Ship Technology

Question 1

What are docking strains?

Answer 1

Temporary static forces imposed on the ships structure during docking periods
Ships hull is no longer supported by the water, the ships hull tends to settle in a state of hog on the docking blocks

Question 2

Draw docking strains/ aft cut up shores

Answer 2

Docket

Question 3

Draw and describe hogging

Answer 3

Docket
Ship is supported midships by the wave crest while the ends are unsupported

Question 4

Draw and describe sagging

Answer 4

Docket
Hull is supported at each end by the crests of adjacent waves while midships is unsupported

Question 5

Draw and describe racking

Answer 5

Docket
External force (wind or wave) on one side of the vessel will tend to change the section so that the sides are no longer perpendicular to the ships bottom

Question 6

What is B quality steel used for

Answer 6

Highly stressed areas of the ships structure where crack arresting properties are required

Question 7

What is BX steel

Answer 7

Improved quality of B quality over 18mm thick

Question 8

When is grade D steel used

Answer 8

Main ships structure except in highly stressed areas and where crack arresting properties are required

Question 9

What are the advantages and disadvantages of aluminium

Answer 9

Adv
Density is 1/3 of that of steel and strength 1/2 of steel
Disadv
Aluminium looses strength at 250°C and melts at 650°C
Structural uses are severely limited and not used for primary structures, ladders or deck plates

Question 10

When is aluminium used

Answer 10

Where weight is an important consideration and for minor bulkheads

Question 11

Advantages of steel

Answer 11

Weldable
Strong
Relatively cheap
Available
Ductile

Question 12

Disadvantages of steel

Answer 12

Corrodes
Heavy
Magnetic
Subject to failure

Question 13

What is the definition of ductile

Answer 13

Ability to define before failure

Question 14

What is the definition of toughness

Answer 14

Ability to absorb energy

Question 15

What is the definition of strength

Answer 15

Ability to resist deformation and retain its shape

Question 16

Describe the 3 categories of structure

Answer 16

Primary, contributes to main structural strength and maintains water tight integrity

Secondary, doesn’t contribute to structural strength but does contribute to water tight integrity and supports local loads

Minor, doesn’t contribute to structural strength or watertight integrity

Question 17

Describe the keel

Answer 17

Flat and vertical keels run fwd to aft
Maximum strengths is at midships to resist against hogging and sagging
Vertical keel is designed maximum strength to resist forces encountered when docking
Where access holes are cut in vertical keel a rider plate must be fitted for the loss of strength

Question 18

Label the strength members of structure

Answer 18

Docket

Question 19

What is the purpose of the water tight subdivision

Answer 19

Divide the buoyant volume of the shop into smaller compartments and preserve the largest amount of buoyancy in the event of the hull being damaged
The underwater volume and a large amount above must be made watertight
The closer the subdivision the more unsinkable a ship becomes

Question 20

What parts of the ship contribute to water tight integrity?

Answer 20

Decks
Bulkheads
Double bottoms
Collision zone

Question 21

Describe the function of main transverse bulkheads

Answer 21

Effectively divide the hull of the ship into separate sections
Overall stiffening of the ships structure
Reduce effects of damage to the ship
Withstand pressures associated with flooded compartments
Valves fitted when ships systems pass through main transverse bulkheads

Question 22

What is the function of a collision bulkhead

Answer 22

Provide watertight barrier from 1 deck to the keel in event of damage to the bow section
Resists hydrodynamic pressure upto cruising speed

Question 23

What is the function of a deck?

Answer 23

Strength members acting horizontally to maintain the hull shape
Form water tight subdivision
Act as platforms and boundary’s of compartments and support equipment
Worked intercostally to the MTB (except strength deck)

Question 24

What is the strength deck

Answer 24

Uppermost continuous deck from the neutral axis
Made of B quality steel

Question 25

What is the superstructure

Answer 25

All structure above the strength deck Offices, accommodation, workshops and hanger Additional support for bridge funnel masts and weapon directors Contributes little to structural strength Supported by MTBs underneath Local stiffening is provided for RAS/davits Aluminium may be used where weight is a consideration

Question 26

How are water tight hatches fitted

Answer 26

Extending the rider plate which prevents water from spilling into the compartment below

Question 27

What are the two groups of hatches and how are they secured

Answer 27

Normally closed at sea- tumbler bolts Access to compartments normally manned or frequently visited - clips

Question 28

What is fitted when a hatch is cut into to the deck

Answer 28

Carlings and half beams to compensate for the loss in strength

Question 29

Describe shaft brackets

Answer 29

Supports the weight of the shaft Strong enough to support the loss of a propeller blade

Question 30

What does each shaft bracket consist of

Answer 30

Barrel Arms Palms

Question 31

What bearing is used in the barrel

Answer 31

NF21 or Orkot

Question 32

Describe the palms

Answer 32

Welded to longitudinale or vertical floors in the ships structure Fitted parallel to she ships structure Shell of B quality steel is welded to the palm and ships shell where it passes through the hull

Question 33

What are the 4 types of corrosion

Answer 33

Oxidation Electrolytic Bacterial Chemical

Question 34

What 2 organisations assist with surveys?

Answer 34

Lloyds register MCTA Hull survey team

Question 35

When are the NSSC conducted?

Answer 35

Initial survey Renewal survey Periodic survey

Question 36

What is the periodicity of the NSSC?

Answer 36

Survey on an annual basis may be required for certain ships that are known to have particular deficiencies All surveys should take place within plus or minus 3 months

Question 37

Why are surveys undertaken?

Answer 37

Ensure hull, upper deck, structure, compartments fixtures and and fittings are kept to a high standard Ensure water and gas tight integrity of the ship

Question 38

How is corrosion recorded?

Answer 38

Depth and area of corrosion Light surface, less than 1mm Medium surface more than 1mm but less than 70% of plate thickness Heavy more than 70% of plate thickness

Question 39

How can the area of corrosion be described?

Answer 39

Localised Scattered Extensive

Question 40

When is compartments air testing carried out?

Answer 40

Every 6 years If work carried out on compartment boundaries If in doubt of water tight/ gas tight integrity

Question 41

What compartments is air testing carried out in?

Answer 41

Red risk zone Flammable gases or ammunition Boundaries of compartments with halon or carbon dioxide drench systems

Question 42

Safety precautions to be observed when air testing?

Answer 42

Don’t station a person in compartment where only 1 entry/ exit point Don’t leave person in too long when carrying out vacuum test Maintain positive communication with the person All pressure is released from compartment prior to releasing the door

Question 43

What is the gutter strake?

Answer 43

Middle line of inner bottom plating forming the rider to the vertical keel

Question 44

Why are anchors and cables surveyed?

Answer 44

Ensure it is fit for purpose and not unduly worn

Question 45

Who carries out the survey for cables and anchors?

Answer 45

A surveyor from an approved classification society Or An authorised navel base personnel

Question 46

What qualifications are required to carry out survey on anchors and cables

Answer 46

Appropriate training Accredited qualifications Hold responsible officer status.

Question 47

What is the procedure for surveying ladders?

Answer 47

Check security of fastenings on all treads Check handles for distortion and security Check stringers for distortion and corrosion Check backplate for security and noise Check hinge positions for security and distortion Checked in accordance with maintenance schedule

Question 48

What 4 strength members prevent hogging and sagging?

Answer 48

Decks Longitudinals Keel Double bottom