The Perfect Storm: A True Story of Men Against the Sea

by Sebastian Junger

To greatly simplify, the lateral distance between the two forces is called the righting arm, and the torque they generate is called the righting moment. Boats want a big righting moment. They want something that will right them from extreme angles of heel. The righting moment has three main implications. First of all, the wider the ship, the more stable she is. (More air is submerged as she heels over, so the righting arm is that much longer.) The opposite is also true: The taller the ship, the more likely she is to capsize. The high center of gravity reduces what is called the metacentric height, which determines the length of the righting arm. The lower the metacentric height, the less leverage there is with which to overcome the downward force of gravity. Finally, there always comes a point where the boat can no longer right herself. Logically, this would happen when her decks have gone past vertical and the center of gravity falls outside the center of buoyancy—the “zero-moment” point.