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Thread: 100% Shade?

  1. #1
    eternalvoyage
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    100% Shade?

    Sitting under a tree around noon in tropical heat, one realizes that partial shade is also partial sun -- and that the difference between partial sun and zero sun is very real.

    Most tarps and tent flies only block some of the radiation.

    Are there lightweight materials that block 100% of the sun's rays?

    Are there coatings that can be applied to existing tarps and flies?

    *******
    [It seems to me that Jack Stephenson wrote something about this somewhere -- one of his tent options might have been aluminized coatings that gave something close to 100% shade....]

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    Runner
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    wouldn't those reflective emergency blankets block almost all of the sun because they would reflect all of it?

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    Long Distance Cyclist Machka's Avatar
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    Why on earth would you want to block 100% of the sun's rays?????

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    Every day a winding road spinnaker's Avatar
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    Encasing yourself in about 15 cubic feet of concrete ought to do it, it's just not very light.
    "The world is a dangerous place to live, not because of the people who are evil, but because of the people who don't do anything about it."

    Albert Einstein

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    eternalvoyage
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    Quote Originally Posted by Machka View Post
    Why on earth would you want to block 100% of the sun's rays?????
    Sometimes you wouldn't, especially if you were in the middle of spending a winter in a sunshine-deprived area (like parts of Canada...).

    Other times, though, it is wonderful to get out of the sun.

    Here's Heinz stücke sitting under a tree while on tour (scrolling down to the second visual),

    http://www.bikechina.com/heinzstucke1z.html

    It looks like he's kicking back in the shade, and he is in a way. He's getting out of the sun, or trying to.

    But if you were actually there, and it was hot as ####, and you were overheating, the difference between 50% shade under the leaves of certain trees, and 100% shade under something that blocked all of the sun's rays...-- it can be a dramatic difference.

    I've been in this situation.

    Being inside a tent shaded by leaves like those in the picture vs being inside a tent shaded by something that blocks all of the rays... -- it's a very real difference.
    The first can be intolerably hot while the second can be (under otherwise identical conditions) comfortable or 'just right.'
    Last edited by Niles H.; 01-30-08 at 05:49 PM.

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    Long Distance Cyclist Machka's Avatar
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    We crave the sun up here in Canada ... or at least I do. The sun is good ... it gives us Vitamin D and makes us happy.

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    Seek the Joy
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    Someone should blot the darn thing out.

  8. #8
    eternalvoyage
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    Quote Originally Posted by Machka View Post
    We crave the sun up here in Canada ... or at least I do. The sun is good ... it gives us Vitamin D and makes us happy.
    In the tropics, even in winter, it can be like experiencing some kind of radioactive burn, being out in the midday sun.

    [I added some text and a link to a previous post. Heinz is trying to get out of the sun....]

    *******
    In Baja, cyclists tend to crave shade.

    Sometimes there are no trees.

    The highlights of some cycle tourists' days there come when they find a rare lone tree to sit under, to get some shade.

    *******
    Here is another example:

    [if you freeze-frame it at 01:18, you can see them appreciating a little bit of shade they've found]

    http://youtube.com/watch?v=hDkKZGHaFtE

    *******
    If you were able to carry and provide your own 100% shade -- when and where needed (for lunch stops, for siestas, etc.)....
    Last edited by Niles H.; 01-30-08 at 06:17 PM.

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    nun
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    I carry a small umbrella in my kit, its good for rain and sun

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    There are some Mylar products that reflect energy in the low 90% range,very lightweight(spaceblanket-like) that are readily available.Make sure your wallet is full for a piece big enough to sit under....Look through a McMaster-Carr catalog,they have it.

    Anything that is solid white will reflect about 80% of the energy and tin foil reflects about 60%.
    Last edited by Booger1; 01-30-08 at 09:03 PM.
    Everything should be as simple as possible...But not more so.---Albert Einstein

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    nun
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    Quote Originally Posted by Booger1 View Post
    There are some Mylar products that reflect energy in the low 90% range,very lightweight(spaceblanket-like) that are readily available.Make sure your wallet is full for a piece big enough to sit under....Look through a McMaster-Carr catalog,they have it.

