Originally Posted by
gregoryshock
I can tell you guys that a .75 OS AX won't fly my 10 lb Corsair 60. I tried it yesterday, the plane got about 4 or 5 feet off the ground and wouldn't climb any higher.
I would say too much prop. If the engine were propped correctly, it would fly fine.
This was a response to an earlier post to a question the OP made... concerning just this issue...
To get optimum power out of your O.S. Max .75AX engine, you'll need to run it near 12,000 RPM or a little more. You have too much propeller on it. The RPM range O.S. states are the limits to RPM that they have gotten during testing. With some propeller, they could idle as low as 2,000 RPM, and with a different propeller could get it up to 16,000 RPM before they decided that more will cause the engine to come apart. Don't expect that RPM range to happen with one propeller. Won't happen.
We'd like to run the engine with a two-blade prop to get good power and efficiency, so a 12 x 8, 13 x 6 or 7 or so. Get the engine between 11,000 and 12,000 RPM for max power with whatever propeller will fly the airplane. Perhaps even running between 10,000 and 11,000 RPM will give you good flight performance. Going below 10,000 RPM will most certainly put you well down on the power curve.
"Scale" propellers are good for display, but almost never good for actual flight. They will be too large for the engine to turn properly.
I'm curious what size prop gregory shock was using.... honestly now.