A sailboat rudder is a vertical, underwater blade-like appendage located at the stern, used to control direction by deflecting water flow to pivot the vessel. It operates like an underwater wing, where turning the rudder creates pressure that moves the stern, allowing the boat to steer. Rudders are operated by a tiller or wheel and come in several types: spade, skeg-mounted, and outboard.

Key Components and Types
Spade Rudder: A high-performance rudder that is only supported by its shaft (or stock) going through the bottom of the hull.

Skeg-Mounted Rudder: A rudder attached to a skeg (a vertical extension of the hull) for increased protection and stability.

Outboard/Transom Hung Rudder: Typically found on smaller sailboats (under 30 ft), this rudder is attached to the outside of the transom.

Parts: The main parts are the blade (or shovel), which sits in the water, and the stock (or shaft), which connects to the steering gear, such as a tiller or quadrant.

Rudder Operation and Performance
Steering Mechanism: A tiller (stick) provides direct, sensitive feedback, often used on smaller boats. A steering wheel is used on larger boats, connecting to the rudder via cables or hydraulic mechanisms.

Dynamics: When the rudder turns, it disrupts the flow of water, creating a force that pushes the back of the boat to one side, causing the bow to turn in the opposite direction.

Maintenance: Rudders are often constructed of fiberglass with a foam core and require regular inspection, as the bond inside the rudder blade is vulnerable to damage.