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A new? cold weather sleep system


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  • #1268049
    Hiking Malto
    BPL Member

    @gg-man

    Most of us have had to fight condensation when sleeping in sub freezing temperatures. The fact that the dew point will occur somewhere in the insulation layer is the challenge. My current sleep system is a UL-20 quilt with a Tigoat Raven Bivy. Moisture will travel into the quilt and remain or condense on the outer fabric of the quilt.

    As an alternative to this current system. What if the quilt had an impermeable inner fabric that also wrapped around like a sleeping bag. The top layer would be permeable to allow moisture to escape the insulation layer should it occur. With a system like this the need for a bivy would be eliminated since you could use the same fabric on the outside of the quilt as current bivies. But the sleeping area would act like a Vapor Barrier Sack except the moisture could escape out the top through any gaps around a cinched neck. Since the inner layer would stay above the dew point it would never condense on the interior.

    Does this approach make sense and has it been done?

    #1686841
    Tim Marshall
    BPL Member

    @marshlaw303

    Locale: Minnesota

    cuben quilts work this way, but are also cuben on the top and they have been lofting and drying well.

    -Tim

    #1686845
    ben wood
    Member

    @benwood

    Locale: flatlands of MO

    I was gonna say "ask tim marshall" oh well.
    But since you are here, how does the cuben quilt feel inside? Does it get clammy and sweaty? Or do you wear baselayers to help?

    #1686851
    Hiking Malto
    BPL Member

    @gg-man

    "cuben quilts work this way, but are also cuben on the top and they have been lofting and drying well."

    In addition to how they feel on the inside, is there any data comparing the insulation effectiveness of the Cuben vs. traditional construction?

    #1686856
    BlackHatGuy
    Spectator

    @sleeping

    Locale: The Cascades

    @Ben: "Does it get clammy and sweaty? Or do you wear baselayers to help?"

    First off, cuben actually feels okay against the skin. I was surprised, thinking it would feel like sleeping against waxed paper or something, but it actually has quite a 'soft' feel to it. I generally always wear at least a shirt and jockeys to 'bed,' but have slept under my summer cuben quilt with only jockeys (no shirt) and was quite comfortable all night.

    As far as clammy and sweaty, it will if you allow it to. I think any quilt material will. I've never had a problem with my cuben quilts getting clammy and sweaty as I use an appropriate fill for the temps/conditions and vent as needed. But I'm a big fan, I own three with another on the way.


    @Greg
    : "is there any data comparing the insulation effectiveness of the Cuben vs. traditional construction?"

    I have no data, only personal observation from having used my cuben quilts exclusively for the last year (except for one trip with my Raku). They keep me a bit warmer than a similarly lofted/filled traditional quilt at less weight. I can't say how much warmer at what temps as I don't keep journals or anything like that. Not much help, I know!

    #1686955
    Tim Marshall
    BPL Member

    @marshlaw303

    Locale: Minnesota

    as to the feel of the cuben they seem to "season" with use. When new the cuben is crisp and makes crinkly noises when stuffed and moved around. After time it softens from stuffing and use. I had a quilt in the shop that was a few months old and the material was soft and quiet. I was very impressed with how well it softens with use. Also it ships shiny and plasticy and this also dulls and softens over time and use. The quilt i mention i added some material to make it longer and the new material (same stuff as original) looked darker (it was black .48) and reflected much more light. the old stuff had dulled (not so reflective or plasticy looking) and i was extremely impressed with it. That was the first time i had seen a .48 quilt that had been used over time (maybe only the 2nd quilt i've ever seen after shipping)

    -Tim

    #1686958
    Hiking Malto
    BPL Member

    @gg-man

    Tim,
    Saw you epiphany quilts on your site… Questions:
    1) Are you sewing throught the inner cuben fabric and if so is it seamed sealed to make it truely vapor sealed?
    2) Do the quilts have a bottom cuben fabric so that you are sleeping in a "plastic bag" or are they more of a standard quilt? Having the bottom fabric would turn make a bivy redundant (from a wind perspective.)

    #1686961
    Troy Childs
    Member

    @tchilds

    I am having success with my 1443 tyvek top. It doesn't condense (I believe this is because air is encapsulated in the tyvek (like a double pane window or ski goggles that trap air in between two layers layers). It breaths really well and in the end is more water proof than needed. I just wish they had a lighter type tyvek but this stuff weighs in about the same as standard sil nylon.

    I am a profuse sweater and cold nature person. The worst combination ever. I can get away with less insulation using a tyvek top quilt/bivy. So the weight penalty isn't that bad in the end. I'm not saying this is true but to me tyvek seems to have insulation properties especially when used on top of my quilt.

