What the rudder does:
A ship's rudder is not the same as a stabilizer fin. The primary duty of the rudder is to steer the vessel. Its hull location is not optimum for roll reduction, nor is the design of its actuator mechanisms necessarily intended for rapid movement. However, the rudder is a necessary component -- it must be present -- whereas the addition of fins often increases the vessel's draft or breadth and causes additional drag that shows up both as an increase in fuel consumption and decrease in top speed. Similarly, stabilizer tanks impose a loss of cargo space. In short, use of the rudder to reduce roll is attractive from several perspectives, but has limitations.
The rudders of most commercial ships are overbuilt for the purpose of ensuring their reliability. The Hyde RRS uses the rudder a much larger percentage of the time and often at a much higher speed than is necessary for normal navigation. Indeed, on a ship with a natural roll period of 8 seconds, the Hyde RRS System can be expected to move the rudder from its amidships position to as large an angle as possible to port, back to amidships and on to the same angle to starboard, then back to amidships in each 8 second period while the RRS system is in use. Operation in this fashion certainly keeps the rudder in motion a larger percentage of the time than normal manual or autopilot steering would cause. Relatively high rudder speed is required so that the rudder can quickly provide large roll torques to counter the roll torque from waves without remaining there so long as to affect the vessel's course. The amount of roll torque available from the rudder is dependent both upon the speed of the ship and how far the rudder can be moved in the given time.
Most commercial rudder systems are very heavily built and have component ratings far in excess of the service demands imposed by Hyde RRS. Of course, it is prudent to check and be sure that the rudder and rudder actuator of any ship on which Hyde RRS is to be installed are well built and use heavy-duty component parts. For new builds, the intention to use Hyde RRS and obtain the maximum possible benefit implies that attention to rudder sizing, placement, and speed must be given due consideration.