Table to estimate the approximate propeller diameter Find the HP
of the engine in the X-axis, then report up this power data line
until it matches with the RPM on the propeller, (that means the
rpm of the engine divided into the gearbox ratio). At the
crossing point, go to the left axis and there you will have the
corresponding propeller diameter in mm or inches. This table is
aproximated for 3 BLADED propellers with a Radio Area = 0.5. For
4 BLADED propellers with a Ratio Area = 0.65, take the result
and decrease it in a 6%.