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  1. #61
    SeŮor Member wisenber's Avatar
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    The VB approach does leave my down remarkably dry in comparison to without. The main spot I do get my TQ damp is right by my face from my breath. My workaround for that has not been exciting as Shug's approach with a bib suspended from the ridgeline, but it does help. I take a remnant of IX and fold it over the end of my TQ. That keeps the condensation from my breath on a waterproof piece of material. If it gets frost on it from my breath, I just shake it off. It also adds a wee bit more warmth to my torso.

    If you're just out for a night or two, getting your insulation damp from insensible perspiration isn't a show stopper, but it does result in progressively less insulation benefit. Longer outing would have greater consequences unless your in a position to accomplish some field drying.

    Most insulating sleep gear has some form of DWR that prevents actual dew and mist from soaking into the down. On the other hand, the insensible perspiration is often realized more in the form of vapor. If the dew point is in the wrong place, that trapped moisture will freeze inside our quilt. A slightly compromised piece of down gear will dry surprisingly well with a bit of sun and wind.-more so than most would expect. However down that has been more heavily compromised with moisture can take hours in a dryer to resolve which despite many comments on the weight of my pack I do not carry.

  2. #62
    MacEntyre's Avatar
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    A similar testimonial about breathable insulation... on Roan Mtn last month I used a 20*F down UQ and a 20*F down TQ with no tarp and a breathable canvas hammock sock, in high winds and temps down to 2*F... and I was toasty!

    Some folks thought I was insensible, so to speak...
    "We must, indeed, all hang together or, most assuredly, we shall all hang separately." - Ben Franklin
    www.MollyMacGear.com

  3. #63
    Senior Member BillyBob58's Avatar
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    Quote Originally Posted by MacEntyre View Post
    A similar testimonial about breathable insulation... on Roan Mtn last month I used a 20*F down UQ and a 20*F down TQ with no tarp and a breathable canvas hammock sock, in high winds and temps down to 2*F... and I was toasty!

    Some folks thought I was insensible, so to speak...


    Yep, those canvas socks seem to be something all right. I'm surprised that they manage to breath so well when it is way below freezing. Actually, I remember the recommendation from 4dogs was use below - or nearly below- zero, is that right? Works better than at plus 20? And without a tarp?

    The reason I am surprised it manages to breath at zero is because even Mossy netting sometimes causes condensation. And that is breathable enough to put it over your head as a Mossy head net.

    Why do you suppose that- regardless of how breathable canvas is- that body vapor does not condense when it hits the below zero canvas surface?

    Very interesting product. Actually, I was thinking of it the entire time I was writing about the VBs. It appears to be one way to get around a need for VB use, at least for the outer shell in place of tarp.

    I guess the temp inside the tarp must not have been much below 20 unless you were wearing some serious clothing. Did you happen to weigh your quilts after the hang? ( Not that folks normally do that, so you probably didn't)
    For I consider that the sufferings of this present time are not worthy to be compared with the glory that is to be revealed to us....that the creation itself also will be set free from its slavery to corruption into the freedom of the glory of the children of God. For we know that the whole creation groans and suffers the pains of childbirth together until now.
    Romans 8:18,21-22

  4. #64
    MacEntyre's Avatar
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    Quote Originally Posted by BillyBob58 View Post
    ...the recommendation from 4dogs was use below - or nearly below- zero, is that right? Works better than at plus 20? And without a tarp?
    FourDog recommends using all breathable stuff below +10*F. Above that, waterproof footwear and outer layer.

    He used the MMG Canvas Sock at -15*F without a tarp because the wind was light. There was light snow during the night.

    Quote Originally Posted by BillyBob58 View Post
    Why do you suppose that- regardless of how breathable canvas is- that body vapor does not condense when it hits the below zero canvas surface?
    It's got to be due to the lack of flow restriction. The vapor can escape without seeing a pressure increase, so it remains a vapor.

    Of course, some of it may condense on the outer surface, and evaporate immediately.

