A Tentative Theory on a Determination of the Power of a Main Steering Gear

Abstract

In regard to the angular velocity of a main steering gear, American Bureau of Shipping and Nippon Kaji Kyokai establish the following rules : In American Bureau of Shipping, the steering gear shall be capable of moving the rudder from 35 degrees on one side through 30 degrees on the other side at an average rate of travel of not less than 2 1/3 degrees per second. Also, in Nippon Kaiji Kyokai, the main steering gear should be capable of moving the rudder from 35 degrees on one side through 30 degrees on the other side within 28 seconds with the ship runnning ahead at the speed specified in art. 13 part 2 of the N. K. rules.At the present stage, these rules are uniformly applied to all vessels, regardless of size and values of maneuverability indices T and K. The writer thinks that the application of these rules to all vessels is not proper, especially for such ships of slow response as supertankers or such ships required of quick response as catcherboats when in turning motion.From the viewpoint of Optimal Control, the writer considers the angular velocity of the main steering gear should be matched with the performance of the steering motion of ships. The next new rule has been obtained as follows : The optimum steering gear shall be capable of moving the rudder from 35 degrees on one side through 30 degrees on the other side at the rate which is 0.96 times of the maneuverability index T, with the ship running ahead at the speed specfied.