Bulb keel

A bulb keel is a keel, usually made with a high aspect ratio foil, that contains a ballast-filled bulb at the bottom, usually teardrop shaped. The purpose of the bulb keel is to place the ballast as low as possible, therefore gaining the maximum possible amount of leverage and thus the most righting moment. An example of a class of boats that use a bulb keel is the International 110 racing class, which uses a 300 lb (136 kg) cast iron bulb keel on a boat whose minimum racing weight is 910 lb (414 kg).