Q9. With respect to Buoyancy of a vessel:
A. What do you understand by reserve buoyancy what happen if the lost buoyancy is greater than the reserve buoyancy?
B. A forward deep tank 12 m long extends from a longitudinal bulkhead to the ship’s side. The widths of the tank surface measured from the longitudinal bulkhead at regular intervals are 10, 9, 7, 4 and 1 m. Calculate the second moment of area of the tank surface about a longitudinal axis passing through its centroid.
Q4. Just before entering drydock a ship of 5000 tonnes mass floats at draughts of 2.7 m forward and 4.2 m aft. The length between perpendiculars is 150 m and the water has a density of 1025 Kg/m3. Assuming the blocks are horizontal and the hydrostatic data given are constant over the variation in draught involved, find the force on the heel of the sternframe, which is at the after-perpendicular, when the ship is just about to settle on the dock blocks, and the metacentric height at that instant.
Hydrostatic data: KG = 8.5 m, KM = 9.3 m, MCT1 m = 105 MNm. longitudinal Centre of flotation(LCF) = 2.7 m aft of amidships.
Q8. A. Explain the effect of trim on tank soundings. B.A ship of 6600 tonne displacement has KG 3.6m and KM 4.3m. A mass of 50 tonne is now lifted from the quay by one of the ship’s derricks whose head is 18m above the keel. The ship heels to a maximum of 9.5° while the mass is being transferred. Calculate the outreach of the derrick from the ship’s centreline.
Q6. A. Explain the purpose of non-watertight longitudinal subdivision of tanks. B. A ship 90 long displaces 5200 tonne and floats at draughts of 4.95m forward a nd 5.35 m aft when in sea water of 1023 kg/m3. The waterplane area is 1100m2, GML 95m, LCB 0.6m forward of midships and LCF 2.2m aft of midships. Calculate the new draughts when the vessel moves into fresh water of 1002 kg/m3
Q6: A. what is ‘form stability’ & ‘weight stability’. b. A Ship of 5000 tonnes displacement enters a drydock trimmed 0.45m by the stern. KM=7.5m., KG=6.0m. MCTC=120 tonnes-m. The centre of flotation is 60m. Frome aft. Find the effective metacentric height at the critical instant before the ship takes the blocks overall, assuming that the transverse metacentre rises 0.075m.
Q8. A. Describe how the force on the ship’s bottom and the GM vary when grounding takes place.
B) 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 0m. Calculate:
(a). TPC;
(b). Distance of the centre of flotation from midships.
(c). Second moment of area of the water plane about a transverse axis through the centre of flotation.
Q1. 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 travelled in that day and the normal distance travelled per day.
Q8. A. Explain the purpose of non-watertight longitudinal subdivision of tanks.
b) A box -barge 30 m long and 9 m beam floats at a draught of 3 m. The centre of gravity lies on the centreline and KG is 3.50 m. A mass of 10 tonne, which is already on board, is now moved 6m across the ship.
i) Estimate the angle to which the vessel will heel, using the formula
ii) Compare the above result with the angle of heel obtained by the metacentric formula. (10)
Q6. A. Describe the stability requirements of a ship for dry-docking.
B. A ship of 8000 tonne displacement, 110m long, floats in sea water of 1.024t/m3 at draughts of 6m forward and 6.3 m aft. The TPC is 16, LCB 0.6 m aft of midships, LCF 3m aft of midships and MCT1cm 65 tonne m, the vessel now moves into fresh water of 1.000t/m3. Calculate the distance a mass of 50 tonne must be moved to bring the vessel to an even keel and determine the final draught.
Q7. A. Derive an expression for the e.m.f induced in an a.c. generator. (6)
B. A 220 V, d.c. shunt motor has an armature resistance of 0.5 ohm and an armature current of 40 A on full load. Determine the reduction in flux necessary for a 50 per cent reduction in speed. The torque for both conditions can be assumed to remain constant. (10)
Q9. A. List the precautions necessary before an inclining experiment is carried out.
Q9. a) Explain why an unstable ship is dangerous. (6)
(b) A vessel travelling at 17 knots turns with a radius of 450 m when the rudder is put hard over. The centre of gravity is 7 m above the keel, the transverse metacentre 7.45 m above the keel and the centre of buoyancy 4 m above the keel. If the centripetal force is assumed to act at the centre of buoyancy, calculate the angle of heel when turning. The rudder force may be ignored. (10)
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