Understanding Ship Hull Form and Geometry

Hull Form & Table of Offsets Sections 2.3 - 2.4

Ship Hull Form and Geometry The ship is a 3-dimensional shape: Data in x, y, and z directions is necessary to represent the ship hull Table of Offsets Lines Drawings: Body Plan (front view) Sheer Plan (side view) Half Breadth Plan (top view)

Hull Form Representation Lines Drawings: Traditional graphical representation of the ship s hull form Lines Half Half- -Breadth Plan Breadth Plan Sheer Plan Sheer Plan Body Plan Body Plan

Hull Form Representation Body Plan Body Plan (Front / End) (Front / End) Half Half- -Breadth Plan Breadth Plan (Top) (Top) Sheer Plan Sheer Plan (Side) (Side) Lines Plan Lines Plan

Body Plan Intersection of planes to define section line Front View Sectional lines show the true shape of the hull form Slices of Bread are called stations Forward sections from amidships : Right Side Aft sections from amidships : Left Side Middle slice = Midships 3 2 1 5 4 3 5 1 4 2 3 3

Sheer Plan Intersection of planes (buttock lines) parallel to the centerline plane Side View Slices are called buttock lines (cut like a hot dog bun instead of loaf of bread) Middle slice = centerline 2 1 1 2

Half-Breadth Plan Intersection of planes (waterlines) parallel to the baseline (keel). Half and Half on top of coffee or Hamburger Bun Typically just one side due to symmetry Slices are called waterlines 3 2 1 3 2 1

Basic Dimensions and Hull Form Characteristics FP AP DWL LOA LOA(length over all) : Overall length of the vessel. Bow to Stern DWL(design waterline) : Water line where the ship is designed to float FP(forward perpendicular) : imaginary vertical line where the bow intersects the DWL AP(aft perpendicular) : imaginary vertical line located at either the rudder stock or intersection of the stern with DWL Stations : parallel planes from forward to aft, evenly spaced (like bread).Normally an odd number to ensure an even number of blocks.

Basic Dimensions and Hull Form Characteristics FP AP Shear DWL Lpp Lpp Lpp ( (length between perpendiculars) : horizontal distance from FP and AP Amidships ( ) Amidships ( ) : the point midway between FP and AP Shear Shear : longitudinal curvature given to deck

Table of Offsets Table of numbers used to convert graphical information to a numerical representation of a three dimensional body Lists the distance from the center plane to the outline of the hull at each station and waterline There is enough information in the Table of Offsets to produce all three lines plans Numerical coordinates for the 3 (Body, Sheer, and Half-Breadth) Plans

Table of Offsets The distances from the centerplane are called the offsets or half- breadth distances.

Table of Offsets Example Given the following table of offsets, draw the body plan for stations 0, 2, 8 and 10

Table of Offsets Example 0 2 10

Questions?