Propellers

In the Aug 75 Article in MA by "Klinsdonk"(sp)

He stataes that Pitch is equal to 2 X radius X Tan of angle.
My question is radius to where?... the distance of station that you are measuring from to the rotational center point is what I assume ------correct or not?

The point to measure is 75% Radius from the center.
Arc Tan of blade angle= pitch/2*PI*.75 radius.
According to "Practical Application of the Blade Element Theory." by Fred Weick.
Or by a pitch gage and just measure at 75%
Andrew Raney.

Well, when you hear about people "washing out the tips" of those Bolly props, they mean there's less pitch there than elsewhere. Which means that, to be thorough, you take several readings at different points along the blade. The radius you use for a particular station is, of course, the distance between the center and that station.