DTS - Ship Const & Stab
DTS - Ship Const & Stab
DTS - Ship Const & Stab
at operational level
Page:2of 12
3. Hull structure
1. Identifies structural components on ship’s plans and drawings
- frames, floors, transverse frames, deck beams, knees, brackets
- shell plating, decks, tank top, stringers
- bulkheads and stiffeners, pillars L (4.0) T-24, T-25,
- hatch girders and beams, coamings bulwarks Ex. (2.0) T-26
- bow and stern framing, cant beams, breasthooks
2. Describes and illustrates standard steel sections
- flat plate
- offset bulb plate
- equal angle
- unequal angle
- channel
- tee
3. Identifies longitudinal, transverse and combined systems of framing on transverse
sections of ships
4. Sketches the arrangement of frames, webs and transverse, members for each
system
5. Illustrates double-bottom structure for longitudinal and transverse framing
6. Illustrates hold drainage systems and related structure
7. Illustrates a duct keel
8. Sketches the deck edge, showing attachment of sheer strake and stringer plates
9. Sketches a radiused sheer and attached structure
10. Describes the stress concentration in the deck round hatch openings
11. Explains compensation for loss of strength at hatch openings
12. Sketches a transverse section through a hatch coaming showing the arrangement
of coamings and deep webs
13. Sketches a hatch corner in plan view, showing the structural arrangements
14. Sketches deck-freeing arrangements scuppers, freeing ports, open rails
15. Illustrates the connection of superstructures to the hull at the ship’s side
16. Sketches a connection of superstructures to deck, sides and double bottom and
the arrangement of stiffeners
17. Sketches a corrugated bulkhead
18. Explains why transverse bulkheads have vertical corrugations and fore and aft
bulkheads have horizontal ones
19. Describes the purpose of bilge keels and how they are attached to the ship’s side
Page:3of 12
4. Bow and stern
1. Describes the provision of additional structural strength to withstand pounding
2. Describes and illustrates the structural arrangements forward to withstand panting L (2.0) T-24,
3. Describes the function of the sternframe T-25, T-26
4. Describes and sketches a sternframe for a single screw ship
5. Describes and illustrates the construction of a transom stern, showing the
connections to the sternframe
5. Fittings
1. Describes and sketches an arrangement of modern weather-deck mechanical steel
hatches
2. Describes how watertightness is achieved at the coamings and cross joints
3. Describes the cleating arrangements for the hatches in 1.5.1
4. Describes the arrangement of portable beams, wooden hatch covers and tarpaulins
5. Sketches an oil tight hatch cover. Describes openings in Oil, Chemical & Gas
Tankers
6. Describes roller, multi-angle, pedestal and Panama fairleads
7. Sketches mooring bitts, showing their attachment to the deck
8. Sketches typical forecastle mooring and anchoring arrangements, showing the L (6.0) T-24, T-25,
leads of moorings Ex. (2.0) T-26
9. Describes the construction and attachment to the deck of tension winches and
explains how they are used
10. Describes the anchor handling arrangements from hawse pipe to spurling pipe
11. Describes the construction of chain lockers and how cables are secured in the
lockers
12. Explains how to secure anchors and make spurling pipes watertight in
preparation for a sea passage
13. Describes the construction and use of a cable stopper
14. Describes the construction of masts and sampson posts and how they are
supported at the base
15. Describes the construction of derricks and deck cranes
16. Describes the bilge piping system of a cargo ship
17. States that each section is fitted with a screw-down nonreturn suction valve
18. Describes and sketches a bilge strum box
19. Describes a ballast system
20. Describes the arrangement of a fire main and states what pumps may be used to
pressurize it
21. Describes the provision of sounding pipes and sketches a sounding pipe
arrangement
22. Describes the fitting of air pipes to ballast tanks or fuel oil tanks
23. Describes the arrangment of fittings and lashings for the carriage of containers
on deck
Page:4of 12
6. Describes the arrangement of a watertight gland round the rudder stock L (3.0) T-24, T-25,
7. Explains the principle of screw propulsion Ex(1.0) T-26
8. Describes a propeller and defines, with respect to it :
- boss
- rake
- skew
- face
- back
- tip
- radius
- pitch
9. Compares fixed -pitch with controllable-pitch propellers
10. Sketches the arrangement of an oil-lubricated sterntuble and tailshft
11. States how the propeller is attached to the tailshaft
12. Sketches a cross-section of a shaft tunnel
13. Explains why the shaft tunnel must be of watertight construction and how water
