Propellor shape

[PaulJ]

Some propellors have blades which are more or less round whilst others, known as "Equipoise", have a curved leading edge and a more or less straight trailing edge...... Can anybody please throw any light on the relative pros and cons of the different shapes of blade?

 

[oldsaltoz]

G'day Paul,

I pulled this off the site listed below, it has lots of other interesting information also, well worth a visit...

Q. Do I use the same size wheel (Prop) if I convert to a cupped edge propeller?

A. No. Diameter remains the same, but additional load placed on the engine by the "cupped edge" requires that pitch be reduced 1", or 2" in propellers above 14" diameter.



Q. What benefits does a cupped-edge wheel (Prop) offer?

A. Cupped-edge props for fast boats and high rpm reduce slip, giving as much as 3 mph more speed on the average, and eliminate cavitation.



<A target="_blank" HREF=http://www.deltaprop.com/linksi.htm>http://www.deltaprop.com/linksi.htm</A>



I Hope this helps.



Avagoodweekend Old Salt Oz /forums/images/icons/cool.gif

 

[dignity]

The equipoise prop has a 15% larger blade area than standard props, allowing you to use a smaller prop when space is a premium, also they more expensive, I've just built my own boat, building it was easy, choosing the right prop well that's a different story!

 

[PaulJ]

Thank you gentlemen for your replies. As you say Old Salt, a good site with lots of info and Dignity you have specifically answered what I wanted to know - I have found a Prop for my boat which is about the right size but it is an Equipoise, which I have not used before. Since it runs in an aperture in which clearance is limited and I cannot quite run the calculated ideal diameter, it seems the Equipoise might be just what I am looking for.