How about a short paper on Pitch effect on prop efficiency?

I dug out an engine test that included test results for 9 different props. And I had just found that the June issue of Model Aviation magazine has an excellent article about propellers and describes a proven prop thrust formula, and includes a speed estimation nomograph that has been accepted and proven for years. I pulled out three props from that old engine test and use them here in my "paper". I used the formula from the MA article and the old nomograph also.

prop___ MPH___thrust__ rpm
14x10___95___ 183___ 8,350
15x8____75___ 162___ 8,150
16x6____57___ 142___ 8,300

The three props were chosen because they show a progression of pitch and have basically identical rpm. The close rpm suggests that the engine was producing basically the same power and probably using fuel at close to the same rate. So if the engine is producing the same power, we can compare the speeds that would result and the thrust generated as an indication of the efficiency of the pitches.

The 10" pitch produced the highest thrust and that results in the highest estimated speed. I believe that the speed nomograph is empirical.
The 8" pitch was proportionally slower and less thrust was produced. The speed is actually almost exactly 80% which is the difference in pitch reduction, 80%.
The 6" pitch is 75% of an 8" pitch, and the speed is almost exactly 75% of the 8" pitch speed.

The comparison shows when an engine is run at a specific power, the higher pitch props provide more thrust and that gives higher speed. The higher the pitch, the higher the output. i.e. the higher the efficiency.