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#11
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#12
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Roger Halstead wrote:
It's been my experience which is admittedly limited, that metallic colors/pigments tend to get hotter than the same colors with out the metallic pigment. (hope I phrased that correctly) Roger Halstead (K8RI EN73 & ARRL Life Member) www.rogerhalstead.com N833R World's oldest Debonair? (S# CD-2) Would that be because the non-metallic paints have a much lower coefficient of heat transfer? That is, the very outer layer heats up, but then acts as insulation and doesn't transfer the heat energy any deeper. The higher metal content would work as a heat wick. Just guessing. -- ----Because I can---- http://www.ernest.isa-geek.org/ ------------------------ |
#13
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Roger Halstead wrote in message . ..
On 4 Aug 2003 12:37:54 -0700, (Jay) wrote: The reason your silver aircraft may have showed up so hot is because your "heat gun" was actually peering at the image of the sun reflected off the glossy surface. But its is true, the apparent color seems to Shiny Aluminum gets really hot in direct sunlight. At work we had a 1 inch thick 4' X 8' Aluminum plate laying on blocks out in the sun. It was in a protected area where it had little cooling. It actually got hot enough to burn a person trying to move it. The temperature was only slightly below the boiling point for water...bout 200 F. I always figured shiny Aluminum wouldn't get all that hot until I saw that. Your perception of it being hot was based on the material conducting heat into your fingers when you touched it. Plain aluminum is an exceptionally good conductor of heat as opposed to a layer of paint over the same material. Example: This guy I worked with told me that growing up in Minnesota, they put a layer of styrofoam on the seat of the outhouse so in the freezing winter they wouldn't get stuck. The styrofoam was certainly below freezing when they sat down, but because its ability to conduct heat was so small, it didn't freeze their empennage off. So a painted airplane could have a higher actual temperature but less ability to make your finger feel hot when you touch it. |
#14
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Your perception of it being hot was based on the material conducting
heat into your fingers when you touched it. This is why I just always assumed that the wrenches I left out in the sun "felt" so hot, but the other day I happened to leave some tools on the outside window sill of my shop. When I went to retrieve them they were almost too hot to hold. The strange thing is that the one black impact extension was far cooler to the touch than the chrome ones. I think there is a lot more to heat gain than just color and surface finish than those of us unschooled in the ways of IR understand. |
#15
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#16
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"Dan Thomas" wrote in message om... Colour selection should be based on more than its emissivity. You want something that will stand out if the Search and Rescue boys have to go start looking for you. ELTs are fine, but they often don't work properly At 57A yesterday they had 50-some airplanes to search for a screaming ELT. Whup-whup-whup-whup-wooop-wooop-wooooop-woooop-woooop. They came by the hangar and harassed a few of us then went on, after I tore into the rear sling to see if mine was on. They finally found it in an airplane that had just landed, apparently about 10 feet above the asphalt. |
#17
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I've seen large areas covered with bright orange trees in the fall. Never
seen any blue trees though. What about "Blue" Spruce? |
#18
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#19
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