464

NICHOLLS'S SEAMANSHIP AND NAUTICAL KNOWLEpGE

RUDDERS.

The most common form of rudder in vessels of moderate speeds ia
the ordinary Single Plate Rudder which turns about an axis at its forward
edge, the hingeing arrangement being in the form of round "pintles"
attached to the "stock" of the rudder whichshipinto "gudgeons" which are
part of the rudder post. The weight of the rudder is taken by the bottom
gudgeon of the stern post into which the lower pintle, the "bearing"
pintle, fits. The end of the bearing pintle is rounded and bears on a
hemispherical steel disc placed in the gudgeon socket, the purpose being
to reduce the area of the metal to metal surface and so minimise friction.
When this disc gets worn it is replaced by another when the vessel is in
drydock.

Fig. 53. Fig, 54,—Single Plate Rudder.
Kgure 53 shows the stock A, the arms B, and the pintles 0, of a
small rudder before the blade is slipped into position, the arms being
on alternate sides of the blade.
Figure 54 illustrates the detail of a single plate rudder* A, the ruddei
blade, the forward edge of which fits into a narrow keyway
scored down the after side of the rudder stock C. #x to B5, the arms
which are shrunk on the stock C at b. They are also shown in plan,
Figure 54 (3 and 4), the lettering indicating the same parts.