Metallic paint's effects on internal antennas

I've got several buried antennas in my composite homebuilt. A com
antenna in the leading edge of the rudder, a VOR antenna in the outer
wing, and a com antenna along the side of the fuselage. One thing
occured to me was that if I paint my plane with a metallic paint,
would the metallic particles in the paint block radio reception?
I know the folks at the old Stoddard-Hamilton said after they built
the NASA funded, lightning protected Glasair 3, they had to move all
the antennas outside. And they also said they couldn't believe how
much better all the radios worked than before using buried antennas in
their original factory G-III. They also said the external antennas
cost them 10 knots in speed. Not insignificant. So even in an airplane
that's all composite, apparently buried antenna's aren't ideal. And
now I worry if I use metallic paint, things might get worse. I'm just
so sick of white airplanes, I'm not going that route. Maybe a light
gray instead of metallic silver as planned, hmm..........

"Sliker" wrote in message
...
Maybe a light gray instead of metallic silver as planned, hmm..........

...or a clever paint design that keeps the metallic paint away from the
buried antennas?

We've been doing the hidden antenna stuff since the '70s. So far as we are
aware, the only problem with metallic paint (including the silver uv dope)
has been with an obscure German paint that messed the antennas up. However,
that was ONE instance from ONE builder with ONE airplane and we never got
the full story, including the paint brand name. Methinks perhaps it was a
loose nut behind the soldering iron that fouled the antennas up.

Jim

--
"If you think you can, or think you can't, you're right."
--Henry Ford

"Vaughn Simon" wrote in message
...

"Sliker" wrote in message
...
Maybe a light gray instead of metallic silver as planned, hmm..........

...or a clever paint design that keeps the metallic paint away from the
buried antennas?

"Sliker" wrote in message
...
I've got several buried antennas in my composite homebuilt. A com
antenna in the leading edge of the rudder, a VOR antenna in the outer
wing, and a com antenna along the side of the fuselage. One thing
occured to me was that if I paint my plane with a metallic paint,
would the metallic particles in the paint block radio reception?
I know the folks at the old Stoddard-Hamilton said after they built
the NASA funded, lightning protected Glasair 3, they had to move all
the antennas outside. And they also said they couldn't believe how
much better all the radios worked than before using buried antennas in
their original factory G-III. They also said the external antennas
cost them 10 knots in speed. Not insignificant. So even in an airplane
that's all composite, apparently buried antenna's aren't ideal. And
now I worry if I use metallic paint, things might get worse. I'm just
so sick of white airplanes, I'm not going that route. Maybe a light
gray instead of metallic silver as planned, hmm..........

For the last 25 years or so, a lot of paint that looks metalic is not and a
lot of paint that looks non metalic is--and I am actually wrong to even call
most of it paint. Most metal-flake is/was mylar and white paint is titanium
dioxide--which is why "white covers black or your money back".

In any case, I have been away from that sort of thing too long and don't
even know whether you may need a "radome coating"; but any good aircraft
paint shop or aircraft paint distributor should know and a lot of avionics
shops that work on major retrofits should know as well.

Best of luck, and please let us all know what you find out.

Peter

On Sat, 29 Mar 2008 14:15:29 GMT, "Vaughn Simon"
wrote:


"Sliker" wrote in message
.. .
Maybe a light gray instead of metallic silver as planned, hmm..........

...or a clever paint design that keeps the metallic paint away from the
buried antennas?

