Learning Objectives Know the parameters essential for the size of the steering gear. Be able to explain how the bearing forces act Know the principles of the most used rudder arrangements.
Rudder Torque In order to move the rudder, the steering gear has to create a certain torque (measured in kilo Newton) The torque requirement is given by the class rules to ensure safe maneuverability of the vessel. The size and also the speed of the vessel is taken into consideration.
Rudder Forces The rudder arrangement is also exposed to these forces: Current forces created by propeller and waves Gravity of components and ship movement Side forces when turning The forces depend upon the type and size of rudder and also the rudder arrangement.
Spade rudder This is the most used rudder type on ferries and smaller boats. This type of rudder gives very good manoeuvrability, depending on the available rudder angle and the rudder profile.
Half Speed Rudder This type of rudder is most commonly used on big vessel.This rudder is not spade rudder of the same size.
Flap Rudder This type of rudder is used when very good manoeuvrability is required. The rear fin “exaggerates” the movement of the rudder, making the rudder more effective. (increasing the side lift)
Assessment Test Question 1 of 3 The water flow creates? A) Vertical forces on the rudder B) Side forces on the rudder C) Both vertical and side forces D)I don’t know
Assessment Test Question 2 of 3 What are the parameters most essential for the rudder torque? A) Shape of the hill, propeller rotation and waves B) Rudder arrangement, size of the rudder and the vessel’s speed C) The vessel’s dead weight and tonnage D) I don’t know
Assessment Test Question 3 of 3 Which one of these three rudders gives the best manoeuvrability, given they have the same size? A) Spade rudder with normal profile B) Semi-spade rudder C) Flap rudder D) I don’t know