Date: Wed, 14 Jan 1998 16:11:00 -0600
My name is Jessica, and I am building a windmill
for a science competition. I have to design a windmill
that will get the maximum power. Do you have any
suggestions as to how many blades I should use?
Date: Wed, 14 Jan 1998 19:39:42 -0600
From: Natalie Rusk
Subject: Re: windmills
I just asked your question to J. Newlin who runs the Experiment
Gallery here at the Science Museum.
He suggests it depends whether you want high speed or
high torque (force of rotation).
If you want high speed, then the fewer blades the better.
He said you could use just two, but it is usually easier
to balance with 3. Are there wind power farms in Illinois?
The windmills on windfarms generally use only 3
blades for maximum speed. (There's a picture of one at
If you want high torque (stronger rotational force), then
you'll want to add more blades. For example, windmills
for water pumps often have 6 or 8 or more blades.
Vollis Simpson the artist in N. Carolina told us he designed
his first windmill ever to power his furnace. It looks to
me like it has dozens of blades.
(But he said it never did work quite right on the furnace.
Which is one reason he started making whirligigs for fun
rather than to do work) And we saw the windmill turn
towards the wind but not spin.
So I guess you have to decide if you want greater rotational
force or faster speed. Vollis pointed out to us that the amount
you pitch (i.e.,tilt) the blades makes a difference too. He also
said the most important part of making a windmill or whirligig
spin is to get it centered.
I'd be interested to hear what you find out--what does and doesn't work.
Science Museum of Minnesota