is prevented from entering the engine room if the tunnel becomes flooded
7. Load lines and draught marks
1. Displacement
.1 states that, for a ship to float, it must displace a mass of water equal to its own
mass
.2 explains how, when the mass of a ship changes, the mass of water displaced
changes by an equal amount
.3 defines the displacement of a vessel as its mass measured in tonnes
.4 states that displacement is represented by the symbol
.5 explains that graph or scale can be drawn to show the relationship between the
displacement and mean draught of a ship
.6 given a displacement/draught curve, finds:
- displacements for given mean draughts
- mean draughts for given displacements
- the change in mean draught when given masses are loaded or discharged
- the mass of cargo to be loaded or discharged to produce a required change of
draught L (2.0) T-21, T-22
.7 defines ‘light displacement’ and ‘load displacement’ Ex.(1.5)
Page:5of 12
.8 defines ‘dead weight’ and ‘displacement tonnages’
.9 uses a dead weight scale to find the dead weight and displacement of a ship at
various draughts in seawater
.10 uses a deadweight scale to determine the change in mean draught resulting from
loading or discharging a given tonnage
.11 given the present draughts and the density of dock water, calculates the draughts
in sea water
.12 uses a ship’s hydrostatic particulars and given mean draughts to determine the
approximate weight loaded or discharged
.13 sketches a ship’s load line indicating marks for various seasonal zones, areas and
periods
.14 defines ‘tonnes per centimetre immersion’ (TPC) & MCTC
.15 explains why TPC varies with different draughts
.16 uses a dead weight scale to obtain TPC at given draughts
.17 uses TPC obtained from a dead weight to find :
- the change of mean draught when given masses are loaded or discharged
- the mass of cargo to be loaded or discharged to produce a required change of
draught
.18 defines ‘block coefficient’ (Cb) & Water Plane Coefficient (WP)
.19 calculates Cb from given displacement and dimensions
.20 calculates displacement from given Cb and dimensions
2. Buoyancy
Page:6of 12
4. Statical stability
1. States that weight is the force of gravity on a mass and always acts vertically
downwards
2. States that the total weight of a ship and all its contents can be considered to act at L (2.0) T-20, T-21, T-22
a point called the centre of gravity (G) Ex. (2.0)
3. Defines the centre of buoyancy (B) as being the centre of the underwater volume
of the ship
4. States that the total force of buoyancy always acts vertically upwards
5. Explains that the shape of buoyancy can be considered as a signle force acting
through B
6. Explains that when the shape of the underwater volume of a ship changes the
position of B also changes
7. States that the position of B will change when the draught changes and when
heeling occurs
8. Labels a diagram of a midship cross-section of an upright ship to show the weight
acting through G and the buoyancy force acting through B
9. States that the buoyancy force is equal to the weight of the ship
10. Labels a diagram of a midship cross-section of a ship heeled to a small angle to
show the weight acting through G and the buoyancy force acting through B
11. Describes stability as the ability of the ship to return to an upright position after
being heeled by an external force T-20, T-21, T-22
12. Defines the righting lever GZ as the horizontal distance between the vertical
forces acting through B and G
13. States that the forces of weight and buoyancy form a couple
14. States that the magnitude of the couple is displacement x lever, A x GZ
15. Explains how variations in displacement and GZ affect the stability of the ship
16. On a diagram of a heeled ship, shows:
- the forces at B and G
- the lever GZ
17. States that the length GZ will be different at different angles of heel
18. States that if the couple A x GZ tends to turn the ship towards the upright, the
ship is stable
19. States that for a stable ship
- A x GZ is called the righting moment
- GZ is called the righting lever
5. Initial stability
L (3.0)
1. States that it is common practice to describe the stability of a ship by its reaction Ex.(2.0) T-20, T-21, T-22
to heeling to small angles (up to approximately 100)
2. Defines the transverse metacentre (M) as the point of intersection of successive
buoyancy force vectors as the angle of heel increases by a small angle
3. States that for small angles of heel, M can considered as a fixed point on the
centre line
4. On a diagram of a ship heeled to a small angle, indicates G,B,Z and M
5. Shows on a given diagram of a stable ship that ‘M’ must be above G and states
that the metacentric height GM is taken as positive
6. Shows that for small angles of heel (), GZ = GM x sin ()
Initial stability (Contd.)