Or a Mica-flake or Pearl instead of a "metallic"

--
Posted via a free Usenet account from http://www.teranews.com

"Sliker" wrote in message
...
I've got several buried antennas in my composite homebuilt. A com
antenna in the leading edge of the rudder, a VOR antenna in the outer
wing, and a com antenna along the side of the fuselage. One thing
occured to me was that if I paint my plane with a metallic paint,
would the metallic particles in the paint block radio reception?
I know the folks at the old Stoddard-Hamilton said after they built
the NASA funded, lightning protected Glasair 3, they had to move all
the antennas outside. And they also said they couldn't believe how
much better all the radios worked than before using buried antennas in
their original factory G-III. They also said the external antennas
cost them 10 knots in speed. Not insignificant. So even in an airplane
that's all composite, apparently buried antenna's aren't ideal. And
now I worry if I use metallic paint, things might get worse. I'm just
so sick of white airplanes, I'm not going that route. Maybe a light
gray instead of metallic silver as planned, hmm..........

A 10kt loss is relative. A 10kt loss in a Cessna 172 is a lot more
signifigant than a 10kt loss in a Lancair ES or a Glasair III. You could
lose 10kts in one of the latter in lots of other ways like fit and finish or
by going overboard and putting in a heavy interior.

"Robert Barker" wrote in message
...
"Sliker" wrote in message
...
I've got several buried antennas in my composite homebuilt. A com
antenna in the leading edge of the rudder, a VOR antenna in the outer
wing, and a com antenna along the side of the fuselage. One thing
occured to me was that if I paint my plane with a metallic paint,
would the metallic particles in the paint block radio reception?
I know the folks at the old Stoddard-Hamilton said after they built
the NASA funded, lightning protected Glasair 3, they had to move all
the antennas outside. And they also said they couldn't believe how
much better all the radios worked than before using buried antennas in
their original factory G-III. They also said the external antennas
cost them 10 knots in speed. Not insignificant. So even in an airplane
that's all composite, apparently buried antenna's aren't ideal. And
now I worry if I use metallic paint, things might get worse. I'm just
so sick of white airplanes, I'm not going that route. Maybe a light
gray instead of metallic silver as planned, hmm..........

A 10kt loss is relative. A 10kt loss in a Cessna 172 is a lot more
signifigant than a 10kt loss in a Lancair ES or a Glasair III. You could
lose 10kts in one of the latter in lots of other ways like fit and finish
or by going overboard and putting in a heavy interior.

That's quite true, but it is worth noting that the antennas usually sold for
lower speed aircraft have nearly as much drag at their lower rated speeds as
the faster speed antannas have at their rated speeds. The result is that
those little round antennas that you see on Cessna 152s and 172s may have at
least as much drag at a little over a hundred knots as the 600mph blades
have at 500kts. I don't know what is currently available, but if I was
personally putting external antannas on a homebuilt, I would certainly look
into it--and build my own antennas if I couldn't buy them at an acceptable
price.

Peter

On Sat, 29 Mar 2008 12:17:48 -0400, "Peter Dohm"
wrote:

Hmm, that makes me wonder. I couldn't figure out why buried antennas
in places like the leading edge of vertical fins weren't getting as
good reception as an external antennas. Titanium dioxide in white. And
white is what the composite kitplane companies want us all to paint
our planes. I wonder where I can get some of that radome coating.....
:-) I always wondered why radomes looked a little different, or the
shade was off the rest of the plane. There must be something to the
paint, or they could just paint the radomes with the same paint as the
rest of the plane. Metal-flake is mylar?! that's the one thing I was
sure was little flakes of aluminum. No wonder it fades out over time
so bad. I can't see metal-flake on a plane though, that stuff is for
hot rods and dune buggies. If paint affects radomes, I wonder if radar
has different needs than just transmitting and recieving VHF radio
signals? And radar had changed so much also. Instead of the old 50,000
watt systems, they now do the same thing with 700 watts. I used to fly
a jet with the old 50,000 watt system, and the radar rotated all the
way around instead of sweeping back and forth. The airline told us a
special paint on the forward bulkhead stopped the beam from entering
the cockpit. But I used to worry about some flakes of it falling
off... Now that was one paint that definitely would stop all microwave
energy, and probably any other radio energy. The problem is if I go to
the paint store and buy a gallon of Imron Pewter Metalic, the can
really doesn't say what makes up the metallic effect of the paint.
Possibly Dupont could supply this info.


