Propeller Pitch Defined by Dummies

Pitch in red

No one of our staffers knows everything (none of them is a J-school grad, after all), but all of them are smart enough to know what they don't know. That's why we don't mess much here with questions about medicine, law, and high finance. None of us has ever owned a boat, either, but even total landlubbers like us could recognize that Cecelia Owens was full of hooey when she attempted to explain "How to Calculate Prop Pitch"¹ for OurPastimes.com.

All it took to realize that Owens was several fathoms out of her depth was to scan her first paragraph:

"The propeller pitch, or prop pitch, depends on the diameter and the pitch of the boat or airplane. The diameter is determined by the revolutions per minute at which the propeller will be turning and the amount of power need to turn the propeller."

That's Cecelia's copy-reword-paste version of a line in one of her references, which actually reads,

"In general, 'Diameter is determined primarily by the rpm at which the propeller will be turning and the amount of power that will be delivered to the propeller,' according to Mercury Marine's manual..."

Apparently Owens didn't understand that the original was already clumsily written, and simply describes determining the optimum diameter of a [boat's] propeller. Dumbass (ditto for the author of the reference, IYAU). Whatever the case, Owens then goes on to "explain" that,

"...pitch is the distance a propeller moves and the amount of power needed to turn the propeller..."

...which is what Cecelia decided her reference meant when he said,

"Pitch is defined as 'the distance a propeller would move in one revolution if it were moving through a soft solid, like a screw through wood.'"

Owens then goes on to provide severely botched instructions for how one measures pitch, including such winning prose as "The pitch station is the middle of the propeller or the part of the propeller that the blades are connected to..." and "Look through the protractor to see what angle the propeller's blade goes through." Let's just say that Cecelia had no idea what she was talking about, and move on from there. If you want to know how to calculate the (theoretical) pitch of a boat propeller, you can find some useful instructions here. For the pitch of an airplane propeller, ask this guy.

Whatever you do, don't try to puzzle through the rubbish that Owens threw at the page – it will only give you a headache. Of course, you can't expect a heckuva lot from a J-school graduate whose eHow.com bio reads, "She wrote for the 'Gonzaga Bulletin' and edits edits e-commerce websites such as Techwave and Bahatech." It's pretty obvious that our Dumbass of the Day does not specialize in attention to detail...

¹ The original has been deleted by Leaf Group, but can still be accessed using the Wayback machine at archive.org. Its URL was   ehow.com/how_6723984_calculate-prop-pitch.html

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