Ship Construction Page 61-66

Question 1

What is the purpose of a transverse watertight bulkhead?

Answer 1

A watertight bulkhead divides a ship into water-tight compartments, decreasing the spread of fire and water if the shell plate is damaged. It also adds to the transverse strength of the ship.

Question 2

What is a bilge keel?

Answer 2

A bilge keel is a long fin-like piece of metal welded along the length of the ship externally on the bilge radius, employed in pairs to restrict the amount of roll a vessel suffers, enhancing the stability of the ship.

Question 3

What is the function of a shear strake?

Answer 3

A shear strake attaches the side shell to the upper deck or weather deck, providing strength to the upper deck, maintaining the shape of the side plating, and protecting the ship from water entering.

Question 4

What is a cofferdam?

Answer 4

A cofferdam is an empty void-like space/compartment situated between two tanks or watertight bulkheads, used to check for leakages or prevent contamination between the two tanks.

Question 5

What are the structural features of the bow and stern that impart structural strength?

Answer 5

Close frame spacings, thicker plating, deep floors, panting beams, breast-hooks, and transverse framing systems.

Question 6

What are the stability implications of using water to fight a fire onboard a ship?

Answer 6

Large uncontained bodies of water can create a vicious free-surface effect. Trapped large bodies of water can severely alter a vessel’s center of gravity, increase weight reducing freeboard, and change the center of gravity, reducing the righting lever and increasing the risk of capsizing.

Question 7

Describe the structural features of the bow that impart structural strength.

Answer 7

At the bow, the framing system is transverse, with solid floors fitted at each frame and horizontal stringers fitted towards the forward collision bulkhead at approximately 2m spacing. The forward hull plating has a thicker section to resist panting.

Question 9

What are the stability implications of using water to fight a fire on a vessel?

Answer 9

Large uncontained bodies of water can create a vicious free-surface effect.

This can severely alter a vessel’s center of gravity.

Question 10

How can trapped large bodies of water affect a vessel?

Answer 10

Trapped large bodies of water can severely alter a vessel’s center of gravity and increase weight, reducing freeboard.

Increased draught and change of center of gravity can increase the risk of capsizing in heavy roll or free surface conditions.

Question 11

What structural features are found in the bow of a vessel?

Answer 11

Features include forecastle store, breast hooks, chain locker, collision bulkhead, fore peak store, wash bulkhead, panting stringers, deep floors, and panting beams.

Question 12

What are the structural features of the Bow? How dos the image look?

Answer 12

Question 13

Describe the structural features of the bow?

Answer 13

At the bow and stern, the framing system is transverse in the bow, solid floors are fitted at each frame,
and horizontal stringers are fitted towards forward collision bulkhead at a spacing of approx 2m

The forward hull plating has a thicker section to resist panting

Question 15

What is a plate floor in ship construction?

Answer 15

A plate floor is a structural component between plates that is welded to an angle iron transverse frame, typically a bulb plate.

Question 16

What is a flanged bracket used for in ship construction?

Answer 16

A flanged bracket is used due to heavy bending stresses and is closely inspected during surveys.

Question 17

What is a margin plate in ship construction?

Answer 17

A margin plate is a structural element in ship construction.

Question 18

What is a keelson plate?

Answer 18

A keelson plate is a structural component in ship construction.

Question 19

What are lightening holes?

Answer 19

Lightening holes are openings in structural components to reduce weight.

Question 20

What is a keel in ship construction?

Answer 20

A keel is a non-watertight structural element that supports the ship’s frame.

Question 21

What is a side girder?

Answer 21

A side girder is a longitudinal component located between plate floors.

Question 22

What is a watertight bulkhead?

Answer 22

A watertight bulkhead is a vertical partition that prevents water from passing through.

Question 23

How can a watertight bulkhead’s integrity be tested?

Answer 23

A watertight bulkhead’s integrity may be tested using various methods:
- Tank: Air test for watertight integrity; water test for strength.
- Void space: Hose test for integrity.

Question 24

Sketch the following ship construction features- a plate floor? (6)

Answer 24

Question 25

Sketch a water tight bulkhead? (6)

Answer 25

Question 26

Describe the construction of forward collision bulkheads.

Answer 26

They are stronger and thicker than other bulkheads to withstand water pressure. Large stakes are welded to the ship's structure, tank tops, side shell, and upper deck. Thicker plates are used towards the base, with plate-work arranged horizontally. Stiffening and strength are arranged vertically using vertical bulb plate stiffeners and/or toe angle bar.

Question 27

What is the function of forward collision bulkheads?

Answer 27

To stop the spread of water throughout the vessel in the event of a frontal collision, maintaining the stability and buoyancy of the ship.

Question 28

Where are forward collision bulkheads positioned and why?

Answer 28

They are placed 5-8% of the ship after the forward perpendicular.

Question 29

Describe a freeing port.

Answer 29

A freeing port consists of a welded bulb angle section, bulwark stay, bulwark, flange, and side frame.

Question 30

How do freeing ports assist in maintaining the stability of a ship?

Answer 30

Freeing ports remove water from the deck, thereby reducing the free surface effect. Accumulated water can cause a free surface effect, leading to a sideways movement of the ship's center of gravity, which can cause listing and possibly capsize.