    Anything that is solid white will reflect about 80% of the energy and tin foil reflects about 60%.
    You know with a cell phone, overnight delivery and a McMaster-Carr catalog I could do anything.

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    Senior Member ken cummings's Avatar
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    In the days before air conditioning people in desert areas would use tarps or tents made of burlap or cotton fabrics. The fabric would be soaked with water. Most of the heat radiation that could have passed through was eliminated by evaporation. A TV show called California Gold described using them so people could sleep near Palm Springs during the summer.

    People in the Great White North could form the reflective mylar sheets into a parabolic surface, face it towards the Sun, and stand at the focal point Eh?
    This space open

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    Lanky Lass East Hill's Avatar
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    Quote Originally Posted by kopid03 View Post
    wouldn't those reflective emergency blankets block almost all of the sun because they would reflect all of it?

    And, would it not be possible to direct some of that energy into cooking food?

    East Hill
    ___________________________________________________
    TRY EMPATHY & HAVE LOVE IN YOUR HEART, PERHAPS I'LL SEE YOU ON THE ROAD...

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    Quote Originally Posted by East Hill View Post
    And, would it not be possible to direct some of that energy into cooking food?

    East Hill
    Oh please! Don't encourage him!

    The body's perception of heat involves several factors -- direct sunshine, ambient temperature (which in turn can be influenced by reflection and radiation from earthly sources), wind, humidity and the body's core temperature plus its reaction to ultraviolet radiation exposure (sunburn).

    If some or all of these is controlled, you are able to mitigate the effects. Shade alone won't do it all.

    The only way to exclude the sun's direct rays is with a solid object... such as a tree trunk, and even a dense, intertwined hedge of leaves. Or else get under a roof. They all create a shadow, and there is 100% sun exclusion behind any one of them -- what is reflected from other sources is another matter.

    As we all know, just sitting under a 100% SPF object won't mitigate the effect of heat if the humidity is high and the air is still, and the ambient temperature is high, too. And if the body is overheated from exercise... well, the effects can compound.

    People work all day in intense sun. In fact, the penetration of UV and IR radiation is probably the same if the sky is clear but on one day a cold wind is blowing, and on another a hot wind is blowing.

    This is all putting aside sunburn and cancer risk.

    A couple of other things that I have picked up along the way. If you want to stay cool in very hot weather, use water and air movement to create evaporation. In the tropics this can be difficult because the air already is overloaded with moisture.

    The experts in desert living, the Arabians, have used canvas tents for eons, and use the evaporative effects of water to provide cooling. It's the one really good asset of cotton garments.

    The opal mining town of Coober Pedy has dwellings mined into the ground. Sure, it excludes sunlight, the 100% exclusion factor, but it's also known that getting down under the ground is a great insulator.

    People who visit Australia ignore at their peril advice to use lots of sunscreen and blocker and especially the further south they go, to Tasmania, for instance. The "thinning" of the atmosphere towards the poles makes penetration of UV radiation more severe (apparently) than at the atmospherically thicker equator (ie, you less likely to suffer such severe sunburn in the tropics).

    And, when apples are prone to sunburn, orchardists spray on a mix of water and kaolin clay to coat the fruit. A simple and very effective protective factor.
    Dream. Dare. Do.

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    Senior Member staehpj1's Avatar
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    In the west we rode for days in 100+ F heat without seeing trees and really missed them, but when available we found their shade quite adequate.

    I often thought that rigging up the tent's rain fly for shade on rest stops might be a worthwhile thing, but never actually did it. I really doubt that I would bother worrying about getting rid of 100% of the sun's radiation though.

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    You have to go a couple hundred feet underground to get rid of all the sun's rays. Even then, you have those pesky neutrinos...

