Chapter 12:Rudder-Stock Angle, Control, and Installation Considerations
hydraulic steering because, compared with a
well-set-up cable system, it gives a mushier
helm feel. For power craft, however, this isn’t
much of a disadvantage. Indeed, it can be a
plus; the slight mushiness damps out prop-
wash vibrations at the rudder, which cable gear
can transmit as a hum or jiggle to the wheel.
Easy Does It
Hydraulics are easy to install because—unlike
the finicky alignment and tensioning required
by cable systems—the hoses or pipes can lit-
erally be run any which way. (Kinks and abra-
sions must be avoided, of course, and the
hoses must be well secured.) Though there
are a few hydraulic systems with a rotary hy-
draulic driver (really a rotary pump acting in
reverse) that fits right to the rudder stock,
most are simple hydraulic cylinders attached
to a short metal tiller arm that swings the rud-
der just as a traditional hand tiller does.
Hydraulic-Steering Torque
Since each cylinder model has a fixed throw
or stroke, it’s designed to work with a
standard-length tiller arm. (Using a different
length would give you either too much or too
little rudder travel—more or less than 35 de-
grees hard over to hard over.) The cylinder
force or power is also governed by the 30-
pound (13.5 kg) limit you can deliver to the
wheel and helm-pump unit at the bridge or
helm station. (Power-assist or full-powered hy-
draulic steering is used on large vessels.) Ac-
cordingly, once again, you’ve got a force times
a fixed distance—a torque—for each hydraulic
cylinder configuration. Obviously, the cylin-
der/tiller system torque should equal or some-
what exceed the maximum rudder torque we
found earlier. All you have to do is look
through the steering-gear manufacturer’s cata-
log and match their torque specifications to
your rudder torque to get the correct cylinder
and wheel-helm-pump combination (the two
work together to generate the required me-
chanical advantage, torque, and helm speed).
Locating the Cylinder, and
Keeping It There
It’s important, however, to install the cylin-
der correctly. You’ll sometimes find it’s in-
stalled at right angles to the tiller when the
Figure 12-5. Hydraulic steering: 2 helms,
1 rudder (Courtesy Teleflex, Inc.)rudder is amidships. This is not good. It
puts the cylinder off angle at either end of
its stroke. Instead, the cylinder must be in-
stalled so that it’s at right angles to the
amidships tiller location when the rudder
is turned 35 degrees either way, as shown
in the Figure 12-7.
Also, the forces on the cylinder mounts
can be quite large. For our example boat, a
typical hydraulic cylinder would be delivering
around 280 pounds (127 kg) of force—back