Originally Posted by NinerBikes
How many Hobbs hours now on your commuter? We don't know what prop you may have started out with? You're adding what, 3 to 7 hours per week, commuting?
You're running a ULPower 120 hp 350 iS of some sort?
Will different rpm's of a gearboxed 912 uls with less HP have huge effect on size of prop you run, in your opinion?
Do share your performance figures, so that others considering powerplants for RV-12's can make an informed decision.
The WhirlWind GA-350UL-2B is the prop I started with, and yes, about 5 hours a week commuting. For the prop size, the diameter is 70", so similar to the one Van's provides with the kit, but has a pretty large chord line.
I have a UL350iS engine, which is a nice EFII engine; it's rated for 130 hp at 3300 rpm, but I don't normally go above 2800, which is the maximum continuous rpm. I don't see a lot value in running an extra 500 rpm to get 7 hp.
For performance, my climb rate, at GW, I climb out at 1400 fpm at Vy and 900 fpm at 90KT and I economy cruise at 120Kt no problem.
What moves the prop is torque, so comparing shaft torque, the Rotax is 228 ft-lbs at 2100 rpm and the UL is 236 ft-lbs at 2400 - maybe it would work - I don't know, but WW has a prop designed for the 912 and that's probably a better choice.