08-27-2000
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Join Date: Jan 2000
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Autopilots
Selecting the right autopilot can enhance the sailing experience by freeing up the crew (and captain) from tedious wheel or tiller attendance. More time is made available to navigate, tweak sails, and relax. Vigilance, though, should never be relaxed. DETERMINING SIZE
Autopilot selection is based on several elements of the vessels' design. - Displacement—
The displacement figure is with the boat fully laden with provisions, fuel, and water. If the fully laden figure is on the upper end of one size, go to the next size up. - Weather helm—Determine the amount of pressure needed to maintain a steady helm when at the wheel or tiller. Keep in mind that the autopilot will have to apply that same pressure or thrust to prevent rounding up when under sail and/or in heavy weather conditions.
- Helm response—
How long does it take to go hard over to hard over on the wheel or the tiller? Does it require forceful pressure and is the response to a following sea quick, slow? This data will help determine the number of degrees of course change per second. An area around the course setting, which is determined by sea state, is called the "deadband" setting. The autopilot won't correct the course unless the vessel goes outside this area. This setting will prevent over steering in heavy and following seas and thereby conserve energy. - Rudder size and type, and steering type efficiency—
Determine the throw required by the autopilot by ascertaining the distance the helm needs to be turned for course correction. The "gain" setting controls on the autopilot are the speed and amount of movement at which the rudder responds to the helm. This setting can be adjusted to suit the sea conditions.
TYPES
There are three types of autopilot systems; tiller, wheel, and below-decks. - Tiller pilots
are the simplest in configuration and installation, making course corrections via a push-pull ram, which is attached directly to the tiller. The unit is usually installed on the coaming with a variety of mounting configurations and accessories to suit the individual vessel and owner requirements. These units are primarily used on smaller vessels for lake and inshore sailing in moderate weather and sea conditions, and when motoring.
- Wheel pilots are typically a belt drive system connected directly to the wheel with a remote drive motor usually attached to the pedestal. With the advancement of technology there is now a drive unit available with the drive motor attached directly to the wheel, eliminating the belt. These units are good in moderate wind conditions, coastal passages of short duration, and motoring. They are not designed for heavy offshore use.
- Below-deck systems are used primarily for heavy displacement cruising vessels and offshore work. The drive can be either a linear, hydraulic, or rotary unit, which is connected directly to either the rudderstock or the steering quadrant.
- Linear units operate in the same manner as a tiller pilot with a push-pull ram, which is either mechanical or hydraulic.
- Hydraulic units
are normally installed on boats already having hydraulic steering systems on board. These systems have a hydraulic ram connected to the rudderstock. The pumpset is connected to the existing hydraulic lines and can be either continuous running or reverse running pumps. Reverse running pumps operate simply by reversing the motor of the pump via electronic controls. Continuous running pumps are either electrical or engine drive. A solenoid controls the flow of oil into the hydraulic steering lines. - Rotary
, or chain drive, units consist of an electric motor, reduction gears, and chains and sprockets attached to the rudderstock, and are found on mechanical steering systems where the location restricts the use of a ram arm unit. They require lubricating and tightening on a regular schedule.
ACCESSORIES
Handheld remotes, interface "brains," joysticks and alarms all make for adaptable autopilots. - Hand held
remotes allow course changes from any location on the vessel. - Interface
with other electronics on board like GPSs permits the autopilot to steer a preset course taking into account set and drift and altering course as needed. - Interface
with wind instruments allows the autopilot to steer to the apparent wind if the vessel is under sail. - Joysticks
can increase rudder response through "power-assisted" manual control. - Alarms
, such as man overboard, off course, watch, and dodge capability offer electronic assistance to the shorthanded crew. - Tiller pilot
installation accessories are available to alter the height or length of the tiller pilot location. - Wheel pilot
belts are available in several lengths to accommodate different mounting locations and the belt-type drive units may require a pedestal-mounting bracket.
INSTALLATION
The average mechanically and electrically skilled person with minimal tools can install tiller and wheel pilots. Time will be required to test and adjust the autopilot for optimum performance. Toolbox: - Screwdriver
- Drill and bits
Under deck pilots, particularly hydraulic units, require skilled mechanical experience and a complete toolbox. Professionals should install these units if knowledge of hydraulic systems is thin or nonexistent.
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