032 – Chief Mate STABILITY PAST PAPERS

032 – Chief Mate STABILITY PAST

PAPERS

March ‘19 – March ‘21

CERTIFICATES OF COMPETENCY IN THE MERCHANT NAVY – DECK OFFICER

STCW 78 as amended CHIEF MATE/MASTER REG. II/2 (UNLIMITED)

032-74 – STABILITY AND STRUCTURE FRIDAY, 29 MARCH 2019 0915 - 1215 hrs Materials to be supplied by examination centres

Examination paper inserts

Notes for the guidance of candidates: 1. Examinations administered by the SQA on behalf of the Maritime & Coastguard Agency.

2. Candidates should note that 200 marks are allocated to this paper. To pass candidates

must achieve 120 marks. 3. Non-programmable calculators may be used. 4. All formulae used must be stated and the method of working and all intermediate steps

must be made clear in the answer.

Candidate’s examination workbook Stability Data Booklet Stability Formulae Datasheets

STABILITY AND STRUCTURE Attempt ALL questions Marks for each question are shown in brackets

1. A vessel is listed 5º to port in salt water. A centreline deep tank is partially full of an oily water mixture (R.D. 0.89), which is to be fully discharged into a salvage barge alongside. The deep tank is rectangular and is 16.0 m long and 10.0 m wide. Present displacement 17 736 t KG 8.16 m Weight of oily water mixture 814 t Kg 5.88 m Using the Hydrostatic Particulars contained in the Stability Data Booklet, calculate EACH of the following: (a) the final list of the vessel; (b) the weight of ballast to transfer from a port tank to a starboard tank in order

to bring the vessel upright. The centroid of EACH tank is 4.90 m from the centreline.

(25)

(10)

2. A vessel is floating upright in salt water and the present particulars are as follows: Forward draught 8.450 m Aft draught 8.550 m. KG 7.90 m. The vessel is to load bunkers (heavy fuel oil) into No.3 D.B. port and starboard tanks and sail upright with a maximum draught of 8.600 m. Using the Stability Data Booklet, calculate EACH of the following: (a) the maximum weight of bunkers to load; (b) the weight of ballast to transfer between the Aft Peak and the Fore Peak so

that the vessel sails on an even keel.

(15)

(25)

3. A box-shaped vessel floating on an even keel in salt water has the following particulars: Length 130.00 m Breadth 28.00 m Draught 6.900 m KG 10.15 m The vessel has a centreline watertight bulkhead with an empty amidships side compartment of length 24.00 m on each side of the vessel. Calculate the angle of heel if ONE of these side compartments is bilged as a result of a collision.

(30)

4. Sketch a vessel’s curve of statical stability showing the effect of EACH of the following conditions on EACH curve: (a) a reduction in draught; (b) an increase in KG;

(c) an increase in beam.

(10)

(10)

(10)

5. Discuss the stability problems associated with the design and operation of offshore supply vessels.

(30)

6. With reference to the current Load Line Regulations: (a) distinguish between the characteristics of a Type A vessel and a Type B

vessel, explaining why they have different tabular freeboards; (b) identify the additional corrections required when converting basic freeboard

to assigned freeboard, explaining the reason for each correction.

(20)

(15)



032-74 – STABILITY AND STRUCTURE FRIDAY, 12 JULY 2019 0915 - 1215 hrs

Materials to be supplied by examination centres:

Examination paper inserts: Notes for the guidance of candidates: 1. Examinations administered by the SQA on behalf of the Maritime & Coastguard Agency.






1. A vessel, floating in a salt water port, is initially heeled 4.2º to port and has the following particulars: Displacement 6 207 tonne KG 11.15 m Tanks are then ballasted/loaded as follows: No. 1 D.B. tank across ballasted full, No. 2 D.B. tank centre ballasted full, No. 3 D.B. tank centre 150 t of heavy fuel oil (R.D. 0.84), Fresh Water After tank filled. (Assume that the above tanks were initially empty and use Kg of tanks for loading purposes) On completion of the above, there remains 130 t of cargo to be loaded. Two stowage spaces are available, each 5.20 m port and starboard of the ship’s centreline. Using the Stability Data Booklet, calculate EACH of the following: (a) the angle of heel on completion of the ballasting and bunkering; (b) the weight of cargo to load on each side so that the ship completes loading

upright.

