Pick your desired pitch and rpm and figure it out
Pitch x rpm x 0.0009 = miles per hour with no slip. Using my known numbers, 0.90 is a good efficiency number; 10% slip.
58 inch X 2700 rpm X .0009 = 140.9 x .90 = 127 mph which is what I would see down low.
Just adjust the pitch and rpm for what you want to do.
Theoretically at 2500 rpm, 58” prop the math shows I should true out 117 miles an hour.
That is exactly what I see.
If anyone wants to see where I got the .0009 I will be happy show you the computation.
inches x rev per min x 60 min per hour divided by (5280 ft per mile x 12 inches per ft.). The units then cancel to miles per hour. Hope you enjoy this as much as I did deriving it.
By the way 61 inch pitch would give you 133.4 with the same conditions. An increase of 6.4 miles per hour. My prop is new. That variable 0.90 will change slightly with prop condition. Bear in mind this is theoretical. Your mileage my vary.
I have doubts about many mph claims. I was getting 135 mph with a 54” prop until I redid my static system and calibrated it with a four course gps flight and some fancy math that camtom12 understands.