7. States the value of GM is a useful guide to the stability of a ship
Page:7of 12
8. Describes the effect on a ship’s behaviour of
- a large GM (stiff ship)
- a small GM (tender ship)
9. Uses hydrostatic curves to find the height of the metacentre above the keel (KM)
at given draughts
10. States that KM is only dependent on the draught of a given ship
11. Given the values of KG. Uses the values of KM obtained from hydrostatic curves
to find the metacentric heights, GM
12. States that, for a cargo ship, the recommended initial GM should not normally be
less than 0.15 m
6. Angle of loll
1. Shows that if G is raised above M, the couple formed by the weight and buoyancy
force will turn the ship further from the upright
2. States that in this condition, GM is said to be negative and x GZ is called the T-20, T-21, T-22
upsetting moment or capsizing moment L (1.0)
3. Explains how B may move sufficiently to reduce the capsizing moment to zero at Ex .(1.0)
some angle of heel
4. States that the angle at which the ship becomes stable again is known as the angle
of loll
5. States that the ship will roll about the angle of loll instead of the upright
6. States that an unstable ship may loll to either side
7. Explains why the condition described in 6.3 above. Is potentially dangerous
8. Corrects angle of loll
7. Curves of statical stability
1. States that for any one draught the lengths of GZ at various angles of heel can be
drawn as a graph.
2. States that the graph described in 7.1 is called a Curve of Statical Stability
3. States that different curves are obtained for different draughts with the same initial
GM
4. Identifies cross curves (KN curves & MS curves)
5. derives the formula GZ = MS + GM sine L (2.0) T-20, T-21,T -22
6 Derives the formula GZ=KN-KG sine Ex.(2.0)
7 Derives GZ curves for stable and initially unstable ships from KN curves
8 From a given curve of statical stability, obtains
- the maximum righting lever and the angle at which it occurs
- the angle of vanishing stability
- the range of stability
9. Shows how lowering the position of G increases all values of the righting level
and vice versa
10. States that angles of heel beyond approximately 400 are not normally of practical
interest because of the probability of water entering the ship at larger angles
1. States that the centre of gravity (G) of a ship can move only when masses are
moved within, added to, or removed froma the ship
2. States that
- G moves directly towards to wards the centre of gravity of added masses
- G moves directly away from the centre of gravity of removed masses L (1.0) T-20, T-21, T-22
- G moves parallel to the path of movement of masses already on board Ex. (2.0)
3. calculates the movement of G (GG1) from
- GG1 = mass added or removed x distance of mass from G
new displacement of ship
- GG1 = mass moved x distance mass is moved
displacement of ship
4. performs calculations as in 2.8.3 to find the vertical and horizontal shifts of the
centre of gravity resulting form adding, removing or moving masses
1. states that if a load is lifted by using a ship’s derrick or crance, the weights is
immediately transferred to the point of suspension
2. states that if the point of suspension is moved horizontally, the centre of gravity
of the ship also moves horizontally
3. states that if the point of suspension is raised or lowered, the centre of gravity of
the ship is raised or lowered
4. calculates, by using moments about the keel, the position of G after loading or
discharging given masses at stated positions
5. calculates the change in KG during a passage resulting from
- consumption of fuel and stores
- absorption of water by a deck cargo
- accretion of ice on deck and superstructures given the masses and their position
9. Lists and its corrections
1. shows on a diagram the forces which cause a ship to list when G is to one side L (1.0) T-20,T-21, T-22
of the centre line Ex.(1.0)
1. states that the listing moment is given by displacement x transverse distance of
G from the centre line
Page:9of 12
10. Effect of slack tanks
1. states that if a tank is full of liquid its effect on the position of the ship’s centre
