The most efficient way to steer a boat is to use the boat's own rudder which was designed to steer the boat in the first place.
The servopendulum works as follows:
Imagine yourself holding an oar with its blade behind a boat that travels forward. You will do fine as long as the edge of the blade is aligned with the direction of the boat. If you twist the oar, even a fraction, the water will hit the flat surface of the blade and you will be unable to keep the oar straight - it will swing to the side. A tremendous leverage is created from the blade, through the shaft, to the end of the oar where you are holding on.
A servo pendulum gear uses this great leverage to keep the yacht on course. An oar or paddle is suspended like a pendulum from the stern of the boat. As long as the yacht is on course, the oar blade trails on the center line. The airvane is the sensor that controls the servo pendulum oar. When the boat wanders off course the airvane will sense this and rotate the oar. The flow of water hitting the blade broadface causes the pendulum oar to swing to the side with great force. The pendulum is connected through lines to the wheel or tiller and the resulting movement of the yacht's rudder brings the boat back on course.