ORIGINAL: DarZeelon
Grant,
The 12.25x3.75W prop is much heavier.
To spin it at 13K, 1.54 HP are required to overcome its high prop constant of 1.5.
To do the same with the APC 11x6, only 1.22 HP are required.
A typical sport engine would spin the 11" prop about 1,100-1,300 RPM faster.
Dar, that may be the case in theory but in many tests the guys at the field and I have run, these two props provide almost exactly the same load, typically within 100-150 rpm of each other at any given rpm point. They are to all intents and purposes the same static load and can be used pretty much interchangeably when determining performance.
For a nominal 11 x 6 rating, the APC is quite a heavy load - an engine that does 12K with the APC 11 x 6 will do 13.5K or thereabouts with an MA 11 x 6.
Edited: Grammar