    Quote Originally Posted by BillyBob58 View Post
    I guess the temp inside the tarp must not have been much below 20 unless you were wearing some serious clothing. Did you happen to weigh your quilts after the hang?
    You mean the temp inside the sock? Who knows what the temp was between the sock and the down? I was toasty, so it was 85 or more next to my skin. I was fully clothed at first, and opened up my clothing during the night.

    I did not weigh anything, but everything was dry. I hung it all up anyway.

    Sometimes I use a VB in that setup, in the form of a Baby Orca between the hammock and the down. It's a 3/4 UQ, so it cannot trap all of the moisture that would be driven through the down. I've never noticed any condensation in the IX layer.

    The only time I have ever gotten any condensation was when I used an IX TQ without a covering. Oh, yeah, there was another time... when I forgot my TQ, and used Hickery's SB. It was about 40*F that night. The SB would get all clammy inside, so I would turn it over. Did that several times through the night, and stayed warm.
    "We must, indeed, all hang together or, most assuredly, we shall all hang separately." - Ben Franklin
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  5. #65
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    My first post at this forum.

    This kind of wanders so lets see if I can put this in a nut shell.

    Dry air (very low dew point) doesn’t hold heat (energy) as well as moist air (high dew point). It is the reason why it get so cold in the desert at night when it is so hot in the day. The air is dry and will not hold the energy.

    Now if you are in a area with a very low dew point and the temps drop down to near the dew point your body will have a hard time keeping the air near your body warm. Now if you take a vapor barrier and create a micro climate of moist air around you that will hold the energy you will stay warmer.

    In Minnesota we call in an outter shell.

  6. #66
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    Quote Originally Posted by Muddog View Post
    Dry air (very low dew point) doesnít hold heat (energy) as well as moist air (high dew point). It is the reason why it get so cold in the desert at night when it is so hot in the day. The air is dry and will not hold the energy.
    I thought the lack of cloud cover was a big factor in deserts being hot during the day and cold at night. During the day there is radiant heat gain from the sun and at night there is radiant heat loss to the sky.
    Youngblood AT2000

  7. #67
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    Low dew points go along with high pressure. With clouds there is moisture in the air (it's the stuff clouds are made of).

    so much for the nut shell. Another name for a cold front is high pressure. Along with the HP you get dry air. If you are above the clouds you have low dew point do to the lack of mosture in the air. The point is if you have low dew points it will get cold at night. It takes more energy (heat) to warm up water then air. Water will hold energy (heat) longer then air. The dryer the air the less energy it can hold. In high humidity it feels hotter in the shade because the moist air can hold the energy longer then dry air.
    Last edited by Muddog; 04-17-2011 at 15:58.

  8. #68
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    Quote Originally Posted by Muddog View Post
    ... The dryer the air the less energy it can hold. In high humidity it feels hotter in the shade because the moist air can hold the energy longer then dry air.
    I have never looked at all this from that perspective. By my way of looking at this I would say that in high humidity if feels hotter in the shade because the moist air is very near saturation and cannot easily accept the moisture that your skin is generating in an attempt to cool you down by evaporative cooling.

    But I think you are talking about the conductive heat transfer of air versus its relative humidity and I had not given that any prior thought. In warm conditions, I had chalked that up high humidity preventing efficient evaporative cooling. In cold conditions I had thought that high humidity made me feel colder because the moisture in the high humidity air trapped within my down insulation had actually moistened the structure of the down itself in some way and made the down less efficient-- but is it because of the conduction (or convection?) characteristics of high humidity air?

    With heat transfer there is often several modes of heat transfer going on simultaneously and which one, or ones, are dominate can change as conditions change... so it can get confusing and often does for me.
    Youngblood AT2000

  9. #69
    Senior Member DaleW's Avatar
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    Interesting stuff!

    One point that may cause confusion: vapor barriers are typically used by ground campers inside a sleeping bag to keep perspiration from freezing in the insulation and typically in sub-zero environments.

    As far as condensation in a cool/wet environment, say 40F and 90% humidity, my concern would be with moisture collecting in the bottom side of my sleeping bag and clothing. Some sort of lofted insulation below the (breathable) hammock fabric should keep things warm enough that the moisture doesn't condense and the OP's good discussion on insensible perspiration kicks in at this point. I'm ignoring any topside issues, as I don't think hammocks are much different than ground tents on the top side.

