• Dipping Rudders
This brilliant solution was devised by Rick Willoughby and is adopted in his monohulls.
Here is the description given by Rick:
The rudders are so-called "dipping" rudders. They are only immersed when required for turning. They normally sit up out of the water and are just immersed when turning or course correction is required. For a full turn the whole rudder is immersed. If it is only a course correction then just a tiny portion is immersed. The rudders have a preset angle of attack roughly set at the maximum L/D ratio for the particular foil.
It means I do not have the continuous drag of the rudder. Depending on the size of the rudder it could be worth 0.5kph.
Another interesting feature of Rick's dipping rudders is shallow water starts, because it is apparent that rudders are usually not in operation during the phase of getting clean of the ground, and when still in vicinity of the beach they can work (even if not very well) also half dipped. And they require just a simple one-axis control.
Our boat is better than mine.