(20)

(10)

2. A box-shaped vessel floating at an even keel in salt water has the following particulars: Length 100.00 m Breadth 21.00 m Draught 5.900 m KG 8.95 m An empty amidship, double bottom watertight compartment 18.00 m long, height of 6.60 m, and extending full breadth of vessel, is bilged. Calculate EACH of the following: (a) the final draught; (b) the change in GM.

(15)

(20)

3. A vessel is to transit a canal with a minimum clearance of 1.20 m under a bridge, the underside of which is 20.55 m above the waterline. Present draughts in dock water (R.D. 1.014): Forward 5.970 m Aft 6.930 m The fore mast is 116 m foap and extends 24.80 m above the keel. The aft mast is 23 m foap and extends 26.10 m above the keel. Using the Stability Data Booklet, calculate EACH of the following: (a) the final draughts forward and aft in order to pass under the bridge with

minimum clearance; (b) the maximum weight of cargo that can be discharged in order to pass under

the bridge with minimum clearance. Note: Assume masts are perpendicular to the waterline throughout

(17)

(18)

4.

(a) Distinguish between the terms Transverse Dynamic Stability and Transverse Statical Stability.

(b) List the information that can be extracted from a statical stability curve. (c) State the intact stability requirements for a vessel assigned with timber

loadlines.

(6)

(8)

(21)

5.

(a) A vessel is to fill a rectangular double bottom extending the full breadth of the vessel with water ballast. Sketch the vessel’s curve of statical stability on the same axis for EACH of the following conditions:

Tank empty;

Tank 5% full;

Tank 100% full.

(b) A vessel has the following particulars:

Initial Displacement 11 220 t KG 8.62 m A double bottom tank Kg 0.80 m, is to be partially filled with 280 t of fresh water resulting in a FSM of 1075 tm. Using the Maximum KG table contained in the Stability Data Booklet, determine whether the vessel complies with the minimum intact stability criteria specified in the current Load Line Regulations.

(30)

(10)

6. The current Load Line Regulations require the master to be provided with stability particulars for various pre-worked conditions. Detail the information to be provided for a given service condition, describing how this information may be presented.

(25)



032-74 – STABILITY AND STRUCTURE THURSDAY, 3 OCTOBER 2019 0915 - 1215 hrs Materials to be supplied by examination centres

Examination Paper Inserts






Worksheet Q2


1. A box-shaped vessel floating at an even keel in salt water has the following particulars:

Length 120.00 m Breadth 26.00 m

Draught 6.000 m KG 10.88 m

An amidship watertight compartment 17.00 m long, height 6.80 m, and extending full breadth of vessel, is bilged. The compartment is fully loaded with cargo of relative density 0.87 and stowing at 1.64 m3/tonne.

Calculate EACH of the following:

(a) the final draught;

(b) the change in GM.

(15)

(20)

2. Worksheet Q2 Trim and Stability provides data relevant to a particular condition of loading in a vessel in salt water. The Stability Data Booklet provides the necessary data for the vessel. By completion of Worksheet Q2 and showing any additional calculations in the answer book, calculate EACH of the following: (a) the effective metacentric height; (b) the draughts forward and aft.

(15)

(20)

3. A vessel, initially upright, is to carry out an inclining test. Present displacement 4854 t. KM 10.52 m Total weights on board during the experiment: Ballast 370 t Kg 3.52 m. Tank full. Bunkers 192 t Kg 3.85 m. Free surface moment 847 tm. Fresh Water 76 t Kg 3.86 m. Slack tank. Free surface moment 756 tm Inclining weights 40 t Kg 8.89 m. At the time of the experiment the boilers are empty. They would usually contain a total of 24 t of water, Kg 4.12 m, with a free surface moment of 142 tm. Both lifeboats, each weighting 12 t are still ashore and will be fitted on the vessel at a Kg of 19.76 m at a later date. The plumbline has an effective vertical length of 7.25 m. The inclining weights are shifted transversely 8.20 m on each occasion and the mean horizontal deflection of the plumbline is 65 cm. Calculate the vessel's Lightship KG.

