Above: Fin installation can be performed during the initial
building process or as a retrofit project. Regardless of when
stabilizers are installed, there are proper, safe methods a yard
should follow. Here, a fiberglass backing plate is ready for
installation of a fin and actuator assembly. Notice the fiberglass
tabbing around the perimeter. Right and below right: Installing
stabilizer fins requires careful measurement and input from the
manufacturer. It’s also important that there be adequate space
inside the vessel to accommodate the installation.
PTO port on the engine or transmission. This allows the
pump to be removed and the PTO port to be covered in
the event of a problem.
Pumps may be installed singly or in pairs, depending
on the application and the stabilizer manufacturer’s
options. For twin-screw vessels, if one pump is installed
and the engine that it’s driven from fails, you’ll be
limping home on one engine and no stabilizers. For this
reason, many builders and stabilizer installers opt for
twin pump installations. Several pump and plumbing
configurations exist; for example, two primaries working
in tandem, or one primary and one backup. Additionally,
a generator equipped with a PTO may be used as either
primary or secondary power for stabilizer hydraulic
support. Finally, hydraulic pumps may be driven from a
powerful AC electric motor. These are often found on
larger vessels or aboard boats that are equipped with
stabilizers that operate while the boat is at rest.
Other components of the hydraulic fin stabilizer
system include a fluid reservoir (which typically
incorporates a system for monitoring fluid level and
temperature), control valves, and filtration. The
continuous-duty hydraulic systems used with stabilizers
generate a considerable amount of heat, which must
be dissipated as quickly as it is created. Heat removal
is accomplished by using a seawater-cooled heat
exchanger similar to that used to cool a generator
or engine.
Fin actuator servo valves receive commands from the
system’s controller, which determines when fins will
receive hydraulic fluid and in which direction they will
turn. A control manifold regulates pressure within the
hydraulic system, ensuring that enough, but not too
much, pressure is always available for fin actuation.
Finally, there are the fin actuators themselves. In
simplified terms, these are made up of hydraulic pistons
that either extend or retract to move the fin shaft, which
rotates on large bearings, rotating the fins in the desired
direction. Electronic sensors permeate the system,
sending information to the controller about vessel
