QUESTION BANK NAVAL ARCHITECTURE PART-2

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Q Explain how the period of the roll varies with

a) The amplitude of roll

b) The radius of gyration

c) The initial metacentric height

d) The location of masses in the ship

Q With respect to trim & stability, describe the following:

a) Effects on  the centre of the gravity of slack tanks.

b) Effect on stability of ice formation on the superstructure.

c) Effects of wind and waves on ship’s stability.

d) Effect of water absorption by deck cargo & retention of water on deck.

Q With reference to Roll-on, Roll-off ferries

a) Describe the problem of free surface effect.

b) Explain how it is intended that water should be cleared from car or cargo decks.

c) Describe possible methods for improving the stability & survivability of these vessels.

Q Describe the general precautions to be taken against capsizing. State the recommended criteria for passenger & cargo ships.

Q Explain what is meant by  the dynamical stability.

With a curve of statical stability explain how the area under the GZ curve represents dynamic stability

Q The value of the maximum righting arm is dependent upon the position of the centre of buoyancy and the:

a) Longitudinal centre of gravity

b) Transverse centre of gravity

c) Down flooding angle

d) Vertical location of the centre of gravity

Deduce the relation of the option you have selected with reference to the value of maximum righting arm.

Q A ballast tank is one-third full when additional ballast is added until it is two-thirds full. The increased amount of liquid in the tank will have the greatest influence on

a) Free surface effect

b) Transverse stability

c) Virtual rise in the centre of gravity

d) Value of the moment to trim 1 inch (MTI)

Give detailed explanations stating why the other options were not considered.

Q Describe the effect on GM of rolling and how bilge keels, anti-rolling tanks and stabilizer fins reduce the amplitude of rolling.

Q Describe the effect of the following on the ship’s stability,

a) Ice formation on superstructure

b) Effect of wind and waves

c) Changes that takes place during the ships voyage

d) Bilging of a compartment

e) While water is being pumped out from the dry dock

Q With reference to International Load Line Statutory Certification:

a) State reasons for freeboard requirements.

b) i. Explain the term conditions of assignment.

ii. List the items that may be examined during a Load Line survey after a vessel’s major repair in the drydock.

Q With reference to the prevention of hull corrosion discusses:

a) Surface preparation & painting of  the new ship plates.

b) Design of the ships structure & its maintenance.

c) Cathodic protection by sacrificial anodes, of the internal & external areas of the ship.

Q a) Describe the safety precautions which are taken when using paints.

b) Describe the use of self-polishing anti-fouling paint, and the proposed banning of tributyltin (TBT)

Q Describe the in-water survey to classification society requirements of the external underwater structure of a very large crude carrier.

Q Describe the preparation necessary before the application (in dry dock) of sophisticated or approved long life coating to the underwater surface of the hull.

a) State the significance of the roughness profile.

b) List the different sophisticated coatings which are available.

Q a) Explain in detail, how an underwater survey is carried out

b) State the requirements to be fulfilled before an underwater survey is acceptable to the survey authority.

c) Construct a list of items in order of the importance that the underwater survey authority should include.

Q With reference to membrane tanks for the carriage of liquefied gas at very low temperatures:

a) Describe with the sketch one method of building up the insulation;

b) State which alloy is used for the membrane & the reason;

c) Explain why a secondary barrier is installed.

i. Longitudinally

ii. Transversely

Q With regard to the carriage of crude oil and its associated products:

a) i. Sketch and describe the operation of an explosimeter suitable for testing pump rooms or tanks.

ii. State why false readings are likely to be given by the explosimeter.

iii. State the dangers involved.

b) State the publication that gives guidance on safety.

c) Define the terms lower and upper flammable limits illustrating your answer by means of a rough sketch of a hydrocarbon vapour oxygen graph.

Q a) Describe briefly the tank system in liquefied natural gas (LNG) vessel.

b) Explain how the boil off from liquefied natural gas is handled.

Q a) Explain the considerations which govern the size & shape of a rudder.

b) Explain why the rudder angle does not normally exceed 35°.

c) What factors influence the frictional resistance of a ship and what formula is used to calculate their resistance?

d) A ship of 12000 tonne displacement has a rudder 15 m² in area, whose centre is 5 m below the waterline. The metacentric height of the ship is 0.3 m and the centre of buoyancy is 3.3 m below the waterline. When travelling at 20 knots the rudder is turned through 30°. Find the initial angle of the heel if the force Fn perpendicular to the plane of the rudder is given by:

Fn = 577 Av² sinα N

Allow 20% for the race effect.

