The RX8 drive shaft is perfect for our needs.
Designed to run up to 9000 RPM and sized exactly
right for the rotary torque. Since the engine is
in the extreme rear of the VTOL canard air craft for weight
and balance reasons  and the gear box is in front for prop
shaft reasons we need a drive shaft to bring the power forward.
-- 
Paul Lamar ...No rotor no motor.

If I were doing this, I would do the composite shaft in S-glass instead of
graphite.  It is just as strong as graphite but it has a lower
modulus--closer to that of the aluminum and much better damping
characteristics.  Also, glass is non-reactive with aluminum--most people
don't know this, but graphite and aluminum make a nice battery.

Steve Brazil

Good advice Steve. Most people use a layer of glass over
the carbon to act as an insulator.