Originally Posted by
harriermate
Hi Guys,
Im resurrecting the build of my Flair Stearman which has been resting in the attic for 'a few' years now but nearly complete. I am toying with the idea of powering it with a UMS 90cc 7 cylinder radial (would have loved a robart radial when they were available!). As the aircraft should fly happily on a single cylinder Saito 180 (which I have already), Im concerned that I might be putting too much power and weight up front for the sake of mounting a scale diameter (9.75 inches) radial.
Any thoughts and advice gratefully received.
Harriermate
As anyone who has dreamed and schemed about putting a "scale" radial on the nose of his RC project has learned, our model radials do not have a linear relationship with their full scale counterparts in regards to size and weight.
While you may find a way to balance your Stearman with the 6.1 pound UMS 90cc radial on the nose, you may also find that flight performance suffers from this grossly imbalanced situation.
My suggestion? Go for the 50cc 7 cylinder. Yes, it is smaller and does not present as a SCALE sized radial, but the power and weight will be ideal and the WOW factor will still be there.
I am guessing with the 90cc 7, IF you could get it to balance, you would rarely go beyond 1/3 throttle.
The 50cc 7 would provide a very good margin of power, but wouldn't create MAJOR balance problems, like the 90cc.
My $0.02