This is the install of the Garmin GMU11 Magnetometer. The unit need to be installed within 0.5 degrees of a cardinal point, within 3 degrees attitude of the plane in cruise, right side up and I would presume somewhere near level.

First up was finding  a line parallel to the aircraft center line. This involved the usual lasers, large set squares and plumb bobs.  Not to mention putting tape on the floor and drawing lots of lines.

The angle of the ruler above is in fact parallel to the center of the plane. A really smart person would have made the pocket opening in this orientation. A person with great vision would have foreseen the issues and the need to make the pocket wider and deeper too.. That’s not the guy building this aircraft.

With the requirement for no ferrous metals  I was working with brass screws, aluminium plate, extrusions and rivnuts. The problems of space, fitting it in and leaving screw clearances was significant,

While coming up with the above idea I did work on the bolt covers. I needed 4 covers for wings, upper and lower and two round covers for the spar bolt access. I found some sheeting, made a lip with a router and fitted all the bits. Just a side job while all this was happening. You can see the round hole cover beginning above.

OK so after more than 4 days work I got to the above configuration, put it in the cavity and had to call it. Epic fail. I got the orientation right but could not get within the needed 3 degrees of the cruise angle. That’s about 2 degrees nose up.

The next configuration was quite easy. I used some 3mm 6061T6 and riveted it to my plate after removing the other attempt. I have no idea why I didn’t see this working earlier. All the fiddling around had me better understand the clearance issues.

All done and I’m happy. On the left side in the pic you might see some aluminium washers. These allow me to angle the magnetometer up or down for my 3 degrees. If it needs a tweak I can add or remove washers. With the flat plate I now have room for this. The orientation to the center-line is correct. The unit is removable but it takes a little patience. We just need to wire it up.