Question 31

Explain the term free surface effect.

Answer 31

The free surface effect is a factor that may cause a vessel to capsize due to the nature of liquid movement and small particle solid materials like grain that behave like liquids. Liquid movement can reduce the righting moment, and shifting weight from side to side can increase the risk of capsizing.

Question 32

Why is free surface effect important in Ro-Ro ferries?

Answer 32

Large open spaces such as car-decks can accumulate large bodies of water, increasing the risk of a strong free surface effect. Large freeing ports, scuppers, watertight bulkheads, and large prow doors are fitted to minimize water ingress and assist in clearing accumulated water.

Question 33

Draw a sketch of freeing port?

Answer 33

Question 35

How is the thrust of the propeller transmitted to the hull of the ship?

Answer 35

Propeller thrust is transmitted to the ship's hull through thrust blocks, thrust bearings, and the propulsive engine mounts.

Question 36

What are the components involved in the transmission of propeller thrust?

Answer 36

Thrust blocks, thrust bearings, and propulsive engine mounts.

Question 37

What factors affect the thrust transmission from the propeller?

Answer 37

Axial thrust from the propeller, engine movements and oscillations, and transmission of vibrations.

Question 38

What is the principle of operation of a Mitchell thrust block?

Answer 38

The Mitchell thrust block operates using metal lined pads, a fluid oil film between the hull and shaft, and hold-down bolts.

Question 39

List eight actions to ensure the safe passage of the vessel through heavy weather.

Answer 39

1. Ensure all bilge wells are emptied sufficiently. 2. Ensure all watertight doors are closed. 3. Ensure heavy items are securely stowed and lashed. 4. Ensure chemicals and flammable liquids are stored correctly. 5. Stop all maintenance work and securely stow tools. 6. Ensure all tanks are sufficiently full. 7. Ensure sufficient water within the boiler system. 8. Ensure all external openings are securely closed.

Question 40

What should be done when transferring large quantities of fuel from double bottom storage tanks to wing bunker tanks?

Answer 40

Inform the deck department to ballast the vessel correctly to compensate for list, trim, and draught.

Question 41

What are the possible effects on the stability of the vessel when transferring fuel?

Answer 41

The centre of gravity will be altered, the free-surface effect increases on tanks that are not full, and the vessel becomes light as fuel is consumed, making it more susceptible to sharp rolling.

Question 42

Draw and describe how althe thrust of the propeller is transmitted to the hull?

Answer 42

Question 43

Show with aid of sketch the the Mitchell thrust block?

Answer 43

Question 44

What checks should be made before and during the fuel transfer operation?

Answer 44

1. No ballast operations are in progress that may be detrimentally affected due to further changes in position of mass. 2. There is sufficient volume remaining within the receiving tank. 3. Fuel should be taken from double bottom tanks evenly to reduce the stress subject to the ship's hull. 4. The correct fuels are being transferred, of similar densities and sulphur contents.

Question 45

What measurement indicates a ship's stability?

Answer 45

GMT measurement, the distance between the transverse metacentre and the vertical centre of gravity (GM).

Question 46

What does the GMT measurement indicate about a ship's stability?

Answer 46

This distance determines how stable a ship is; if the distance is small, the ship is less stable than if the distance is larger.

Question 47

What is stable stability?

Answer 47

This is when the M value is higher than the G value.

Question 48

What is unstable stability?

Answer 48

This is when the G value is higher than the M value.

Question 49

What is neutral stability?

Answer 49

This is when the G value and M value are at the exact same point.

Question 50

What is the purpose of a bilge injection system onboard a ship?

Answer 50

Direct emergency discharge of floodwater using the highest capacity pumps within the ER systems.

Question 51

Where is a bilge injection system located onboard a ship?

Answer 51

Manual operated wheel, bottom plates after sea-strainer.

Question 52

What is the purpose of ventilation for lubricating oil or fuel tanks with ventilators on the vessel's main weather deck?

Answer 52

This is to allow the tank to be filled or discharged, gases to leave or enter the tank as necessary. Also used to prevent the build-up of pressure and the tank expanding.

Question 53

Draw a bilge injection system?

Answer 53

Question 54

Draw a bilge injection system?

Answer 54

Question 55

How is the ingress of sea water in bad weather prevented?

Answer 55

A non-return valve, such as a ball float valve, is used to shut off the valve. When water builds up, it pushes the float up, blocking the valve and stopping water from entering the tank.

Question 56

How is the risk of fire entering the ventilator reduced?

Answer 56

A flame arrestor is used to stop hot sparks and absorb heat from flames, preventing them from entering the tank.

Question 57

How is the risk of pollution reduced?

Answer 57

Alarm systems (e.g., high level alarms), overflow lines, and float levels in the tank are used to reduce pollution risks.

Question 58

What inspection is required for a weather deck water-tight door to ensure compliance with load line survey?

Answer 58

Water-tight door integrity can be tested by the chalk test and hose test. ## Footnote Chalk test: Apply chalk to the sealing, close the door, then check for continuity. If not continuous, seals may need replacing. Hose test: Close the door and spray with a 2 bar water jet from 1.5m away to check for leaks.