Carolina Wind Power - Manual (Page 4)

28
Adjust the blade angle by
twisting the rod mount on
the hub. The angle template
cutouts will help.
angle template
The three angle
templates
for 2 blades
for 3 blades
for 6 blades
Each wing or propeller shape is determined
by a specific lift ratio, or the so-called coef-
ficient of lift (C
L
). It has a drag coefficient (C
d
)
as well. The coefficients of different wing
shapes have been determined in special wind
tunnels. So have the drag coefficients of vari-
ous automobile bodies and other vehicles.
Airplane model in wind tunnel
Your rotor blades are fairly arched and
intended for a low-speed model. But what’s
slow and what’s fast?
What determines rotation speed?
Rotation speed indicates the number of rota-
tions or revolutions per second or minute.
The following facts determine the rotation
speed:
The wind speed
The size of the windmill
The number of blades
The shape of the blades
The required power
For our experiments, we will have to be able
to determine the wind speed. To do that, we
will assemble a wind gauge.
11
Experiment
Materials: wind speed scale (cutout), 40 cm of
string (8), joint pin (1)
Cut the wind vane with the wind speed scale
out of the cut-out sheet at the end of this
experiment manual. Guide the string through
the hole, and pull it through the joint pin as
well. Tie its ends together so that the joint
Wind speed scale
Cut out along
the dotted line
Cut out four
holes