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Basic design of shipBasic design ofship

Dimensions

Cargo carrying capacity

Length minimized (longitudinal bending stresses)

Breadth (stability influence on speed)

Depth (reduction longitudinal bending stresses area of operation)

Displacement

Lightweight (= as low as possible) + deadweight

Stability Sufficient all possible conditions of loading

Important:

o Freeboard

o Sheer

o Weight distribution

Propulsive characteristics & hull form

Attain required speed Hull minimum resistance to motion

Service speed = average speed at sea with normal service power and loading under

average weather conditions (80 90 %)

Trial speed = average speed obtained using maximum power over a measured course

in calm weather with a clean hull (friction) and specified load condition

General arrangement

Co-operation with owner

Efficient working of vessel

Structural details

Classification societys

Owners requirements

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Ship dimensions and formsShip dimensions and forms

Ship dimensions

After perpendicular (AP) : perpendicular to waterline where aft side of rudder postmeets summer load line

Forward perpendicular (FP) : perpendicular to waterline where foreside of stem meets

summer load line

Mean perpendicular (MP) : perpendicular to waterline halfway between AP and FP

Length between perpendiculars (LBP) : length between AP and FP measured along

summer load line

Amidships: point midway AP and FP

Length Overall: length of vessel over all extremities

Base line: horizontal line at top of keel plate (vertical moulded dimensions measured

relative to this line) Moulded dimensions: inside of plating

Moulded beam

Moulded draft

Moulded depth

Extreme beam

Extreme draft

Extreme depth

Half breadth

Freeboard: vertical distance at ships side between summer load line and freeboard

deck Sheer: curvature of decks in longitudinal direction

Camber / round of beam: curvature of decks in transverse direction

Rise of floor / deadrise: rise of bottom shell plating line above base line

Half siding of keel: horizontal flat portion of bottom shell to port or starboard (useful

when dry-docking

Tumblehome: inward curvature of side shell above summer load line

Flare: outward curvature of side shell above waterline

Stem rake: inclination of stem line from vertical

Keel rake: inclination of the keel line from the horizontal

Tween deck height Parallel middle body: length over which midship section remains constant in area and

shape

Entrance: immersed body of vessel forward parallel middle body

Run: immersed body aft parallel middle body

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Coefficients

Water-plane coefficient (Cw)

o Fullness of water plane

o

Low Cw => fine ends & high Cw => fuller endso High Cw improves stability & handling behaviour in rough conditions

Midship section coefficient (Cm)

o Fullness of underbody

o Low Cm => cut-away mid-section & high Cm => boxy shape section

Block coefficient / coefficient of fineness (Cb)

o High Cb => full forms

o Low Cb => fine shapes

Prismatic coefficient (Cp)

o Evaluate distribution of volume of underbody

o

Low Cp => full mid-section and fine ends & high Cp => fuller ends

Line plans

Impression of vessel => clear image of exact geometrical shape

Shape vary in height, length and breadth => transverse & 2 longitudinal plans

perpendicular to one another

Ordinates / stations

o Vertical

o Transverse direction

o Usually 20o Centre of rudder stock = ordinate 0

o Combination => frame plan

Waterlines

o Horizontal

o Design water line = water line at level of immersion in full cargo

o Baseline = waterline 0

o Combination => waterline model

Verticals / buttock blocks

o Vertical

o Longitudinal directiono Combination => sheer plan

Diagonals / sent-lines

o Longitudinal direction

o On longitudinal plan => curves

o Most common diagonal = bilge diagonal

Mid-ship sectionMid-ship section

Shows transverse sections and principal dimensions, quality & thickness of shell plating, deck

plating, all longitudinal stiffening, transverse frames and web frames, and important data ofequipment

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SEE BLACKBOARD

Shell expansionShell expansion

Gives information about distribution of different plates of the shell and other details(hull openings)

At each level and each frame number, quality and thickness can be seen

Drawing:

o Basis: centreline of bottom shell at actual length

o Each frame is rectangular to baseline

o Frame spacing at scale apart with length of total developed length (girth) from

keel to rail (as if a rope drawn along the frame)

o Also shows seams & landings and shell openings

Production of steelProduction of steel Steel = alloy of iron and carbon

Carbon percentage varies (0,1 % mild steels, 1,8 % hardened steels

Open hearth process

Uses waste heat by furnace

Directing fumes through a brick checkerwork => heating bricks => same pathway for

introduction of air into furnace => preheated air increases flame temperature

Electric furnaces

Horizontally placed carbon electrodes produce electric arc above container of metal

Now: vertically positioned graphite electrodes

In induction furnace: coil carrying alternating electric current surrounds a container /

chamber of metal => currents induced in the metal => circulation of these currents

produces extremely high temperatures for making alloys of exact composition

Oxygen process

Pure oxygen blown into molten blast furnace iron and scrap => oxygen initiates series

of intensively exothermic reactions including oxidation of impurities

Commercial advantages:

o High production rates

o Less labour

o Steel with low nitrogen content Chemical additions

o Several purposes

Deoxidise metal

Remove impurities

Desired composition

o Amount of deoxidising elements determines quality of steel

Testing of materials