(30)

4. A vessel is lying at an angle of loll to starboard in saltwater, with the following particulars: Present displacement 14 576 tonne KG 8.40 m (a) Using the Stability Data Booklet, calculate EACH of the following:

(i) the angle of loll; (ii) the GM at the angle of loll.

(b) Water ballast tanks, No. 2 D.B. tanks, port, centre and starboard, are available for use in restoring positive stability. With reference to the Stability Data Booklet, explain EACH of the following: (i) why the ballasting No. 2 port tank first should be avoided; (ii) the advantage(s) of ballasting No. 2 centre tank first instead of No. 2

starboard tank; (iii) the disadvantage(s) of ballasting No. 2 centre tank first instead of No. 2

starboard tank; (iv) the advantage(s) of ballasting No. 2 starboard tank first instead of No. 2

centre tank.

(10)

(5)

(4)

(4)

(6)

(6)

5. A vessel is to use a ship’s heavy lift derrick to load a locomotive from ashore. Describe, with the aid of a sketch, the vessel’s curve of statical stability, the effects on the overall stability of the vessel when the weight is first lifted from a position well away from the ship’s centreline.

(35)

6. With reference to the current M.S. (Load Line) Regulations: (a) State the minimum stability requirements for a vessel under the current Load

Line Regulations. (b) At ballast draught a vessel complies in every respect with the stability

requirements of the Load Line Regulations. At load draught, with the same GM, the vessel does not comply.

Explain, with the aid of a sketch, of a statical stability diagram, why the vessel no longer complies.

(c) The regulations specify a minimum area under the Curve of Righting Levers

(GZ Curve) to ‘40º or any lesser angle at which the lower edges of any openings in the hull, superstructure or deckhouses which lead below deck and cannot be closed weathertight, would be immersed.’

Describe the method to calculate the area up to 36º to verify compliance.

(6)

(18)

(6)

TRIM & STABILITY

CONDITION: LOADED

Compartment Capacity

m3

Stowage Factor

m3/t

Weight t

KG

m

Vertical Moment

tm

Free Surface Moment

tm

LCG foap

m

Longitudinal Moment

tm

All Holds 14708 1.88 5.84 68.48

1 TD 1320 2.25 10.85 113.40

2 TD 1450 2.25 10.48 92.40

3TD 1390 2.88 10.39 73.70

4 TD 1560 1.97 10.31 52.80

Fuel Oil 850 1548 534 29987

Fresh Water 95 700 76 4534

Lightship 3766 8.14 69.59

DISPLACEMENT

HYDROSTATICS

True Mean Draught LCB foap LCF foap

MCTC

TRIM

KMT

KG

DRAUGHTS: F. A. GM

No.5 Hold

T.S. Tk p & s

AP

FW FW

sgE.Room

FP

CL

No.1 Tween

Stores

No.1 HoldNo.2 HoldNo.4 Hold No.3 HoldDeep Tk

No.2 TweenNo.3 TweenNo.4 Tween



032-74 – STABILITY AND STRUCTURE FRIDAY, 29 NOVEMBER 2019 0915 - 1215 hrs Materials to be supplied by examination centres

Examination Paper Inserts Notes for the guidance of candidates: 1. Examinations administered by the SQA on behalf of the Maritime & Coastguard Agency.





Worksheet Q3


1. A box shaped vessel floating on even keel in salt water has the following

particulars:

Length 130.00 m Breadth 22.00 m Draught 7.600 m KG 9.80 m

There is an empty watertight aft end compartment, length 15.00 m,

height 6.30 m, extending the full width of the vessel.

Calculate the draughts forward and aft, if this compartment is bilged.