Q a) Why is it important in a tender ship to keep the double bottom tanks pressed up?

b) A ship of 6000 tonne displacement has a wetted surface area of 2500 m² & a speed of 15 knots.

i. Calculate the corresponding speed and wetted surface area of as similar ship of 2000 tonne displacement.

ii. If the skin resistance is of the form R=0.45 S V1.83 N; find the resistance of the 6000 tonne Ship.

Q a) Explain how to distinguish between list and loll and describe how to return the ship to the upright in each case.

b) Describe briefly the significance of the factor of subdivision.

c) A ship 120m long has a light displacement of 4000 tonne and LCG in this condition 2.5m aft of the midships.

The following items are then added:

Cargo 10000 tonne LCG 3.0 m forward of midships

Fuel 1500 tonne LCG 2.0 m aft of midships

Water 400 tonne LCG 8.0 m aft of midships

Stores 100 tonne LCT 10.0m forward of midships

Using the following hydrostatic data, calculate the fine draughts:

Q a) Describe the general precautions to be taken against capsizing.

b) Explain what is meant by torsional stress.

c) The ½ ordinates of a water plane at 15m intervals, commencing from aft, are 1, 7, 10.5, 11, 11, 10.5, 8, 4 and 0 m. Calculate:

i. TPC

ii. Distance of the centre of flotation from the midships

iii. Second moment of area of the water plane about a transverse axis through the centre of flotation.

Q a) Describe the effect of cavitation on the propeller blades.

b) A propeller 4.6m diameter has a pitch of 4.3m and boss diameter of 0.75. The real slip is 28% at 95 rev/min.

Calculate the speed of advance, thrust and thrust power.

Q a) Describe the stability requirements of a ship for dry-docking.

b) A ship 130 m long displaces 14000 tonne when floating at draughts of 7.5 m forward and 8.10 m aft.

GML – 125 m, TPC – 18, LCF – 3 m aft of midships.

Calculate the final draughts when a mass of 180 tonne lying 40 m aft of the midships is removed from the ship.

Q a) Describe how water tightness is maintained where bulkheads are pierced by longitudinal beams or pipes.

b) A triangular bulkhead is 7 m wide at the top and has a vertical depth of 8 m. Calculate the load on the bulkhead and the position of centre of pressure if the bulkhead is flooded with sea water on only side:

i To the top edge

ii With 4 m head to the top edge

Q a) Describe how the distribution of mass within the ship affects the rolling period.

b) Describe the general precaution to be taken against capsizing.

c) The righting moments of a ship at angles of heel of 0, 15°, 30°, 45°, and 60° are 0, 1690, 5430, 9360 and 9140 kNm respectively. Calculate the dynamical stability at 60°.

Q a) List the main factors which affect the rolling period of a vessel.

b) A box-shaped vessel is 20 m long and 10 m wide. The weight of the vessel is uniformly distributed throughout the length and the draught is 2.5 m. The vessel contains ten evenly spaced double bottom tanks, each having a depth of 1m.

Draw the shear force diagrams:

a) With No.1 and No.10 tanks filled

b) With No.3 and No.8 tanks filled

c) With No.5 and No.6 tanks filled.

Which ballast condition is to be preferred from the point of view of strength?

Q a) Describe the procedure for speed, power and fuel consumption trials.

b) List the variables which affect the force on a rudder.

c) A propeller of 4m pitch has an efficiency of 67%. When turning at 125 rev/min the real slip is 36% & the delivered power 2800 kW. Calculate the thrust of the propeller.

Q a) What is the effect on fuel consumption per unit time, if the ship’s speed is outside its operating range?

b) The frictional resistance of a ship in fresh water at 3 m/s is 11 N/m². The ship has a wetted surface area of 2500 m² and the frictional resistance is 72% of the total resistance and varies as speed1.92. If the effective power is 1100 kW, calculate the speed of the ship.

Q a) Explain how the distribution of masses affects rolling and pitching.

b) A ship turns is a circle of radius 100 metres at a speed of 15 knots. The GM is 2/3 metres and BG is 1 metre. If g = 981 cm/sec² and 1 knot is equal to 1.8532 km/hour, find the heel due to turning.

