On the water surface there are many currents which affect all surfaces of the rudder blade. As an example, we mention only one current in our article.
We tested the crossbar on special equipment in the water (waves 0.5m-3m high). This device showed us the changes in the crossbar length. The length of the crossbar changed from 10mm to 30mm, with a frequency 2-5 seconds (depending on the boats direction against the wave). All changes in the size were constant, but not irregular – one second it was smooth, one second it was like a spurt. This clearly proves that in the crossbar there are forces. During all tests none of the skippers lost control or feeling of the boat. Moreover they indicated that boat goes more smoothly through the wave.

In the sailing world there is a myth that the mast has to be flexible and must work together with sails, but foils must be stiff like concrete.
Even on a car, we can see that there are flexible parts – rubber tires and amortization system.

Notwithstanding, you never lose control of the steering. If you imagine this system that is completely stiff with aluminum tires, it would crash very quickly…
This example can also explain catamaran rudder breakages, when a skipper can’t feel loads on the crossbar and tiller extension.

According to the Ackerman principle, when turning on different radiuses, tillers must have particular toe-in angle. Meaning when the turn radius is large - tillers have little toe-in angle, but on sharp turns (small radius) tillers must have a larger toe-in angle. Usually sailors choose an average angle, about 7 or 8 degrees. Our system in this case automatically allows for a more optimal angle.
Usually in order to change the direction a skipper turns the rudder about 20-40 degrees. Our amortization system can only turn for 2-3 degrees, again optimizing the Ackerman principle – adding or taking the angle.
There are no slop, dead zones, delays etc… The skipper perfectly interacts with the catamaran.

Let’s return to water currents on the rudder blade taking into consideration all resultant loads on an example of a dolphin. Dolphins are known for their amazing hydrodynamic characteristics. An ideal rudder in this case would be something flexible with a surface like dolphin skin, a surface which can process pressure differentials on all of the rudder blade area. But at the moment, it is impossible to make it.

All dolphin fins (rudders) are not absolutely stiff, but flexible.

With a sharp increase of the load on the blade a flexible rudder damps hydrodynamic oscillations, fading the pressure of the blade if you compare with aluminum rudder stock, Dotan rudder stock deals better with dynamic loads. Flexibility gives an increase in endurance of the rudder system dramatically.

The article example shows how everything would work with 10kg load. If there are no wave loads between the rudders the load is very close to 0kg. When there are large wave loads it can reach about 100kg before the rudders will break.
Anyway, even with a condition when load is 10kg you can decrease drag for 0.4kg. As Wouter’s calculations show, you can gain about 1 minute on a finish during a 3-hour race. If you take into consideration large waves that can cause loads to reach about 100kg your final result on the finish line can be many times better.