(35)

2. A vessel completes underdeck loading in salt water with the following particulars: Displacement 16448 tonne KG 7.96 m The Stability Data Booklet provides the necessary data for the vessel. Consumption during the passage was as follows; 180 t of Heavy Fuel Oil (R.D. 0.84) from No. 3 D.B. tank centre (full on departure), 12 t of Diesel Oil from No. 4 D.B. tank port (partially full on departure), 12 t of Diesel Oil from No. 4 D.B. tank starboard (partially full on departure), 16 t of Fresh Water from Forward Water Tank (full on departure). (Use the VCG of tank for consumption purposes) Calculate the maximum weight of timber to load on deck Kg 12.85 m. Assume 15% water absorption during the passage in order to arrive at the destination with the minimum GM (0.05m) allowed under the Load Line Regulations. Note: Assume KM constant.

(35)

3. A vessel is floating in dock water of R.D. 1.018. Present draughts:

Forward 7.213 m Midship (Port) 8.092 m Midship (Starboard) 8.032 m

Aft 8.474 m

The draught marks are displaced as follows:

Forward: 1.54 m aft of the FP

Aft: 1.86 m aft of the AP

Midship: 0.58 m aft of amidships

The Stability Data Booklet provides the necessary hydrostatic data for the

vessel.

Using Worksheet Q3 and showing any additional calculations in the answer book,

determine EACH of the following:

(a) the vessel’s displacement;

(b) the maximum cargo to load for a Summer Load Line Zone.

Note: Assume no hog or sag in the Summer Load condition.

(30)

(5)

4. (a) Sketch a vessel’s curve of statical stability, on a single set of axis, showing the effects of EACH of the following:

(i) a steady beam wind;

(ii) gusting strong beam wind.

(b) With reference to Offshore supply vessels:

(i) explain why the Fixed and Free Trim curves are the same up to the angle of Deck Edge immersion;

(ii) sketch a supply vessel’s statical stability diagram showing how the GZ

curve for the vessel calculated on a Free Trim basis may differ from that calculated on a Fixed Trim basis.

(10)

(5)

(5)

(10)

5. With reference to the Passenger Ship Construction Regulations: (a) explain the function of the Factor of Subdivision; (b) describe the use of sub-division loadlines; (c) state the extent of assumed hull flooding and damage when calculating the

vessel’s ability to survive hull damage; (d) describe the purpose of the Stockholm Agreement and identify the type of

vessel to which it applies.

(9)

(9)

(9)

(8)

6. (a) Describe how increasing the beam of a box shaped vessel increases the ship’s BM and GM.

(b) Explain why the “True Mean Draught’ should be used to obtain a ship’s

Hydrostatic particulars when performing transverse and longitudinal stability calculations rather than using the ‘Arithmetic Mean Draught’.

(c) Describe, with the aid of a sketch, how a vessel’s Centre of Gravity moves

due to the free movement of the liquid in a slack tank and how this causes a loss of GZ.

(6)

(6)

(18)

DRAUGHT SURVEY REPORT

metres

Draught Forward

FP Correction Dist. marks displaced

Dist. between marks x Observed Trim

Draught at FP

Draught Aft

AP Correction Dist. marks displaced

Dist. between marks x Observed. Trim

Draught at AP

True Trim

Draught (M) Port

Draught (M) Star.

Draught

Midships Mean

Amidship line

correction

Dist. marks displaced

LBP x True Trim

Draught at

Amidships

Corrected

Midship Draught

dFP + (6 x dM) + dAP

8

TPC LCF foap

tonne

Displacement

1st Trim Corrn.

(Layer)

Dist. of CF from Midships x Trim x TPC

LBP

2nd Trim Corrn.

(Form)

50 x True Trim2 x (MCTC2 - MCTC1)

LBP

Corrected

Displacement

Dock Water

Displacement Δ x

R.D. Dock Water

1.025



032-74 – STABILITY AND STRUCTURE FRIDAY, 10 JULY 2020 0915 - 1215 hrs Materials to be supplied by examination centres Examination Paper Inserts







1. A ship is lying starboard side to on a salt water berth with a 5º port list. She has an even keel draught of 6.280 m and a KG of 8.19 m. A 15 t piece of project cargo is to be loaded using the ship’s own derrick. It is currently on the quay, 13.30 m from the centreline and the head of the derrick when slewed during loading will be 21.50 m. The stow position is Kg 3.50 m and on the centreline. Using the Stability Data booklet provided, calculate EACH of the following: (a) (i) the maximum list experienced during the operation;

