> Paul,
> I am commited to using the P port configuration  and started looking at
> specs for props.  I do not think a 74" prop will fit on a pusher even
> though I have 48" from the ground to the thrustline.  I went to your
> website where you have two P Ports with different runner lengths.  Is
> there any advantage running the 2.85 PSRU over the 2.17?  The curve on
> the higher performance runner looks flat in the range from 6500 to
> 7800.  I think I could swing a 68" prop.  Just trying to find the right
> combination.
>
> Joe Berki
> Limo EZ
>
> Yes. There definitely is a HP advantage. If you can not handle 74
> inches think
> of a wider blade or 3 bladed prop that will absorb 240 HP of lower
> diameter.
>
> Just explain things to the prop builder and he will build a prop
> for 240 HP as little as 65 inches in diameter. Could be as many
> as four blades if he does not have a wide blade version.

-- 
Paul Lamar ...No rotor no motor.


With a 2.85 psru and a "small" diameter prop, you are turning the prop
slower than if you had a 2.17, so the tip speeds would be relatively low
- good for noise reduction. To go fast with a "slow" turning prop will
require a lot of pitch, which might tend to stall more at the start of
takeoff roll. But you have lots of power so a prop can be built that
will work. What is max RPM you want to operate the engine?

Perry

Perry,
I do not want to go much beyond 7500 RPM and would go lowest at 5000
I have 48 " from the thrustline to the ground and the prop flang is 41.5" to
42" from the firewall.  Right now this is theoretical as I have not
purchased the PSRU because I am trying to decide on a ratio.  Thanks for any
input.

Joe Berki
-

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