ORIGINAL: Flyboy Dave
In theory the 12-8 and the 14-6 give about the same load, however the
12-8 will allow higher RPM, and more speed due to the increase in pitch.
This is theoretically incorrect, Dave.
With the prop sizes that we use,
2" of pitch are the load equivalent of
1" of diameter, so a 14x6 offers the same load as a 13x8, 12x10 and 15x4 props. The RPM will be very close with all these sizes.
A 12x8 will give about the same RPM as a 13x6.