(ii) the size and direction of any list once the weight is stowed;

(iii) the quantity of ballast to load into the relevant No. 2 D.B. side tank in order to bring the vessel upright;

(iv) the KGeffective of the vessel on completion of the ballasting in Q1(a)(ii) (Use

Kg of the tank). (b) With reference to the Maximum KG Table, determine, whether the vessel

complies with the minimum intact stability criteria of the current Load Line Rules in this final condition.

(15)

(10)

(2)

(4)

(4)

2. A box shaped vessel floating at an even keel in dock water (RD 1.018) has the following particulars: Length 135.00 m Breadth 21.00 m Draught 6.360 m KG 7.10 m A midship watertight compartment 20.00 m long and extending the full breadth and depth of the vessel is bilged. Permeability of the compartment is 0.75. Calculate EACH of the following: (a) the new draught; (b) the change in GM; (c) the moment of statical stability in the flooded condition for an angle of heel

of 16º.

(12)

(16)

(7)

3. A vessel, initially upright, is to carry out an inclining test. Present displacement 5450 t KM 10.88 m Total weights on board during the experiment: Ballast 280 t Kg 3.52 m Tank full. Bunkers 167 t Kg 4.11 m Free surface moment 823 tm Fresh Water 41 t Kg 3.96 m Free surface moment 36 tm Boiler water 14 t Kg 4.59 m Free surface moment 137 tm Inclining weights 50 t Kg 10.57 m The ship’s free fall lifeboat, weight 18 t, is temporarily located on the aft deck, Kg 10.25 m and will be stowed the following week at Kg 13.54 m. The plumblines have an effective vertical length of 9.93 m. The inclining weights are shifted transversely 11.30 m on each occasion and the mean horizontal deflection of the plumbline is 0.74 m. (a) Calculate the vessel's Lightship KG. (b) Explain why it is important to restrict the amount of Free Surface Moments

on board during the inclining test.

(25)

(5)

4. A box shaped vessel’s forward end compartment, extending the full breadth and depth is flooded as a result of a collision. (a) State and explain any effect that this flooding may have on EACH of the

following:

(i) the vessel’s Centre of Gravity ‘G’;

(ii) the height of the vessel’s Centre of Buoyancy ‘KB’;

(iii) the vessel’s Centre of Flotation ‘F’;

(iv) the Displacement of the vessel. (b) When calculating the change of trim due to the flooding of a forward end

compartment of a box shaped vessel it is necessary to obtain the MCTC. Explain why the metacentric height in the bilged condition is required to be used in preference over the initial GML when doing so.

(c) Identify and explain the circumstances when the KB of a bilged box shaped

vessel cannot be calculated as half the bilged draught.

(4)

(4)

(4)

(3)

(10)

(10)

5. A general cargo ship is loading in a port in a Tropical seasonal zone for a port in a Winter seasonal zone during winter months. Describe the various precautions and considerations which must be borne in mind at the loading port in order that the voyage is accomplished safely, in accordance with the requirements of the Load Line Rules.

(30)

6. (a) Describe how the effect of icing on a vessel’s stability may be determined when a vessel is operating in severe winter conditions.

(b) Sketch a vessel’s curve of statical stability showing the effect of non-

symmetrical ice accretion on decks and superstructure.

(10)

(25)



032-74 – STABILITY AND STRUCTURE FRIDAY, 21 AUGUST 2020 0915 - 1215 hrs Materials to be supplied by examination centres








1. A ship is alongside a berth in salt water with a list of 4º to port. She is nearing completion of cargo operations with a present displacement of 8422 t and a GM 0.18 m. There are three parcels of cargo remaining to load weighing: 10 t, 5 t and 19 t. The available locations are: Kg 11.80 m tcg 6.00 m starboard Kg 10.20 m on the centre line Kg 5.40 m tcg 4.00 m starboard Using the Stability Data Booklet, calculate EACH of the following: (a) which parcel of cargo should be loaded into each of the available locations so

that the vessel completes upright with an improved GM; (b) whether the ship, on completion of loading as determined in Q1(a), complies

with the minimum intact stability criteria using the Maximum KG table, commenting on the result.

