Upgrade: Autopilots

Autopilots. These days, more sailors swear by them than at them, as they used to do in the bad old days when the technology wasn’t anywhere near as solid as it is today. Autopilots for small craft arrived after World War II, when Simrad introduced its first models for use on commercial fishing boats. The technology gradually found its way onto recreational boats, and the major manufacturers have
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Autopilots. These days, more sailors swear by them than at them, as they used to do in the bad old days when the technology wasn’t anywhere near as solid as it is today. Autopilots for small craft arrived after World War II, when Simrad introduced its first models for use on commercial fishing boats. The technology gradually found its way onto recreational boats, and the major manufacturers have been honing the features and functions ever since. As with many other aspects of modern technology, prices have come down while the technology has advanced. Today, even basic autopilots are sophisticated electronic devices that earn their keep on sailboats of all sizes.

An autopilot easily becomes an essential helper, freeing shorthanded crews from helm duties and allowing them to concentrate on navigation, seamanship, and sail trim. A modern autopilot can tack or gybe the boat with the push of a button. When interfaced with a GPS or chartplotter, it can make steering to waypoints easier and more accurate by adjusting the course to compensate for current or wind. If the autopilot is properly matched to the boat, it will steer a better course than a person can, a real advantage when navigating through thick fog, though it won’t replace the human brain.

Most autopilots can adapt to changing sea states and wind conditions, thus reducing speed-sapping rudder movement that consumes precious electricity; most of the more-sophisticated autopilots have software that learns and remembers the steering characteristics of a particular boat. And many of them can be operated with a handheld wireless remote-control unit, enabling you to make course corrections from anywhere on the boat.

All offshore sailors (and most coastal sailors, too) are familiar with fatigue and its tendency to lead to potentially dangerous mistakes. Autopilots are an effective way to reduce this danger while under way, particularly for a shorthanded crew. The downside is the tendency of some skippers to set and forget their autopilots, losing all semblance of situational awareness. An autopilot will steer you right onto an obstruction or into the path of an oncoming ship if you aren’t mindful of your surroundings and your course. An autopilot is a great tool, but it’s only as good as the sailor operating it.

How autopilots steer

The most common autopilots on small to mid-size sailboats are tiller and wheel models that are connected directly to the helm. They include a fluxgate compass sensor, a microprocessor, and a drive unit to do the heavy lifting.

A tiller autopilot for a boat displacing up to 10,000 pounds is typically housed in a single watertight unit that includes the controls, the microprocessor, and the drive motor, which is mounted in the cockpit and attached to the tiller. A pushrod moves in and out of the drive unit’s body, pushing or pulling the tiller as needed. Larger tiller-steered boats that displace up to 15,000 pounds need more-powerful autopilots, and some of these feature a separate drive unit and a control head that can be mounted in the cockpit.

Originally, wheel-mounted autopilots relied on a wire run in the cockpit connecting the drive belt and its various parts; the wire often got stumbled over or ripped out. Modern autopilots circumvent this problem.

Tiller and wheel pilots for small to mid-size boats typically draw 0.5 amp in standby mode and from 1.5 amps to slightly more than 2 amps when steering in boisterous conditions. Draw depends on the specific model, the boat’s displacement and steering characteristics, and the sea state.

Cockpit-mounted autopilots are a simple solution for coastal passages aboard boats displacing up to 15,000 pounds. A belowdeck autopilot, however, is the answer for larger boats and for long-distance passages or races. It will also perform better in rough seas.

Belowdeck autopilots include a fluxgate compass sensor, a microprocessor, drive components, a control head, and often a rudder sensor to feed rudder-position data to the computer software. Instead of connecting directly to the helm, these systems turn the rudderstock either with linear drives connected to a tiller arm or the steering quadrant or with rotary drives, thus taking the load off steering cables and chains and safeguarding backup steering if the mechanical steering (cables, chains, or sheaves) is damaged.

A mechanically steered boat will have an electrical-mechanical drive unit or a hydraulic drive with a bypass valve that is opened for manual steering. Boats with hydraulic steering will typically have an electrical-hydraulic autopilot system with an electric pump set and a hydraulic cylinder to move the rudder. Regardless of the steering, mechanical or hydraulic, the installer will need to fabricate a mount for the drive unit, either on a bulkhead or to the hull. Power draw varies widely, but it’s substantial—roughly 8 amps for a linear drive that’s capable of steering a boat displacing 40,000 pounds in average conditions.

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