SHIP MEASUREMENTS

Ship measurements consist of a multitude of terms and definitions specifically related to ships.

Definitions

Beam:
The width of the ship

Complement :
The full number of people required to operate a ship. Includes officers
and crewmembers; does not include
passengers. For warships , the number of
people assigned to a ship in peacetime may be considerably less than her full
complement.

Cube :
The cargo carrying capacity of a ship,
measured in cubic feet. There are two
common types:

Bale Cube (or Bale Capacity )-

The space available for cargo measured in cubic feet to the inside of the cargo battens, on the frames, and to the underside of the beams.
It is a measurement of capacity for cargo
in bales, on pallets, etc., where the cargo
does not conform to the shape of the ship.

Grain Cube (or Grain Capacity )-

The maximum space available for cargo
measured in cubic feet, the measurement
being taken to the inside of the shell
plating of the ship or to the outside of the
frames and to the top of the beam or
underside of the deck plating. It is a
measurement of capacity for cargo like
grain, where the cargo flows to conform to the shape of the ship.

Displacement -

A measurement of the weight
of the vessel, usually used for warships.
(Merchant ships are usually measured based
on the volume of cargo space; see tonnage ).
Displacement is expressed either in long
tons of 2,240 pounds or metric tonnes of
1,000 kg. Since the two units are very close
in size (2,240 pounds = 1,016 kg and 1,000
kg = 2,205 pounds), it is common not to
distinguish between them. To preserve
secrecy, nations sometimes misstate a
warship's displacement.

Displacement, Light

The weight of the ship excluding cargo, fuel, ballast, stores,passengers, and crew, but with water in the
boilers to steaming level.

Displacement, Loaded

The weight of the
ship including cargo, passengers, fuel,
water, stores, dunnage and such other
items necessary for use on a voyage,
which brings the vessel down to her load
draft.

Deadweight Tons (DWT)

The difference between displacement, light and displacement, loaded . A measure of the ship's total carrying capacity.

Cargo Deadweight Tons

The weight remaining after deducting fuel, water,stores, dunnage and such other items necessary for use on a voyage from the
deadweight of the vessel.

Draft, Loaded

The depth of water necessary
to float a vessel fully loaded.
Length - The distance between the
forwardmost and aftermost parts of the ship.

Length Overall (L.O.A.) -

The maximum
length of the ship

Length at Waterline (L.W.L.) -

The ship's
length measured at the waterline

Shaft Horsepower (SHP) -

The amount of
mechanical power delivered by the engine to a propeller shaft. One horsepower is equivalent to 746 watts in the SI system of units.

Ton -

The unit of measure often used in
specifying the size of a ship. There are three completely unrelated definitions for the word. One of them refers to weight, while the others refer to volume.
Measurement Ton or Ship Ton Calculated
as 40 cubic feet of cargo space.
(Abbreviated M/T). 
See Bale Cubic -
example, a vessel having capacity of
10,000 M/T has a bale cubic of 400,000
cubic ft.

Register Ton -

A measurement of cargo
carrying capacity in cubic feet. One
register ton is equivalent to 100 cubic feet of cargo space.

Weight Ton -

Calculated as a long ton
(2,240 pounds) (abbreviated W/T)
Tonnage - A measurement of the cargo-
carrying capacity of merchant vessels. It
depends on not on weight, but on the volume available for carrying cargo. The basic units of measure are the Register Ton , equivalent to 100 cubic feet, and the Measurement Ton , equivalent to 40 cubic feet. The calculation
of tonnage is complicated by many technical factors.

Gross Tons -

The entire internal cubic
capacity of the ship expressed in tons of
100 cubic feet to the ton, except certain
spaces with are exempted such as: peak
and other tanks for water ballast, open
forecastle bridge and poop, access of
hatchways, certain light and air spaces,
domes of skylights, condenser, anchor
gear, steering gear, wheel house, galley
and cabin for passengers.

Net Tons -

Obtained from the gross
tonnage by deducting crew and navigating
spaces and allowances for propulsion
machinery.