Metallic paint's effects on internal antennas

[Sliker[_2_]]

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..........

[Vaughn Simon]

"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?

[RST Engineering]

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?
>

[Peter Dohm]

"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

[clare at snyder dot ontario dot canada]

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

[Robert Barker]

"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.

[Peter Dohm]

"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

[Sliker]

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
>
>
>
>

[Peter Dohm]

"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
..

[Sliker]

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
>.
>

[Morgans[_2_]]

"Sliker" > wrote in message
...
> 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..

I could be wrong, but I recall that Jim Weir has done extensive testing on
airplanes, and what structures block radio signals, and carbon fiber has
been found to not be a problem. I hope I remembered right, and Jim will
probably jump in here and clarify the situation.

When it comes to antenna mounting and performance, I think we are lucky to
have a resource such as Jim to help us get on the right path. He is an
expert on the subject, IMHO.
--
Jim in NC

[Peter Dohm]

"Morgans" > wrote in message
...
>
> "Sliker" > wrote in message
> ...
>> 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..
>
> I could be wrong, but I recall that Jim Weir has done extensive testing on
> airplanes, and what structures block radio signals, and carbon fiber has
> been found to not be a problem. I hope I remembered right, and Jim will
> probably jump in here and clarify the situation.
>
> When it comes to antenna mounting and performance, I think we are lucky to
> have a resource such as Jim to help us get on the right path. He is an
> expert on the subject, IMHO.
> --
> Jim in NC
That's very true, and the little that I did was 20 years ago. Jim Weir is
current.

Peter

[WJRFlyBoy]

On Tue, 1 Apr 2008 16:34:13 -0400, Morgans wrote:

> I could be wrong, but I recall that Jim Weir has done extensive testing on
> airplanes, and what structures block radio signals, and carbon fiber has
> been found to not be a problem. I hope I remembered right, and Jim will
> probably jump in here and clarify the situation.

This is concurred in F1 racing now for better than a decade.
--
Remove numbers for gmail and for God's sake it ain't "gee" either!
I hesitate to add to this discussion because I'm not an instructor,
just a rather slow student who's not qualified to give advice that
might kill someone.

[RST Engineering]

There are hundreds of variations of carbon fiber "mixes". Some have
absolutely no effect on internal antennas, and some that are absolutely
wonderful Faraday shields (blocks) of radiation performance. My work with
Rutan on Voyager pretty much proved that.

HOWEVER, having said that, we proved in the Bellanca experiments that
regular old silver UV dope on fiber has absolutely no effect on internal
antennas. Even the FAA accepted our experiments on that.

On the other hand, mixing carbon black, which is not a conductor, nor an
insulator, but a lossy medium is in fact an antenna attenuator. For some
manufacturer of kits to come out and say, "hey, we started putting in carbon
black to our mix and now we've got internal antenna problems" isn't a great
surprise.

I work real cheap. I'm not a thousand dollar an hour consultant. You'da
thought that all you who are spending tens of thousands of dollars a kit
would have had professional antenna consulting from these yahoos who are all
of a sudden discovering that moving this or changing that is having an
effect on their antenna performance would come to the source for advice.
Not a one of them, other than Bellanca and Beech. Cheap *******s.

To the person that asked whether carbon black has an influence with internal
antennas, I pose the following question:

We proved at Bellanca that reflection from aluminum particle to aluminum
particle to the outside world didn't affect transmission through "silver
dope" UV protectant to any measurable degree. However, carbon black is not
a reflector, but an absorber. Signals don't get reflected in carbon; they
get converted to heat and absorbed. That ain't rocket science; that's what
I teach to my freshman engineering students. Is that understood?

You folks that are paying tens of thousands of dollars for your kits need to
have your vendors take my freshman engineering class.

Jim



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

"Morgans" > wrote in message
...
>
> "Sliker" > wrote in message
> ...
>> 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..
>
> I could be wrong, but I recall that Jim Weir has done extensive testing on
> airplanes, and what structures block radio signals, and carbon fiber has
> been found to not be a problem. I hope I remembered right, and Jim will
> probably jump in here and clarify the situation.
>
> When it comes to antenna mounting and performance, I think we are lucky to
> have a resource such as Jim to help us get on the right path. He is an
> expert on the subject, IMHO.
> --
> Jim in NC
>

[Sliker[_2_]]

Sounds like the carbon black mixed into the gelcoat could have been
the culprit. But I know how to fix that! the 'ole power sander in the
areas where the antenna's are. That carbon black will sand off, and is
not structural at all. And a good layer of primer and paint will
provide enough UV resistance, especially for a plane stored in hangar.
I've noticed that the tech support folks at the old Stoddard-Hamilton
would advise to sand off the gray primer at the drop of a hat for just
about any issue. Such as possible fuel leaks over the spar, they would
just say to sand off the gray primer to make the structure underneath
transparent, and the leak easier to find. Or if any laminates needed
to be applied in areas of the primer, off it comes again. The carbon
black was probably a bad idea in hindsight, and no doubt why they
quietly stopped using it. Thanks for the great insight!

The main negative to sanding off the gray gelcoat is it opens up the
pinholes. And I'm just getting into dealing with those. I hear so many
different ways to cover them up. Some say mix some dynalight bondo
with acetone and use a razor blade to sqeege it inside the holes. I
just wish that carbon black was never used in the first place. More
work for us builders.
Rich

On Tue, 1 Apr 2008 23:47:30 -0700, "RST Engineering"
> wrote:

>There are hundreds of variations of carbon fiber "mixes". Some have
>absolutely no effect on internal antennas, and some that are absolutely
>wonderful Faraday shields (blocks) of radiation performance. My work with
>Rutan on Voyager pretty much proved that.
>
>HOWEVER, having said that, we proved in the Bellanca experiments that
>regular old silver UV dope on fiber has absolutely no effect on internal
>antennas. Even the FAA accepted our experiments on that.
>
>On the other hand, mixing carbon black, which is not a conductor, nor an
>insulator, but a lossy medium is in fact an antenna attenuator. For some
>manufacturer of kits to come out and say, "hey, we started putting in carbon
>black to our mix and now we've got internal antenna problems" isn't a great
>surprise.
>
>I work real cheap. I'm not a thousand dollar an hour consultant. You'da
>thought that all you who are spending tens of thousands of dollars a kit
>would have had professional antenna consulting from these yahoos who are all
>of a sudden discovering that moving this or changing that is having an
>effect on their antenna performance would come to the source for advice.
>Not a one of them, other than Bellanca and Beech. Cheap *******s.
>
>To the person that asked whether carbon black has an influence with internal
>antennas, I pose the following question:
>
>We proved at Bellanca that reflection from aluminum particle to aluminum
>particle to the outside world didn't affect transmission through "silver
>dope" UV protectant to any measurable degree. However, carbon black is not
>a reflector, but an absorber. Signals don't get reflected in carbon; they
>get converted to heat and absorbed. That ain't rocket science; that's what
>I teach to my freshman engineering students. Is that understood?
>
>You folks that are paying tens of thousands of dollars for your kits need to
>have your vendors take my freshman engineering class.
>
>Jim