Page 282 - Introduction to Naval Architecture

MANOEUVRING 267

The Kitchen rudder
This rudder is a two-part tube shrouding the propeller and turning
about a vertical axis. For ahead propulsion the two halves of the tube
are opened to fore and aft flow. For turning the two halves can be
moved together to deflect the propeller race. The two halves can be
moved to block the propeller race and reverse its flow.

Figure 10,9 Kitchen rudder

Vertical axis propeller
This type of propeller is essentially a horizontal disc carrying a number
of aerofoil shaped vertical blades. As the disc turns the blades are
caused to turn about their vertical axes so that they create a thrust. For
normal propulsion the blades are set so that the thrust is fore and aft.
When the ship wishes to turn the blades are adjusted so that the thrust
is at an angle. They can produce lateral thrust even at low ship
speed.

Lateral thrust units
It is sometimes desirable to be able to control a ship's head and course
independently. This situation can arise in mine countermeasure vessels
which need to follow a certain path relative to the ground in conditions