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General Ship Knowledge > Ship Construction > Flashcards

Ship Construction Flashcards

1
Q

Define: freeboard deck

A

The upper most continuous deck that can be closed weathertight.

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2
Q

Assigned freeboard

A

The distance measured vertically downwards at amidships from the upper edge of the freeboard deck to the upper edge of the summer load line

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3
Q

Weathertight

A

In any sea condition water will not penetrate the ship

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4
Q

Define Panting

A

Panting is the in and out movement of the shell material due varying pressure changes

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5
Q

Briefly explain how the locality is stiffened to resist this stress (Panting)

A

Reduce the unsupported opener area by close frame spacing and/or additional stiffening members (eg panting beams) and/or increase shell thickness

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6
Q

Wood - advantages

A

Floats, strength, appearance, easy to work with

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7
Q

Wood - disadvantages

A

Rots,
expensive
poor radar reflector

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8
Q

Steel - advantages

A 
Relatively strong, 
widely available
easy to work with
cheap
good radar reflector.
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9
Q

Steel - disadvantages

A

Corrosion,
relatively heavy
conducts heat
needs regular maintenance

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10
Q

Aluminum- advantages

A

High strength to weight ratio, doesn’t corrode as easy as steel, good radar reflector

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11
Q

GRP/FRP - advantages

A

High strength to weight ratio,
non corrosive
low cost if moulds are used
Readily available

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12
Q

GRP - disadvantages

A

Blistering and delamination,
once of fire - burns intensely giving off toxic gas,
poor radar reflector
Specialist Labour

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13
Q

Explain How chemical corrosion in steel occurs

A

Caused when the oxygen in the atmosphere combines with the metal and forms iron oxide. The oxide film is not firmly attached to the parent plate and thus permits further oxidation to occur

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14
Q

Discuss the factors and conditions that would cause chemical corrosion to be accelerated and how good ship design could reduce this

A

Accelerated by heat and moisture

Prevention : 
Good ventilation
Reduce heat
Avoid water traps
Accessibility for preservation
Regular inspection and maintenance
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15
Q

Center grider - importance/function

A

Furthest from the neutral axis

Contributes substantially to the Longitudinal strength to resist sagging and hogging

Receives load when in dry dock

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16
Q

Plate floor - importance/function

A

Vertical plates running transversely across the bottom to stiffen the bottom

Transfer loads from the tank top and gives support to the side and center griders

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17
Q

Shell material - importance/function

A

Watertight skin of the ship. Major part of the ships strength.

Efficiently unites the supporting longitudinal and transverse members the make up the framing system.

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18
Q

Upper deck -

importance/function

A

Furthest from neutral axis;

Top flange of the grider

Strength deck

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19
Q

Deck beam - importance/function

A

Part of deck framework (with griders)

Supports deck plating

Transfer loading to frames bulkheads and pillars

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20
Q

Beam knee - importance/function

A

Unites the beam and frame enabling stresses to be transferred from one to the other

They offer some resistance to racking

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21
Q

Transverse frame - importance/function

A

Part of the framing system

Receives the deck loading via the beams and transfer the load to the bottom structure

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22
Q

Transverse bulkhead - importance/function

A

Subdivides the yacht into separate compartments

Contain flooding and fire

They contribute greatly to the structural integrity of the ship by providing the primary resistance to transverse deformation and so resist racking

They also are efficient load bearers and effectively distribute loads to the adjacent structure

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23
Q

Pillar - importance/function

A

Supports deck and transfers loading downwards, the unsupported span of the beam is reduced and hence beam sections can be reduced in depth so the clear space

Where extra deck loading is need ie: helicopter

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24
Q

Give four items of information to be found on a general arrangement drawing

A

plan, profile and section views

Division into compartments (tanks, engine room, holds)

Location of bulkheads

Location and arrangement of superstructure

Parts of the equipment (winches, loading gear, bow thruster, life boats)
 Dimensions (Length, Breadth, Draft)
Volumes of the holds (Cargo Capacity Grain & Bale)
Tonnage
Deadweight
Engine power
Speed (Service Speed)
Class
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25
Q

Sketch and explain the term “pounding”

A

Is the vertical slamming of the forefoot of the vessel onto the trough of a wave being caused by a combination of pitching and heaving.

