Think about it. You have a carbon webb , all interconnected with resin running around the web. The Jel coat is an insulator, but is very thin and about as relevant as the non conducting paint on a metal aircraft.
During the construction of my MCR fus I touched a 1.5 v bulb to the skin at one end, a battery at the other and a wire to complete the circuit, it lit as it would if it had been two wires. The resistance was very low indeed at any point on the fus. This would be just as capable of forming a faraday cage as a metal structure. Carbon fibre is strands of carbon woven together and conducts just fine. Glass fibre, Dealin or Kevlar are all good insulators, (and composite materials along with carbon)
Rod1