What is an Autopilot?

An autopilot is not unlike cruise control in a car, except that instead of holding a steady speed it allows the vessel to hold a steady course.  This course is derived either from an electronic compass (e.g. fluxgate, Transmitting Magnetic Compass, satellite or gyro compass) or from a waypoint referenced from a chart plotter.  The vessels course is corrected by movements to the rudder and this can be done either through a hydraulic or electrically operated steering ram.  Just like cruise control in a car the autopilot still needs to be supervised - it needs someone on watch!. 

An Autopilot installation has several components and it is important that they are matched to the vessel which they are controlling.  However the good news is that suppliers are now providing autopilot kits so that where the owner has the ability and understanding to install, they can do so. 

Selecting an Autopilot

There are many autopilots to choose from. When selecting an autopilot for your boat, there are important factors to consider. Surprisingly it's not so much the sophisticated electronics and display that are critical but the selection of a suitable unit to control the rudder.

The boat’s size is rarely a critical issue in the choice of autopilot. However for smaller boats, it is natural to think of available space and select an autopilot that occupies the least space.  The display is the visible part and often the smallest part.  Autopilots may also include a control/junction box, a compass, rudder feedback unit and will need connecting to the exsiting steering system.

The control/junction box often needs to be installed in a protected space away from the elements.  The TMQ AP47 has a major advantage here in that it does not have a control/junction box and is ideally suited when space is at a premium.  The compass will need placing in a suitable location so that it can provide optimum performance.

The most critical decision concerns the boat’s steering system. The autopilot is not a complete system until a drive unit is chosen. The drive unit transforms the electrical signals from the autopilot into mechanical movements which turn the boat’s rudder, stern drive or outboard motor. The existing type of steering system dictates what kind of drive unit the autopilot needs to complement it.  These drive units can take up a fair amount of space particularly at the mechanical connection to the rudder.

The following sections give a simplified method of selecting an autopilot for your boat.  These are generalised solutions and if you need assistance please feel free to contact us.

With it's virtual rudder feed-back the AP47  makes for an easy installation on boats with outboards and stern drives under 8 mtrs.

If your boat already has hydraulic steering fitted then you only need to install a hydraulic drive unit, such as a reversible electric pump which connects to the existing hydraulic hoses. Chosing the right size of the pump is dependant on the volume of the existing hydraulic ram that moves the rudder. Most kinds of autopilots need a “hard over” time between 8 to 14 seconds this in turn specifies the pump flow rate.  Reversible hydraulic pumps are smaller and use less power than continuously running pumps.

The TMQ AP47 is a popular autopilot for trolling fishing as it can steer the boat accurately, particularly at very low speeds of  around 1-2 knots.

Small and medium-sized motorboats with a steering wheel frequently have a rotary drive with a cable attached to the outboard motor or stern-drive. Drive units are available that complement existing cable systems. The most common solution for cable steering is to replace the rotary drive behind the steering wheel with an electric motor. Setting the autopilot in it's active mode allows the boat to be steered automatically. When the autopilot is in standby mode the boat is manually steered by the wheel.

Boats longer then 8 meters need an autopilot with a rudder feed-back unit like the AP47R. Most of them have hydraulic steering systems and the autopilot can connect to the existing hydraulic systen with a reversible pump.

Chosing the right size of pump is dependent on the volume of the existing hydraulic ram that moves the rudder. Most kinds of autopilots need a “hard over” time between 8 to 14 seconds which in turn specifies the pump flow rate.

Where a boat has two steering positions,one on the fly-bridge and one internally for example, an autopilot such as the AP55 should be choosen. Most boats of this size would have hydraulic steering systems and the autopilot should be fitted with a reversible pump.

To chose the right size of the pump is dependant on the volume of the existing hydraulic ram that moves the rudder. The previously stated “hard over” time between 8 to 14 seconds specifies the pumps flow rate.

The Remote Sailboat Drive System makes it easy and economical to install an autopilot on light displacement Sailboats steered mechanically by a cable or tiller. The drive is very responsive and has little feedback resistance when in ‘Standby’ Pilot mode making it very suitable for use in racing Yachts.

Linear drives can be fitted into very small spaces which makes them ideal for the smaller to midsized modern yachts (up to 7000 kg displacement) where there is often limited space in the stern to fit drive units.

Sailboats above 14 mtrs require a more powerful hydraulic linear drive system. To select a suitable drive it is neccesary to calculate the required rudder torque to select the right drive system. Contact us and we will be happy to assist you with selecting the correct drive unit.

We can supply a wide range of kits that are tailored to your specific needs. Some of the more popular ones are available in our store now. Please feel free to contact us for more details.

Source material TMQ Europe