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Second Mate's Perspective,important notice for deck



Ship Construction( PART 1 )

                       Ship Construction 

Part 1

1) Length between Perpendiculars (LBP )

The length between the forward and aft perpendiculars measured along the summer loadline.

2) Length Overall (LOA )

The distance from the extreme fore part of the ship to a similar point aft and is the greatest length of the ship.

3) Aft Perpendicular 

Perpendicular drawn to the waterline at a point where the aft side of the rudder post meets the summer load line .If no rudder post is fitted it is taken as the centre line of the rudder stock.

4) Forward Perpendicular

Perpendicular drawn to the waterline at the point where the foreside of the stem meets the summer load line.

5) Amidship 

A point midway between the aft and forward perpendicular

6) Breadth Extreme 

The greatest breadth of the ship measured to the outside of the shell plating.

7) Breadth Moulded

The greatest breadth of the ship measured to the inside of the inside strakes of the shell plating measured in midship section.

8) Depth Extreme 

Depth of the ship measured from the underside of the keel to the top of the deck beam at the side of the uppermost continuous deck amidships.

9) Depth Moulded

The depth measured from the top of the keel to the upper deck beam at ships side amidship.

10) Draught Extreme

Distance from the bottom of the keel to the centreline .The load draught is the maximum draught to which the vessel may be loaded.

11) Draught moulded 

The draught measured from the top of the keel to the waterline .

12) Base line 

A horizontal line drawn at the top of the keel plate . all vertical moulded dimensions are measured relative to this line.

13) Freeboard 

The distance from the waterline to the top of the deck plating at the side of the deck amidships

14) Half Breadth 

Since a ships hull is symmetrical about the longitudinal centre line often only the half beam or half breadth at any section is given. 

15) Camber or Round of beam

The transverse curvature of the deck from the centre line down to the side . this camber is used on exposed decks to drive water to the sides of the ship.

16) Sheer 

Curvature of decks in the longitudinal direction (in fore and aft direction) rising from midships to a maximum at ends . the sheer forward is usually twice that aft . sheer on exposed decks makes a ship more seaworthy by raising the deck at the fore and aft ends.

17) Rise of Floor or Deck Rise 

Rise of the bottom shell plating line above the base line 

18) Bilge Radius 

The radius of the arc connecting the side of the ship to the bottom at the midship position of the ship.

19) Tumble home 

The inward curvature of the side shell above the summer load line towards the centreline .

20) Displacement 

The mass of the ship and everything it contains . a ship has different values of displacement at different draughts.

21 ) Lightship 

The mass of the empty ship without stores, fuel, water, crew and their effects.

22) Deadweight  

The mass of cargo, fuel, water, stores etc a ship carries . deadweight is the difference between the displacement and light weight .

( displacement = light ship + deadweight )

23) Half Siding of Keel 

The horizontal flat portion of the bottom shell measured to port or starboard of the ships longitudinal centre line .

24) Flare 

The outward curvature of the side shell above the waterline .it performs dryness and is therefore associated with the fore end of the ship.

25) Stem rake 

Inclination of stem shell from the vertical .

26) Keel rake 

Inclination of keel line from the horizontal.

27) Tween Deck Height 

Vertical distance between adjacent decks measured from the top of deck beams at ships side.

28) Parallel middle body 

The length over which the midship section remains constant in area and shape.

29) Entrance 

The immersed body of the vessel forward of the parallel middle body.

30) Run 

Immersed body of the vessel aft of the parallel middle body

31) Duck Keel

Duck keels are provided in the double bottoms of some vessels .these run from the forward engine room bulkhead to the collision bulkhead and are utilized to carry the double bottom piping.the piping is then accessible when cargo is loaded. an entrance to duck being provided at the forward end of the engine room.

32) Deep Tanks 

Deep tanks were often fitted adjacent to the machinery spaces amidship to provide ballast capacity , imposing the draft with little trim when the ship was light. These tanks were frequently used for carrying general cargoes and also carry specialist liquid cargoes.

33) Shaft Tunnel 

To enclose the propeller shaft in a watertight tunnel between the aft end of the machinery space and the aft peak bulkhead.

34) Stern tube

Stern tube forms the after bearing for the propeller shaft and incorporates the watertight gland where the shaft passes through the intact hull .

35) Cofferdam 

An empty compartment which separates cargo tanks and machinery spaces.

36) Bilge Keel 

Most ships are fitted with some form of bilge keel which is to help the rolling motion of the vessel .which contributes to longitudinal strength .does not reduce ballast capacity or cargo space.


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