Q a) Define longitudinal of gravity (LCG) and longitudinal centre of buoyancy (LCB).

b) Describe the effect of GM on rolling.

c) A ship 120 m long floats at draughts of 5.50 m forward & 5.80 m aft; MCTI cm 80 tonne-m, TPC 13, LCF 2.5 m forward of the midships. Calculate the new draughts when a mass of 110 tonne is added 24m aft of midships.

Q a) List the precautions necessary before an inclining experiment is carried out.

b) Describe briefly the significance of the factor of safety.

c) A box shaped vessel, 50 metres long X 10 metres wide, floats in salt water on an even keel at a draft of 4 metres. A centre line longitudinal watertight bulkhead extends from end to end and for the full depth of the vessel. A compartment amidships on the starboard side is 15 metres long and contains cargo with permeability 30%. Calculate the list if this compartment is bilged. KG = metres.

Q a) Explain the purpose of the rudder carrier and pintles.

b) The speed of a ship is increased to 18% above normal for 7.5 hours, and then reduced to 9% below normal for 10 hours. The speed is then reduced for the remainder of the day so that the consumption for the day is the normal amount. Find the percentage difference between the distance traveled in that day and the normal distance traveled per day.

Q a) Explain the term angle of loll and state what, if any, dangers it poses to a vessel.

b) Describe the factors to consider in order to determine whether a list is due to a negative GM or to uneven distribution of masses in a ship.

c) A ship whose length is 110 m has MCTI cm 55 tonne m: TCP 9, LCF 1.5 m forward of midships & floats at draughts of 4.20 m forward and 4.45 m aft.

Calculate the new draughts after the following masses have been added

20 tonne 40 m aft of midships

50 tonne 23 m aft of midships

30 tonne 02 m aft of midships

70 tonne 06 m forward of midships

15 tonne 30 m forward of midships

Q A box barge of 45 m long and 15 m wide floats at a level keel draught of 2 m in sea water, the load being uniformly distributed over the full length. Two masses, each of 30 tonne, are loaded at 10 m from each end & 50 tonne is evenly distributed between them. Sketch shear force diagram & give the maximum shear force.

Q a) Explain what is meant by permissible length of compartments in passenger ships.

b) Describe how the position of the bulkheads is determined.

c) Describe briefly the significance of the factor of subdivision.

d) A box shaped vessel 65m X 12m X 8m has KG 4 m and is floating in salt water upright on an even keel at 4 m draft F and A. Calculate the moments of the statically stability at (a), 5 degrees and (b) 25 degrees heel.

Q a) Explain what is meant by ‘assigned summer free board’.

b) A ship 120 m long has draughts of 6.6 m forward & 6.9 aft. The TPC is 20, MCTI cm 101 tonne-m and the centre of flotation 3.5 m aft of midships. Calculate the maximum position aft at which 240 tonne may be added so that the after draught does not exceed 7.2 m.

Q a) Describe the relationship between frictional resistance and:

i. Ship speed

ii. The wetted area

iii. Surface roughness

iv. The length of the vessel.

b) A ship travels at 15 knots and has a QPC of 0.865 with a delivered power of 2600 kW. The apparent slip is 5% & the real ship is 28%

Calculate the total resistance and the wake friction.

Q a) Explain why the GM must remain positive until the critical instant at which the ship takes the blocks overall.

b) What is “form stability” and “weight stability”.

b) A ship of 5000 tonnes displacement enters a drydock trimmed 0.45 m by the stern. KM=7.5m, KG=6.0 m. MCTC=120 tonnes-m. The centre of flotation is 60 m from aft. Find the effective metacentric height at the critical instant before the ship takes the blocks overall, assuming that the transverse metacenter rises 0.075 m.

Q a) Distinguish between ships of Type “A” & Type “B” for the purpose of computation of free board.

b) The draughts of a ship 170 m long are 6.85 m forward and 7.50 m aft. MCTI cm 300 tonne m, TPC 28, LCF 3.5 m, forward of midships.

Calculate the new draughts after the following changes in loading have taken place.

160 tonne added 63 m aft of midships

200 tonne added 27 m forward of midships

120 tonne removed 75 m aft of midships

70 tonne removed 16 m aft of midships