ship construction

Forward and Aft

Terms used to describe the general location on the vessel or in a general direction to the front or back.

Astern / Abaft

Both of these terms are used to mean in a direction towards the stern of the ship.

Athwartships

This refers to across the width of the ship or perpendicular to the ship’s centreline. It is often expressed as transverse direction or abeam

Bow

The bow of a ship is the forward end or head of the vessel and normally refers to the section above the waterline. This region may include structures such as the forecastle, forward mooring station, store rooms and chain locker.

Stern

The stern of the ship is the after end of the vessel. It normally refers to the section above the waterline and this region may include structure such as the poop, the steering gear compartment and the stern mooring station.

port

left

starboard

right

transverse, longitudinal, vertical direction

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centreline

A ship’s centreline is a vertical plane running fore and aft along the length and through the centre of the ship form. The hull form is symmetrical on both sides of this plane.

Amidships

Amidships is a point found midway between the forward and after perpendiculars. It is used as a reference point for stability calculations as well as to describe the positioning of structures on a vessel. A symbol denoting this point is normally used (see in slide above).

Midships

This term may be used in place of amidships thus indicating a position midway between the forward and aft perpendiculars. It might also be used to describe a position midway between the sides of the ship thus representing the centreline plan.

Waterlines

With an increase in depth, changing water density and changing displacement, the same hull may have different waterlines when at rest. At even trim, these waterlines are parallel to the keel line.

stations of the ship

When extrapolating the midship section plane and duplicating it at equal intervals forward and aft, the resulting series of planes are called the stations of the ship. When viewed in the plan view, sections look straight, however, when viewed in the front view, they show how the hull changes at various locations. In the front view, stations aft of midship are usually shown on the left while stations forward of midship are seen on the right.