Dave Gerr - Boat Mechanical Systems Handbook-How to Design, Install, and Recognize Proper Systems in Boats

only articulated-flap rudders but rudders

with rotating drums built into their leading

edge. These companies primarily manufac-

turer rudders for ships.

The Deflector Rudder

A U.S.-fabricated articulated rudder is the

Deflector Rudder, made by Deflector Marine

Rudder of Naselle, WA. Figure 13-10 shows a

stern view of the Deflector Rudder at dead

center and Figure 13-11 shows a side view of

the rudder in a starboard turn. The basic

workings of the rudder are automatic and

require no external power to move the flap

(that’s accomplished by the geometry of the

flap linkage and pivot location alone). Like

most flap rudders, the Deflector Rudder

articulates to a total of 90 degrees. The

main/forward rudder blade swings to 45 de-

grees, and the trailing-edge flap swings to

twice that—so 90 degrees (Figure 13-12).

Double Fixed-Geometry

High-Lift Rudder

Another unusual rudder configuration is the

double fixed-geometry high-lift rudder. This

is two balanced rudders (usually with end-

plates) acting in unison behind a single

propeller. The twin rudders turn together but

usually use differential steering (similar to

the Ackermann steering described in the

PART FOUR:RUDDERS AND STEERING SYSTEMS

Figure 13-9.
Bulbous flap
rudder (Courtesy
Ulstein Hinze
FB/MH)

Figure 13-10. Deflector Rudder amidships

Figure 13-11. Deflector Rudder to starboard