In order to continue my experiment with using VB to sleep in I was thinking of sleeping under a silnylon tarp. I want to simulate sleeping under a cuben quilt with the VB it would create to see how I would like it. Would sleeping under a silnylon tarp such as the S2S poncho/tarp have a similar effect? I could also add a pertex quantum bivy. This would be on my livingroom floor. I have slept in a trash bag and it was comfortable, but was thinking that under the tarp might better simulate a cuben quilt VB? Thoughts?
Thanks
Evan

http://www.westernmountaineering.com/index.cfm?section=Products&page=Accessories&ContentId=44

If you can find a translator, maybe this thread from the achives can help?

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=1793

More links on VB:
http://www.verber.com/mark/outdoors/gear/clothing.html#VaporBarrier

Edited by rambler on 03/09/2010 14:47:03 MST.

Hi Evan

No resemblance at all.

Under a silnylon tarp: all the condensation from your body will go through the quilt, maybe condensing inside the quilt, and then finally (maybe) condense on the underside of the tarp.
With a proper VB: the condensation stays at skin level and never even gets into the quilt.

The two cases are poles apart. Almost opposites.

Cheers

Roger -

I may have misinterpreted, but I think Evan may be talking about using the sil-nylon tarp as a quilt/blanket inside of his bivy on his living room floor. In other words, he's not talking about pitching his tarp at all, just draping it over himself.

Matt

Hey guys-
Sorry about the ambiguity! I have slept under a tarp many times and love it. Here was I talking about using the tarp as a quilt in order to better understand the effects and my reaction to sleeping with a VB next to my skin. Thank you for clearing that up Matt.
I have read extensively on the use of VB clothing and sacks and understand the theory behind them, however I feel that I do not know if I will like it until I try. That being said, would this create a similar VB effect as using a cuben quilt? Thanks
Evan

Hi Evan

Ah yes, I misunderstood!
Well, I am sure the tarp will prevent most of the water vapour from getting into your quilt. What a tarp would feel like as a 'sheet' under the quilt ... hum ... dunno ... try it and let us know!

cheers

Yeah I dont think it will feel very good...
I will have to try it while wearing some light base layer so that its in contact with a minimal amount of skin. But would the VB created by the sil nylon be comparable to a VB created by cuben fiber?
Anyway, I'll let ya know tomorrow! :)
Evan

I use a MYOG quilt with silnylon for the inner layer acting as a VB and don't mind it at all. As Roger said, give it a try! The nice thing about a VB in a quilt is that any mugginess/perspiration is very easy to avoid given the vastly superior venting ability of a quilt!

See thats what I was thinking-
The ONLY disadvantages I have heard about the cuben/sil VB quilts are the condensation from insensible perspiration, price, and next-to-skin feel. If I find it at a reasonable price (need a quilt anyway) and wear a light base layer, couldnt all these problems be solved except the condensation? And cant that be solved by venting when it gets too hot, or leaving half the quilt off my body?
Gosh I should just go to sleep now and get it over with :)
Evan

Hard line theory says the VB layer should be against the skin.
Most users however keep a light base-layer on ... and sleep cool!

Cheers

I haven't noticed a problem with next to skin feel as I usually sleep with a base layer, but even without, I don't think it's so much the "feel" as the sweat/condensation (which in turn feels moist and not great). i.e. you can solve both those problems with adequate venting, which with a quilt is easy in theory. One problem is that if you are a deep sleeper or your body doesn't have the auto-reaction memorized yet to stick a foot/arm out when warm, then you might not wake up to vent (or subconsciously vent) until you're drenched in sweat. This is where the "feel" comes in to play it seems...if you're not venting you're going to sweat and it's going to stay inside the VB regardless, having a base layer on may make that situation less uncomfortable, but then again it might also delay your body's tendency to wake/vent and actually make the problem worse. Did that make any sense?

At any rate, I sleep with base layers and just let the quilt setup do the auto-venting. Depending on the temps I'll start either at: with it half on, mostly on with a limb or two out, completely draped but loose, wrapped all the way and strapped behind me, or fully wrapped and with the neck cord tightened. As I get cold during the night I'll just progressively tighten it up just like pulling more covers on at home, (and adding hats and/or other layers if necessary, though insulation layers should be draped over the quilt rather than worn under it due to the VB). I haven't had any sweat/condensation issues, and I've been happy with the setup so far.

