Orval Fairbairn wrote:
In article ,
Jerry Wass wrote:

Orval Fairbairn wrote:
In article ,
Brian Whatcott wrote:

Orval Fairbairn wrote:
In article ,
Brian Whatcott wrote:

This is a pointer to a home build 20 ft diam windmill on a 70 ft pole.
It features three 10 ft long laminated red cedar blades and nice looking
generator, tower couplings and gin....


http://www.otherpower.com/20page1.html

Brian W

(Thanks to Larry for the pointer on rec.boats)
I hope that you have good lightning suppression!

Ha! I noticed the maker specified a blade angle of 3 degrees at the
tips, increasing to (approaching) 9 degrees at the roots.
It took me a little while to get my head round this. The maker mentioned
the blades are set flat (undersurface) forward into the wind, and I
think he mentioned a target rotation rate of 65 rpm.
I imagine he was thinking of an AoA of 15 degrees at the rated wind. The
tips do a revolution in pi x 20 ft = 63 ft per rev - so the rotation
rate at 65 rpm would give a tip speed of 65rpm X 63ft/rev X 60 min/hr /
5280 ft/mile or 47 mph.

I guess the pitch angle for zero AoA at the starting windspeed 16 mph
would be atan 16/47 = 19 degrees from the plane of revolution, so for 15
deg AoA the pitch angle might be 4 degrees from the plane of revolution
at the tips.
And he mentions 3 degrees. But getting up to speed with stalled blades
would be an issue...
What's your take, Orville?


Regards

Brian W
My first take is that you misspelled my name.

We had a big windmill on our farm when I was growing up. The plane of
rotation was parallel to the wind, rather than at a right angle. The fan
acted more as a wind turbine than a propeller. IIRC, the fan had about a
dozen curved steel blades. It also had a brake on it for when the winds
got too high.

The blades were turned sideways (parallel to the tail) if they didn't
want it to pump any water---If you needed water you operated the lever
that placed the blades perpendicular to the rudder, tail,
whatever,-pointing into the wind, then you got some POWER..---OR--
did you have one of those weird looking things where the blades were
raked back severely at an angle about like the back 2/3 of a snowcone
cup? Jerry

Neither. The fan was 10-12 ft diameter, fixed so the wind would always
turn the fan. Since the blades were curved (cambered), the advancing
blade had less drag than the receding blade. I think it was a
Fairbanks-Morse product, but don't hold me to that, and it was built
about 1910.

A lot of windmills in our area (Northern Illinois) were of similar
design.

Sounds like a pelton wheel.
http://www.google.com/search?hl=en&q...on+w&aqi=g 10