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Stability Flashcards

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1
Q

What tests are required on a loading computer?

A

Annual Test against Standard Conditions in stability book

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2
Q

What ships have WNA loadlines?

A

Less than 100m

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3
Q

What is a draft survey for?

A

Allows for calculation of displacement
and from that, calculation of loaded cargo

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4
Q

Can a draft survey with a list? How?

A

Yes, Drafts need to be taken from both sides of the ship

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5
Q

How do you take the drafts for a draft survey?

A

Visually

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6
Q

How do you read draft marks?

A

You are studying for your chief mates and you don’t know how to read draft marks!?

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7
Q

What do measure for a draft survey?

A

Drafts
Dock Water Density

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8
Q

How do you find the dock water density?

A

Using a Hydrometer

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9
Q

What kind of hydrometer do we use on ship?

A

Draft Survey hydrometer or Glass bulb hydrometer

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10
Q

What is a hydrometer used for?

A

To find the density of water

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11
Q

Describe a hydrometer

A

Looks like a thermometer with a huge bulb

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12
Q

How do you use a hydrometer?

A

Fill a bucket with the water to be tested
Lower the hydrometer, bulb first, into the water
Once the bulb is fully submerged spin the hydrometer
Read the resulting measurement

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13
Q

Why do you spin a hydrometer?

A

To break the meniscus

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14
Q

Where do you get the water for measuring the dock water density?

A

Not Near Suctions/Sources of heat
Not Near Discharges
On the Sea Side of Vessel

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15
Q

How tall are the draft mark figures?

A

10cm Each

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16
Q

Why does the vessel have maximum drafts?

A

Retain sufficient reserve buoyancy / survivability
Not overload the ship

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17
Q

Why does the vessel have minimum drafts?

A

Propellor Immersion
Minimum required deadweight
Thruster Immersion
Stability
Suction Intakes

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18
Q

Does a stability book have to be approved?

A

Yes

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19
Q

How would you know your stability book is approved?

A

Stamp on the front page

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20
Q

Where does the requirement for a stability book come from?

A

SOLAS CH2-1 Part B-1 - 5 - 1

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21
Q

When do you do a draft survey?

A

Before and after loading

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22
Q

Can a vessel load if the loading computer breaks down?

A

Yes, do manual calculations using the stability booklet

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23
Q

Is the plimsoll mark or the loadlines more fwd on the hull

A

The load lines are FWD, the plimsoll mark is aft

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24
Q

What is the problem with sailing with a list?

A

Increases the draft

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25
Should you sail with a list?
No, ship should be upright
26
What causes a ship to be tender vs stiff?
High GM causes a stiff ship
27
Is a bigger GM always better?
No, if the GM is too high the whipping of the ship can cause issues E.G. Cargo lashings broken, Liquids sloshing up vents, Containers lost, Passenger comfort, stresses on ship
28
What is the difference between metacentric height and height of the meta centre?
Metacentric height = GM Height of the meta centre = KM
29
Can you give an example of a stiff ship and a tender ship?
Stiff - Ballast Tanker Tender - Loaded Timber
30
How do you sound a WBT/compartment/cofferdam?
Down the sounding pipe, a brass dipping rod with water-finding paste on it - Paste turns pink when dipped in water
31
Where do you find information on the ships stability?
Stability booklet Stability computer
32
When can a ship load to her timber loadlines?
When the timber deck cargo is lashed in accordance with the timber code
33
Why does a timber deck cargo allow you to load to the deeper timber loadlines?
When lashed, as per the timber code, the timber deck cargo adds to the reserve buoyancy of the ship
34
Does every type of wood loaded on deck allow you to use the lumber load lines?
No, the timber code has some exceptions (wood pulp etc)
35
Are the added lumber loadline fwd or aft of the plimsoll mark?
Aft of the plimsoll mark
36
What is the main stability concern with a timber deck cargo?
On passage, the wood abosrbs water, increasing its weight, and so decreasing GM
37
What information is in the stability book?
Approval indication (Stamp) Ships Particulars Max/min drafts + displacements Draft Survey Template Sample Conditions Hydrostatic Tables Tank Curves Gz Curve Figure Table
38
When must you be at a particular loadline?
When you enter the area for that loadline (e.g. at your winter marks, when you enter the winter area)
39
What was the typical gm on your last vessel?
Loaded - Ballast -
40
Where do you find the stability requirements for: i) All ships ii) Grain Cargoes iii) Tinber Deck cargoes
i) code of intact stability ii) Grain Code iii) Timber Deck Cargo Code
41
What is the maximum recommended GM on a timber deck cargo ship? Why?
3% of Breadth Any larger and the stiffness of the ship may break the lashings
42
What is on an arrival/departure stability sheet?
Drafts (f/m/a) Trim List LCG, VCG LCB, VCB GM Prop immersion SF/BM Displacement Bridge Visibility Stability criteria (Pass/Fail) List of weights + Locations
43
Where does the requirement for a damage stability book come from?
SOLAS Chapter 2
44
What is the GM?
Distance from the Centre of gravity to the metacentre
45
Minimum GM?
0.15m
46
What is the minimum GM for grain cargoes?
0.30m
47
What is the minimum GM for timber deck cargoes?
0.10m
48
How could you check if a vessel was sagged or hogged?
Discrepancy between fore/aft/midship drafts Hatch covers not closing properly (bulker) Sheering forces and bending moments too high Calculated on loading computer Cargo obviously distributed incorrectly Ballast obviously ditributed incorrectly
49
What is gross tonnage?
The overall size or capacity of ship, as per the tonnage convention i.e. the total volumetric capacity of the ship
50
What is deadweight?
It is the weight in tonnes of cargo, stores, fuel, passengers,crew and their effects which a vessel is able to carry
51
What is net tonnage?
It is the gross tonnage minus the non-earning spaces used for crew, navigation, machinery and fuel i.e. the cargo capacity
52
What is the order of the draft marks and what do they mean?
TF: Tropical Freshwater F: Freshwater T: Tropical Freshwater S: Summer (Plimsol Line) W: Winter WNA: Winter North atlantic L = Lumber prefix
53
What was the summer draft on your last vessel?
12.15m (lng tanker) 15.22m (aframax tanker)
54
How do you know when the ship has been loaded? How could you get a quick indication?
When the cargo plan is finished Check the load lines
55
Explain FWA?
The difference between the summer draft and the fresh water draft. It allows for the difference in density between the sea and fresh water
56
Where would you find the FWA?
Stability book Loadline certificate Official Logbook Notice of sailing drafts
57
Explain DWA?
Dock water allowance, the amount you can load below the summer marks to allow for the difference between the density of sea water and the water at the berth
58
What is the DWA calculation?
(SWD-DWD)*FWA / 25
59
How do you calculate the dock water analysis?
Find the Fresh water allowance and the dock water density and use the DWA formula
60
Where does the requirement for a damage stability book come from?
SOLAS Chapter 2
61
What information is included in the sample conditions in the stability book?
Loaded weights and locations Drafts, trim Kg etc GZ curve and stability tests Bridge visibility figures
62
What are the stability criteria?
Area under the curve (0-45,0-30,30-45), Min GM Angle of maximum GZ Angle of deck edge immersion Bridge Visibility
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