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NICHOLLS'S SEAMANSHIP AND NAUTICAL KNOWLEDGE

which is an ordinary unbalanced one. No. 60 is a type supported on
a bearing pintle, and No. 61 is a "spade" rudder.

Fig. 63.—The Streamlines of an Oertz Rudder.

Figure 62 is an Oertz streamline rudder. The part on which the
draught marks are painted is fixed to the stern post and designed to
smoothen out, the confused flow of water thrown against the rudder by
the action of the propeller and the streamlines of the vessel as indicated
in Figure 63, which shows, in plan, the form of the Oertz rudder and the
local flow of water.

The following plates are inserted by courtesy of Submarine Boat
Corporation, Newark, N.J.,

Kffl28

Fig. 64,—-The Keel Jaid on the Blocks.
Figure 64, C, the centre line keelson; B9 vertical angles to take