props and windmills

[redneck joe]

why are windmills 3 blades and props have an option for four blades?

 

[Frank Acampora]

So people like you can ask why! That's why.

If you are talking about electric generating windmills remember that although the blades are lightweight carbon fiber, a 40 foot blade still has significant weight to it. You get a significant increase in rotational energy with the addition of only one more blade.

Just like helicopters have 2, 3, 4, 6, and more blades, It is all in the mind of the designer and he/she has a reason to which we are not privy.

 

[GA_Boater]

I don't know.

 

[steelespike]

marine props are available in 2,3,4 and 5 blades each has its own characteristics.

 

[redneck joe]

marine props are available in 2,3,4 and 5 blades each has its own characteristics.

ok what are they as compared to what one is after on a windmill?


Drove from Bakersfield to Lancaster CA yesterday and hit a windfarm of a few thousand of various sizes and location (top of hill, side of hill, flats) and several configurations of towers but all had three blades.

 

[Maclin]

Not sure what the pitch is on those pod mounted wind generators, variable I think. Looks like on the windmills they have a lot more options on the diameter than you have on your boat though

 

[Tail_Gunner]

ok what are they as compared to what one is after on a windmill?


Drove from Bakersfield to Lancaster CA yesterday and hit a windfarm of a few thousand of various sizes and location (top of hill, side of hill, flats) and several configurations of towers but all had three blades.

Well i would elaborate on this a bit but it would turn into a polotic's......so if you like to tinker on the left it would be a __ blade and if you tinker on the right it would be a __ blade. Now with that said enough said.

 

[steelespike]

Very basically;
A 2 blade marine prop is said to be the most efficient with somewhat less blade drag but they are limited to light reasonably fast hulls
or smaller motors. A 3 blade is a better all around prop, stronger hole shot less sensitive to ventilation. More design variations.Only slightly more blade drag.
The 4 blade Is considered to improve hole shot,improve handling,stay on plane easier with a slight loss go top speed a minor fault.
A 5 blade has absolutely amazing grip on the water ,usually does best on the more powerful boats,lots of exotic designs.
They do require deep pockets.
All I can tell you about wind generators is the blades are airfoils, they do adjust to keep rpm within design parameters
and they feather in the event of high winds.