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Rudders originally consisted of single plate,with supporting arms riveted to either sides. This is called single plate rudder which has been superseded by double plate rudders which are normally streamlined and are either balanced , unbalanced and semi balanced. They may be hinged to pintle or gudgeon or they may turn about an axle which oasses down through the rudder.

The stock that turns the rudder passes vertically upward to the steering gear through a gland in the shell plating, or a watertight rudder trunk. Stock is normally connected to rudder by bolted couplings , which can be disconnected to take out rudder for maintainance without disturbing stock.

The centre of pintle or axle should be in the same line as that of the stock to enable the rudder to turn.

The weight of the rudder is taken by carrier bearing.

DOUBLE PLATE RUDDERS:-

The frame work of this may be castinh or may be build up by welded plates with playing on either side.

It is of following types :

1. Balanced rudder:- is the one with about 30-40% area is forward of turning axis.

2. Semi balanced rudder:- is the one with less than 20% are is forward of turning axis.

3. Unbalanced rudder:- is the one with all area aft of the turning axis.

Water pressure tries to force the blades of the unbalanced rudder amidship and hence a considerable amount of stress on rudder stock and steering gear comes. If some part of the rudder is made forward then the force of forward part counter act that of aft and stress reduces. Unfortunately the ratio be the pressure varies with the rudder angle hence it is not possible to balance rudder at all angles. It normally remain balance till 15 degrees.

CONSTRUCTION OF RUDDER:-

Rudder frame maybe forged or cast steel or maybe constructed by web plates welded together. Plating is normally welded to the frame. Slot wleds or continuous butt welds are commonly used for this purpose .when plate Frames are used, flat bars at welded to their edges to take the slot weld.