We want to mount a transponder antenna in the belly of our LIV. Does the carbon fiber provide an adaquate ground plane?

I spent a lot of time agonizing about this in installing my antennas on a LIV-P.  I liked the idea of an external ground plane for all my antennas.  With the conductive paint option I was concerned about flexing, especially in the pressure vessel areas, creating micro cracks over time. 

So, FWIW, this was my solution.  I mounted a thin (.021) sheet of solid copper from McMaster-Carr (http://www.mcmaster.com/#copper-alloy-110-sheets/=90sbjr) for the ground plane on the outside of the fuselage.  I tried copper or brass screen, but that was even thicker than the sheet material.  I soldered a brass flat head screw to the copper plate and directed it into the fuselage for a ground.  When I mount the antenna I can positively ground the ground plane to the base of the externally mounted antenna through this screw.  I sanded the skin until I could see some carbon fiber showing through.  In the picture, you can see where I clecoed the plate to the external skin of the fuselage to epoxy it in place.

I then covered the plate with 1 bid of glass, exposing the copper in the center where the antenna base contacts it.

It was really fairly easy to do.  If the carbon fiber adds to the ground plane, so much the better.  With body work, I anticipate that the thickness of the copper and the 1 bid will be fairly easy to hide on the belly of the fuselage.  I'm hoping that the electrolysis between the dissimilar metals (and carbon fiber) will be slow enough that it will not be a factor in the life of the airframe.

I did a similar process for my com antennas which will be mounted externally on the belly of the fuselage.  Due to the need for a larger ground plane I used copper foil tape with conductive adhesive soldered to a solid copper mounting surface on the exterior of the fuselage.  Then I covered the foil with 1 bid glass.

Now, the testable performance...ask me in a few years.

Barry Knotts
LIV-P