Produces large impulsive forces on bottom plating

26
Q

Explain how the locality is stiffened to resist this stress (pounding)

A

Frame spacing reduced

Additional stiffeners introduced

Shell plating thickness increased

27
Q

State two reasons/functions for fitting each of the following :
Deck beams

A

Supports deck plating

Transfers loads to frames

Transfers loads to bulkheads

Transfers load to pillars

28
Q

Describe the routine maintenance necessary to ensure that a weather-tight door prevents ingress of water

A

Ensure rubber seals intact, paint free

Ensure securing arrangement fully functional and greased

No obstructions to door closure

Door fits frame, seals.

29
Q

Sketch aluminum and steel immersed in slat water and connected electrically,

Explain how a current is caused to flow from one material to the other and how this gives rise to ‘galvanic corrosion’

A

The galvanic action is a form of electrolysis whereby different metals will react with one another to form an electric cell when they are placed in suitable medium (an electrolyte)

In this case the less noble metal is the aluminum which will give up its ions and become eaten away.

The aluminium is known as the anode whilst the steal becomes the cathode. The process is speeded up due to the Efficient salt water electrolyte

30
Q

Describe a method of cathodic protection

A

Sacrificial -
That galvanic action is an electro-chemical form of corrosion where one fo two dissimilar metals are eaten away. The metal that is eaten away is the one higher in the galvanic series ( ie the ignoble or anodic end) to counteract this in respect to mild steel, a metal more ignoble/anodic eg zinc or magnesium may be used and these are termed sacrificial anodes which will waste in presence to the steel

31
Q

Describe another method of cathodic protection

A

Impressed current
That galvanic action is a flow of electrical particles (iones) through an electrolyte (SW) from the anodic metal to the cathodic metal - i.e an eclectic current. By passing a current of the same strength through the electrolyte but in the opposite direction the galvanic action is cancelled out and no corrosion occurs. Comprises of a controller rectifier and anodes

32
Q

Sketch a ship being made to hog in a seaway

Explain why the upper deck will be subjected to high stress

A

As neutral axis is below half depth of vessel, tensile stress will be high

33
Q

State four tasks provided by a classification society

A 
Construction rules
Statutory authority 
Material spec
Insurance premium 
Resale value
Surveyors available
34
Q

Explain the term ‘fresh water allowance’

A

Amount by which the summer mark can be immersed when in FW due to less dense FW allowing floating at correct marks when emerging into higher density SW

35
Q

Advantages and disadvantages of -

Aluminium alloy

A

Advantages -
Easy to work with
Less maintenance
Light

Disadvantages-
Melts at lower temp than steel
bi-metallic corrosion
Distortion with welding

36
Q

Sketch a pumping system that could be fitted to a yacht

Identify all the associated valves and fittings

A 
Needs to have-
Mud box
Strum
Vale’s
Fwd-middle-laz sections
Holding tank
Pump/s
Disch-ashore facility
O/b discharge
Others
37
Q

Sketch -

Sagging

A

Compressive stress in deck

Tensile stress in keel

38
Q

Sketch -

Racking

A

Swell/waves on the beam of the vessel

39
Q

Sketch -

Panting

A

+ & -

Panting is an in-and-out movement of the shell plating resulting from the variations of water pressureas waves pass along the hull and when the vessel pitches.

40
Q

Sketch -

Pounding

A

Bow lifting at the crest of a wave and slamming/pounding in the trough of the next

41
Q

Explain-

Reserve buoyancy

A

Intact volume between waterline and freeboard deck

42
Q

Explain-

Gross tonnage

A

Internal volume of ship

43
Q

Explain-

Net tonnage

A

Gross tonnage less deductions

44
Q

A yacht is to undergo an annual survey.

