A Question of Balance
Judo is a sport all about balance. A judicious touch, push or pull, executed in the right place at the right moment, can cause huge weights (your opponent) to move in ways they least intended. I was reminded of this by the recent Banksy artworks which appeared in Ukraine after the liberation of Kherson. Apart from the obvious symbolism, the picture of 'little guy throwing much bigger guy' beautifully illustrates what timing and balance can achieve.
Which is perhaps a tenuous introduction to a piece about the Hydrovane self-steering on Skyfall. Let me explain. Clearly, if you want to carry your home around the world with you, it is going to be heavy. Skyfall is (loaded) the best part of 16 tonnes. And to move such a heavy object, as quickly as Skyfall sails, requires quite some power. The power comes from the sails. I forget the actual square metres of sail but the photo below makes the point.
So what if someone told you that they could build a system where the power to control all this weight and all this sail, would come from a small vane with about half a square metre of area? "Impossible!", I hear at least some of you exclaim. But it is possible: with our hydrovane system.
There is a small vane which is angled into the wind.The vane is fixed to the boat so if the boat changes course then the angle of the vane to the wind changes. The wind now exerts more pressure to one side (or the other), pushing the vane down. This force is transmitted, via a gearbox, to move an auxiliary rudder mounted below. But the force from the vane is tiny. Firstly the area of the vane is small. But, more importantly, you need a rudder correction with a course change less than 10degrees. So there is a sine(10 degrees) multiplication factor too - which is also small. It ought not to work but, of course, it does. It is all a question of balance.
Here the hydrovane is steering Skyfall in 25 knots of wind and 3m waves.