Superyacht Stability

Article about effects of gravity and buoyancy on stability

GRAVITY AND BUOYANCY

Archimedes claimed that any object thrown in to water will displace the same amount of water that it was emerged in and then come to equilibrium. Every boat obeys Archimedes principles and displaces the same amount of amount as the weight of the boat. If you move a boat through the water, the water will push the boat up while the center of gravity is pulling the boat down. The force of gravity pulls down the boat, the force of buoyancy is the force of displacement (upward force by the water attempting to displace the weight of the boat). The center of gravity (G) is the balance point of the weight. If you change the weight on various parts of the boat, you will change the center of gravity. The center of buoyancy is the point where the upward force of the water is located. The center of gravity’s balance point will shift if you change the weight. Depending on how the water is displaced, you can determine where the balance point of the center of buoyancy is located. The center of buoyancy will be directly located under the center of gravity. If the boat is heeling (tipping), the center of gravity will not change its location but the center of buoyancy will change its location. The force of gravity is pushing down on the boat while the center of buoyancy is pushing the boat up. The Metacenter is a theoretical reference point used in naval architecture to determine a boat’s stability. The Metacenter is the point where the Center of Gravity and Center of Buoyancy intersect. The Metacentric height is the height of the Center of Gravity to the point which the Center of Buoyancy intersects. The Metracentric height is used to help determine the stability of a boat.