How do antiroll fins work to oppose a ship’s roll?

Antiroll fins, also known as fin stabilizers, are active devices used in naval architecture to counteract a ship's rolling motion. Unlike passive bilge keels, which provide damping through their physical presence, antiroll fins are dynamic components that extend transversely from the ship's hull.12

These fins operate by rotating mechanically about their axes to create specific angles of attack as the ship moves through the water. By adjusting these angles, the fins generate hydrodynamic forces that continually oppose the rolling motion caused by waves. This system is typically controlled by a gyroscope, which detects the ship's roll and adjusts the fins accordingly to quench the motion.23

Because the effectiveness of these forces increases with the square of the ship's speed, active antiroll fins are most efficient on fast vessels and become ineffective at low speeds. While highly effective at reducing roll, they require significant space and cost, and they must be retracted into the hull when the ship is docked.21