Jet turbine engines

Indeed, Unlimited Hydros have been dominated by GT [Moderator: I think he 
means turboshaft - T55s to be exact] engines for years. This past season 
was unique in that a piston-engined boat won several races, I think the 
first races won by piston power in several decades.

In both cases shaft drives a prop. I won't call it a conventional prop,
since these are pretty high tech props- I think they may be
super-cavitating.

Of course, this brings up the problem of what is the difference between
a prop and an axial compressor or fan.  To me the term 'unducted fan' is
an oxymoron :-)  I guess it is a moot point, since the engine/propulsion
system did not succeed in market place.  How many blades can a propeller
have before one calls it an unducted fan?

If you put a two-bladed prop in a shroud or a duct, does that now make
it a fan or axial compressor rather than a prop?

Seems to me that a prop accelerates air itself, while in earlier engine
technology a ducted axial flow compressor actually slowed down air, then
the duct accelerated it in a nozzle.  So a velocity profile through the
ductwork would be the key to the definition, in my mind.  And no way an
unducted fan is a compressor or fan, it is a PROP! 

Mike Miller wrote:

--
Don Stauffer in Minnesota
[EMAIL PROTECTED]
webpage- http://www.usfamily.net/web/stauffer