System suitability

This type of system is particularly suitable in cases where:

1. the boat is too large or heavy to be managed by a simple auxiliary rudder;

2. the transmission paths are too long for efficient use of a servo-pendulum gear (especially on boats with a centre cockpit);

3. the planned voyage is long, the crew small and consequently the very best steering performance is sought;

4. the presence of an emergency rudder is considered to be important, for instance on boats where the main rudder is not protected by a skeg;

5. the boat has a hydraulic rudder system - double rudder systems are the only form of self-steering which can be used on such boats (see remarks on hydraulic wheel steering).

Worldwide only two double rudder systems have ever gone into series production:

Fïg 5.19 H vane double rudder system. /

Fïg 5.19 H vane double rudder system. /

Wind Steering Systems
Windpilot Pacific Plus fitted on a Hallberg Rassy 36.

SAILOMAT 3040

This unit was originally designed for boats between 30 and 40 ft long (hence the name 3040). An H vane passes the steering impulse to a pendulum rudder whose shaft is inclined by 30°. The shaft has an upper extension which is attached to the auxiliary rudder so as to exert a force in the opposite direction to the movement of the pendulum rudder blade. The inclination of the shaft provides yaw damping.

This gear was produced between 1976 and 1981 and features a particularly compact linkage housing, the top and bottom of which also serve as the bracket for mounting the gear on the transom. The small size of the bracket means that the loads from the gear are concentrated in a very small area.

GRP boats consequently require large-scale reinforcement work at the stern to support the very high loads generated by the auxiliary rudder.

The fastening points of an auxiliary rudder system, and hence of a double rudder system, should ideally be spaced well apart to ensure good load distribution on the transom. The upper and lower regions of the transom naturally possess greater dimensional stability than the centre, so spacing the fastening points apart all but eliminates vibration as well.

The chief drawback of this particular system, aside from expense, is that it is rather complicated for everyday use. Removing the pendulum rudder involves releasing its fastening and then dropping it out of the bottom of its shaft - an awkward operation to perform every time you need to manoeuvre in harbour. The nature of the design restricts the lateral swinging range of the pendulum rudder arm to 20 degrees in each direction. Any further than this and the top of the shaft hits its end stops in the gearbox. This can be a real problem in big seas: Naomi James worked her way through a good handful of replacement rudder blades in the course of her remarkable circumnavigation with Express Crusader.

Sailomat 3040 fitted on a Hallberg Rassy 352.

Windpilot Pacific Plus

Windpilot's Pacific Plus has been around since 1986. It is probably the only double rudder system in the world to have been series-built during that period. The design reflects all the progress made over four decades of windvane steering development. The steering characteristics have been optimised and the system uses a bevel gear linkage for yaw damping and a horizontal windvane inclined by 20°. An endless worm gear provides remote operation. The pendulum rudder can be raised when the system is idle and the auxiliary rudder makes a good emergency rudder. The design aesthetics are modern and the modular construction makes installation of the system and removal of the pendulum components a simple task. The positioning of the auxiliary rudder right at the aft end of the boat also provides optimum leverage and, as a result, particular effective steering. These are the effective auxiliary rudder areas.

Fig 5,20 Windpilot Pacific Plus: 1 Windvane is deflected by wind and gives steering signal. 2 Via linkage, it turns the pendulum rudder 3 Water flowing past pushes the pendulum arm out to one side; a linkage (4) connecting the pendulum arm to the auxiliary rudder (5) transmits the steering signal. 6 The vane mounting can be rotated through a full 360°,

Fig 5,20 Windpilot Pacific Plus: 1 Windvane is deflected by wind and gives steering signal. 2 Via linkage, it turns the pendulum rudder 3 Water flowing past pushes the pendulum arm out to one side; a linkage (4) connecting the pendulum arm to the auxiliary rudder (5) transmits the steering signal. 6 The vane mounting can be rotated through a full 360°,

Pacific Plus I

0.27 m2 / 2 % ft2

Pacific Plus II

0.36 m2 / 3 2/3 ft2

Pacific Plus III

0.50 m2 / 5 / ft2

The pendulum rudder sits immediately behind the auxiliary rudder. This means that the two elements can be connected directly, eliminating the transmission losses (due to slack, stretch or bearing friction) typical of servo-pendulum systems, where the steering force reaches the main rudder via lines. This linkage between the gear's two rudders originally comprised a novel ball-and-socket joint. Once the ball socket in the tiller part of the auxiliary rudder had been loosened, the connection could be released, allowing the pendulum arm to be swung up out of the water. The pendulum rudder on the equivalent Sailomat unit, which lacked this feature, could only be removed by dropping it out of the bottom of the system.

Starting with the 1998 model, the Pacific Plus now has a bevel gear rocker segment connection between the pendulum and auxiliary rudder. This 'Quick-in, Quick-out' linkage can be released with one hand even under load. A special device ensures that the auxiliary rudder remains centred when it is out of use and the pendulum rudder is in the raised position. The Pacific Plus also has a facility which allows the windvane to be fixed on centre. Engaging this feature prevents the pendulum rudder from starting to swing around as soon as it is lowered into the water. Once the bevel gear linkage has been reconnected, the windvane is released and the system begins to work. A retaining pin for connecting up a tiller autopilot is also standard on the current model.

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