One other thing on prop pitch, and let my qualify this by saying that I am in no way a prop expert but I am relaying the knowledge I learned from Ed Sterba over many conversations.
Increasing prop pitch does not necessarily increase speed. Many times, including the prop change I did on my KR and the recent repitch I did on the M1, less pitch increases speed. The speed you get is proportional to the power that you extract from your engine. The power you get from your engine is directly related to the RPM it turns. I can't remember the exact number that Ed told me, but for my O-200 it was something like an additional 10 horsepower with a 300 RPM increase. Someone out there has he exact formulas and will likely chime in. This is why a 150 pokes along at 2,900 max RPM, I blast along at 3,200 RPM, and the O-200 racers are turning up to 4,200 RPM. Increasing pitch will increase your speed if you turn the prop at the same RPM, but if you just increase the pitch you will not be able to turn it at the same RPM. If you are turning your prop near red line or above you will want to increase the pitch, if you are turning it far below red line you need to decrease the pitch or the diameter and get the RPM up. On my KR I decreased the pitch and increased the diameter two inches to raise the RPM 200 RPM. That increased my rate of climb by 200 FPM and my speed by 4 MPH. On the Mustang I had Sterba rework the prop from a 62 X 68 to a 60 X 64. That increased my rate of climb from 850 FPM to nearly 1,500 and increased my cruise speed by 4 MPH. There are some good formulas at http://www.greatplainsas.com/edrules.html. For even more great information call Ed Sterba. He is a wealth of knowledge. Obviously, there are many factors involved and there is no cut and dry answer for every situation. Just like more pitch does not necessarily mean more power, less pitch does not necessarily mean more power every time either. Brian Kraut Engineering Alternatives, Inc. www.engalt.com
