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Chuck Husick: Techno-Talk, May 2004, BoatUS Magazine -
Autopilots
Available immediately:
competent helmsman for virtually any power or sail boat, will learn
your boat’s behavior to improve existing skills, can stand
watch endlessly without tiring, never need to go to the head and
will live on only a few watts of electrical power per hour. Contact
“Autopilot” in your marine equipment catalog.
If you already have an autopilot on your boat you know the value
of this non-tiring, undemanding crewmember. However, if your autopilot
is more than a few years old you may not be aware of the very substantial
performance improvements that have been achieved, especially in
their ability to accurately steer the boat in difficult sea conditions.
Run a boat equipped with one of today’s microprocessor based
pilots and you will discover a whole new boating experience.
With the autopilot controlling the helm you will be free to survey
the activities of other boats and the sea ahead, simultaneously
improving your appreciation of the day and increasing your safety.
An autopilot will improve the performance of your vessel by steering
a course or holding a heading with more precision than a human helmsman.
Connect two wires from your GPS or Loran C to the autopilot and
it will precisely steer the boat to a waypoint or track the series
of waypoints that define a route.
The autopilot operates by repeatedly comparing the boat’s
magnetic heading to the boat’s actual heading. The comparison
is done many times each second with any deviation resulting in a
correcting movement of the tiller or the wheel. When connected to
a GPS or Loran C the boat’s course over the ground can alternately
be compared with the COG to the waypoint, The autopilot’s
“brain” accomplishes this task precisely while a human
helmsman is easily distracted, becomes tired and often allows substantial
steering errors to go unnoticed. The human helmsman performs best
when maintaining a general lookout necessary to ensure safe navigation
and an enjoyable boating experience.
The addition of powerful microprocessors and gyro-stabilized heading
sense systems have improved even modest cost autopilot performance
to levels previously achieved by only the most expensive yacht autopilots.
Sailboat owners benefit from new low electrical power drain rudder
control servos. Many of today’s autopilots automatically recognize
varying sea conditions, changing the way in which they move the
helm in response to the changing impact of wind, waves and currents.
Some of the latest pilots use a form of “fuzzy logic,”
software programs that accumulate a history of the boat’s
reaction to varying operating conditions and then use the information
to improve the behavior of the steering system and thereby the performance
of the boat.
Autopilot steering performance in a following sea has always presented
a problem when the force of the sea throws the boat’s stern
to one side or the other. A well trained human helmsman can sense
the initial acceleration force that occurs a fraction of a second
before the boat’s heading changes and can move the rudder
the small amount needed to offset the turning force, preventing
the boat from yawing to port or starboard. In the latest autopilots,
a miniature solid-state gyro sensor in the heading sense system
provides the autopilot with a “seat of the pants” sensitivity
to the initial acceleration forces. The autopilot uses this acceleration
information to emulate the best human helmsman, correcting for the
yawing force before it can materially alter the boat’s heading.
An autopilot will make your time on the water more enjoyable, while
it contributes to safety, by ensuring that the boat is always heading
in the direction it should and allowing the person on watch to devote
attention to the entire navigation situation. Connected to a wind
vane, the autopilot can hold the boat precisely into the wind, simplifying
the raising and lowering of sails. Some autopilots will automatically
steer the boat in precise circles or other patterns about a fixed
point or automatically execute a search pattern.
However, just as with the cruise speed control in a car, the operator
must always remain aware of and attentive to what is going on around
the vehicle or the boat. Running full tilt into the harbor seawall
because you forgot that the autopilot does not have eyes will spoil
your day and do nothing to enhance your reputation as a proficient
captain.
By Chuck Husick
Chuck Husick is a pilot, engineer, sailor and former president of
Chris Craft Boats.
© Copyright BoatUS Magazine 2004
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