(25)

(10)

2. A vessel is upright, alongside and on an even keel in dock water of RD 1.011 with the following particulars: Draught 8.740 m KG 7.20 m A midship rectangular deck 32.00 m long and extending the full breadth of the vessel is flooded with dock water to a depth of 0.60 m. Height of the deck above the keel 12.15 m. Using the Stability Data Booklet, calculate EACH of the following: (a) the fluid GM; (b) the angle of loll.

(25)

(10)

3. A vessel is floating upright in salt water with the following particulars: Forward draught 7.860 m Aft draught 8.540 m The vessel is to proceed on a short coastal voyage to a neighbouring port. On arrival the vessel has to navigate over a shoal. On the passage the following items of deadweight will be consumed: 26 t of Heavy Fuel Oil from No. 3 D.B. Port tank, 26 t of Heavy Fuel Oil from No. 3 D.B. Starboard tank, 9 t of Diesel Oil from No. 4 D.B. Port tank, 7 t of Diesel Oil from No. 4 D.B. Starboard tank. Additionally, the After Peak tank was fully de-ballasted of saltwater from an initially full condition. (a) Using the Stability Data Booklet, calculate the minimum clearance of the

vessel over the shoal with a predicted depth of water of 9.60 m. (b) State the minimum clearance over the sand bar, if the vessel is brought to an

even keel condition by internal transfer of ballast.

(30)

(5)

4. (a) The bilging of an empty midship compartment will affect a vessel’s draught and may also result in a change in the vessel’s intact waterplane area.

Identify and explain a possible scenario (incorporating a watertight flat if appropriate) where such bilging could result in EACH of the following:

(i) an increase in the vessel’s GM; (ii) a reduction in the vessel’s GM.

(b) The bilging of an empty midships, side compartment will negatively affect a

vessel’s stability. Explain, with the aid of a sketch of a curve of statical stability, how cross flooding is likely to restore some of this loss.

(10)

(10)

(15)

5. List TEN items of the stability and stress data required to be supplied to ships under the current Load Line Regulations, stating for EACH how such information might be used.

(30)

6. Discuss the stability problems associated with the design and operation of a conventional Ro-Ro vehicle ferry.

(30)



032-74 – STABILITY AND STRUCTURE FRIDAY, 09 OCTOBER 2020 0915 - 1215 hrs Materials to be supplied by examination centres


Notes for the guidance of candidates: 1. Examinations administered by the SQA on behalf of the Maritime & Coastguard Agency. 2. Candidates should note that 200 marks are allocated to this paper. To pass candidates




STABILITY AND STRUCTURE Attempt ALL questions Marks for each question are shown in brackets All formulae used must be stated and the method of working and all intermediate steps must be made clear in the answer.

1. (a) A vessel is alongside an upriver berth in fresh water with the following particulars: (b) (c) Forward draught 7.350 m Aft Draught 8.570 m (d) (e) A single consignment of cargo, weighing 743 t is to be loaded. (f)

Using the Stability Data Booklet, calculate EACH of the following: (a) the distance FOAP and compartment onboard to load this parcel of cargo in

order to maintain the current aft draught; (b) the final draught forward.

(35)

(5)

2. A box shaped vessel floating upright on an even keel in salt water has the following particulars: Length 145.00 m Breadth 28.00 m Draught 7.400 m KG 10.78 m The vessel has two longitudinal bulkheads 5.00 m from EACH side of the vessel. Calculate the angle of heel if a midships side compartment 29.00 m long is bilged.

(30)

3. A container vessel’s particulars are as follows: Displacement 14 000 t KG 7.75 m Draught 7.200 m Lateral windage area 5800 m2. Centroid of the windage area 10.20 m above the waterline. (a) Construct a righting moment curve to 60 degrees heel using the KN Tables in

the Stability Data Booklet; (b) Using the righting moment curve constructed in Q3(a), determine EACH of the

following:

(i) the angle of heel due to a steady lateral wind pressure of 48.5 kgs/m2;

(ii) the angle of heel if the wind pressure increases by 50 % due to gusting.

