A canting keel is a type of ballast unit used on sailing vessels. The unit will thrust toward the windward side of the vessel as the wind pushes the sail in the other direction, providing stability when the vessel is being propelled forward or executing turns. The canting keel extends far below the hull of the vessel, and it is attached to the hull by a canting strut, which is an extension made from rigid material. This strut must be extremely rigid to withstand the forces of the water and wind on the boat.
The canting keel is often used in conjunction with fin keels to further enhance the stability of the craft. Fin keels are useful for steering and stability capabilities when the craft is heeling, or leaning, but when the craft is righted, the fin keels do little to provide stability or the ability to right the craft when necessary. A canting keel, therefore, performs this function by providing counter-ballast to the force of the sail being propelled by the wind when the vessel is righted. It does so by resisting movement through the water and providing a lower ballast for the hull. The canting keel pivots independently of the angle of the craft, which means it can provide counterbalance when necessary.
Foils fore and aft, or on the front and back of the hull, can be used for quick steering and maneuverability independent of the canting keel. Foils are sometimes shaped like airplane wings, and they extend down into the water vertically from the hull. This design was most commonly used on larger sailing vessels, but the design has become more common on smaller vessels as well. Many racing vessels use the design for quick steering and stability at high speeds.
One of the biggest problems with a canting keel is the potential for leakage through the plates that connect the keel to the hull of the boat. Leakage can lead to damage of the hull, which can in turn pose a risk for sinking the ship. Several racing vessels have been lost to such leakage, and many designs have been developed to counteract such problems, though the problems do tend to persist. This keel design is not allowed in all types or sailboat racing, as some race officials consider the design to be an unfair advantage over other competitors without the keel design.