GHA 15 Antenna Doubler (Tunnel Mount)
I will be installing a Garmin GHA15 Height Advisor, and based on recommendations in the installation instructions and seeing what other builders have done for their RV-10's, I am planning to install the antenna under the tunnel (below the fuel selector).
After determining a suitable location, I 3-D printed a drill template for the doubler plate that I will need to fabricate. The antenna mounting holes were located per the measurements given in the G3X Installation manual, and I then marked additional locations for nutplate attach holes and rivet holes to attach the doubler to the bottom skin
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| 3-D printed doubler laid in place to verify that everything fit within the tunnel as expected |
Next I took a piece of 1/16" aluminum and cut it to the same size as the doubler template using the bandsaw. After deburring all edges, I used the template to mark the center 1.25" hole and used a hole saw in the drill press to cut it out.
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| Drilling the center hole in the GHA15 antenna doubler |
I then driiled the 4 antenna screw attach holes to #10 and the associated nutplate attach holes and rivet holes to #40.
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| Using the template to drill holes into the doubler and clecoing as I go |
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| With all holes drilled and deburred, I put the antenna in place to verify the holes were correctly located, and everything lined up perfectly |
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| Nutplate attach holes were then countersunk |
To prepare the skin for doubler attachment, and for a good electrical bond, I decided to remove primer from the skin that would lay underneath the doubler.
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| Doubler location taped off on bottom skin. A rag dipped in acetone was used to carefully remove primer |
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| Primer in the doubler location removed without affecting any of the surrounding area |
I also decided to alodine the doubler for corrosion resistance. The process for alodinig was the same as that used to alodine the COMM antenna doublers previously.
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| GHA15 antenna doubler alodined and laid in place on the bottom skin |
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| Doubler is nicely centered in the tunnel |
After attaching nutplates to the doubler and test fitting the antenna with the installation screws, I was not happy with the final fit as it appeared that one of the nutplates was slightly off casuing the screw to tighten at a slight angle.
I decided to remove the nutplates and switch to using regular lock nuts. Rather than fabricating another doubler without the nutplate attach holes, I instead filled the nutplate attach holes with rivets and proceeded with the doubler installation by match drilling the screw and rivet holes into the bottom skin.
I then marked the location of the center hole on the bottom skin, removed the template, and drilled a pilot hole to 3/4" using the step drill so that i could use a punch to knock out the hole to the correct size.
Next I dimpled the doubler rivet holes using the DRDT-2, and back riveted the doubler in place
While looking ahead in the plans at the Control System in section 39, I realized that the W-1010 control column has an arm that swings right over where the antenna comes into the tunnel. To check for potential interference, I temporarily attached the antenna with all associated fittings, and rigged that portion of the control system together.
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| Match dilling #40 rivet holes into the bottom skin |
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| Match drilling the #10 screw holes into the bottom skin |
I then marked the location of the center hole on the bottom skin, removed the template, and drilled a pilot hole to 3/4" using the step drill so that i could use a punch to knock out the hole to the correct size.
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| Pilot hole drilled with a step drill. It was slightly off center but perfectly fine to locate the punch at the correct position |
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| Using a knockout punch to punch out the center hole. Instead of purchasing a 1-1/2" punch, I used a 1-1/8" punch that I already had for the skin hole. This turned out to be a perfect size to fit the center antenna post while limiting the amount of skin removed |
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| Doubler once again laid in place to verify hole locations |
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| Test fitting the antenna under the doubler once again verified that all holes were perfectly located |
Next I dimpled the doubler rivet holes using the DRDT-2, and back riveted the doubler in place
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| Doubler rivet holes dimpled |
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| Doubler riveted in place |
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| View of doubler from tunnel access panel. This will provide easy access in case of maintenance needs |
While looking ahead in the plans at the Control System in section 39, I realized that the W-1010 control column has an arm that swings right over where the antenna comes into the tunnel. To check for potential interference, I temporarily attached the antenna with all associated fittings, and rigged that portion of the control system together.
With a few test swings, of the control column, it appears to just clear the antenna fitting as seen below, so I don't think there will be an issue. In hindsight I probably should have located the antenna about 1/2" further forward, but I think I will be fine with where it is. In any case, I could get a lower profile amphenol cable fitting if clearance does become an issue because I certainly want to make sure that there will be absolutely no potential for interference with control movement when everything is final assembled.
For now, we build on!
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| Coltrol column passes about 1/4"from the top of the strain relief screw on the amphenol antenna fitting |
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| Antenna is directly under the control column at its farthest forward swing |
Time Taken: 5.9 hours
Dates: June 8 2025 - June 15 2025
Fwd Fuse Ribs, Bhds & Bottom Skin Total Time: 41.7 hours
RV-10 Build Total Time: 1061.7 hours
Priming Total Time: 133.5 hours (not included in build time totals)