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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.......... |
#2
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Metallic paint's effects on internal antennas
"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? |
#3
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Metallic paint's effects on internal 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? |
#4
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Metallic paint's effects on internal 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 |
#5
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Metallic paint's effects on internal antennas
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 |
#6
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Metallic paint's effects on internal 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.......... 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. |
#7
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Metallic paint's effects on internal antennas
"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 |
#8
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Metallic paint's effects on internal antennas
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 |
#9
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Metallic paint's effects on internal antennas
"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 .. |
#10
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Metallic paint's effects on internal antennas
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 . |
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