Q6. A single screw vessel with a service speed of 16 knots is fitted with an unbalanced rectangular rudder 6 m deep and 3.5 m wide with an axis of rotation 0.25 m forward of the leading edge. At the maximum designed rudder angle of 350 the centre of effort is 30% of the rudder width from the leading edge.
The force on the rudder normal to the plane of the rudder is given by the
expression:
Where:
20.2 A v2 a newtons
A rudder area (m2)
v ship speed (m/s)
- rudder helm angle (degrees)
The maximum stress on the rudder stock is to be Limited to 70 MN/m2.
Calculate EACH of the following:
(a) the minimum diameter of rudder stock required; (9)
(b) the percentage reduction in rudder stock diameter that would be achieved (7)
if the rudder was designed as a balanced rudder, with the axis of rotation 0.85 m from the leading edge.
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