Sustainable Free Energy from the Wind

Development of a self-trimming automatic wingsail system

By Peter Worsley

Traditional  sailing rigs for boats have been around for hundreds of years, and have not changed much in that time. But with the development of aircraft it can be seen that wingsails are possible that get rid of the difficulties of traditional sailing and are more effective too. A self -trimming wingsail system can take away the need for constant attention and monitoring all the time which you need to do with sails, and can be made completely automatic, requiring no specialist skills from the operator.

For 20 years I have been researching and experimenting with self-trimming wingsail systems. Firstly with models.
Then with fullsize versions and now I have a patent granted for my wingsail control mechanism.

This is the system where you have an additional surface mounted behind the wingsail (the tail) which aligns the wing at all times to the wind.
Every shift or change in the wind direction adjusts the wing to the optimum angle and manual control is no longer needed.

In other words the wind does the work  more accurately  than manual sheeting can do on traditional sailing rigs.

To prove the concept I started by testing radio controlled models - later I progressed to a man-carrying version

 Model Testing


This model used the control system in the diagram below.

Looking carefully at the video you will see there is a windvane which shows wind direction.

Its interesting to see is that the craft is never blown downwind even when directly pointing into the wind.
Controlled by the tail the wing is making tiny changes in angle of attack which gives just enough thrust to counter the drag. This demonstrates  the amazing efficiency of a correctly controlled wingsail.

Because of the cable controlled system the rig had to be prevented from rotating more than 180 degrees.
A "stop" line was used for this, and as you can see in the video this made a "gybe" necessary
when coming through the wind from behind.


The wing and tail swing with the wind like a windvane. When the wind is directly ahead the
two surfaces are directly inline and cause minimum drag (less than a bare mast) but when
the wind comes from the beam across the boat the tail is pulled to an angle causing the main
wing to assume an angle of attack to drive the boat. The usual setting is 15 degrees on broad
reach either side. As the wind comes more from ahead the angle decreases until head to wind
it is zero (minimum drag)

The addition of a wing flap

Although the above system works well and has been used on models and fullsize with just a simple aerofoil on the wing.
I have made some tests to see if there is an advantage in having a flap on the trailing edge of the wing. This would
enable the wing to form an asymmetric shape on either tack (undercamber) which should provide more lift.

But how to make the flap move in direction from one tack to the other?

The system I used was to connect the flap to move in opposition to the movement of the tail. So it was connected to the
tail by a rod that would move it in the opposite direction thus:

Would it work? I tested the system on my 2 metre test catamaran

As can be seen it worked well. Sometimes I could hardly keep up with it!


Page Two fullsize experiments
Click here)


P. Worsley 2013/2020