Part Four
RUDDERS AND
STEERING
SYSTEMS
CHAPTER 10
Rudders and the steering systems that con-
trol them make it possible for a boat to get
where it’s going. Crisp, responsive steering
in all conditions and at all speeds make a ves-
sel a pleasure to operate. Poor steering re-
sponse (or worse, a broken steering system)
is not only unpleasant but potentially danger-
ous. In this and the next three chapters we’ll
discuss the basics of rudders and steering
systems for inboard boats: power and sail.
We’ll also review some important considera-
tions that are often neglected, as well as look
at a few special or unusual rudders.
Putting the Rudder to Work
Fundamentally, a rudder is no more than a
board hung aft on the centerline of a boat
such that it is free to pivot around hinges
calledgudgeons and pintlesalong its lead-
ing edge, or around a roughly vertical shaft
called the rudder postor rudder stock
(Figure 10-1). (On modern twin-screw craft,
the rudders are hung just aft of each pro-
peller on rudder stocks.)
If we deflect the rudder blade of a boat
to one side—say to port—we increase the
force of the water hitting the port, or left,
side of the rudder, which in turn swings the
boat’s entire stern in the opposite direction,
to the right, or starboard. Since we’ve used
the force of water flowing past the rudder
to kick the stern around to starboard, the
bow has now been swung to port, and off
we’ll go to port—presumably what we had
in mind when we put the helm over in the
first place.Describing the Rudder and
Aspect Ratio
Rudders come in many shapes and sizes, so
designers have adopted some airplane termi-
nology to help describe them accurately. The
depth or vertical height of a rudder is called
itsspan. (Span is always measured vertically,
and not along the length of an angled or
swept-back rudder.) The fore-and-aft length
of the rudder is referred to as its chord.
Designers tend to visualize airplane wings
and hydrofoils—like rudders or keels—as
growing out of the fuselage or hull; this is,
after all, where they are attached. Accord-
ingly, the top of the rudder, near the hull un-
derbody, is known as the root, and the fore-
and-aft length at the root is the root chord.
Similarly, the bottom end of the rudder—
farthest from the hull—is named the tip, and
the fore-and-aft length there is the tip chord.
The average rudder length fore and aft is
called the mean chordor the midchord, as
it’s usually at or near midspan (midheight).