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Q9. a) Explain why the rudder angle does not normally exceed 35°. (6)

b) A ship of 12000 tonne displacement has a rudder 15m2 in area, whose centre is 5 m 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 20 knots the rudder is turned through 30 .  Find the initial angle of heel if the force Fn perpendicular to the plane of the rudder is given by: Fa=577 Av2 sin  N, Allow 20% for the race effect. (10)