    I also tried the Adventure Medical Kit emergency bivy. It is that aluminized spun bound something or other. I have great success using this then draping my quilt over the outside. So far this method has left me snug as a bug in a rug, and again has allowed me to shrink the insulation in my quilt down… or just leave it behind completely in the summer.

    Anyway I've enjoyed the cheap happy go lucky use of tyvek. I don't know much about it, or eco friendly it is, or how durable. I'm going out on a limb here and assuming the reason nobody uses it around here has to do with these problems.

    Next I'm going to attempt adding reflective thermal shields to my quilt top. I figure I can strategically place these and take advantage of more than one type of insulation. I'm not saying it will be any better than what I already have, but am hoping this will bolster my system in some weak points. This kind of insulation certainly works better when wet! Only time will tell if combining loft with reflected radiation adds any kind of improvements to well, just loft! hehe

    #1686963
    todd
    BPL Member

    @funnymo

    Locale: SE USA

    Troy,

    Is your tyvek a separate "quilt" or the top layer of your quilt? Pics available?

    Thanks,
    Todd

    #1686970
    Troy Childs
    Member

    @tchilds

    Just used the "cloth" tyvek as a top in place of other materials. Sorry I can't offer a lot of advice. Its the same as working with all these other funky materials.

    The only other useful information I can offer is wool wicks. I've added these in strategic locations since my second or third quilt and they work! The problem is they work in two directions… so heavy condensation (certain conditions you just CAN NOT AVOID IT) or a bad location/pitch can really compromise your quilt/bivy even further with these added.

    I run the wicks from the outside top, through the insulation, then about 4 inches sandwiched between the insulation and bottom fabric of quilt, NOT through the bottom shell! I've woken up before with no condensation on my quilt and just frozen little balls on these wicks so I tend to believe they are channeling the moisture out of my insulation. I tried running them all the way through the quilt in a traditional manner but found non wicking threads much better for stabilizing the insulation. Otherwise you have a wick pulling even more moisture into the insulation.

    My theory on the wicks is they collect the vapor faster than the insulation, by properties and proximity, then begin to cool the exposed tip through evaporation, as they saturate with moisture the wicking action gets more dramatic because the bottom is hot and tip is cold. As the heat flows from high concentration to low, it pulls the moisture out of the quilt and to the tip where the evaporation and coolest point of the wick is located. I believe running it 4 inches along bottom of the quilt then 2 inches up through insulation gives it just enough mass/volume to work in this way. In dry conditions, the yarn is just heavy insulation.

    Again no basis or testing on any of this! I'm building a baal's wind tunnel as we speak which will help a lot to enlighten me on some of my ideas. It is very difficult to say if this stuff really makes a difference due to the varying conditions of every single second in the back country. Lets face it though, there ain't no reinventing the wheel!

    I do want to try that 40% aluminized tyvek next. According to dupont sales reps, it could work quite well in this application. The tyvek has very little R value but is supposed to increase the effectiveness of existing insulation. Something as thick as a winter quilt might really benefit from this kind of tech. After messing around with this Adventure Medical Kit thermal bivy thing I'm very interested in the actual benefits of radiated heat versus loft. There has to be a sweet spot in there but I doubt it beats current materials and construction in sheer weight. My hope is that for very little additional weight I can build a quilt for broader range of conditions. Not a lighter one. I'm pretty sure that has been covered!

    #1687295
    Tim Marshall
    BPL Member

    @marshlaw303

    Locale: Minnesota

    "Tim,
    Saw you epiphany quilts on your site… Questions:
    1) Are you sewing throught the inner cuben fabric and if so is it seamed sealed to make it truely vapor sealed?
    2) Do the quilts have a bottom cuben fabric so that you are sleeping in a "plastic bag" or are they more of a standard quilt? Having the bottom fabric would turn make a bivy redundant (from a wind perspective.)"

    The first generation of the epiphany is sewn which does leave a tiny possibility of vapor entering the insulation. I am currently redesigning the quilt to use short baffles in multiple directions instead of long baffles in one direction. this gives me much less total baffle length so i am planning to use mylar tape to adhere these short baffles which will create a sealed inner and outer cuben layer. The edges will still be sewn together and there will be a nylon stripe to allow for lofting the quilt. I am also considering a blowup valve that would remove the nylon but would require an inflation bag and add weight. we'll see where it ends up. They are standard quilts with no bottom as a top bag would have and the footbox opens up so they can be fully vented as needed.

    If any cuben quilt users are following please speak to vapor entering through the sewing. i haven't heard of this happening (other than Lyn's intentional test) but would love your comments.

    -Tim

    #1687300
    drowning in spam
    Member

    @leaftye

    Locale: SoCal

    I've sweat heavily several times, but I have not noticed any vapor entering the sewing, at least not where it would make a difference. If any sweat ever got through to collapse the down, it was where the quilt was tucked…although if this is happening, it's strange that I haven't noticed it in the footbox even though I've had sweat dripping out the vent hole most nights.

    A taped cuben quilt with better baffle style, taped, and with an inflator…talk about bomber and incredible potential.

    #1687315
    BlackHatGuy
    Spectator

    @sleeping

    Locale: The Cascades

    I haven't had any issues with the vapor entering through the sewing in any meaningful way. I used my cuben quilt on a weeklong trip in Wyoming this year – it was lofting just as well the last night as it was the first. I do wear VBL socks to sleep as that's where I used to get a lot of condensation – pretty much solved that issue.

    #1687366
    Lynn Tramper
    Member

    @retropump

    Locale: The Antipodes of La Coruna

    The sewn cuben quilts can get moisture through the stitching. It's happened twice to me. Once when it was pretty cold and I had the quilt completely closed up all night. It gained around 30g of moisture, but dried out quickly. The other time was when using it in a very heavy mist…sleeping in a cloud really. These conditions are not the usual, and over all the cuben performs really well. I suspect a nylon quilt would have had even more issues, especially when sleeping in a cloud!

    #1687380
    Steve M
    BPL Member

    @steve-2

    Locale: Eastern Washington

    I’ve wanted to make the leap from using L/W sleeping bag+VBL (silnylon) to a cuben quilt. Tim sounds like he’s on the right path by taping the baffles vs. sewing.

    I still don’t like the idea of that nylon stripe down the middle. How about allowing for the air to enter/exit only on the edges—using a fine mesh or highly breathable fabric? Edges would then be folded over (Velcro?) to seal while in use. This would allow the quilt to have excellent rain protection vs. having that non-waterproof stripe.

    #1687402
    Lynn Tramper
    Member

    @retropump

    Locale: The Antipodes of La Coruna

    My quilt was made (on request) without the nylon strip. Tim is very flexible. He may well make you a quilt as you described, if you can give him detailed plans on how to make the breathable edges.

    #1687714
    Tim Marshall
    BPL Member

    @marshlaw303

    Locale: Minnesota

    I can't picture a situation where water should be getting on the top of the quilt enough that a 10" stripe of nylon will then soak the quilt. Almost every other quilt on the market is 100% nylon or polyester and only a few of them have WPB shells. The stripe is considered a weakness by many but that is confusing for me as it is the only quilt out there that only has 10" of nylon instead of all nylon(it comes standard with no nylon right now but when taped will require the nylon). The nylon i use is 20D intrepid (same as TiGoat) and the DWR is fantastic. it is used on bivy tops all the time. If you want to sleep in a snow cave that is dripping water all night i can for sure find a way around the stripe but i don't see it as a weakness in 99.99% of situations we face. Velcro edge adds weight and complexity as well as will then be a hard spot under you all night. I can do this custom but wouldn't change the line to use this feature. I am going to prototype a quilt with tapped baffles, sewn edges, a side gusset of nylon sealed inside an attached stuff sack that acts as a billows to loft the quilt. The nylon will also act as a purge valve when you roll the quilt the air will exit the gusset then stuff the quilt into the sack which would then have a breathable bottom(the gusset) allowing the quilt to loft to the max space of the bag. If i am happy with how this works this may become the new model but i still worry that a sealed quilt that gets dropped in the river will be very very hard to dry and a quilt with 10" of nylon will dry much better. Now the sealed quilt shouldn't get very wet if dropped in the water but i want to make sure it is able to dry if the down ever does get wet as i can't come up with a good way to seal the edges of the quilt and will need to sew them. If you have suggestions on sealing the edges i am all ears.

    -Tim

    P.S.
    I have considered making the edges breathable many times but always come back to the fact that you will be sleeping on them which means the down can't loft any more than it does before you goto bed as you will be tucking the breathable part under you making it non-breathable. I also worry that you are moving the most moisture susceptible part of the quilt to the bottom where if you do overheat your sweat will be trying to exit which makes me think it will be possible to expose the quilt to much more moisture this way. this is my thinking on the matter but i'd love to be shown my error.

    #1687761
    Hiking Malto
    BPL Member

    @gg-man

    Tim,
    What's your thought about putting a bottom on to make it fully enclosed like a bivy? Are there negatives that would outweigh the wind/draft resistance?

    #1687782
    Tim Marshall
    BPL Member

    @marshlaw303

    Locale: Minnesota

    i think a cuben top bag could get a bit sticky, but Lynn has one maybe she can comment. hers is a quilt with wings on each side to allow her to close it under her.

    -Tim

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