Corsair J,

I went thru the calcs and you are right, with a span of 66" this would make the plane 1:7 scale, and a 6 pitch might be OK. But I still think that an 8 pitch would be better. And if the plane weighs in around 12 lbs it will take some power to run an 8 pitch and still get reasonable thrust.

I learned my lesson on propping bigger warbirds when I maidened my first 77" H9 Mustang (1:5.7 scale) with a 6 pitch prop. After a scary flight I went home and did the math- with the big 4-stroke turning 8900 RPM the theoretical airspeed was only 50 MPH. And since "scale" top speed for the plane was more like 75 MPH it was no wonder I had to keep the throttle wide open to feel comfortable flying it! With an 8 pitch prop it flew much better, and with a 10 pitch it flew very scale. The bigger pitch meant less thrust and so the plane was nowhere near unlimited, but the higher airspeed attainable was well worth it.

I see a lot of folks moving to larger warbirds making the same mistake that I did, hence my advice.

Of course my latest 77" Mustang is sporting a big YS and a 12 pitch prop. OK so it does not exactly fly scale without holding back on the throttle, but it sure is fun!

Walt