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  1. #31
    Senior Member Walking Bear's Avatar
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    Post source

    I forgot to say that the source for the pervious post was Virginia.edu

    Probably the best testing of outdoor clothing is located Kansas State University. The Institute for Environmental Research..

    http://www.k-state.edu/ier/index.htm

    For a small payment of $$550 -$650

  2. #32
    Senior Member kohburn's Avatar
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    as it applies to houses (think of it as a large ridgid sleeping bag) the technical data available says that about 85% of the downward heatloss is radiant, where as about 80% of upward heatloss is convective.

    now in hammocks the bottom has a problem with wind. heat will conduct from your body to the bottom layer where the wind will carry it away. suddenly we have a major downward loss problem from conduction/convection rather than radient. stop the conduction of heat to where the wind can carry it away is the 1st step. thats why the garlington insulator (air-gap) works so well. what would make it better? if it was made out of mylar. radiant heat will still cross the air gap and then warm the outter layer and be cooled by the wind. if you keep that radiant energy from warming the outer layer but trap it against your body you no longer lose heat downward.

    you can still have convective loses in an open air bubble but its much reduced. thats why the mirrored glass vacuum thermoses work so well. no air molecules between the layers to trasfer heat from one side to the other.

    of course there is still a water vapor issue at that point.

  3. #33
    yes, but an air gap is not the same as a vacume. an uq or a ccf pad essentially have thousands of tiny air gaps, this is why a down filled air mat is far warmer than an air only one.

    if 80% of bottom heat loss is indeed radiant, a reflective layer should be considered more important, but it makes more sense that the % of heat loss from radiation or convection would have more to do with the properties of your chosen insulation, and be less specific than simply 80/85% like the conductive differences between lofted down and ccf for instance, or if you used only a sb, you would lose little radiant heat, but alot more by convection since you have no actual insulation other than a big empty bag of air. people have tried garlington insulators with reflective maylar inside, and i don't think the results were that astonishing. weather a gi completely coated with reflective maylar would make a huge difference over just having a sb laying in there loosely, i cannot say.

  4. #34
    Senior Member Just Jeff's Avatar
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    Quote Originally Posted by Kirkman View Post
    OK ,are not all sleeping bags ( good ones ) black on the inside?
    Did a quick survey in an outfitters last week - 10 bags, all TNF and Mountain Hardware. 3 were black inside, 7 were some shade of dark gray/silver.
    “Republics are created by the virtue, public spirit, and intelligence of the citizens. They fall when the wise are banished from the public councils because they dare to be honest, and the profligate are rewarded because they flatter the people, in order to betray them.” ~Judge Joseph Story

    - My site: http://www.tothewoods.net/
    - Designer, Jeff's Gear Hammock / Pack Cover by JRB

    IMPOSSIBLE JUST TAKES LONGER

  5. #35
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    [QUOTE=warbonnetguy;38599
    just because a color reflects light, doesn't mean it reflects all wavelengths (like infared radiation) just look at the color green, it reflects all visible light except the color green, it absorbs the green part of the spectrum, which is why it's green. But what i don't know and am wondering is does green reflect all visible light except green, and reflect all other non visible wavelengths of radiation as well, like infarred and others?

    QUOTE]

    Other way round, I think- the green light is reflected from the object to your eye, the red/yellow/blue are absorbed. When the chlorophyll is gone, more red/yellow colors are reflected and the green/blue is absorbed.
    Just my .02 lira, Betsy

  6. #36
    [QUOTE=beamarshall;39690]
    Quote Originally Posted by warbonnetguy;38599
    just because a color reflects light, doesn't mean it reflects all wavelengths (like infared radiation) just look at the color green, it reflects all visible light except the color green, it absorbs the green part of the spectrum, which is why it's green. But what i don't know and am wondering is does green reflect all visible light except green, and reflect all other non visible wavelengths of radiation as well, like infarred and others?

    QUOTE

    Other way round, I think- the green light is reflected from the object to your eye, the red/yellow/blue are absorbed. When the chlorophyll is gone, more red/yellow colors are reflected and the green/blue is absorbed.
    Just my .02 lira, Betsy

    yeah, it's the other way around i guess, but my point is still the same, reflecting visible light might not mean it reflects infarred radiation.

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