The temperature ranged from about 60 degrees at 9:00 PM when I set it up to about 40 degrees in the morning. It was clear and dry.

I took a few pictures but don't know how to post them here. I guess I need some sort of hosting service?

Lessons learned:
1. I need to close the bottom, either with some form of attachment or permanently. As I feared, it rode up on me overnight and the bottom of my bag was out on the ground.

2. There was absolutely no condensation. Of course, in this weather it wasn't much of a test.

3. Polycro was a bad call for the 2x2-ft section in the head area. It ripped almost as soon as I opened it up and tried to drag it just a few inches with my pack sitting on the polycro section. I'll replace that section with more of the soft Tyvek.

4. There were no issues with twisting the bivy up while tossing and turning. My pad is pretty narrow so any turning over has to be pretty deliberate. The inside of the Tyvek is pretty grippy and the pad doesn't slide around at all so the whole things stays oriented correctly.

5. I like having the 4x5-ft floppy head section. It's very versatile. I lay it out at 5PM at a campsite beside a river while I lounged and snacked and played with different ways to keep the fabric over my head but off my face. In one configuration, I put the end of the flap on top of a 2-ft high rock pile people used as a seat and held it in place with another rock. When I set it up again later that night I thought about building a tripod out of sticks but it was crystal clear so I didn't bother -- I just left it down while I watched the stars and sometime in the night pulled it over my head when it got cold.

I'm confident I would have been fine in a light rain. If it had gotten bad I would have had an uncomfortable slog about two miles from a shelter, but at least all of the river crossings were done before I stopped. Testing under heavy conditions will have to wait for stormy weather and free time to overlap.
Posted by: topshot

Re: open-footed bivy? - 04/12/15 09:50 PM

Originally Posted By 41253
3. Polycro was a bad call for the 2x2-ft section in the head area. It ripped almost as soon as I opened it up and tried to drag it just a few inches with my pack sitting on the polycro section. I'll replace that section with more of the soft Tyvek.

Must have been some cheap brand to rip that easy. I'd used a piece (Duck brand I believe) for a groundcloth for several trips (some on rocky sites) that held up quite well until I sacrificed it to bundle up 15+ pounds of trash I hauled out.

However, another piece ripped the first time I used it. That may have been Ace brand.

Nonetheless, I can't envision how you're using this, and the head end is not where I'd want to since it's not at all breathable and you'd have significant moisture from your breath there.
Posted by: 41253

Re: open-footed bivy? - 04/12/15 11:09 PM

It was Frost King brand, I got it at Home Depot. That section is for the ground side under my head and shoulders, the floppy section over my head and the rest of it is Tyvek.

good job on the trash. The less folks see the less they throw down more.