    So we have this nice warm and slightly moist environment under the sleeper. At some point as we descend through the insulation, we will hit the dewpoint and the warm moist air starts to condense. If you are laying directly on a CCF pad, that might be where your clothing or sleeping bag meets the pad-- the pad can't pass moisture and if there isn't enough insulation for the conditions, you get that ol' cold clammy feelin'. Not good.

    If you have a layer of breathable hammock fabric below your clothing/sleeping bag, with insulation below, the moisture may migrate below as warm vapor and hit the dewpoint when it hits the proper temperature air in that "system" --- someplace inside your UQ, regardless if it is polyfil or down. That will reduce the efficiency of the insulation and the moisture will allow more heat to be "sucked" out of the system--- water is much better at transferring heat than air. Remember, there is no such thing or force as "cold," only more or less heat.

    The more moisture condensing farther up in the layer of insulation, the closer the cold air is to your backside. How much and how bad depends on the ambient temperature and humidity, freezing temps, wind, permeability of the hammock and UQ fabric, air leaks, how much moisture the insulation will absorb, and how much moisture the sleeper is producing. And then there is the cold tolerance of the sleeper. That is a lot of variables!

    Add a UQ. What happens?
    *Cold air is spaced from the sleeper by x" loft
    *Wind is blocked
    *Down-proof fabrics are fairly windproof too and there are more options for breathability, DWR, etc, etc.

    Add a space blanket between the hammock and the insulation. What is happening?
    *Some heat is radiated back towards the sleeper
    *There is a vapor barrier
    *Wind is blocked.
    *Some dead air is trapped on both sides of the space blanket, particularly if it is loose and crumpled

    Add a foam pad below the space blanket. What is happening?
    *More dead air spaces are created
    *Another thermal block is produced--- it is harder for the heat to migrate across the pad
    *With a CCF pad, another vapor barrier is added
    *A windproof layer is added
    *With an OCF pad, you get dear air space, some wind blocking, some breathability, more conformity to the shape of the sleeper and the hammock (fewer gaps), smaller stowage under way.
    * From there, I don't know!
    *I want to know how the efficiency of two loose space blankets compare to a "hung" CCF pad.
    *What about a space blanket on either side of a CCF pad? - it's about the air spaces I think.
    *what about a space blanket and a UQ? Some radiant reflection, definitely vapor barrier, some dead air space and wind blocking.
    *What about the whole enchilada--- space blanket, CCF, and UQ in that order?
    *Of course cost, weight, convenience, and real efficiency should be considered.

    Add a weather shield. What happens?
    *Wind and rain are blocked
    *There is a closed environment created
    *Moisture can accumulate inside
    *How much?
    *Where does the moisture tend to accumulate?
    *What is the best layering/insulation scheme with a weather shield?
    *What temperature/humidity ranges are best?
    Last edited by DaleW; 07-19-2011 at 15:58.

  10. #70
    Senior Member BillyBob58's Avatar
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    Wow, Dale, you have a whole bunch of things to consider all in one post! Some one here might know the answers.

    A couple of items included within your entire post are 1: space blanket 2: on top of OCF and 3: weather shield.

    All 3 of these are used in the HH Supershelter. This has always worked great for me, dry and warm. Also good to great for some others. Stinks on ice for some others, who ended up wet,cold or both. Never have figured out why it works good for some and not for others, but that's the way it is.

    Adding the space blanket seems to bump the warmth 15 to 20F for me. I don't know if that's all due to only VB effect or if some of it(or how much) is radiant block as advertized. I have also added that space blanket under my hammock which is wrapped in a Speer PeaPod, 5 or 10 times. Mostly I just did this to keep the bottom of my pod dry, which worked spectacularly. But the first time I tried it was trying to use my 20F PeaPod at 10F, which again seemed to get the job done.
    For I consider that the sufferings of this present time are not worthy to be compared with the glory that is to be revealed to us....that the creation itself also will be set free from its slavery to corruption into the freedom of the glory of the children of God. For we know that the whole creation groans and suffers the pains of childbirth together until now.
    Romans 8:18,21-22

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