Why does Althea Float?
At first glance, it may seem surprising that Althea, a large yacht made primarily of steel, is able to float while a solid piece of steel sinks. The answer lies in Archimedes’ Principle, discovered over 2,000 years ago by the Greek mathematician Archimedes. His principle states that an object immersed in a fluid experiences an upward buoyant force equal to the weight of the fluid it displaces. In other words, when Althea is placed in the water, it pushes aside (displaces) a large volume of water. The weight of that displaced water creates an upward buoyant force that acts against gravity.
Although steel is much denser than water, a yacht is not a solid block of steel. Althea’s hull encloses a large volume of air, making the average density of the entire yacht (steel, wood, equipment, people, and air combined) less than the density of water. As the yacht settles into the water, it continues to displace more water until the buoyant force exactly equals the yacht’s weight. At this point, the forces are balanced, and Althea floats in equilibrium.
This balance between gravity and buoyancy is one of the fundamental principles of naval architecture. Every voyage aboard Althea is a demonstration of Archimedes’ Principle in action. The carefully designed shape of her hull allows her to displace thousands of pounds of water, producing enough buoyant force to support the weight of the yacht while allowing her to sail safely and efficiently across Grand Traverse Bay.