Hi, Doug!
My three-blade was made by Craig Catto; it is fibreglass over a wood
core. As far as efficiency vs Hartzell is concerned, I would guess that
my prop is anywhere from 3% to 9% more efficient in cruise, depending on
the model of Hartzell. That would give 1% to 3% more cruise speed on the
same power. Of course, if we're talking about mine in a CS model, I
would guess it will be as good if not better in takeoff and climb. It is
very important to have the root section of a CS fitted with a glove or
fairing so as not to have a high drag, circular form, projecting into
the free-stream! This also keeps the root section from appearing as
another tip with attendent drop of differential pressure and lift.


Paul Lipps

Thanks Paul,

From the way you describe it this glove or fairing would be an optimum

airfoil shape and be attached to the spinner so as to  allow the tubular C/S
prop root section to rotate within it.  Depending on the cowl shape I would
think a large spinner like the Nemesis racer would serve the same function.
I say this because I have not designed the cowl yet and realize that the
prop cowl and resulting airflow need to be considered together for best
performance.

I am waiting on data from SeaWind now on the flat plate drag and wetted
surface area.


Regards


Doug Fir




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