Rupert Holmes looks at how to choose a suitable autopilot system for cruising yachts
There’s a bewildering array of options available for autopilot systems, which can make selecting the best for your yacht a daunting task.
Some manufacturers offer such a plethora of products covering everything from outboard-powered fishing boats to large motor yachts it can be difficult to pick out those that are ideal for sailing yachts of moderate size.
Equally, you may be able to retain some elements of your existing system, such as the drive unit and control pads, which will reduce the cost of upgrading your autopilot.
Many systems are sold as packages, which can add to the confusion.
However, these make more sense once you figure out the key items – especially the compass, 9-axis sensor or course computer – most boats will benefit from updating.
Integration with other on board electronics is an important factor if you want the autopilot to steer to a constant wind angle, or to display compass course on the instruments.
Mixing autopilot brands?
While many items from different brands will talk to each other, it makes sense to limit the variety as far as possible to avoid any problems.
However, there’s usually no need for drive units to be the same brand as the remainder of the system.
These are generally fairly simple 12/24V motors that respond in the same way to the output from the course computer, without other complex electronics that need a data feed with specific protocols.
It’s always worth checking with suppliers, or directly with a manufacturer’s technical helplines, to be sure that the products you plan to buy will work together as expected.
Before going shopping, make an audit of the elements of your existing autopilot system – and what will benefit from replacement.
In many cases an autopilot system can be updated significantly without replacing the drive unit, control keypads or display units, which can make upgrading more affordable.
In most cases drive units are specified for a maximum laden displacement.
For many yachts this can easily be in excess of 20% above the boat builder’s quoted figure for light displacement.
Many companies bundle the parts that are most likely to be needed to upgrade an existing system into packages, often at reduced prices compared to the individual components.
Garmin, for instance, calls these ‘Corepacks’ and, unlike other manufacturers, this is the prime way in which key components other than control units and drives are sold.
The GHP Reactor Mechanical Retrofit Corepack (£1,460) includes a 9-axis sensor, course computer, and the higher-spec GHC20 control display.
It’s therefore a cost-effective option offering for anyone looking to update an existing system.
Raymarine’s EV-200 Sail Pack (£2,115) consists of an EV-1 Sensor Core, ACU-200 pilot computer, p70/70s control head, plus a cabling kit.
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1. Below deck drive units
These are a key in getting good pilot performance and in maximising reliability.
Yet in many ways the physical means of moving the rudder has changed little in the past decade or two.
Whether driven directly by an electric motor, or via hydraulics, these are non-intelligent items that simply respond to the changing 12V (or 24V) outputs from the course computer.
The two key choices are between hydraulic and electric-mechanical units and between a linear or rotary drive.
Linear drives are used to connect directly to the quadrant and are the most common type, especially on relatively recent boats.
Rotary drives can drive a gear wheel where the steering system incorporates a chain drive.
Electric units are more efficient on power consumption, easier to install and cheaper than hydraulic options.
However, the latter can be more powerful, so are typically found on larger yachts.
Garmin offers a number of Linear Drives, including the Class A Mechanical Linear Drive (£1,600) for yachts up to 12,900kg loaded displacement.
The company’s Class B units include a compact model rated for 22 tons, while the standard size model will cope with 35.8 tons loaded displacement.
Similarly Raymarine’s mechanical linear drives (£1,800-2,065) are offered in three sizes for boats with displacement of up to 11,000kg, 15,000kg and 20,000kg laden displacement.
Above this a hydraulic drive will be needed.
2. Tiller pilots
These naturally fall into two different categories – all-in-one units that include a basic course computer, fluxgate compass, control pad and, in some cases, a one-line display.
Some can also interface with other on-board electronics.
Raymarine’s ST1000 (£525) and ST2000 (£630) are basic all-in-one models for boats up to 3,000kg and 4,500kg respectively.
They are now dated units that include only a basic fluxgate compass and limited connectivity via Raymarine’s original SeaTalk, or NMEA0183 for GPS and apparent wind data.
If you’re able to spend more there are much better options available.
Raymarine’s EV-100 Tiller Pilot is a motor-only unit for boats up to 6,000kg that can be paired to an ACU-100 course computer and EV-1 9-axis sensor.
It’s therefore capable of steering a much better course than the ST1000/2000 models, though won’t match the performance of a belowdeck system as it’s impossible to fit a rudder angle sensor.
In addition, unlike B&G’s SD10 drive there’s no automatic clutch, so switching between automatic steering and standby modes may not be a smooth operation in challenging conditions.
The EV-100 tiller pilot is priced at £1,365, packaged with an ACU-100 course computer, EV-1 sensor and cabling kit, though a control unit is still required.
While the Navico group’s products for sailing have been sold under the B&G brand for almost a decade, this isn’t true of its all-in-one tiller pilots, which are legacy products that still carry Simrad branding.
The TP10 (£470) is a basic standalone model for smaller boats, while the TP22 (£610) and TP32 (£760) models can operate in either standalone mode, or networked with wind instruments and/or separate compasses via NMEA0183 or 2000.
