Antennas

Installations of the antennas was bumped to the top of my punch list after I was told that I shouldn't power up the avionics without them. I was going to push this off until I had the wings on and what not but instead I decided to go ahead and do it.  This will allow me to test out things in my driveway, so maybe it's best that way.

I'm not sure I realized just how many antennas I was going to need to mount all over the plane.  It's very much dependent on what you're throwing in there and since I'm doing a full glass panel with several redundant components I knew I was going to need to do some placement planning. For my set up I needed the following antennas; 2 for radios, 1 for ADSB, 3 GPS pucks, NAV, a magnetometer and then of course on for the ELT.  That's 9 antennas that I had to figure out where and how to mount.  There's certain spacing and installation parameters you need to consider.  I originally wanted to shove most everything in the tail minus the NAV antenna that's out in the right wingtip. I have to wait until the wings are on to install the NAV and I'm still debating on how and where to install the ELT antenna, so I'll do those later.

Doublers

Obviously when you install antennas you end up cutting up to 3/4 inch holes into the airplane skins.  Doublers are typically suggested but not required.  My 172 had GPS pucks with no doublers and never had an issue.  But since I tend to overbuild so I wanted to go ahead with doublers for all antennas.  Making them wasn't an issue, for the GPS pucks I actually had a factory made one that I was able to replicate, and then using some ideas online make them for the rest.

Attaching them is a different story.  I've seen some elaborate rivet patterns which frankly look like drilling, dimpling and two person rivet driving.  I read that the rivets actually help with the strength, but that guy was using metal the same thickness of the skins (thin).  I decided to go thicker metal and use 3M aviation two part epoxy to secure in place. I also went ahead and primed the exposed side.  In the end these things aren't going anywhere, the skin is thicker and it adds to the rigidity.

Here's a picture showing my GPS puck doublers.  The one on the left is from Garmin, the other two I made.

Comm antennas

Not surprisingly there are a number of strong options on how and where to place your comm antennas.  The two schools of thought is you should put one on top of your tailcone and the other on the bottom.  This would prevent any shadowing or possibility of dropped comms.  Then you have the other group that prefers to mount both antennas on the bottom, either the front or read seats.  The idea is shorter runs, a bit out of the way and suitable.  I've read plenty from both sides and my conclusion is people have been successful installing either way so I needed to pick what will work best for me.  My tailcone is pretty cramped so I decided under the back seats was the way to go.

First I needed some way to access these.  I had seen people use the Vans wing access panels but those are pretty big.  All I needed was enough space to get my hand in to do the initial installation and any future maintenance.  Luckily I have baby hands so it will fit between the ribs fairly easy.  However you don't want a gaping hole beneath your seats and still need a way to cover it.  I just went head and essentially made a door on some hinges.

For this doubler I didn't want it over the rib piece.  So decided to go ahead and epoxy the piece in there first and then drill the mounting holes.  This saved me the trouble of trying to match holes, just slap it on and let it cure.

Once it was cured I drilled out the holes based on the gasket I received and used drawn lines to center.  Then it's just a matter of bolting on the CI 122 VHF comm antennas, one each side.  Two person job to tighten and to torque I had to do about 8 inches of extensions to reach the nuts.

ADSB

Hmm, I didn't take any pictures but I went with the CI-105 and I mounted it under the copilot seat, basically centered and making sure it's not hitting any brake or fuel lines.  I also made a doubler specific for this antenna.

GPS

I have two GA 56's for the G3X and G5 and a much larger GA 35 for the GTN 650.  Using the doublers pictured above I installed one behind the firewall but in front of the windscreen.  For that one I used the stock Garmin backing plate and didn't epoxy.  Mainly out of laziness, I didn't want to try to mess with that stuff crawled under the panel.  Interesting note I used a antenna I got off Ebay for my 172 that I never ended up using.  It's dirty looking but only cost maybe $40.

The last two I installed behind the cabin on the top of the tailcone.  I had to wait to talk to Bill at Airflow Systems to ensure this position wasn't going to interfere with the AC system I haven't fully installed yet.   It was easy to work with since the top skin isn't riveted down, just had to mark it and then match drill the holes, epoxy up and after cured clean the holes and bolt them on.

Magnetometer

I can't even pronounce what this is.  It's basically an electronic compass that needs to be clear of all sorts of things while limiting what's called the CAN bus down to 40 feet.  Stein did the harness and really the only place to put this is in the tailcone.  Also it needs to be level, within a few degrees of the plane heading and away from all sorts of things.  I saw all sorts of elaborate things hanging off the top of the tailcone but given that would be fairly close to my AC and lots of spinning metal I decided to make some type of shelve to span across the longerons.  That would ensure it's level in flight and hopefully give enough space to not run into interference.   I haven't tested this so the jury is still out.

What I did was make a tiny shelve across two aluminium angles to mount behind between the 2nd and 3rd compartments in the tail.  I do this I had to make part of it removable that I can rivet post testing.  I'll also epoxy it down to the longerons vs drilling holes to hold it in place.  Again going to do this after all the testing is done.

Short post for the amount of work that went into all this.  When it cools off a bit I'm going to go ahead and pull the plane to the driveway and start doing some testing and calibration... actually I'll probably get impatient and start messing with it.