For the last 25 years or so, a lot of paint that looks metalic is not and a
lot of paint that looks non metalic is--and I am actually wrong to even call
most of it paint. Most metal-flake is/was mylar and white paint is titanium
dioxide--which is why "white covers black or your money back".

In any case, I have been away from that sort of thing too long and don't
even know whether you may need a "radome coating"; but any good aircraft
paint shop or aircraft paint distributor should know and a lot of avionics
shops that work on major retrofits should know as well.

Best of luck, and please let us all know what you find out.

Peter

"Sliker" wrote in message
...
On Sat, 29 Mar 2008 12:17:48 -0400, "Peter Dohm"
wrote:

Hmm, that makes me wonder. I couldn't figure out why buried antennas
in places like the leading edge of vertical fins weren't getting as
good reception as an external antennas. Titanium dioxide in white. And
white is what the composite kitplane companies want us all to paint
our planes. I wonder where I can get some of that radome coating.....
:-) I always wondered why radomes looked a little different, or the
shade was off the rest of the plane. There must be something to the
paint, or they could just paint the radomes with the same paint as the
rest of the plane. Metal-flake is mylar?! that's the one thing I was
sure was little flakes of aluminum. No wonder it fades out over time
so bad. I can't see metal-flake on a plane though, that stuff is for
hot rods and dune buggies. If paint affects radomes, I wonder if radar
has different needs than just transmitting and recieving VHF radio
signals? And radar had changed so much also. Instead of the old 50,000
watt systems, they now do the same thing with 700 watts. I used to fly
a jet with the old 50,000 watt system, and the radar rotated all the
way around instead of sweeping back and forth. The airline told us a
special paint on the forward bulkhead stopped the beam from entering
the cockpit. But I used to worry about some flakes of it falling
off... Now that was one paint that definitely would stop all microwave
energy, and probably any other radio energy. The problem is if I go to
the paint store and buy a gallon of Imron Pewter Metalic, the can
really doesn't say what makes up the metallic effect of the paint.
Possibly Dupont could supply this info.


DuPont is an excellent source, and will also be able to point you to a
distributor for their aviation products.

The only thing that I remember about the radome paint/coating is that it was
very slightly conductive--even at the surface. But the bulkhead was another
matter, since the metal bulkhead was a pretty good barrier in its own right
and I believe that there was a fairly substantial energy absorbing blanket
ahead of the bulkhead for those old C-band Sperry radars. Purely as an
aside, I have no idea why they continued to only display 90 degrees of arc
long after larger and brighter displays could have easily provided a
reliable display of more than 200 degrees--since the only limitation would
have been blanketing by the engines and wing tips.

Peter
..

On the older Glasair kits like mine, it's covered with the dark gray
gelcoat that contains 2% carbon black for UV resistance. I wonder if
the carbon interferes with radio reception? I've read that cabon fiber
structures block signals, but how much carbon it takes to do that I
don't know. But for the Glasair folks to say the radios worked so much
better when the moved the antennas outside, makes me think some part
of the structure was blocking radio signals..

On Sun, 30 Mar 2008 20:29:38 -0400, "Peter Dohm"
wrote:


DuPont is an excellent source, and will also be able to point you to a
distributor for their aviation products.

The only thing that I remember about the radome paint/coating is that it was
very slightly conductive--even at the surface. But the bulkhead was another
matter, since the metal bulkhead was a pretty good barrier in its own right
and I believe that there was a fairly substantial energy absorbing blanket
ahead of the bulkhead for those old C-band Sperry radars. Purely as an
aside, I have no idea why they continued to only display 90 degrees of arc
long after larger and brighter displays could have easily provided a
reliable display of more than 200 degrees--since the only limitation would
have been blanketing by the engines and wing tips.

Peter
.