Page 2 of 2 FirstFirst 12
Results 11 to 19 of 19
  1. #11
    Member
    Join Date
    Jan 2009
    Location
    Rochester, NY
    Posts
    97
    Yeah, that does make sense to an extent, but "insulation" isn't the complete picture. Being a physicist, there are lots of fun things you can do with simple barriers (as opposed to the more traditional insulation) - and barriers can do wonders with heat retention and reflection.

    Without something to hold the dead air, there won't be any as you mention. There can be dead air if you want there to be, you simply have to put it there. Take the pockets on the Clark NA model for example. I simply filled each of the pockets with a couple of large ziplock bags that I inflated with air. This created lots of dead air directly against my back. No insulation per se, but lots of dead air. This created a barrier with one side being warmer air from my body heat and the other side being the outside (below freezing, snowing and quite breezy). The result of this simple dead air barrier? I was quite cozy in the Clark.

    The days I camped in the Clark were specifically to test the barrier idea to keep warm, and it worked fairly well. Without the inflated ziplock and drybacks in the pockets, there was no effective dead air (and certainly no insulation) - resulting in a very cold hammock. The pockets by themselves did not do much help stay warm except block breezes. Once they were filled with the airbags, I was able to stay warm using only an ultralight 3 season bag. I was pretty happy with that result. The next part of the experiment was to add reflectors to the barrier, but I didn't get around to it by the time I gave the Clark back to it's owner. The trapped/dead air barrier is not a new concept, lots of survival gear uses it - from a blow up vest to keep your torso warm to a blanket with enclosed air cylinders to make it much warmer than it's thinness would suggest.

    The problem that many of these have is that they aren't breathable. If it's airtight, it simply won't breathe and that can be clammy, sweaty, condensing, etc. All bad things. It wasn't a problem with the Clark, I think because the pockets had gaps between them, as did my very high tech ziplock freezer bags. That seemed to be enough that it wasn't a major problem. I had frost on the netting and weather shield on top, but nothing too major.

    Bottom line, I'd be fine heading out in winter with the Clark NA and a set of Glad freezer bags to hold some dead air. Much lighter than the heavy UQ that my partner was using, and he complained he was freezing (he's a cold sleeper though). I want to add a similar capability on my DIY hammock. It would be nice to be able to do it without adding airbags or insulation or something like that. Unfortunately, as you mention - there just isn't any dead air that way so I don't think that idea has legs. If I add a double bottom that can hold some airbags in place - I should be able to create a barrier to reduce/limit cold transmission/heat loss. If I need more warmth, then I add radiant reflectors to it. Super easy to do, but getting durable reflectors is a challenge.

  2. #12
    Senior Member Eliteoomph's Avatar
    Join Date
    May 2011
    Location
    Montgomery, AL
    Hammock
    Clark NX-250, ENO Doublenest
    Tarp
    Clark Vertex Tarp
    Insulation
    Clark Pockets
    Suspension
    Whoopie Slings
    Posts
    223
    Re bristolview

    I had almost the exact same experience as you did with the Clark.

    I was loaned a Clark nx-200. I just used it a week ago in New Zealand on top of a mountain at temps below freezing. I didn't have aired ziplock bags though... All I did was use a few heavy objects I had in my pack to extend the weight of that pocket downward. I felt that this would create an airspace in between my body heat and the cold air. And it apparently worked. I was toasty all night as well. My feet were a little cold in the morning but nothing out of the norm for cold weather camping... I gotta tell yah it turned me into a Clark fan... Just wish I could afford one, but it does make it a little cheaper knowing I don't have to buy a pad or uc. ;-)
    It's hard to have a bad day in a good hammock. - Jeremy Flatt

  3. #13
    but enough about me hppyfngy's Avatar
    Join Date
    Feb 2011
    Location
    Crozet, Virginia
    Hammock
    The one in the van
    Tarp
    CamoHexMonster
    Insulation
    Fluff
    Suspension
    Flying Trapeze
    Posts
    3,217
    Images
    36
    I see what you mean. In essence though, your thermarest is just a fancy ziplok bag, (and a lot heavier.)

    If you come up with another solution for creating this dead air, we'd sure like to hear about it. Do they make ziploks in human size?
    Caution: Happy Fun Guy may suddenly accelerate to dangerous speeds.
    If Happy Fun Guy begins to smoke, get away immediately. Seek shelter and cover head.
    Do not taunt Happy Fun Guy. - Randy

    TDStand Instructions

    TDStand Disclaimer! I'm Not Kidding!

  4. #14
    Ramblinrev's Avatar
    Join Date
    Apr 2008
    Location
    Milton, PA
    Hammock
    Hennessey Explorer Ultralight
    Tarp
    Hennessey Hex
    Insulation
    HH Super Shelter
    Suspension
    ring buckle
    Posts
    7,298
    Images
    101
    You might want to read this thread. You might find it helpful in terms of some of your questions. Youngblood is/was one of our resident quants.
    I may be slow... But I sure am gimpy.

    "Bless you child, when you set out to thread a needle don't hold the thread still and fetch the needle up to it; hold the needle still and poke the thread at it; that's the way a woman most always does, but a man always does t'other way."
    Mrs. Loftus to Huck Finn

    We Don't Sew... We Make Gear! video series

    Important thread injector guidelines especially for Newbies

    Bobbin Tension - A Personal Viewpoint

  5. #15
    Senior Member JohnSawyer's Avatar
    Join Date
    Sep 2009
    Location
    San Diego, CA
    Hammock
    WB RidgeRunner
    Tarp
    8x10 DIY (speer)
    Insulation
    KAQ Lost River
    Suspension
    Straps
    Posts
    4,696
    Images
    108
    You might be intersted in the Garlington Insulator:
    http://www.garlington.biz/Ray/Hammoc.../Insulator.htm
    "Do or do not, there is no try." -- Yoda


  6. #16
    Member
    Join Date
    Jan 2009
    Location
    Rochester, NY
    Posts
    97
    Yes, I wish I could afford a Clark too. It was amazingly nice. I might be able to stretch for one, but I need 3 and that's just not going to happen. That's why I'm going DIY.