They are suitable for boats up to 34ft and 37ft respectively.
A neat alternative to a conventional tiller pilot
The B&G SD10 drive (£1,059) is a neat alternative to a conventional tiller pilot that uses a Bowden cable (as used for steering most RIBs) to connect a below-decks motor to the tiller.
It has two further big advantages over conventional tiller pilots.
Firstly there’s a clutch, so the pilot is always connected to the tiller and doesn’t need to be removed when returning to manual steering mode.
Secondly, it incorporates a rudder angle sensor, so offers tiller steered yachts that don’t have a quadrant all the advantages of a below decks system.
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3. Wheel autopilots
These have an on-deck motor much as for tiller pilots, making them a cost effective option with relatively easy installation.
However, unlike a below deck system, the motor unit is exposed to the elements and there’s a limit to the size and weight of a yacht that can realistically use a wheel pilot.
In addition, they generally can’t use a rudder angle sensor, so course keeping is compromised.
Raymarine is the only company that now offers a wheel pilot, the EV-100 Wheel Pilot (£665).
It produces 30Nm of thrust and is suitable for boats with a laden displacement of up to 7,500kg.
Both SeaTalkNG and NMEA2000 data protocols are supported.
It’s designed to be used with an ACU-100 course computer and EV-1 Sensor.
4. Course computers
This area has seen huge development and significant improvements to course keeping.
All current systems will interface with the 9-axis sensors that measure rate of yaw, pitch and heel, as well as having a built in gyro compass.
They can therefore respond to gusts and waves even before the boat has changed course.
Raymarine produces several different course computers (Autopilot Control Units, or ACU) to suit different types of boat and drive unit.
Although not all are suited to sailing yachts.
Designed to simplify use where possible, much of the set up process is automated, and there are no user-adjustable settings beyond three easy to select modes.
The latest Lighthouse II software update includes stabilisation of wind speed and angle using data from the 9-axis sensor; which means even better course keeping.
The ACU-100 (£420) is for smaller sailing yachts using the EV-100 tiller or wheel pilot.
The ACU-200 (£845) is for any vessel with one of the company’s Type 1 drive units.
It can supply up to 7A of power to the drive unit and suits most boats up to 11,000kg laden displacement.
The more powerful ACU-400 (£1,905) can supply 30A to 12V or 24V systems; capable of steering very large yachts, including those with hydraulic drive units.
In both cases the units are capable of using both Raymarine’s SeaTalkNG data protocol and NMEA2000.
Outside its high-end H5000 series B&G offers the NAC-2 (£950) and NAC-3 (£1,700).
The former provides output current of up to 8A for yachts of up to 35ft, whereas the latter is rated at 30A continuous, for larger yachts.
Garmin’s course computers are offered as part of its Core Packs.
5. Essential accessories for autopilots
The choice of system elements, including rudder angle sensors, compasses – or 9-axis sensors – and control keypads or displays is determined by the brand of your pilot computer.
Note that some drive units include a rudder angle sensor.
Rudder angle sensor
Sometimes supplied with the motor; check specs when comparing prices.
- Garmin GRF10 Rudder Feedback Sensor (£199)
- Raymarine M81105 Rudder angle transducer (£265)
- B&G has four options to suit different systems (priced from £290-320)
All the main manufacturers now use 9-axis sensors that measure heading, rate of turn, pitch, roll and yaw, giving far greater data inputs to the course computer than gyro compasses that were the best option less than 10 years ago.
Garmin only lists this sensor in its pilot packages, but Raymarine’s EV-1 Sensor is available separately for £740, while B&G’s Precision compass is £680.
6. Control pads and remotes
These can add significantly to the cost of an autopilot system.
But if you ever sail short handed, then a controller at the helm and one at the companionway, allowing the boat to be conned from the shelter of the spray hood, are a minimum for any offshore yacht.
This also offers a layer of redundancy should a unit fail.
In many cases a multifunction display (MFD) can be used to control a pilot of the same brand, though can be a lot more convoluted than using a keypad.
Remote controls are great for anyone on watch alone, but can be an expensive upgrade, especially if you need to also buy a base station to communicate with the remote.
- Raymarine’s p70s control head is the company’s latest unit designed for sailing yachts, with the four familiar buttons for course changes (£630)
- Raymarine Smart Controller (remote) with base station (£630)
- Raymarine S100 wireless remote with base station (£440)
- Garmin GHC10 Marine Autopilot Control Unit (£500)
- Garmin GHC20 Marine Autopilot Control Unit (£580)
- Garmin CHC10 Remote (£270)
- B&G’s Triton2 keypads (£350 each)
A Triton2 display (£530) is needed as well, but can also be used to display other data.
TECHNICAL HELP FOR AUTOPILOTS
Once you’ve outlined what you think is the best upgrade route don’t be shy about asking for help to confirm you’ve identified the best options.
Many manufacturers have both online and telephone helplines:
About the author
Rupert Holmes is a freelance yachting journalist with more than 85,000 miles’ experience in a wide variety of craft, including cruising and racing yachts, and significant shorthanded sailing.
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