ADHARS and GPS Antanae Shelf

Time: 8 Hours

My last post had some fairing work and it turned out so-so, I’m not an artist by any shot and this will have a lot of work needed. 


I moved on to getting my ADAHRS mounted in the tray I made for them. I just needed to get them lined up with the axis of the airplane and attach them with non-ferous screws, I went with nylon screws and nuts with a little vibra-tite thread locker. 

I then connected the three lines between the two ADHARS. White is for static air pressure, blue is for pitot or ram air pressure and green is for AOA (angle of attack). I had already ran the Skyview network cables to the shelf area but needed to run the OAT (Outside Air Temperature) probes, one for each ADHARS. These will allow the units to give accurate readings with respect to airspeed. You need to keep the probes out of direct sunlight and away from any exhaust so I decided to put them under each wing. I placed them close to the access panels and in the same spot on both wings. 


With all the wires run I climbed into the tunnel to put the shelf back in place and make all the connections. I forgot how tight that space is and what a pain it is to work back there. So I powered up the Skyview and all worked perfect and crossed checked the two ADHARS units with no errors. I decided that I wanted to put my two GPS antanaes under the engine cowling and out of sight after talking with several builders this year at Oshkosh. I took some photos of a really nice setup and decided to replicate it. I started with a cardboard template. After I was happy with the shape and layout I transferred the dimensions to some .032 sheet and cut it out. I drilled all the holes for the mounting hardware as well as some lighting holes. I grabbed the two antanaes and mocked them up so I could drill the attach holes. I also drilled all the holes for the nutplates and dimpled them.I cleaned up all the edges and scuffed all the surfaces to be primed and painted. 


In between the priming and painting I worked on the firewall pass thru. I came up with the perfect spot on the right side of the firewall so that wires that needed to go to the engine area would run nicely.  I drilled a 3/8″ hole for a punch bolt to go through, I bought this tool just for this task. It is two peices that get pulled together and cut thru the sheet. It made a clean and perfect hole and was a lot easier than drilling the stainless steal. I used the pass thru as a guide and drilled the attach holes. After they were drilled and deburred I put the screws in and slid the fire sleeve on. I will run my wires thru this and seal it up at a later date when all the wiring is done. 

Vans had prepunched 3/4″ holes, one on each side, that I was originaly going to use but they are just to close to the edge of the firewall and I think they would be in the way of the Skybolt fasteners I’m planning on using. That was the main reason for switching to these firewall pass through from Cleaveland Tools. So what to do with the holes that Vans punched? Well after a little research I decided on using two large washers and a bolt/nut to sandwich the firewall between them. Once the paint on the GPS shelf was dry I bolted it in place. 

I’m real happy with how it turned out and have Bob M. to thank for the inspiration. One last task for the day was to clean up the wiring in the battery compartment since I’m done running grounds and wires through the firewall, at least on the right side. I have a little more work straighten out the ground wires, but I’m happy without turned out!

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