(15)

(10)

(5)

4. (a) Describe the changes in stability which may take place on a voyage. (b) Provide a sketch of statical stability showing the effects on the curve of

righting levers (GZ) of the changes described in Q4(a).

(15)

(20)

5. (a) State the surveys required in order that an International Load Line Certificate remains valid.

(b) List the items to be inspected during the surveys stated in Q5(a), stating the

nature of the examination required for each.

(4)

(26)

6. Describe the general provisions of the current Load Line Regulations governing the ability of Type B vessels with reduced freeboard to withstand flooding due to damage, and the stability in the final condition after such damage.

(35)



032-74 – STABILITY AND STRUCTURE FRIDAY, 04 DECEMBER 2020 0915 - 1215 hrs Materials to be supplied by examination centres


Notes for the guidance of candidates: 1. Examinations administered by the SQA on behalf of the Maritime & Coastguard Agency. 2. Candidates should note that 200 marks are allocated to this paper. To pass candidates



Candidate’s examination workbook Stability Data Booklet Stability Formulae Datasheets Graph Paper


1. A vessel is preparing to enter dry dock at a port with an RD of 1.018. The present particulars: Aft draught 4.627 m Forward draught 3.227 m KG 9.78 m It has been determined that a maximum trim of 1.150 m by the stern is required prior to docking in order to ensure adequate effective GM at the critical instant. With reference to the Stability Data Booklet: (a) calculate the weight of dock water ballast to transfer from the After Peak

tank to the Fore Peak tank in order to achieve the required trim; (b) calculate the GM of the vessel after the transfer of dock water ballast

(RD 1.018).

Note: After Peak tank was full and the Fore Peak tank empty prior to the transfer of ballast (Use KG of the tanks);

(c) calculate the effective GM at the critical instant; (d) comment on the calculated effective GM in Q1(c).

(8)

(8)

(12)

(2)

2. A vessel is floating upright alongside a berth in salt water and is due to load a cargo of grain (stowage factor 1.68m3/t). All five holds are to be fully loaded and the tween decks are variously full and partially full. Assume that cargo surfaces will be levelled on completion. After tabulating the weights and moments for the planned load of grain the following final totals were obtained;

Item Displacement KG Volumetric Heeling Moments

Final totals 18 501 t 7.50 m 6 309 m4

(a) Using the KN Table included in the Stability Data Booklet construct a GZ curve

for this condition of loading. (b) Use the information obtained in Q2(a) to determine whether the vessel

complies with all of the minimum criteria specified in the International Grain Code (IMO).

(14)

(21)

3. A vessel completes underdeck loading in salt water with the following particulars: TMD 6.758 m KG 7.74 m The Stability Data Booklet provides the necessary data for the vessel. During the passage 223 tonne of Fuel Oil (R.D. 0.81) is consumed from No. 3 D.B. tank centre which was full on departure (use Kg of tank for consumption purposes). Calculate the maximum weight of timber to load on deck Kg 13.50 m assuming 15% water absorption during the passage in order to arrive at the destination with a minimum GM of 0.20 m. Note: Assume KM constant.

(35)

4. Identify and explain the corrections to be applied to the Tabular Freeboard for a ‘Type A’ ship in order to obtain the Assigned Freeboard, and provide the reason why the freeboard could be increased or decreased in each case.

(30)

5. (a) Discuss the factors affecting the virtual loss of GM due to a free surface within an undivided rectangular tank.

(b) Explain the effect on the virtual loss of GM due to the free surface when the

slack tank is equally divided in EACH of the following situations:

(i) by a longitudinal bulkhead;

(ii) by a transverse bulkhead.

(c) Explain why it is preferable that stability information relating to free surface for a particular tank is usually expressed as a Free Surface Moment (FSM) rather than Free Surface Correction (FSC).

(d) A double bottom tank, initially empty, is to be ballasted full of salt water.

