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Self trimming wingsail - the pulley/cord control system.

Wingsail that can sail directly into the wind!

I tested this wingsail system on my experimental 72 inch catamaran.
The wing and tail assembly pivots on the centre of pressure of the wing.
The angle of the tail (which controls the angle of incidence of the wing)
Is connected with cords to the pulley situated on the pivot axis of the wing.
This pulley is fixed to the boat and does not rotate.
As the rig rotates in response to the direction of the wind the cords pull
The tail to different angles please study the diagram below.

In practice what happens is that when the wind is directly ahead the tail
adjusts the angle of attack of the wing to 0 degrees.
But as the wind comes round  the side, the cord pulls the tail to make
the wing adopt an increasing angle of attack until it is at maximum
at 90 degrees to the boat. On either tack. (I used about 15 degrees tail
angle. Although this seems complicated to describe in words. In reality
it is very simple!

Study the video and you will see that the boat displays the remarkable
property of moving directly windward when the wind is directly ahead.
I assume this is possible because of the low drag or windage of the
boat in relation to the wing area. Also the wind is varying constantly
in direction and thus the wing is still giving tiny amounts of thrust.
Just enough to keep the boat stationary or creeping directly windward.

Sideview

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Video

Any questions? click here