adjustable sails

variable geometry windmill sail (23K bytes)

In the Millennium Mill, the cap and sails will be turned to face directly into wind and the area of the sails adjusted under computer control according to wind direction and strength, and will rarely require human intervention except for maintenance and repairs. The electricity required by the computers and other mill functions will be generated by the mill itself. The cloth sails work on the roller blind principle to achieve changes in area.

Changing the sail area

The streamlined leading edge of the sail is hollow apart from the main structural member at the front, and contains two servo-driven rollers. Sailcloth is rolled onto one, and a rope outhaul on the other. Variable amounts of sailcloth can be drawn backwards out of the leading edge to increase the sail area in lighter winds or drawn back onto the roller to decrease the area in stronger winds. The cloth is guided and restrained by the channelled ribs which extend back from the leading edge. The outhaul ropes operate around pulleys at the outer ends of the ribs.

Changing the sail area