This is a type of sailboat which differs from dinghys and catamarans in that it relies on ballast in its keel to remain upright. The sails of a sailboat when in the wind tip it over. In dinghys this is counteracted by the crew moving to windward, in catamarans the wide base provides stability. In a keel boat the ballast, usually lead, is put as low as possible, usually at the end of a foil, to make sure the centre of gravity is below the centre of bouyancy, ensuring by the laws of statics that the form stays upright.