Also found in: Dictionary, Thesaurus, Medical, Legal, Financial, Acronyms, Idioms, Wikipedia.
the contours of the outer surface of a vessel’s hull. They are depicted graphically by the lines drawing plan of the vessel. The shape of the lines affects the water resistance to the vessel’s motion, the operating conditions of the engines, the vessel’s ability to mount waves, its icebreaking performance and seaworthiness, and other service characteristics. The lines of water-displacing vessels show the shape of the bow and stern frames (U-shaped and V-shaped), and the sharpness of the lines indicates the block coefficient (the ratio of the submerged volume of the vessel’s hull to the volume of a parallelepiped having the same overall dimensions). The optimum lines are determined by model tests of a vessel in an experimental pool. Slow-speed vessels and those that are not self-propelled can have bluff lines (simplified lines formed by flat surfaces).