ceiling fan blades

[willisl]

We see ceiling fans with 3, 4 and 5 blades. Does blade number matter for performance, quiet, vibration, etc?

Thanks

Lynn Willis Indianapolis

[spammer]

Fans with three or four blades move more air than five or six blade fans. They are harder to balance than the five or six blade fans though.

[HamNCheese]

I completely disagree. I would never buy a four blade fan. Five blade fans move MUCH more air. I've replaced all the 4 blade fans in my house with 5 blade fans and the results are much better.

Go for the biggest diameter you can, too. Makes a difference.

[Edwin Pawlowski]

The number of blades indicates nothing. The size, pitch, airfoil design, and rotational speed determines how much air it will move. Take a look at airplane propellers.

[bigjim]

You proved the other poster's point. Many light civil aircraft have two bladed props. Light and low powered WWI had two. High performance fighters and heavy bombers from WWII have four blades. More blades move more air.

[George]

fixed top posting

Actually he didn't. The number of blades have nothing to do with efficiency. The most efficient propeller is actually one blade. Multi blade designs are used for other reasons.

[DerbyDad03]

Here's my response from an earlier thread regarding ceiling fan blades:

Disclaimer: I don't work for a fan company so none of this is a testmonial or sales pitch. It's just info...

Here's some quick info on ceilings fans, both of which include some verbage on blades angles.

Stolen without permission from

*** Begin Included Text ***

"Don't let your ceiling fan leave you hot under the collar... Just because a ceiling fan moves air doesn't mean it moves enough air to keep you comfortable. The blade pitch (or angle) determines how much air is moved when the fan is on. Some fans have blades with a very shallow pitch because their motors are not powerful enough to handle the extra demand made by steeper blade pitches. Casablanca fans use a motor which is engineered to be more than powerful enough to operate fan blades with a full 14 degree pitch. So you always get the right amount of air to keep cool and comfortable."

*** End Included text ***

Interesting fact: The first 3 fans listed under the model section at that site are 3, 4 and 5 blade fans. The 3 blade has an air flow rating of 4 out 5, while the 4 & 5 bladers are rated 5 out of 5. Casablanca claims 5 is the best, but I don't know if that's their standard or an industry standard.

Bottom line: If a fan isn't bragging about it's blade angle and motor quality as selling points, that may mean it's not as steep or strong as one would like. My guess is that no one is putting a motor that can handle a 14 degree pitch on a fan with an 8 degree pitch, if you know what I mean.

[HeyBub]

Like modern submarines with, what, TWENTY blades on the propeller?

[Steve]

Now you're touching on why you want more blades - they run quieter.

--Steve

[Edwin Pawlowski]

Still goes back to total design, not just numbers. Look at the blades on the huge windmills used to generate electric. Usually three long narrow blades.

As for aircraft, one reason to use the three or four blades over just two is ground clearance. When the tail comes up, you don't want the blade to hit.

[George]

Exactly, a lot more to do with trying to achieve stealthier operation than any other reason.