    Hey - thanks for the two links guys. The Garlington insulator is using a barrier and reflector like I had mentioned; using the reflector to actually heat the dead airspace. I haven't tried his approach, but it seems like it would be effective. My DIY idea is a similar variant, but using the double bottom to hold the barrier and possibly the reflector if I add one. I didn't need the reflector part in the Clark, and that was a very cold few days so maybe I won't need one on my DIY. Great writeup on barriers by Youngblood.

    Space blankets are very effective reflectors, but they tend to not hold up well over time. I know, they're cheap and you can just replace them. I want durable items though (it's a personal fault), so it can hold up for a month or more on the trail without needing replacement or breaking down. I suppose a space blanket could, but I'm actually working on a more durable option - that also breaths (hate sweaty backs). If it's successful, I'll post more. Until then, I'll keep quiet. It worked great on a 14inch scale model - and we all know things scale up perfectly... right? Ok, it might not.

    I may be a physicist, but I need to learn more about ultralight fabrics. Does anyone know of a good link to learn about them. Strength ratings, durability, breathability, types of coatings, etc. All that can make a big difference on application, and I'd like to learn about them. In theory, I should be able to make a decent barrier without the ziplock bags. Eliteoomph basically indicated that the pockets on the Clark worked decently for him, with some objects put into them, but no airtight bags. His use created a partial insulator (his gear) and partial dead air (the expanded pocket) that proved effective.

    I've never had a thermorest pad actually. When I slept on the ground, I never carried a pad, just used sticks to make a small gap between me and the ground so it wouldn't soak up my heat. After hiking, I never had trouble sleeping on the sticks. I like to go light, so if I can do without without too much burden - I do. No sleeping bag anymore, no stakes, no UQ, no pad. For awhile now, I've just used my poncho for cover - but I'm heading back into the trees with a hammock. It'll be heavier than my poncho (which I'll still take), so that's a luxury for me. I'm getting older and the luxuries are more appealing.

  7. #17
    Senior Member Eliteoomph's Avatar
    Join Date
    May 2011
    Location
    Montgomery, AL
    Hammock
    Clark NX-250, ENO Doublenest
    Tarp
    Clark Vertex Tarp
    Insulation
    Clark Pockets
    Suspension
    Whoopie Slings
    Posts
    223
    Keep me posted on ur DIY. I just started on one myself and it sounds like we are thinking along the same lines. I would love to see what direction you go.
    It's hard to have a bad day in a good hammock. - Jeremy Flatt

  8. #18
    in it for the naps oldgringo's Avatar
    Join Date
    Aug 2009
    Location
    Checotah, Oklahoma
    Hammock
    Varies
    Tarp
    GargoyleGear Ogee
    Insulation
    UQ-varies w/season
    Suspension
    onrope buckle
    Posts
    5,982
    As explained to me years ago, "dead air" on the scale of ziploc bags is a misnomer. There's lots of movement and heat exchange in there on the molecular level. This is why a tightly sealed stud wall by itself provides little insulative value, and requires some sort of material in there to isolate and limit air movement and heat exchange. Inflated bags are undoubtedly better than nothing, but really, all you've created is an air mattress, and they require down or foam in them to be effective.
    Dave

    http://www.uark.edu/misc/xtimber/rna/pattonsbluff.html

    It has always been my private conviction that any man who pits his intelligence against a fish and loses has it coming.
    John Steinbeck

  9. #19
    Member
    Join Date
    Jan 2009
    Location
    Rochester, NY
    Posts
    97
    I think it's hard to seal stud walls enough to make much of a difference. The channel in them goes straight up (usually) and makes for an excellent heat rise. Air is a tricky thing to keep in place, and if there is a heat differential, it'll move. I have an old house, and most of it is certainly not tightly sealed. Even in the new construction section, that is 'tightly sealed' air moves. It is nothing like dead air. I suppose a house could be build such that it is, but I haven't ever seen that done

    Trapped dead air like a ziplock provides next to no insulation, and that's what I think you are thinking about. Insulation and barriers are not the same thing, but can be used together. A barrier requires a heat source for it to have any benefit, in this case your body and possibly a well placed reflector as well. The way it works, and it does BTW, is that it discourages the transfer of temperature differentials. Air itself is a poor heat conductor. When there is a heat differential, the heat will try to equalize - outside cold air and inside (hammock) warm air will try to swap blend so that there is no heat differential. The dead air in a dry bag or ziplock cannot flow with the other area, and is essentially a block. It can't blend or flow with the other air, so it just sits there. Like a dam in a stream, it blocks the flow. The warm air flowing out is partially blocked and the cool air flowing in is also partially blocked. So, what you get is a slowdown of the warm air leaking out and the cool air coming in, but it offers you nearly no insulation at all - the result? You stay warmer.

    The concept works, and is a simple physics experiment that most 100-200 level physics students do. It isn't perfect by any means, but it works. It's essentially the same thing that many inflatable sleeping mats do. The ultralight ones tent to be just expensive air bags. Others add some sort of insulation in addition. Enough insulation by itself can keep you warm enough, but I doubt a barrier by itself can. You'd still need to suppliment it, but it should help you stay significantly warmer. If you can, try a Clark on a good winter storm (bring some dry bags or ziplocks) and then try a regular hammock without an UQ, you'll feel a difference. Which is better? Neither, they each have their benefits and shortcomings.

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •