TERMINOLOGY & DEFINITIONS
In the shipbuilding and construction industry we all need to speak the same language. We need to talk like Naval Architects. This is to ensure that everyone knows exactly what is talked about and referred to when working with technical documentation or when on the shipbuilding site.
The following terms should never be used to describe a ship:
- The Aft end of ship is not called “the back”.
- The Forward end of ship is not called “the front”.
- The middle of ship is not called “the middle bit”.
- What you stand on when on a ship is never called “a floor”.
- Trim has absolute no relation to keeping fit.
- Sheer is not “steep”.
- A web frame is not accessible via the internet.
- A stem is definitely not part of a flower.
The correct terms to use for what has been described in the list above are as follows:
- The aft end of a ship is referred to as the stern.
- The forward end of a ship is called the bow.
- The middle of a ship is referred to as midships.
- What you stand on when onboard a ship is called the deck.
- Trim is the longitudinal attitude of a ship.
- Sheer is used as the term to refer to the longitudinal curvature of a ship structure.
- A web frame is a transverse side frame.
- A stem is the centreline (CL) apex of a ship’s bow.
The terminology used to indicate direction onboard a ship is also important. The following definitions are used to describe the general shipboard directions. Take note that the bow of the ship is the forward end of the ship while the stern is the aft end of the ship. The port side is the left side of a ship, indicated by a red light, while the right side of a ship is referred to as starboard, indicated by a green light.
General Hull Terminology
Forward Perpendicular: a vertical line extending from the point at which the stem of the vessel is intersected by the design load waterline on the profile view.
Aft Perpendicular: A line drawn perpendicularly to the design load waterline through the after side of the rudder post or through the axis of the rudder stock.
Freeboard: Freeboard is defined as vertical distance measured at the ship’s side between the summer load line (or service draft) and the freeboard deck. The freeboard deck is normally the uppermost complete deck exposed to weather and sea, which has permanent means of closing all openings, and below which all openings in the ship’s side have watertight closing.
Draft: Measured from the base line to the summer load line at the midship section.
Keel: The lengthwise steel structure along the base of a ship, supporting the framework of the whole and in some vessels extended downwards as a ridge to increase vessel stability.
Skeg: It is a tapering or projecting after section of a vessel’s keel.
LBP or LPP: The distance between the AP and FP.
LOA: The total overall length of the vessel parallel to the design water line of the ship.
Sheer: Sheer is defined as Curvature of decks in the longitudinal direction. Measured as the height of deck at side at any point above the height of deck at side amidships.
Depth: The vertical distance from the freeboard deck to the baseline of the vessel.
Turn of Bilge: The part of the bottom of a ship where the relatively flat shape begins curving up to form the topsides.
Beam: The overall width of the ship measured at the widest point of the nominal waterline.
Flare: Flare is the angle at which a ship’s hull plate departs from the vertical in an outward direction with increasing height.
Rake: A rake is an angle of slope measured from horizontal, or from a vertical line 90° perpendicular to horizontal. Stem Rake refers to the sloped angel of the stem.