Autopilots are essential for any craft planning long distance passages, particularly when shorthanded, and can also be valuable for boats looking to steer repetitive courses while those on board are otherwise occupied, for example fishing. They genuinely do add another crew member who works 24 hours a day without food or pay, and who never loses concentration. That said, a human member of the crew must always be on watch to look out for other vessels and similar hazards.
An autopilot system will steer a boat without human interference once the necessary data has been entered. The purpose of this article is to remind purchasers that they have a number of types from which to choose, and also that they are generally made up of a number of components that may need to be selected and purchased separately.
The most basic autopilots are tiller pilots, used to control the tiller on board small sailing boats. These can in fact be single units that contain a compass, motor and pushrod to move the tiller back and forth, and a simple keypad with which to set the heading. Once that is fitted all that is then required is a power source which connects to the tiller pilot via a cable. However more sophisticated systems for craft that have a wheel that by definition is not directly connected to the rudder will require some or all of the following components to function.
this is the visible component of an autopilot system that you will see on display at your dealer or at a manufacturer’s stand at a boat show. They come in both remote and mounted versions, and it is into these that the information required to set a course is entered and which may, in some models, also display relevant data regarding the current operation of the system. Top-of-the-line systems can enable the user to also pre-programme course alterations and steering patterns, as well as display information including the heading required, actual compass bearing, rudder angles and more. The extent to which the buyer will need all the supporting functionality that is now available will depend on the type of boating that they do.
– these are the brains of the system that receive of the data inputs from the control heads and other instruments (see below), analyse it and then issue the necessary commands to the drive units. These are ‘black box’ units that have no direct controls of their own and are generally mounted out of sight.
– the ‘muscle‘of the autopilot system, the drive units are responsible for moving the rudder or, in some cases, the propulsion unit itself. On smaller sailboats with cable steering the most common type use is a linear drive unit, which users a rod attached directly to the steering quadrant to move the rudder. Linear drive units can come in both mechanical and hydraulic versions, with the latter generally designed to be more powerful. Another variation is a rotary drive unit that can be fitted at the helming position to control the rudder by using a sprocket to move the steering chain. Larger craft with hydraulic steering systems will generally require a complementary hydraulic steering system.
Compass
– every self-steering system requires a compass input in order to steer to a heading. This is generally provided by a fluxgate (electronic) compass connected to the autopilot computer.
Rudder position sensor
– this tells the autopilot computer the angle of the rudder at any particular time. Rudder position sensors are not always considered essential, but can both aid the performance of the pilot and contribute to more gentle and accurate steering.
– when the autopilot needs to be programmed to steer to a specific Lat / Lon position it will require connection to a GPS unit in order to direct the craft from its present position to its required destination. Advanced pilots can however be additionally programmed to undertake manoeuvres such as steering around obstacles or following the line of the seabed, and at this stage they will generally connected to become part of a wider integrated navigation system using an NMEA2000 or equivalent networking protocol to both receive and broadcast data to other instruments such as echo sounders and GPS chartplotters.
Additional optional accessories may include remote controls and steering joysticks.
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