thanks everyone for the help. i am starting to lean more in a different direction after all of this. I am having to do things that both benefit my Army life and my recreational life, so my decisions lean toward multi-functional in that regard. i started a new thread based off what i learned here. im hoping i dont need a bivy while being under my tarp.

new thread here with more questions if you all would like to help there too.

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=64011&skip_to_post=547703#547703

So Tim, what would you recommend for a bivy top to balance breathability and splash protection? I picked up the M50 thinking it was more breathable (my preference), with lighter being a nice side benefit. But now I'm rethinking the choice.

I guess I am not choosing fabrics for their performance in bivys but in quilts so what a bivy needs hasn't been on my radar. I think 7d is the most breathable of the still highly wind/water resistant options. I know new fabric options will be coming soon and I think you'll be happy with the options, I am just not in a place to spill the beans just yet.

-Tim

http://www.youtube.com/watch?v=ObH-y0s8RaY&feature=related

i inadvertanly stumbled across this video, he is doing what i mentioned, except with the USGI patrol bag (which i currently use). he didnt mention any moisture issues, although that isnt saying he didnt have any, i just note it as an unanswered question to me while watching his video.

We tried a similar settup a few times using synthetic bags. There is condensation but its not such a big deal on a synthetic bag (I think it would have been very bad on down). I don't consider it and ideal set up especially long term but for one or two nights its okay and it does seem to add some warmth but probably not as much as he claimed in the video. Also remember that as you get tired your body won't keep itself as warm. When I'm really exausted and weak after a hard day I sleep colder.

Edited by Cameron on 05/12/2012 23:36:43 MDT.

I think my solution to liking the SOL bivy's reflective interior is going to be just sandwiching my ground sheet, which a durable survival blanket, over me when i sleep. i think it will do the same thing pretty much. am i wrong thinking this?

Can someone point out the benefits of a bivy? (Other than using them as originally intended emergency shelter/sleep systems.)

Here are a couple of issues I have with a bivy vs just using a tarp:

1. Doesn't the combined weight of a DWR bivy, such as one with a M50/M90 shell, plus a small WP (silnylon) tarp weigh *more* than the weight of a regular/large WP tarp + GC?
2. To expand on #1, isn't the weight of a shrinkwrap GC less than a bivy bottom layer, since it has to be strong enough to sew (like silnylon)?
3. Doesn't a tarp provide better/adequate ventilation so as to help reduce condensation? (Assuming it's large enough not to brush the fabric.)
4. Isn't the weight of addition high loft insulation (such as 900FP) more efficient than using a bivy to increase the effective temperature range? For example, won't 6oz of add'l 900FP down provide greater warmth than a 6oz bivy?

I looked @ all these factors and realized it makes more sense (at least for me) to:
1. take an oversized WP tarp
2. use a shrinkwrap GC
3. take a warmer quilt

The one advantage I see in using a bivy is ease of setup ie lack of setup. But, with my warmer quilt, I can throw it down cowboy style. If there is any dew, up goes the tarp. I guess the bivy would allow you to still sleep under the stars in that situation, but all the negatives seem to outweigh a few pluses.

You bring up valid points, ones that everyone needs to weight out for themselves and see what makes most sense

I use a bivy w/ a poncho tarp- it's a small tarp, but it's also my raingear- some weight savings there

the bivy also adds a few degrees to sleep system

bivy is my bug protection

bivy helps a lot w/ wind

the bottom of my bivy is tougher than most of the very lightweight gc,thus my inflatable inside the bivy gets a little added protection

as you bring up- cowboy camping is nice and a bivy allows me more opportunities to do it as a light moisture (rain or snow) just beads up and I can shake it off in the morning

there is no one way for a sleep system, each has there advantages and disadvantages

I think the big advantage if a bivy is to cut down wind chill, and seal the edges of a quilt to eliminate drafts when you toss and turn. If you have a bigger tarp, wind blown rain is not a problem except in very severe storms.

plus the fact that where we tarp camp there are ticks in the summer time at some spots and i don t really want to invite any of them home :)

kevin

Kevin and Tim are correct on the issue of M50 vs M90 breathability, the M50 is a tad less breathable than the M90. I was expecting otherwise due to the lightness of the M50, but it has a very high quality DWR coating that makes it less breathable. Still perfectly usable for bivys, but when the conditions are just right, you might have to deal with some condensation.

I think it all comes down to whether or not you normally have condensation issues with your bag/bivy combo. I use one of the M50 bivys that we sell, and I've only encountered condensation issues a few times with it, mainly in conditions that most any top fabric would have had condensation.

The current M90 is probably my personal favorite in terms of breathability. But if you use a bag that isn't too warm for the conditions, the M50 works great. I sell more bivys in M50 than any other fabric offered, and only a couple people have reported that they experienced condensation in theirs.

Let's not forget your size here when purchasing your bag or quilt. Your a big guy like me (you are taller by a couple inches but I am rounder). The only way I fit using quilts is because I am a hammock camper and the quilt only needs to go over me while the underquilt takes care of my sides and back. If I were on the floor, I would pull one of the sides of the quilt from underneath my pad and get a cold spot on my shoulder.

Taking that into consideration, purchasing a quilt that will go around you and your pad is a hard find when you are big. Another option (all be it not as light as some of the customs you can purchase) is a Big Agnes Deer Park is a 30 degree bag. This is sort of a bag/quilt hybrid. all the loft is on top, but has a sleeve on the bottom for your pad. This bag gives you plenty of wiggle room. If you want one that is rated colder, go with the summit. This option will add about a pound (pound and a half) to your total pack weight than a regular quilt, but for big guys sometimes you have to take the extra weight.

I can't help you on the bivy as I am a hammock camper whenever possible.

SOL now makes a breathable bivy, the Escape. I got one for me and one for my wife. Breathability is good but it's a little tight. I'm going to buy another and expand the two we have, add a longer zipper. Using a light bag as a liner provides a really light, waterproof (at least before I start cutting)and warm bag. I just use a 45 degree bag inside the Escape. The Escape weighs 8 oz. check it out on their website. Shop around and you can find it for $40