RV-3: A Flat Antenna on a Curved Skin

One of the tricky things about the RV-3 being so small is that the top skin curvature is pretty tight. This makes it tricky when it comes to mounting an antenna like the one for the Garmin GNS 430W ? it has a fairly large (several inches across) flat bottom, and doesn?t match the curve at all. If you try to mount it flat, the four screws will deform the fuselage ? not good!

The solution I came up with was pretty simple ? I just built a shim (more like a ?shoe") out of micro and resin. I started by drilling the appropriate holes in the fuselage for the mounting screws and Coax connector. Next, we taped the fuselage with vinyl tape, and covered the bottom of the antenna the same way. Wax or mold release completed the preps, then we mixed up a squirt of resin and a bunch of micro (nice and dry), buttered the bottom of the antenna, and squished it in place using the screws to hold it in position. After it cured, I pulled it all off, removed the tape, cleaned up the fuselage, and remounted the antenna with the shim in place. A razor blade was all I needed to trim the ?flashing? off flush.







Paul

Just don't try that with a comm antenna.............

Paul, are you going to post the pictures that you took of N3NU.... the yellow and red 3?

gasman said:

Just don't try that with a comm antenna.............

Paul, are you going to post the pictures that you took of N3NU.... the yellow and red 3?

Click to expand...

You're right - Comm antenna has to be grounded - I checked with Garmin on this before making the spacer!

I have to dig through pictures before postign John's pics - have to find them all.

Paul

Very nice! I've seen this done with bigger airplanes too although we machined it out of Al plate since it had to be grounded.

Paul trying to figure out where to mount all the gps antennas on my 8 and I know you have yours mounted under the cowl on your 8 any reason you moved the antenna on the 3? I have the 430w dynon skyview and TRU TRAK ADI to mount somewhere. Was thinking about like your 8 on a shelf to firewall. I don't think they look bad mounted on fuselage what is your opinion and what would you do? I know they will either place. Nice work on the 3 looks like it will fly before my 8. My 8 puts a whole new meaning to slowbuild going on 8 years and at least 2 to go

RV8MW said:

Paul trying to figure out where to mount all the gps antennas on my 8 and I know you have yours mounted under the cowl on your 8 any reason you moved the antenna on the 3? I have the 430w dynon skyview and TRU TRAK ADI to mount somewhere. Was thinking about like your 8 on a shelf to firewall. I don't think they look bad mounted on fuselage what is your opinion and what would you do? I know they will either place. Nice work on the 3 looks like it will fly before my 8. My 8 puts a whole new meaning to slowbuild going on 8 years and at least 2 to go

Click to expand...

Hi Mike,

Well, it was pretty easy to place the antenna on the -3's fuselage underneath the canopy, right on the centerline, and since that has an overall better view of the sky then under the cowl, there was no reason not to go with it there.

The under-cowl position has worked GREAT on my -8 for years, but when I switched to the WAAS version, I have noticed that it is a little more finicky (being lower than the top of the firewall, it technically is blocked from seeing the horizon to the rear), and drops lock on the satellites more quickly than before when I do a little Acro.

Now you are unlikely to be doing ACRO during a WAAS approach, so it may make little difference, but since I had no penalty putting on the fuse with the -3 (no rear canopy track, as on the -8), I went ahead and optimized for signal strength.

Paul

Using this technique for anticollision beacons

Ironflight said:

The solution I came up with was pretty simple ? I just built a shim (more like a ?shoe") out of micro and resin. I started by drilling the appropriate holes in the fuselage for the mounting screws and Coax connector. Next, we taped the fuselage with vinyl tape, and covered the bottom of the antenna the same way. Wax or mold release completed the preps, then we mixed up a squirt of resin and a bunch of micro (nice and dry), buttered the bottom of the antenna, and squished it in place using the screws to hold it in position. After it cured, I pulled it all off, removed the tape, cleaned up the fuselage, and remounted the antenna with the shim in place. A razor blade was all I needed to trim the ?flashing? off flush.

Paul

Click to expand...

Paul,
I'm considering using this technique for my Aveo Red Baron beacons, and have some questions:

- What resin did you use?
- By "micro," are you saying micro-balloons?
- No hardener?
- How did you apply the wax?
- Where can I find mold release?
- How long did you let the butter set up before removing the antenna from the newly formed shim?

Thanks for being patient with me...this is going to really help my install.

scrollF4 said:

Paul,
I'm considering using this technique for my Aveo Red Baron beacons, and have some questions:

- What resin did you use?
- By "micro," are you saying micro-balloons?
- No hardener?
- How did you apply the wax?
- Where can I find mold release?
- How long did you let the butter set up before removing the antenna from the newly formed shim?

Thanks for being patient with me...this is going to really help my install.

Click to expand...

West Systems Resin and hardner

Micro - yes, any filler by West Systems will work

Of course hardener - choose the slow or fast, depending on your temperatures

Wax applied using a car wax pad

Let it harden completely before removing!

HTH - Paul

Many thanks, Paul

Ironflight rocks!

Another way to do this is run some black foam weatherstripping around the edge of antenna (or beacon). I mounted the GPS antenna for my GX60 on top of the RV-8 this way. I think it was 3/16 (?) thick foam, 1/4" wide but not sure. The foam compresses at the tight point of curvature.