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What is a linear drive?

- Fast reaction times thanks to direct power transmission -

Mechanical linear drives are among the most common propulsion systems for autopilots on sailboats: they are in fact silent and characterised by short rudder adjustment times. In electromechanical autopilots, a motor drives a linear thrust unit. This type of autopilot is always used when the steering system is purely mechanical. Regatta sailors in particular prefer this type of system because it provides better feedback and reacts faster to changes than, for example, a hydraulic drive. The disadvantage is significantly lower power. Nowadays, however, manufacturers promise ranges of application up to 20 t displacement and autopilots with hydraulic linear drives are also on the market. These devices are used on larger vessels, usually with a displacement of over 20 tons.

How does a linear drive autopilot work?

- Linear drive autopilots: automatic steering for motor and sailing vessels -

An electromechanical linear drive autopilot has a drive unit, compass sensor, course computer and control element. It engages mechanically in the rudder system with a movable bolt which is moved horizontally via an electric motor. This drive unit can be attached to the vessel via a suspension mounted on a base below deck near the radar unit. The push arm is connected to the rudder stock via the rudder quadrant or via a tiller arm, also called an auxiliary tiller.

The skipper sets the compass course for the autopilot via a control unit. This recognises the current course and carries out necessary course corrections independently. Typically, the autopilot receives data from an electronic compass sensor and additional GPS information. Additional sensors can be integrated via the NMEA2000 interface to help maintain course: for example, an autopilot equipped with a wind sensor is able to steer the sailboat autonomously according to the wind. Autopilots do not need to be calibrated, they can so themselves.

Which linear autopilot is right for my boat?

- Boat size is decisive -

Modern autopilots with mechanical linear drive are capable of providing considerable rudder power and are often installed on sailboats due to their compact size. Manufacturers describe their suitability for boats with a displacement of up to 20 tons. The ideal autopilot drive unit for your boat depends entirely on how much power you need. The decisive parameters are: stroke length, displacement in t, maximum thrust in kg, operating voltage (12 V / 24 V) and maximum rudder torque in Nm. This type of autopilot drive may only be used if it is possible to move the rudder manually. Experts also recommend that if you already have electronics on deck, such as a chart plotter or course computer, you should choose the same brand. Your autopilot should also always be able to deliver more power than intended: this reduces wear and tear and the risk of having to make unnecessary repairs.

You might also be interested in: Accessories for Marine Linear Drives

In our other shop categories you will find additional accessories such as drive or connection cables for the installation of your linear drive unit. For perfect linear drive control, we recommend a suitable controller or display from the manufacturers RAYMARINE and GARMIN.