Hello all,
I'm building my new pattern plane, it will be equipped with a new OS 140RX. I'm thinking about propellers: I see most people suggest APC 17x12 (N? why?), while others love 15.5x12 4 blades for its breaking effect. Actually, I'm very interested in breaking on downlines, since my plane is a bit old, not like those new planes with thick airfoils and fuselages...

So the 15.5x12 is the best choice? What do you use and what amount of nitro? It is ok this 4 blade with 10% nitro? Its is not too much for that engine? And the 17x12?

Thank you all for the replies.