Aspect Ratio & Force Acting on Rudder

 Aspect Ratio

> The rudder area is usually relative to the area of the immersed metal plane.

> The ratio of the depth to width of a rudder  is known as the aspect ratio and its value is generally 2. 

> Higher aspect ratio reduces the stern torque considerably so, in large vessels a high aspect ratio is used

Aspect Ratio = (Depth of Rudder / Width of Rudder)

The force acting on rudder depends on 4 factors;:

> The form of rudder

> Area of the rudder

> The angle of helm

> The speed of the ship

Force acting on the rudder, F = k A V²


k = Constant depending upon the shape of the rudder, water density, rudder angle. It varies from 570 to 610.

A = Area of rudder in m²

V = Speed of ship in m/s

Area of rudder is 1/60 to 1/70 th of the immersed middle plane area of the vessel. Faster vessels require less rudder area.

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