Maneuvering the Sally Maersk

MANEUVERING THE SALLY MÆRSKIntroductionBasically the movements of a seagoing vessel—its maneuvers—are determined bythe interaction between controllable and uncontrollable physical forces. Thus, fromthis perspective safe and timely maritime operations are a matter of applying thecontrollable forces on the uncontrollable forces in a way that results in the desiredmovements.Controlable forcesEngineRudderThrusterAnchorTugHawserUncontrolable forcesWindCurrentSwellSeaSuction effectBank effectFigure 1. The Controllable and uncontrollable forces involved in maneuvering a seagoing vessel.The present report presents the controllable forces available to the crew of theSally Mærsk during at-sea maneuvers. Focus will be on steering and propulsion, thatis, the rudder and its control systems and the propulsion system driving the vessel.SteeringSally Mærsk is fitted with a streamlines semi spade-type balanced rudder. Themassive 100m 2 rudder is mounted on a vertical rudder stock which is turned by fourelectro-hydraulic cylinders. The maximum rudder angle 'hard over' to port orstarboard is 35°.As seen from the perspective of the actor on the bridge of the vessel the steeringgear is an object to be controlled with the purpose of achieving certain movements ofthe vessel. In order to facilitate different modes of interaction with the steering gearan elaborate control system has been placed between the actor and the steering gear.The purpose of the following is to illustrate how the rudder is operated in the contextof maneuvering rather then explicating in detail the engineering details of the steeringsystem. To this end we will consider the physical steering gear (rudder blade, rudderstock, cylinders, etc.) the object of control, while the system in-between the humanactor and the actual steering gear will be understood as the control system. Our3