Pitch speed is easy to calculate

A prop of 10" pitch rotating at10,000 rpm has a pitch speed of 95 mph. This speed should be adjusted in direct proportion for other pitches and rpm's.

For example;  5" pitch, 10,000 rpm,  pitch speed = 47.5 mph

What is the benefit of knowing the pitch speed ?

     *  When using a conventional motor it can help in choosing the best gear ratio

     *  When using a direct-drive high-torque outrunner motor it can help in choosing the most suitable winding.

What should the pitch speed be?

As a first guess, about 30% above the required max level speed.

What are the consequences of choosing the wrong pitch speed?

If the pitch speed is unnecessarily high, the result is a loss of efficiency, and a loss of thrust at the lower end of the flying speed range.

If the pitch speed is below the ideal value then the desired max level speed will not be attained. In an extreme case the model will not be able to fly at all, even with abundant installed power.

The purpose of this note is to provoke some interest in a neglected topic. More could be written, but it would be of little value until we have better information on the flying speeds of our models.