State four items that would be inspected

A

Any examples of weather tight openings (doors, hatches, vent openings, side scuttles). Stability data, general structural condition

45
Q

Explain -

Camber

A

Is the transverse curvature of the deck

46
Q

Explain-

Flare

A

Is the outward curvature of the bow

47
Q

Explain why camber may be incorporated in a yachts design

A

To shed water from the deck. Provides additional longitudinal strength

48
Q

Explain why flare would be incorporated into a yachts design

A

Increases buoyancy of the bow - helps head up. Reduces breaking water on deck

49
Q

A motor yacht with a steel hull is to have a 300mm hole cut in the bottom plating amidships in order to install an underwater fitting
i)Explain how stresses would arise in this vicinity

A

High stress area already due to being amidships (tensile/compressive) and farthest from neutral axis

Change of section due cutting of hole will cause stress lines to be concentrated

50
Q

A motor yacht with a steel hull is to have a 300mm hole cut in the bottom plating amidships in order to install an underwater fitting
ii)describe the structural compensation that should be fitted in way of opening

A

By use of an insert plate of increased scantling with chamfered thickness reduction

51
Q

Give four examples of information to be found on a general arrangement drawing

A

Side elevation/profile and plan of decks showing: accommodation; storerooms

Tanks bridge layout

Principle dimensions: LOA, LBP; opening/doors/windows/ports/scuttles/alleyways/ladders/companionways

52
Q

Explain reserve buoyancy

A

Intact volume between waterline and freeboard deck

53
Q

Explain the reason for fitting sacrificial anodes to a steel hull in the vicinity of a propeller made of non-ferrous material

A

The galvanic action (electro chemical process)-
Is a form of electrolysis whereby different metals will react with one another to form an electric cell when they are placed in a suitable medium (an ELECTROLYTE)

In this case the less noble metal is the zinc which will give up its IONS and become eaten away (it corrodes)

The zinc is known as the ANODE

Whilst the prop non ferrous metal becomes the a CATHODE.

The process is speed up due to the efficient salt water electrolyte

54
Q

Explain the term sheer?

Give two reasons why the upper deck of a yacht might be given sheer?

A

Rise of the deck above the horizontal.

Added buoyancy forward, keeps head dry, aids drainage

55
Q

Explain, with reference to galvanic corrosion, why the means of joining aluminum superstructure to a steel upper deck needs to be carefully made?

A

Galvanic corrosion is an electrochemical process whereby one metal corrodes in preference to another metal the it is in contact with through an electrolyte.

In this case aluminum is anodic to steel and needs to be insulated
(Example of an insulated product is ‘triclad’)

56
Q

Give any explain of ‘discontinuity of strength’ in a yacht’s construction and explain how stress concentration will arise in the vicinity?

A

Local loading stress-
Can be caused by heavy weights concentrated on small areas
(under main engines)
(Longitudinal stress carrying members of the structure meet transverse members)

Poor design
(A sharp angle cut in a plate produces a discontinuity) - When a Tensile stress is applied, the stress is concentrated at the angle

Vibration
Causes cyclic forces in steel usually resulting in tensile stresses. After a long period this will cause the structure to fail by cracking. This can cause corrosion in steel, and weld fractures particularly in aluminum

57
Q

Summarize the Lloyds notation below

X100A1
LMC
UMS

A

100 - considered sutiable for seagoing service

A - built in ACCORDANCE with lloyds class rules

1 - anchor and mooring equipment comply with lloyd’s class rules.

X(Maltese Cross) New ship built under supervision of a society surveyor

LMC Lloyds Machinery Certificate

UMS unmanned machinery spaces

58
Q

What is assessed/checked during an annual survey

A

General condition of the vessel,machinery and equipment

Other items include:

Closing appliances such as, hatches, ventilators and air pipes

Water tight doors and bulkheads

Steering arrangements

The provision of structural fire protection is verified

Anchors and cables

59
Q

Disadvantages of aluminum?

A 
Weaker than steal (half strength)
More expensive
Special technique to weld
Not fireproof
Not ecologically friendly.
60
Q

Illustrate how dissimilar metals should be fitted

A

Can’t be touching

Washes rubber plastic

General Ship Knowledge (4 decks)

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