Steering
A sailing boat is steered by the rudder under water. The pressure of the water flowing past the rudder blade at an angle generates a lateral force at the stern, which turns the boat about its vertical axis. For the rudder to be effective the boat must have way through the water.
Rudder
The rudder consists of the rudder blade and the rudder stock connected to the boat's hull. Depending on the boat type and size, it is operated in different ways:
- Tiller: a simple lever directly on the rudder stock. Common on dinghies and smaller yachts.
- Wheel: connected to the rudder stock by cables or rods. Common on larger yachts, since the operating forces are smaller.
Steering with the Tiller
The tiller works opposite to the desired direction of turn:
- Tiller to port → boat turns to starboard.
- Tiller to starboard → boat turns to port.
When steering with a wheel, the boat turns directly into the desired direction, as in a car.
Rudder Effectiveness
The effectiveness of the rudder depends on several factors:
- Way through the water: without flow there is no steering effect.
- Rudder angle: up to about 35° the lateral force grows; beyond that, the flow separates and the rudder loses effect.
- Flow at the stern: the propeller wash from a motor strongly increases the steering effect, so during manoeuvres "give it some throttle".
Steering Under Sail
When sailing, the sail trim also affects the turning behaviour:
- Mainsail alone set: the boat luffs (turns into the wind).
- Headsail alone set: the boat bears away (turns out of the wind).
- Both sails balanced: the boat keeps a neutral course.
This property can be used to make course changes with little rudder deflection and therefore little braking effect.
Luffing and Bearing Away
- Luffing: turning the boat into the wind.
- Bearing away: turning the boat out of the wind.
When luffing, the sails are sheeted in; when bearing away, they are eased correspondingly so the angle of attack to the wind is maintained.
Compass Course
On the water, you generally steer by compass course. Steering is done with the magnetic compass, taking variation and deviation into account.