of gravity is the same as if the liquid were a solid of the same mass L (1.0) T-20, T-21, T-22
2. show by means of diagrams how the centre of gravity of the liquid in a partly Ex.(1.0)
filled tank moves during rolling
3. states that when the surface of a liquid is free to move, there is a virtual increase
in KG, resulting in a corresponding decrease in GM
4. states that the increase in KG is affected mainly by the breadth of the free
surface and is not dependent upon the mass of liquid in the tank
5. states that tanks are often constructed with a longitudinal subdivision to reduce
the breadth of free surface
11. Trim
1. defines ‘trim’ as the difference between the draught forward and draught aft
2. states that trim may be changed by moving masses already on board forward or
aft, or by adding or removing masses at a position forward of or abaft the centre
of flotation
3. define ‘centre of flotation’ as the point about which the ship trims, and states
that in is sometimes called the tipping centre. L (3.0) T-20, T21, T-22
4. states that the centre of flotation, is situated at the center of area of the water Ex (4.5)
plane which may be forward of crabaft amidships
5. uses hydrostatic data to find the position of the centre of flotation for various
draughts
6. defines a trimming moment as mass added or removed x its distance forward or
aft of the centre of flotation or for masses already on board, as mass moved x
the distance moved forward or aft
Trim (Contd.)
7. defines the moment to change trim by 1 cm (MCT Icm) as the moment about
the centre of flotation necessary to change the trim of ship by 1 cm
8. uses hydrostatic curves or deadweight scale to find the MCT Icm for various
draughts
9. given the value of MCT Icm, masses moved and the distances moved forward or
aft calculates the change in trim
10. given the value of MCT Icm, the position of the centre of floatation, masses
added or removed and their distances forward of or abaft the centre of floatation
calculates
11. Given initial draughts and the position of the centre of floatation, extends the
calculation in 2.11.9 to find the new draughts
12. Given initial draughts and TPC, extends the calculation in 2.11.10 to find the
new draughts
13. Uses a trimming table or trimming curves to determine changes in draughts
resulting fron loading discharging or moving weights
14. States that in case where the change of mean draught is large calculation of
changes of trim moments about the centre of floatation or by means of trimming
tables the centre of flotation or by means of trimming tables should not be used.
15. Calculates final draughts and trim for a planned loading by considering changes
to a similar previous loading
Page:10of 12
16. given the draught amidships and dock-water density, calculates the amount to
load to bring the ship to the appropriate load line in sea water
17. uses hydrostatic data to find the position of the centre of floatation, MCT and
TPC for a given draught
18. calculates the change of trim resulting from loading or discharging a given
weight at a specified position
19. given the initial draughts, forward and aft, calculates the new draughts after
loading or discharging a given quantity of cargo
20. uses a trimming table or curves to determine changes in draught resulting from
loading, discharging or moving weights
21. calculates final draughts and trim for a planned loading by considering changes
to a similar previous loading
Page:11of 12
12. Actions to be taken in the event of partial loss of intact
buoyancy
1. States that flooding should be contained by prompt closing of watertight doors, L(1.0) T-22
valves and any other compartments
2. States that cross-flooding arrangements, where they exist, should be put into
operation immediately to limit the resulting list
3. States that any action which could stop or reduce the inflow of water should be
taken
13. Demonstrates the use of Stress Tables & Stress Calculating L (1.0) T-22
14. Explains the Intact Stability Criteria as per IMO Code of L (1.0) R-33
Intact Stability
15. Explains the use of Stability Booklet & Calculations based on L (1.0) T-20
it Ex.(1.0)
Page:12of 12