What I would consider making if I could make my own bivy,

It would double as a full protection bivy and a summer bug bivy.

A waterproof bathtub bottom like others, but the top would be two layers, the bottom layer would be full no-see-um mesh and the top layer DWR ripstop material like others use.

The top layer would have a zipper that would extend beyond the full length so that it could be zipped down and rolled out of the way when only the no-see-um is wanted in hot buggy weather, then zipped up as far as needed when the wind is blowing rain in under your shelter or during light rain while cowboy camping.

This of course would weigh a few ounces more than your typical UL bivy, but would be more practical for trips that could hit extremes of hot buggy to cold and wet. A thru-hike comes to mind.

The flexibility could also reduce the size of tarp needed.

Steven - you were the one who convinced me that with a large wnough tarp, a bivy is simply not required. Stop this nonsensical talk!!

; )

Hey Dave,

I agree that a large enough tarp doesn't require a bivy, but I still bring some kind of bug net for bug season.

I often find that the bugs can be intolerable where I hike and so will use a Meteor Bivy(half bug net) under m tarp.

I also find that if it doesn't look like rain, I'll sleep only in the Meteor and then when it does rain in the middle of the night, deal with getting the upper half of my bag wet or get up and throw the tarp over me.

Many cases that I wished I could just zip up for full coverage in a light rain, even though I know some water would get through the DWR.

I'm only speculating on the double top layer idea, but thought people might have some ideas.

Also Dave and others,

On previous discussions about bivys not being needed under a big tarp, I also stated that you can get by with a smaller tarp if you use a UL bivy.
I also stated that I usually do use a Meteor bivy in bug season, which is usually most of my hiking season.
The Meteor also allows me to get by with a 9x5 tarp as it provides some coverage from the rain.
I just sometimes wish that I could get better coverage with the Meteor when the weather get snotty and rain is blowing under my small tarp from all directions:-)

The problem with this is that for it to work as a double wall and keep condensation off you will need to keep the layers separate somehow- like a pole system. In which case you just end up with a very tight fitting tent. If the idea is to just be able to zip off/back the nylon layer for when the bugs are out when its hot, you still might have the problem of keeping the netting off you. It may work that way but you might end up preferring the space of a bug net insert over it. Plus the weight savings of a smaller tarp will be minimal and the double layer bivy will make up the difference. I would personally prefer my Skyscape which does what you are talking about but has decent room to sit up and sets up pretty easily.

I agree about keeping the net off. I always suspend the top of my Meteor. Not only because bugs can bite through the mesh, but also to allow better air flow/comfort.

I also suspend the top of my full coverage bivy, for comfort and to reduce cold weather condensation in the cold.

I guess I would want the two layer concept to also have the same possibility, like other bivys.

I recently made a Meteor Bivy and replaced the netting with breathable fabric to the bottom 6 inches of the netting area as it wraps around the head end of the top. This gives me more protection from drafts and splash but maintains the breathability. It was easy to modify the six moons designs pattern that is available for free on their website.-Scott

Steven,
How about using the same three layers with separate cross-chest zippers in the netting and DWR layers rather than a full perimeter zipper.

For stormy weather, you have two options:
1. Sleeping with the WP layer under you and the other two layers above you.
or
2. Sleeping with both the WP layer and netting under you and just the DWR above you.

For warm and buggy weather, turn the bivy inside out and sleep with the WP and DWR layers under you and the netting over you.

FWIW, I've been using this hybrid bivy:



I seldom use the DWR cover and sometimes wish for a larger area of netting, but the cover is nice when it's needed.

I like that idea, Scott. Thanks for sharing.

I like Scott and Lance's ideas both.
I can see both ideas being optimum depending on where you hike.

For a thru-hike with a smallish tarp, Lance's idea sounds lighter than my idea, less finicky and more reliable.

Yes, after reading Lance's idea again and more carefully, I agree. I like it too. Being I have a Meteor though, I may modify it so it's similar to what Scott described. So simple. Why didn't I think of that? Love this forum for all the ideas!