3 Or 4 Blade Propeller?

i have questions : What is the diffrent between 3 or 4 bladed propeller?
And i need propellers.Where can i get propellers ,but cheap ones.Can anyone help me about this?Thanks in advance..

 

Try with "www.erispropellers.com".
Your question is too vague....sorry.

RANCHI OTTO

 

Aside from the obvious... one having three blades and the other four... there tends to be a preference towards an odd number of blades to reduce vibration. Props operate in a wake field behind the boat... at the top the blades are loaded the least, and at the bottom the most... It's best to not have a blade at the top and bottom at the same time... More blades tend to make props more expensive, but they might be more efficient as blades have higher aspect ratios while the prop has the same amount of area, and therefore blade loading...

Cheers,

Dave

 

There are a lot of screw shape, from the traditional Wageningen B Series to the high skewed at the top of the blade.
It depends what it is the meaning of "better", only efficiency, vibration, cost, or what else...
Propeller for which speed?
Only for this reason I've sad that the question was to vague.
Ask someone if it is better to by a sport car or a van.....
It depends because if you have 1 wife and 5 children.....

thanks

RANCHI Otto

 

I never get it right. I have 1 child and 5 mistresses.

 

1 child...but who is the mother?

You have 9 months to give the answer..

RANCHI Otto

 

Thanks

Thanks DaveB !

 

The FEWEST number of blades will give the most efficent propulsion

IF,,, the blade area is sufficent , and the resulting diameter is not too large for the boat.

A 2 blade will use less fuel and give the same thrust as a 3,4 or 5 blade , as the induced drag is least from the fewest number of blades.

There was an early aircraft that had a single blade prop (with proper counterweight) but the "look" wasn't right so it was given up , efficent or not.

Small blade number requires LARGE diameters , better suited for the displacement boats.

FAST FRED

 

Thank you for your suggestion Eris Propellers RANCHI OTTO.

Here is main informings for ''LIFETIME''
a) 3-blade propeller should always be more efficient than a 4-blade
b) 3-blade vibrate more than a 4 blade cause vibration is generally more
noticeable in a propeller with fewer blades.
c) 3-blade propeller on top-end gains achieve, performance expectations on the low-end diminish.
d) There is a loss of blade area in the transition from four blades to three.
e) Some of our 3-blade models has been expanded to equal that of the 4-blade.So that you can get nearly the efficiency of 4 blade .

 

You can also read something from our Technology Exchange about this topic. Look for the July 2003 issue.

Don MacPherson