Page 3 of 4 FirstFirst 1234 LastLast
Results 21 to 30 of 36
  1. #21
    Senior Member
    Join Date
    Aug 2007
    Location
    Western New York
    Posts
    370
    polar bears have black skin to absorb sunlight as warmth in the frozen tundra they live in.

  2. #22
    Senior Member Just Jeff's Avatar
    Join Date
    Oct 2006
    Location
    Charlottesville, VA
    Hammock
    Blackbird
    Tarp
    MacCat Standard
    Insulation
    Winter Yeti, MWUQ4
    Suspension
    Whoopie Slings
    Posts
    8,012
    Images
    32
    I guess that means it doesn't matter what color the quilt is, but black hammockers will always be warmer that white ones? (joke....joke.... )
    “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

  3. #23
    Member Kirkman's Avatar
    Join Date
    Nov 2007
    Location
    NY
    Hammock
    Claytor
    Tarp
    claytor
    Insulation
    foam pad
    Suspension
    straps with cinch
    Posts
    69
    OK ,are not all sleeping bags ( good ones ) black on the inside?.....Polar bears have clear fur that actually acts just like a optical fiber and focuses the light on there black skin to warm them....That is why when it is above 20 or so you see them laying on there belly on the ice when it is sunny. They do that to try to cool them selves.
    A computer lets you make more mistakes faster than any invention in human history - with the possible exceptions of handguns and tequila.

  4. #24
    Senior Member Just Jeff's Avatar
    Join Date
    Oct 2006
    Location
    Charlottesville, VA
    Hammock
    Blackbird
    Tarp
    MacCat Standard
    Insulation
    Winter Yeti, MWUQ4
    Suspension
    Whoopie Slings
    Posts
    8,012
    Images
    32
    I haven't noticed that all good sleeping bags are black on the inside, but I don't have experience with a lot of good bags. My PeaPod and Sierra Designs are silver, my JRB is black, and my Wiggys are black all over b/c they're marketed to the military.

    Maybe it's b/c black doesn't show hiker grime as easily?
    “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. #25
    my marmot is black inside, my slumberjack is light grey

  6. #26
    Senior Member headchange4u's Avatar
    Join Date
    Oct 2006
    Location
    Kentucky
    Hammock
    Dual Layer WB Blackbird
    Tarp
    OES Cuben
    Insulation
    SnugFit
    Posts
    6,267
    Images
    35
    My Western Mountaineering, Marmot, and North Face bags are black on the inside.
    “Light thinks it travels faster than anything but it is wrong. No matter how fast light travels, it finds the darkness has always got there first, and is waiting for it." -Terry Pratchett



    Premium Quality, Fresh Roasted Coffee
    www.meancatcoffee.com

  7. #27
    Senior Member Walking Bear's Avatar
    Join Date
    Mar 2007
    Location
    Fairbury NE
    Hammock
    DIY Bridge
    Tarp
    DIY 11x10
    Insulation
    DIY UQ & down bag
    Posts
    854

    Shade that quilt

    The color of the outside of the bag may will make a difference in the amount of cooling that is radiated to the cold night sky. During the night the coldest thing that you can radiate heat to is the cold night sky. However, shading will stop some of this radiation to the night sky. The tarp over the hammock will shade the hammock from the night sky.
    Think about where frost is in the morning. You often don’t see frost under shade items like trees or other structures. A car windshield under an open carport may not have frost, but a car in the drive behind it will. Same temperature and humidity, just a difference in shading from the cold night sky.
    Generally lighter colors will have a lower reflectance than dark colors. Keeping the tarp over the hammock will do more than keep the rain and snow off. It will shade from the cold night sky. The tree canopy may also provide some shade depending on density.

  8. #28
    [QUOTE=Walking Bear;38594]The color of the outside of the bag may will make a difference in the amount of cooling that is radiated to the cold night sky.

    so are you saying a light color on the outside will reflect warmth back into the fill rather than absorbing it and then radiating it away? can this really be a signifigant amount of warmth reflected?

    i imagine 2 ponchos of 1.1 ripstop. one white and one black, you are in some situation where you are stuck out in the cold with nothing for warmth, so you wrap one around you space blanket style. is the white one going to be any noticable amount warmer? i wouldn't think so.

    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?

    if somebody can borrow some kind of infarred seeing goggles or something (maybe jeff since he in the AF , you could get 2 identically sized and heated somethings and drape black white and space blanket over them and see how much heat is comming through each. come on, i know somebody out there has access to some expensive equipment that they play with

  9. #29
    Senior Member Just Jeff's Avatar
    Join Date
    Oct 2006
    Location
    Charlottesville, VA
    Hammock
    Blackbird
    Tarp
    MacCat Standard
    Insulation
    Winter Yeti, MWUQ4
    Suspension
    Whoopie Slings
    Posts
    8,012
    Images
    32
    Quote Originally Posted by Walking Bear View Post
    Generally lighter colors will have a lower reflectance than dark colors.
    Maybe just a typo - lighter colors reflect more and absorb less. Black reflects less and absorbs more (and radiates more depending on the temperature gradient).
    “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

  10. #30
    Senior Member Walking Bear's Avatar
    Join Date
    Mar 2007
    Location
    Fairbury NE
    Hammock
    DIY Bridge
    Tarp
    DIY 11x10
    Insulation
    DIY UQ & down bag
    Posts
    854
    I did a search for clothing insulation and found the following site:
    I coppied part of it on radiation. It has a good discussioon of clothing insulation and how it works. Quilts and speeping bags would work the same way.

    http://howthingswork.virginia.edu/su...insulation.pdf

    Retaining Body Heat: Radiation
    You also exchange heat via radiation. Your skin emits electromagnetic waves to ward your surroundings and they emit electromagnetic waves toward you. The amount of heat transferred by these waves depends on the temperature of each surface and on how well they absorb and emit light. The amount of heat radiated by a surface depends roughly on the fourth power of its temperature, measured in an absolute temperature scale, so that hotter objects radiate far more heat than colder objects.
    As always, heat flows from the hotter object to the colder object. However, while conduction and convection transfer heat in proportion to the temperature difference between objects, radiation transfers heat in proportion to the differ ence between the fourth powers of their temperatures. That is why radiative heat transfer to or from your skin is most noticeable when you are exposed to an un usually hot or cold object.
    The sun warms your skin quickly because it radiates more heat at you than the rest of your surroundings combined. Measured on an absolute temperature scale, the sun’s surface temperature (6000 K) is about 20 times that of your skin (310 K). Though it’s very distant and appears small to your eye, the sun radiates about 20 4 or 160,000 times as much heat toward you as you radiate toward it.
    In contrast, the dark night sky cools you quickly because of its extremely low temperature. The mostly empty space beyond the earth’s atmosphere is only a few degrees above absolute zero. When you stand in an open field at night, you radiate about a hundred watts of thermal power toward space but it radiates very little back toward you. Since you lose heat quickly, you feel cold. You can improve your situation by standing under a leafy tree. Even in cold weather, the tree is much hotter than space and emits far more thermal radiation. While the tree can’t replace a crackling campfire, it will still help to keep you warm. Fig. 6.5.2 Convection only occurs if the hotter object is below or next to the colder object so that the heated fluid is able to rise. If you heat a tube of water near its top, the hot water stays near the top and the cold water remains at the bottom. Because water itself is a poor con ductor of heat, the water at the top of the tube can boil while the bot tom of the tube is cool enough to hold in your hand.

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
  •