Sketch a labelled diagram to show the way in which the effective KG of the ship will change from the instant of starting to fill the tank until it is full.

(8)

(5)

(5)

(5)

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6. (a) Explain the difference between the Angle of Deck Edge Immersion and the Angle of Flooding, stating typical values from the Stability Data Booklet.

(b) Explain how when a vessel heels to an angle of loll it now has a small positive

GM. (c) Explain why a vessel carrying timber on deck may be allowed a smaller GM

than is usual for a cargo vessel. (d) Explain how an increase in the beam of a vessel can improve a vessel’s

stability and why such improvement is more pronounced at smaller angles of heel.

(5)

(10)

(10)

(10)

CERTIFICATES OF COMPETENCY IN THE MERCHANT NAVY –DECK OFFICER


032-74 – STABILITY AND STRUCTURE FRIDAY, 26 MARCH 2021 0915 - 1215 hrs Materials to be supplied by examination centres







STABILITY AND STRUCTURE Attempt ALL questions Marks for each question are shown in brackets All formulae used must be stated and the method of working and all intermediate steps must be made clear in the answer

1. A vessel is floating upright in salt water with an even keel draught of 6.850 m. GMeff 0.57 m. The vessel has a rectangular double bottom tank of length 20.0 m, breadth 18.0 m, depth 1.80 m, which is subdivided by two equally spaced longitudinal bulkheads resulting in the port, centre and starboard compartments having equal dimensions. At present all three compartments contain saltwater ballast to an ullage of 0.60 m. Using the Stability Data Booklet calculate the angle of heel after emptying the centre and portside tanks. Note: The starboard tank failed to de ballast due to a valve failure.

(35)

2. A vessel is to transit a canal with a minimum clearance of 1.40 m under a bridge, the underside of which is 22.50 m above the waterline. Present draughts in dock water of R.D. 1.019: Forward 4.880 m Aft 5.960 m The aft mast is 23 m foap and extends 28.10 m above the keel. The fore mast is 118 m foap and extends 26.60 m above the keel. Assume the masts are perpendicular to the waterline throughout. Using the Stability Data Booklet, calculate EACH of the following: (a) the draughts required, forward and aft, in order to pass under the bridge with

minimum clearance; (b) the minimum weight of ballast to load in order to pass under the bridge with

minimum clearance.

(20)

(15)

3. A vessel is planning to enter drydock in salt water. Present draughts: Forward 3.850 m Aft 5.750 m and KG 8.79 m Using the Stability Data Booklet, calculate EACH of the following: (a) The maximum trim at which the vessel can enter drydock so as to maintain a

GM of at least 0.25 m at the critical instant.

Note: Assume KM constant. (b) Comment on the result of Q3(a) identifying any possible operational issue that

may occur during the critical period. (c) Other than reducing the trim of the vessel, identify and describe alternative

methods of improving the condition of stability prior to entering the dry dock.

(25)

(5)

(5)

4. (a) Explain with the aid of a sketch why a vessel will usually heel outwards when a steady rate of turn has been achieved.

(b) Sketch a stable vessel’s curve of statical stability showing the effect of heel

when turning. (c) Describe the effects that heel when turning has on the stability of a vessel.

(10)

(10)

(10)

5. (a) List THREE possible causes, excluding changes to ship’s structure and fittings, for a change to the lightship KG over a period of time.

(b) Explain the necessity for EACH of the following precautions to be taken before

and/or during the inclining experiment:

(i) Slack tanks should be avoided when possible and preferably be restricted to tanks with a rectangular shape;

(ii) Moorings should be appropriately arranged;

(iii) No passing vessels;

(iv) Fine weather, with little or no wind;

(v) Lifeboats, cranes, anchors and such should be secured in their seagoing

positions;

(vi) The test inclination should not exceed 4º from the upright zero position.

(6)

(4)

(4)

(4)

(4)

(4)

(4)

6. Describe a Type ‘A’ vessel under the current Load Line Regulations, including the flooding, stability and assumed damage requirements.

(35)

032 – Chief Mate STABILITY PAST PAPERS

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