Bill Freeman wrote:

Paul,

I must strenuously object!   This is what has been claimed
was the problem with Mr. Parkman's prop!   You do NOT
want to see max or even very near max RPM at static
conditions with a fixed pitch prop.

With a fixed pitch prop, you pitch it so it is efficient at
cruise or climb speed, both much higher than either static
(zero) or early in the takeoff roll.   As you accelerate the
prop will be more effective and TO RPM will be higher
than static, increasing the HP available and the thrust.

Bill

I am not so sure a ducted fan works exactly like a prop
Bill. Perry's RPM does not pick up that much
RPM between static and 90 mph taxi speed as I recall.

What does happen Perry? What is max RPM static and
what is the RPM at 90 MPH?

If the duct/fan was even smaller I suspect the RPM would
pick up even less. In other words it would be near constant
RPM. I could be wrong.

In any event it is still bogged way down at 90 MPH
at only 3700 RPM or so as I recall.

Also the rotary is unlike a piston engine and power continues
to increase beyond 6500 RPM because it breathes so much better.

Another factor could be the 15% or so Clark Y airfoil blades 
tip tops may be going transonic and running into a drag brick 
wall at only 3700 RPM. Perry has a strongly converging 
inlet duct on there.

It is not going to climb well at 70-90 HP and 3700 RPM
at 90 MPH the way it is.

Paul Lamar

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