George,
   Please tell me if I'm wrong but I seem to remember that efficiency
   of boat
   props improved with an integral shroud i.e. the shroud is attached
   to the
   prop and turns with the prop. That to my mind indicates that the
   inefficient
   encountered because of the gap between the prop and shroud can be
   eliminated - perhaps a shroud within a shroud arrangement would be an
   improvement.

   Of course this brings up problems with centrifugal forces because of the
   weight of the rotating inside shroud. To my mind this could be
   solved with a
   bearing/ guide arrangement between the inside and outside shroud.

   I remember discussing this with Perry Mick and he was of a similar mind,
   however he couldn't at the time envisage how he could contain the
   centrifugal forces.
   It would be an interesting exercise, I wonder if NASA has looked at
   this.
   George ( down under)

   There is no free lunch. The rotating shroud has skin
   friction which would cause very high HP losses
   at near sonic speeds.

   --
   Paul Lamar ...No rotor no motor.

Group,
Using carbon uni arranged in a ring the rotating outer would be easy to
make. That wouldn't eliminate the efficiency problems Paul is mentioning
however.
Bill Jepson



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