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Self-Steering Principle

SAILOMAT self-steering systems use the all-mechanical 'servo-pendulum' principle. This is the most advanced and most reliable principle known, offering a desirable combination of high sensitivity, high steering torque and high yaw damping. The self-steering is fast, automatic and efficient.

Basically, a 'servo-pendulum' system consists of a dual-axis air-vane sensor for course deviation, a servo blade ('oar blade') suspended from a pendulum carriage into the waterflow for signal amplification, and torque output lines from the pendulum carriage to the tiller or the wheel of the yacht. The figure shows a simple 'servo-pendulum' SAILOMAT 536 (predecessor to model 601) system operating a tiller-steered yacht.

The course is selected by turning and then locking the vane base (turret) on the mast tube around its vertical axis. When the yacht is sailing on the desired course, the air flow is parallel to the flat surface of the air vane, which is well balanced (with the counterweight) around the near-horizontal pivot axis. The vane is in it's neutral, vertical position.

Self-steering action is described in the following steps (1) to (5):

1. With the yacht slightly off course, the air vane is pivoted by side air flow ( small angle of attack). A mechanical torque is generated. This is the course deviation signal.

2. The vane torque (signal) is mechanically transferred to axial pushrod motion inside the circular mast tube of the SAILOMAT.

3. The pushrod motion is converted into a slight turning motion of the servo blade.

4. With the turned servo blade the water flow generates hydrodynamic side force , driving the servo blade and the servo-pendulum assembly to the side (swing motion), away from the neutral position. The servo blade thus extracts mechanical energy from the water flow. The pendulum pulls the line circuit with a high (amplified) force, typically 100-1000 times higher than the 'signal' force on the air vane sensor.

5. The line circuit controls the helm (tiller or wheel) with pull/pull lines, and the yacht's main rudder steers the yacht back to the desired heading. Air vane , servo-blade and main rudder then return to original their (neutral) positions. The self-steering course correction is then completed. Properly designed, the steering correction should be fast, highly accurate and also damped to avoid course oscillations.

Self-Steering PrincipleTechnical DataOff-Center MountingInstallation Examples


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