Layman's prop pitch measurement

[stefan_r]

Layman\'s prop pitch measurement

Having some problems with my props/top speed/high consumption etc and have been told by a prop manufacturer that they should have 30" pitch.

All very useful...but before taking the props to him I would like to see if they are 30" pitch.

How can I measure this locally with basic tools?

I do have access to a lathe if that will help...

 

[pampas]

Re: Layman\'s prop pitch measurement

Model boat people lay the boss on a flat surface,measure and mark equally each blade approximately 7/10 tenths of the diameter from centre and measure the angle of the blade to the flat surface with a ruler against a protractor the pitch can be roughly calculated by this formula

Pitch=2 pye R Tan of the angle x AB where A and B equal the vertical heights from the edge of the blades to the flat surfacealond the 7/10ths line. Hope that this makes sense. most props have the info you require stamped one one of the boss faces, if it is and is not very readable, with white paint fill in and rub down with very fine wet & dry,then you may be able to read off the pich more clearly

 

[MapisM]

Re: Layman\'s prop pitch measurement

30" pitch props? /forums/images/graemlins/shocked.gif
Don't even bother checking your current ones - they aren't 30" pitch for sure.
You'd better look for a more reliable opinion instead.

 

[stefan_r]

Re: Layman\'s prop pitch measurement

erm, okay, 26" diameter X 30 something - and it is the "30" i am trying to work out.

boat is a 46 foot flybridge cruiser...

 

[MapisM]

Re: Layman\'s prop pitch measurement

Well, diameter and pitch are indeed the main characteristics of a prop.
And they're both typically measured in inches.
My comment on the 30" pitch was not because it didn't make sense, but because such high pitch is normally used for surface propellers on extremely high speed boat (80+ knots, just to give you the idea).
That's why I safely guessed that whoever gave you such recommendation was talking boIIox....

 

[stefan_r]

Re: Layman\'s prop pitch measurement

ahhhh. I may have got it wrong my end. the have said 26" and '30' but not qualified whether the 30 is inches CM or what.

Either way I still want to know what I have got on currently because if they offer me the same again that is the "wrong answer"!!

 

[stefan_r]

Re: Layman\'s prop pitch measurement

Have looked at the props (as supplied on the boat) and they are stamped 660 and 900.

The 660 would equate to 26" diameter (which they are)....so guessing the 900 is 900mm for the pitch???????!!!!!!!

You can see why I want to do my own analysis before spending cash on a change-over!