Principles of naval engineering - Historic Naval Ships Association

PRINCIPLES OF NAVAL ENGINEERINGWATERLINES\V B ^-~ _.BDIAGONALSFigure 2-33.— Horizontal planes and half-breadth plan.23.194forward and after perpendiculars is known as 6-foot waterline, an 8-foot waterline, a 10-footthe middle perpendicular.waterline, and so forth.An actual body plan for a YTB is shown infigure 2-32. Note the projection of the diagonalson this body plan.HALF-BREADTH PLANTo visualize the half-breadth plan, we mustimagine the ship's hull cut horizontally inseveral places, as shown in part A of figure2-33. The cuts are designated as waterlines .although the ship could not possibly float atmany of these lines. The base plane whichserves as the point of origin for waterlinesis usually the horizontal plane that coincideswith the top of the flat keel. Waterlines aredesignated according to their distance abovethe base plane; for example, we may have aThe waterlines are projected onto the halfbreadthplan, as shown in part B of figure 2-33.Since the hull is symmetrical, only half of thewaterlines are shown in the half-breadth plan.Diagonals are frequently shown on the other halfof the half-breadth plan.SHEER PLANTo visualize the sheer plan, we must imaginethe ship's hull cut vertically in several places,as shown in part A of figure 2-34. The resultantcurves, known as buttocks or as bow and buttocklines , are projected onto the sheer plan,as shown in part B of figure 2-34. The centerlineplane is designated as zero buttock . Theother buttocks are designated according to their32