What these measurements tell us is what we knew before making any
measurements - that darker colors absorb the sun's radiant energy more than
light colors. This is why the Europa factory correctly advises that white
is the only acceptable color for the fiberglass airframe. What these
measurements do not tell us is how much of the sun's energy is reflected
---From the outer surface of the cockpit covers, only what heat is transferred
by conduction through the cover. The metallic grey material is probably a
very good reflector of radiant energy in the part of the spectrum most
important for reducing the temperature within the cockpit.
It is erroneous to conclude that "the metallic-grey material is totally
unsuitable for sun heat protection" because cockpit air temperature is not a
function of the temperature of the heat shield, and cockpit air temperature
was not measured. At the temperatures involved, radiant heat transfer is
inconsequential so therefore the measured temperature on the interior side
of the cover material is insignificant and irrelevant
Now, having said that the conclusion was erroneous I should point out that
the cover in question may indeed be a rather poor means of reducing the
cockpit temperature. We simply do not know from the available information.
As with academic studies, here we must conclude that further research is
necessary.
For the absolutely best reflection of infrared energy use a gold coating on
the metallic shield.
Best regards,
Rob Housman
Irvine, California
Europa XS
Rotax 914
S/N A070
Airframe complete
Avionics soon
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com] On Behalf Of Sidsel & Svein
Johnsen
Sent: Sunday, July 15, 2012 4:02 AM
Subject: Europa-List: Cockpit cover - Any colour as long as it's white
On our recent trip to Venezia where we had 35 degrees during takeoff at 9:30
AM, Stephan and I were quite puzzled by the negative effect our
metallic-grey cockpit covers had when it came to keeping the heat out. The
temperature inside the cockpit was HIGH.
I have now received the report from the Norwegian Institute of Advanced
Europa Cockpit Cover Research. The reason it took so long, was that only
today has the sun been out sufficiently long to carry out such an important
field study. Here is the summary of the institute's findings (temperatures
in degrees Centigrade):
- Ambient air: 23.5
- Under car window sun protection material (I have now made covers
to place inside all windows from a set purchased at auto supply store):
26.9
- Under white pillow case material (single sheet cotton, thinner
material than the metallic-grey cover, tight weave): 38.7
- Under metallic-grey cockpit cover, made professionally to many
Europas: 58.7
All cases: Temp. sensor held up against the underside of the test piece by
pins, to ensure minimum ambient air influence. All test pieces at right
angle to the sun's rays. No wind.
It is evident that the metallic-grey material is totally unsuitable for sun
heat protection. The colour is just for show, and has the opposite effect
of what we common folks believe. It is of course water tight, but I am sure
there is also white fabric available that keeps the water out.
If you see a Europa at Popham next year, all covered in white bed sheets,
it's mine!
May the sun shine every day the rest of the summer,
Svein
LN-SKJ
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