This isn't technically using the quilt as a full vapor barrier until you're at the fully wrapped phase, since a partially open quilt isn't acting as much of a vapor barrier. However, I think this is actually a benefit to using it with a quilt. I've used the same quilt at 15 degrees as at 50 degrees, although I don't know how much of that is helped by having the silnylon layer. I might have been just as comfortable at 15 (not very) in a comparable quilt made of breathable material.

edit:
I must have been typing all that when Roger was posting, but his comment sums it up nicely...keep it cool and your body won't overreact.

And as for the "hardliners," read Jack Stephenson's take on VB as the very next-to-skin layer for a strongly opinionated VB proponent's views! www.warmlite.com

Edited by nmiller08 on 03/09/2010 22:13:05 MST.

That was a great summary of what I can expect tonight. I figure that unless it is very cold I will not use it as a true VB, instead allowing the moisture to slowly seep out by venting. Will post again in the morning when I wake up :)
Evan

Hey guys-
So I slept with the sil nylon tarp over me the entire night. Before going to sleep I tucked it in under my legs and put my down quilt on top of it. I awoke hours later feeling refreshed and ready for this beautiful day! As if something terrible would happen :)
The weird thing is that I wasnt wet or damp at all. This is similar to when I wore the trash bag to sleep over a week ago in another VB experiment. Could this be because I dont give off much insensible perspiration? I wasnt much warmer than if I was just using the quilt. Weird...
Evan

> I wasnt much warmer than if I was just using the quilt. Weird...

No, not weird. If you didn't get too warm you would not have sweated very much - which is the way to be in a VB.

So, got the confidence to go a little bit further now?

Cheers

Evan, I'm currently building an integrated system of jacket/quilt so if you're interested in trying out a sil quilt on a budget I'd sell you mine (after I finish the new one ~ 3 weeks?) for the cost of materials if you're 5'9" or less. Let me know if you're interested and I'll send pictures.

Roger,
Definitely more interested now. I thought I would overheat sleeping under a VB and a quilt while in my house at about 68 deg. F but that didnt happen! YAY!
Nicholas,
I would be interested but I am 6'3 and leaving in 2 weeks for the PCT! Thanks anyway though, and I would love to see that jacket/quilt system you are creating. Will it have a VB? I am going to try a MYOG quilt with a VB for the PCT I believe...
Evan

It would fit more like a half bag;) the new system won't have a vb layer, as I'm intending to use it with a hooded down jacket inside the quilt, and the quilt will have the baffle sizes adjusted to compensate for the jacket. I'll definitely post pictures when done!

Yeah I am a little tall :)
Cant wait to see those pics. Is the sil nylon quilt you have made with down? Can I ask how you measured the dimensions and compensated for the loft? Like, how much longer do I have to cut the fabric to compensate for length and width loss when I add the down?
Evan

You mean loss of fabric length due to the up-down-up created by the baffle chambers? Not much as long as your baffles are adequate height. If you're doing sewn through baffles for a lighter weight quilt you might lose more fabric length. here's my fine paint skills to try to illustrate the difference. I maybe lost an inch or two? (2.75-3 inch baffles).

Edited by nmiller08 on 03/11/2010 00:07:09 MST.

forgot to add that width wise you don't really lose anything except the curve used to join the inner and outer. However, be sure to compensate for loft when deciding how much fabric width you need on the shell.

You can make the inner and outer the same width and you will get extra fabric folds in the liner when the quilt is wrapped around you or you can use a differential cut and make the liner narrower to compensate for the curve. (like the circumference of a tire is greater than the circumference of the wheel it is wrapped around). I'd recommend against a differential cut just due to complexity...to get a true semi-continuous differential you have to cut the baffle material (noseeum or whatever you decide to use) full length and pleat it every so often on the liner side to achieve a nice curve. If you don't, and just baffle it normally and then stitch the outer to the inner, you get a quick curve on the outer edge of the quilt with minimal differential effect across the bulk of the width.

Edited by nmiller08 on 03/11/2010 00:17:44 MST.