Question

(a) List the variables which affect the force on Rudder (6)

(b) A ship of 12000 tonne displacement has a rudder 15m3 in area, whose centre is 5m below the waterline. The metacentric height of the ship is 0.3m and the centre of buoyancy is 3.3m below the waterline. When travelling at 20knots the rudder is turned through 30 degrees. Find the iniital angle of heel if the force Fr perpendicular to the plane of the rudder us given by Fr = 577 A v^2 Sin∝ N. Allow 20% for the race effect (10)

Answer 1

when a rudder is turned from the centreline plane, to any angle, a force acts on the rudder, given by,

$$F=kAV^2N$$

Where,

k = Constant
A = Area of rudder in m2
V = Ship's speed in m/s

The constant is dependent on size of rudder, rudder angle and density of water.

Variables affecting force on rudder:

Rudder angle
Density of water
Ship speed

These are the three variables, while all other are constant parameters i.e.

Area of rudder
Size of rudder.

✓ Verified Model Answer (Text Solution)

Variables affecting force on rudder: