Prop model and length options?

[Murray Parr]

Thanks for all the responses.

I received a bit of guidance from Sensenich too, here is the response I got from them with me telling them the static of 4900rpm.


I would do a high speed run down the runway.
Propeller should unload to about 5200 rpm during takeoff roll.
If it does that, I would expect the propeller to unload to 5600 – 5700 FLTF (full throttle level flight.

Can’t really change the pitch on a fixed pitch wood propeller.
It could be trimmed in diameter.
Each 2 inches of diameter reduction will get you another 75 rpm in static and about 125 rpm FTLF

It looks like I might be in the ball park of what Brett is seeing so I am about to rule out anything wrong with the engine, will do another leakdown test soon.

Another thing I might do in the future is put a big bore kit in the engine to get the power up to 114hp, yes I know, I am a tinkerer... and who ever said more power sucks!!!

[Skippydiesel]

Just a word on the "Digital Laser tach" -
Mine , which looks very much like the one Graeme recommended, does not work well in strong light. Pick a dull day, early/late or undercover, to do your testing.
It takes two people to do the readings - one in cockpit "driving" (must aim for nice steady engine RPM) and one operating the Laser.
I used masking tape on the cowling to mark the best location, so as to place the "machine" in close proximity to the prop.
I also had to mask my nice shiny spinner & any shiny "bits" on the prop root, as reflections seemed to interfere with the readings.