  17. #17
    40 yrs bike touring
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    Go-Lite makes an aluminized light weight umbrella called the Chrome Dome. I have found it useful while bike touring, kayak touring and backpacking. http://www.backcountrygear.com/catal...oductID=GO9011

  18. #18
    Slowpoach
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    Long sleeves, I find, are better when cycling in sunny weather - the air movement over the wet (sweat or, if lucky, dipped in a river) material decreases heat retention and the sun protection more than makes up for it.

    +1 umbrella

    I'm considering gluing some space blanket (aluminized mylar) material to a dying umbrella, if it is superior I have also considered the Go-lite umbrella

    Space blankets don't last very long, they are very susceptable to abrasion. You can get aluminised material as safety blankets, also some tents are made of it - one side aluminised, the other side plain nylon - presumably you put the silver side in on cold nights and the silver side out in hot weather.

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    Slowpoach
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    The opal mining town of Coober Pedy has dwellings mined into the ground. Sure, it excludes sunlight, the 100% exclusion factor, but it's also known that getting down under the ground is a great insulator.
    Actually it provides thermal mass, not so much insulation. The day-night temperature variation is high; earth-bermed or fully dug in housing (or any high thermal mass construction) smooths this out as the heat absorbed during the day is radiated back into the house overnight.

  20. #20
    Slowpoach
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    Also Niles, you can get reflective white paint. I'm not sure if it is the same stuff they use for road markings, it might be. It is a white paint containing glass microspheres that reflect a higher proportion of the light than white paint alone does. Sorry, not sure of the product name and manufacturer, but I imagine commercial road marking paint would do the trick.

  21. #21
    nun
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    Quote Originally Posted by Cave View Post
    Also Niles, you can get reflective white paint. I'm not sure if it is the same stuff they use for road markings, it might be. It is a white paint containing glass microspheres that reflect a higher proportion of the light than white paint alone does. Sorry, not sure of the product name and manufacturer, but I imagine commercial road marking paint would do the trick.
    Barium sulphate has a good broad reflectance spectrum, however, this is not a forum for how to make integrating spheres or compare the albedo of materials, lets get back to cycling and stop indulging these
    rather oblique posts.

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    Slowpoach
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    Quote Originally Posted by nun View Post
    Barium sulphate has a good broad reflectance spectrum, however, this is not a forum for how to make integrating spheres or compare the albedo of materials, lets get back to cycling and stop indulging these
    rather oblique posts.
    I think most of us enjoy browsing (or contributing) to these threads.

    BTW why complain about this one - I think it is one of Nile's more immediately practical threads! There's many a time I've wished for more shade, even swapped to the wrong side of the road to get out of the sun for a few minutes.

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    Senior Member staehpj1's Avatar
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    Quote Originally Posted by Cave View Post
    I think most of us enjoy browsing (or contributing) to these threads.

    BTW why complain about this one - I think it is one of Nile's more immediately practical threads! There's many a time I've wished for more shade, even swapped to the wrong side of the road to get out of the sun for a few minutes.
    I find Nigel's threads to be like a train wreck, horrible, but I can't look away

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    Dream. Dare. Do.

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    Quote Originally Posted by Cave View Post
    I think most of us enjoy browsing (or contributing) to these threads.

    BTW why complain about this one - I think it is one of Nile's more immediately practical threads! There's many a time I've wished for more shade, even swapped to the wrong side of the road to get out of the sun for a few minutes.
    I did a small tour with a group from Hobart. It started at Swansea on the East Coast and traversed some gravel roads on a particularly hot day (the East Coast of Tasmania can get very hot and dry in mid-summer). Several of us with wiser heads spent much of the day on the wrong side of the road riding in the shade of big ol' gums overhanging the embankments; there was no traffic on this route, so all was OK. One guy, poor thing, ended up with a slight case of heat exhaustion, and with the use of a rope, was towed up some of the hills by another stronger rider.

    Trees are indeed wonderful shade givers and their other practicality is that they let air movement through that can help to take the edge of the sun's heat.
    Dream. Dare. Do.

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