Scott's RV-14 Build

Pitot Tube Mast

Most of the wing wiring has been installed. I'm waiting on some items to install AOA and pitot air lines and pitot heat wiring. Meantime, I'm starting the pitot tube mast installation. Since this is a deviation from the plans, I'm on my own here. Fortunately, it's a pretty common modification so there's plenty of info online. I'm using a Dynon mast and a Garmin GAP26 nonregulated heated pitot tube. I really wanted a predrilled Gretz mount but since they're no longer available I went with the Dynon. The mast needed a little massaging with my rotary tool to fit properly. Then I chamfered the edge to fit better against the pitot tube lip. Now the problem was how do I drill the mast mounting holes for the pilot tube's threaded holes? There was some head scratching as I pondered that. It was made more difficult due to the curved nature of the mast and .050 thickness of the material so making a template didn't seem feasible. The mast is a $94 part so I really wanted to get it right the first time. In the end I measured very carefully, marked the holes with a punch and started out drilling very small #45 holes. Then incrementally increased the hole size to #27 massaging the location slightly as needed by tilting the drill. I was rewarded with all 4 holes lining up for the #6 screws needed. I'll use 4 short stainless domed screws for final installation. Some guys countersink the screw heads but given that its a curved surface I'm not convinced that's the best way.

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