Originally Posted by maxadventure
I'm not sure the relevance here, unless you are suggesting I run only a scale diameter propeller. Thank you for all the engine comparisons I have been curious about some of the .80/.82, however - I was specifically asking about running a smaller than optimum prop, and I didn't need any engine suggestions, I have that covered. - sorry for the confusion.
My mistake, I thought that you had posted that you were thinking of changing engines.
As far as the "scale" prop. I just used that as perhaps being the largest diameter prop due to it being a Cub & a "scale" diameter prop is pretty close to maximum diameter as far as prop clearance during take-off & landing.
Generally speaking, for the airframe & what you seem to be trying to achieve, run the largest diameter prop you can while pitching it for the maximum amount of thrust as long as desired flight speed envelope is not compromised .
Try this thrust calculator. It has come very very close to factory HP spec's on several Saito engines i own, from an FA91S, an FA150, 2 idfferent FA180s.
Do a run-up on your present prop & observe HP. Then, adjust prop sizes/pitches via RPM to get the same HP output. Then you can compare thrust & flight speed.
As long as your Cub will buzz around @ a sufficiernt airspeed to suit you, prop it for the most thrust.
Your base line HP might not be 100% accurate & it need not be, It will give you a comparative power/thrust/airspeed factor to calculate from.