ORIGINAL: LNEWQBAN
The right combination of engine, prop diameter and pitch will provide the max thrust force, which is seldom found at hyper-rpm's.
It has been said that the max thrust is found at a range of rpm's at which any engine can develop max torque.
That range of rpm's is always below the max rpm that the manufacturer recommends as ''safe'' for the engine.
In practical terms: select the max prop diameter that your airframe (ground clearance) can take, and increase prop pitch until the engine is loaded to rev's in the range of max torque.
That just doesn't sound right to me...
Max thrust is obtained at maximum engine
power not torque
"Ground clearence" has nothing to do with the prop selection for maximum speed. [X(]
You'll need the smallest diameter that will still pull your airframe so that you can have a high pitch...