ORIGINAL: devens
OK guys report from this morning. to recap: stock ARF, sig tail wheel, 2 elevator servos, pilot
, battery on back of motor mount, OS .91FX 2 stroke, slimline pitts muffler, stock spinner, no lead!
7lb 9 oz
CG at -5 inches from leading edge of top wing
15/8 prop; clearence ok but cut grass, could barely idol low enough to keep plane from moving on ground, flew well with great verticle, little fast at back throttle sweet spot.
14/6 prop; did not cut grass too much, idled well without pulling plane, flew well great verticle but seemed little less than 15/8, still fast at full throttle but slows nicley at the back throttle sweat spot, more scale speed seemed like to me.
I will try 13/8 in the morning. This prop is supposed to maximise horse power of the motor and run at the highest rpm of recommended props 11,500. 2000 rpm over the 15/8
the rated rpm of my motor is like 15000 rpm and no recommended props over 11500rpm whats the true horse power....who knows
The OS Max representative suggests propping the 91FX to run at about 9,000 on the ground. We've got a number of them running at the field that like the 15x6 and the 14x8 best.
A couple of us did a prop testing session just yesterday. Swapped through a handful of props, one right after the other. Flew the test mule with one, swapped it out, cranked, set needle, flew the next one. Consensus on the test mule was that the Master Airscrew K 14x8 did the best in the 14"ers. And all the 15x6s seemed about equal. 16x6 was too much fan. and anything over the 15x6 was too much load on the engine.