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What is a Rudder?

Harriette Halepis
Harriette Halepis

A rudder is a mechanism used to steer a boat, airplane, ship, hovercraft, or submarine. Rudders function by cutting through any kind of fluid, water or air, and forcing the fluid to pass by the body of a ship or airplane. A modern rudder looks like a flat piece of material that is attached to a vessel's tail or stern. However, rudders didn't always look like flat panels.

Archaeologists have found evidence that the Ancient Egyptians used to use special oars as rudders in order to steer canoes. Up to five different oars were used at one time to steer a boat in a desired direction. The Chinese Zhou Dynasty also used various oars to bring boats inland safely. Many people in China still use oars as rudders, since they are more practical than the modern rudder when it comes to bringing boats ashore and navigating tough waters.

Hovercraft use rudders to steer on both land and at sea.
Hovercraft use rudders to steer on both land and at sea.

The Ancient Romans developed the sexille rudder that was capable of steering massive ships through the Mediterranean. Once the Romans had perfected the sexille, Roman ships became some of the biggest, and most dependable, in the world. Mounted rudders were later developed during Medieval European times. These rudders were attached to ships through a pintle, a type of pin, and gudgeon,a circular piece that allows an oar or rudder to pivot, attachment. The placement of mounted rudders allowed Medieval ships to navigate particularly treacherous waters with relative ease.

On a boat with outboard motors, the hydrodynamic lower units that hold the propellers underwater also serve as rudders.
On a boat with outboard motors, the hydrodynamic lower units that hold the propellers underwater also serve as rudders.

Modern boat rudders may be installed either outboard or inboard. Outboard rudders are attached to a boat's stern or transom, while inboard rudders are generally attached to a skeg, an extension of a ship, or keel. Due to the placement of an inboard rudder, these rudders are completely submerged beneath water.

Aircraft rudders are generally referred to as the control surfaces. An aircraft's elevator, a control surface located at the rear of an airplane, and ailerons, control surfaces that are attached to the edge of a wing, help to control the aircraft. All of these things combined make up an airplane's control surface. Due to the immense pressure that an aircraft often confronts, it is not unusual for an aircraft rudder to break or become damaged. When this occurs, trained pilots must maneuver an airplane manually, which is often difficult to do.

To help maintain its stealthy profile, the rudders and vertical stabilizers on an F-22 Raptor are set at an angle.
To help maintain its stealthy profile, the rudders and vertical stabilizers on an F-22 Raptor are set at an angle.

From boats to airplanes, rudders are an important part of any aircraft or ship. Even though original rudders were nothing more than oars attached to the side of a ship, today's rudders are complex and intricate. Without the invention of the rudder, controlling an airplane or ship would be nearly impossible.

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    • Hovercraft use rudders to steer on both land and at sea.
      By: Commander, U.S. 7th Fleet
      Hovercraft use rudders to steer on both land and at sea.
    • On a boat with outboard motors, the hydrodynamic lower units that hold the propellers underwater also serve as rudders.
      By: Wimbledon
      On a boat with outboard motors, the hydrodynamic lower units that hold the propellers underwater also serve as rudders.
    • To help maintain its stealthy profile, the rudders and vertical stabilizers on an F-22 Raptor are set at an angle.
      By: dreamnikon
      To help maintain its stealthy profile, the rudders and vertical stabilizers on an F-22 Raptor are set at an angle.
    • The rudder of a sailboat, which can be found at the stern, can be clearly seen when the vessel is laid up on land.
      By: acnaleksy
      The rudder of a sailboat, which can be found at the stern, can be clearly seen when the vessel is laid up on land.