Dr. Ewen Thompson, formerly of the University of Florida Lightning Center has opinions about carbon masts. In his experience seeing them after lightning strikes is that they are NOT good conductors.
I have to concur. Of course carbon will conduct if the electrical pressure (voltage) is high enough. Most auto spark plug wires use fiberglass cords dipped in carbon dust for the conductor. As long as there are multi tens of thousands of volts, you get current flow. OTOH lightning has lots of voltage and current so instantly heats up carbon/epoxy to destruction.
I work in aerospace and have repaired/refinished quite a few carbon fiber aircraft parts. I noticed that they always have so-called 'diverter' strips built in, just like fiberglass parts on airplanes. In this pic, the diverter strips can be seen as radial lines on the fiberglass nose radome:
http://www.airliners.net/open.file/843505/M/ These are thin strips of copper bonded at or just below the surface at intervals along the surface. They are there to conduct lightning strikes back to metal structure. With airplanes, lightning strikes are not a remote possibility but inevitable. Sometimes an aircraft can be struck seveal times during one flight.
If carbon conducted OK, they would not bother to use the diverters on carbon fiber parts. So it's not a conductor like a metal. Certainly not near as good a conductor as aluminum.
Jimbo
