VB Experiment

[Evan Chartier]

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

[Frank Deland]

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

[Roger Caffin]

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

[Matt F]

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

[Evan Chartier]

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

[Roger Caffin]

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

[Evan Chartier]

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

[Nicholas Miller]

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!

[Evan Chartier]

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

[Roger Caffin]

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

[Nicholas Miller]

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! http://www.warmlite.com

[Evan Chartier]

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

[Evan Chartier]

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

[Roger Caffin]

> 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

[Nicholas Miller]

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.

[Evan Chartier]

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

[Nicholas Miller]

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!

[Evan Chartier]

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

[Nicholas Miller]

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).

[Nicholas Miller]

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.

[Evan Chartier]

Ah I see, so I should not lose too much of the dimensions…
I spoke with Tim about the quilt dimensions for my size (6'3 145lbs) and he told me 81" length 49" top straight taper to 37" foot would probably be good. I was wondering why the length is so long, and figured it was because I would lose some with the sewing. I plan on making baffles with mesh. Would you suggest baffles every 5,6,or 7 inches? I am looking to go about 15-20* minimum with the quilt, so was thinking like 2.5" loft? This should be about 10.8oz of down, I have ordered 12. Thanks for the comments!
Evan

[Nicholas Miller]

One reason for the length might be your design. I don't know what you're planning, but if you do a drawcord footbox you lose a fair bit of length. By closing the drawcord, the bottom 6-8 inches of your quilt are now used up making the footbox. Additionally, if you have a neck drawcord you need some extra length so that it can wrap around your shoulders (same idea as the footbox). If you are actually constructing a footbox then your quilt length can be more precise, but assembly and design change.

Either way, you can't go wrong with Tim's advice when it comes to quilts. He makes tons of them and people are always very happy with them. Especially when it comes to dimensions, etc., nothing counts more than experience.

[Nicholas Miller]

forgot your other comments. For baffle height, I think I used 6.25 or 6.5"? I don't know that it's super critical, you're in the right range anyway. I took my overall length and divided it by 11, 12, 13, etc., until I got a number that looked good so that I could just make them evenly spaced and it would come out to equal my desired length.

I used about 12 oz. of down, but stuffed it more than I expected (I think my calculation, assuming perfectly rectangular baffles, was high 9s or 10?). I used 2.75-3 inch baffles if I recall, and ended up with over 3" of actual loft throughout. It's barely tolerable at 15 as long as I can keep drafts out, I only got caught with it in such temps one time without additional insulation layers. Maybe it's just me but my head gets really cold when pushing the limits of the quilt, hence the new setup with the hooded jacket for under-layering. Everyone is so different with sleeping temperatures, and even personal factors such as what and when you eat, etc, can affect your sleeping warmth.

One night I was in my current quilt with my down jacket (no hood) draped over the top, about 19 degrees on my cheap mini thermometer, and I actually took the jacket off to wrap around my head rather than leave it over my torso.

[Evan Chartier]

Ah ok, I was planning on putting in a drawcord. Now I am a little nervous about the durability of the cuben when I sinch it down with a drawcord though. I wonder if I can use a setup with some snaps to get a reasonable closure…
Although Tim does use the drawcords, so I guess it works.
Tim makes really great stuff. Just didnt understand the dimension thing :)
I will try that dividing thing to find the baffle spacing. If I cut out the dimensions of the quilt as 81×49 taper to 37, what do you estimate the final dimensions would be? Maybe an inch or two less everywhere for seams, etc? Dont want to end up with something too small.
So 3" would be barely enough for 15 huh. Do you sleep warm or cold usually? I know its hard to compare.
Evan

[Nicholas Miller]

temps: I would say hard to compare, some nights I sleep cold, some nights I feel fine when others are cold. I wouldn't use my experience as a baseline. Plus that "barely tolerable" night was without any insulation other than 150 weight Icebreaker longsleeve top and my light hiking pants.

cuben: From what I've seen with people's cuben projects I don't think you have anything to worry about with simply repeated pulling/loosening of the drawcord.

dimensions: I don't know if Tim meant that 81 inches would be your finished dimension or your cut dimension, but to be safe I would actually add an inch to each end to allow for the drawcord channel (unless adding a separate drawcord channel, in which case add 1/2 inch each just for seam margin). at 6' 3", your foot-shoulder height is probably what, 5'5"? so 65", add 8" for footbox to be safe, 8" for shoulder wrap and 81" finished length seems reasonable. 8" for the shoulders is generous, as the taper will accomodate your sides, and the actual length running on top of you doesn't have to cinch up much. If you want to be safe, you could add a couple inches without significant weight penalty just for peace of mind. Either way I would personally add seam width to those dimensions, but maybe best to ask Tim what he meant. You know, that whole "experience" thing!

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