Very interesting, and not just on topic. Your measurements are certainly
consistent with the published chart. The Europa chart looks to me to
indicate about 5F/3C offset at low temperature and less than 10F/6C at
high temperature, of the yellow above the white curve. As an engineer I am
usually distrustful of data that are offered without indicating the source,
but I do tend to trust the folks at Europa (as I should since my life will
depend on their design being adequate!) to have selected representative
real-world colors so I must conclude that the chart is valid, and therefore
also conclude that it would be prudent to limit our choice to white.
Perhaps I am a bit more sensitive on this subject because any eastward
departure from the LA basin involves crossing the Mojave Desert where the
temperature on the ground will often exceed 115F/46C. I guess the folks
in UK don't comprehend how hot it gets here because the chart doesn't go
above 110F ambient.
Not even suggested in the Europa manual is the variation with latitude of
the amount of the sun's energy reaching the ground (or an aircraft in
flight). Closer to the equator there will be a greater heating effect on
the aircraft structure at any given ambient air temperature, and this is
also true at altitude. Using ambient air temperature as an indicator of how
hot the structure will get ignores the affect of latitude.
Having said all this I must admit I have considered painting the bird a
metallic silver, but not without making some measurements first. Your
observation regarding metallic tan gives pause to that idea, however. Have
you made any measurements at higher ambient temperatures (and I do
understand that you won't experience anything close to desert heat so near
to Lake Erie)? Will you elaborate, off list if appropriate, about your
measurement scheme?
Now for the interesting off topic part: my business is manufacturing
components for infrared cameras so I had considered asking one of my
customers to make elevated temperature emissivity measurements of a metallic
silver painted epoxy-fiberglass surface, and also of a white sample for
comparison.
Best regards,
Rob Housman
A070
----- Original Message -----
From: "Fred Fillinger" <fillinger@ameritech.net>
Subject: Re: Calling All Cars ....
> Rob Housman wrote:
> >
> > Surely you have read the manual's admonitions regarding color (or colour
> > if you prefer).
> > ....
>
> No disagreement that this is very important, but the chart provided by
> Europa is approximate and likely for pure colors. The original poster
> was contemplating "pale yellow," and I tested (using an infrared,
> digital sensor) white verses yellows, and found (on a 65F day, bright
> sun, a 2F deg. difference for pastel yellow, 3 for bright yellow.
> Surprisingly, metallics must affect heat absorption, as a light tan
> metallic, for example, gets much hotter.
>
> Regards,
> Fred F ., A063
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