Ship construction Ship dimensions

SHIP CONSTRUCTION-

SHIP DIMENSIONS

Definitions and

Ship’S DimenSionS

Hull:

The structural body of a ship including shell plating, framing, decks

and bulkheads.

Afterbody :

That portion of a ship’s hull abaft midships.

Forebody:

That portion of a ship’s hull forward midships.

Bow :

The forward of the ship

Stern :

The after end of the ship

Length Overall

STARBOARD

Beam

PORT

bow midships

bridge stern

starboard bow

starboard beam

starboard quarter

Dead ahead

Dead Stern

Port bow

Port beam

Port :

The left side of the ship when looking forward

Starboard :

Length between perpendicular (LBP) Length on waterline (LWL)

Length overall (LOA) freeboard Amidships

Aft

perpendicular Fwd

perpendicular

Sheer aft Sheer fwd

Summer load line

SHIP DIMENSIONS

floor Half siding of keel

Base line Draft

• After Perpendicular (A.P.)

: A perpendicular

drawn to the waterline at the point where the aft

side of the rudder post meets the summer load

line. Where no rudder post is fitted it is taken as

the centre line of the rudder stock.

• Forward Perpendicular (F.P.):

A perpendicular

drawn to the waterline at the point where the

foreside of the stem meets the summer load line.

• Length Between Perpendicular (L.P.P. / L.B.P.):

The length between the forward and the aft

perpendiculars measured along the summer load

line.

• Amidships:

A point midway between the after

and forward perpendiculars

• Length Overall (L.O.A.):

Length of the vessel

taken over all extremities.

• Base line:

A horizontal line drawn at the top of

the keel plate. All vertical moulded dimensions

are measured relative to this line

• Moulded beam:

Measured at the midship

section is the maximum moulded breadth of the

ship

• Moulded Draft/ Draught:

The distance from

the bottom of the keel to the waterline. The

load draft is the maximum draft to which a

vessel may be loaded

• Moulded Depth:

Measured from the base line

to the heel of the upper deck beam at the

ship’s side a idships.

•

Sheer:

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

• Camber / Round of Beam:

Curvature of decks

in the transverse direction. Measured as the

height of deck above the height of deck at

side

• Rise of floor / Deadrise:

The rise of the

bottom shell plating line above the base line.

This rise is measured at the line of moulded

beam

• Half sliding of keel

: The horizontal flat portion

of the bottom shell measured to port or

sta oa d of the ship’s lo gitudi al e t e

line. This is useful dimension to know when

dry-docking.

• Tumble home:

The inward curvature of

the side shell above the summer load line.

• Freeboard:

the vertical distance measured

from the waterline to the top of the deck

plating at the side of the deck amidships.

Normally exposed to weather and sea.

• Flare:

The outward curvature of the side

shell above the waterline. It promotes

dryness and is therefore associated with

the fore end of ship

Extreme Beam:

The maximum beam taken over all extremities.

Extreme Draft:

Taken from the lowest point of keel to the summer load line.

Draft marks represent extreme drafts.

Extreme Depth:

Depth of essel at ship’s side f o uppe de k to lo est poi t

of keel.

Half Breadth:

Si e a ship’s hull is sy

et i al a out the lo gitudi al

centre line, often only the half beam or half breadth at any

section is given.

SCANTLING

The dimensions of the structural items

of a ship, e.g. frames, girders, plating , etc.

INTERCOSTAL

Composed of separate parts,

non-continuous

CENTER OF FLOATATION

It is the center of the waterplane area and is the

axis about which a ship changes trim.

CENTER OF BUOYANCY

It is the center of the underwater volume of the

ship where the force of buoyancy acts.

CENTER OF GRAVITY

It is the point at which the whole weight of the

object may be regarded as acting. If the object is

suspended from this point, it will remain balanced and

not tilt.

TONNAGE MEASUREMENT

• This is often referred to when the size of

the vessel is discussed, and the gross

to age is uoted f o Lloyd’s egiste .

• Tonnage is a measure of the enclosed

internal volume of the vessel, 100 cubic

feet representing one ton

• Its normally divided into categories as

follow:-

1. Displacement Tonnage

• A ship’s displa e e t is the su of the ship’s

a tual eight light eight a d it’s o te ts

(deadweight).

• The metric unit of measurement is 1 tonne (=

1000 Kg).

• The displacement represents the amount of

water displaced by the ship expressed in tonnes.

• The weight of water displaced therefore equals

TONNE PER CENTIMETRE (TPC)

It is the mass required to increase the mean draught by 1

centimetre.

LOAD DISPLACEMENT

The weight of the ship and its content, measured in

tonne

. The value will vary according to the ship’s draught.

DEADWEIGHT SCALE

It is a scale diagram indicating the deadweight of the ship

at various draughts.

FORM COEFFICIENT

It is devised to show the relationship between the form of

the ship and the dimension of the ship.

2. Lightweight Tonnage (LWT)

• The lightweight is the weight of the ship as

built (hull, machinery) including boiler water,

lubricating oil and the cooling water system.

• Lightweight like displacement is expressed in

units of tones.

• It assumes importance in a commercial sense

only when considering the value of the vessel

which is to be broken up for scrape

.

3. Deadweight tonnage (DWT)

• Deadweight is the weight of the cargo

which a ship carries plus weights of fuel,

stores, water ballast, fresh water, crew

and passengers and baggage.

• It is the difference between the loaded

ship displacement and the lightweight.

4. Gross Tonnage (GT)

• Measurement of total internal volume of

a vessel and includes all under deck

tonnage and all enclosed spaces above

tonnage deck.

• 100 cubic feet of space being considered

as 1 ton

5. Nett Tonnage (NT)

• Ship measurement derived from gross

tonnage by deducting spaces allowed for crew

and propelling power.

• 100 cubic feet of space being reckoned as 1

ton

Ship side markings

• LOAD LINE

The marking on the ship side that relate to the loading

condition of the ship termed as the load line mark.

• Load line mark

– consists of a ring 300 mm in outside diameter and 25

mm thick which is

– intersected by a horizontal line 450 mm in length and 25

mm thick, the upper edge of which passes

through the centre of the ring. The centre of the ring is

placed amidships and at a distance equal to the

assigned summer freeboard measured vertically below

the upper edge of the deck line.

ANY QUESTION?