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Q7. A. Describe stability requirement 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.

Q6. The following data applies to a ship operating on a particular voyage with a propeller of 6 m diameter having a pitch ratio of 0.95:

Propeller speed = 1.8 revs/s

Real slip = 34%

Apparent slip = 7%

Shaft power = 10000 kW

Specific fuel consumption = 0.22 kg/kW-hr

Calculate EACH of the following:

(a) The ship speed in knots;

(b) The Taylor wake fraction;

(c) The reduced speed at which the ship should travel in order to halve the voyage consumption;

(d) The voyage distance if the voyage takes 3 days longer at the reduced speed;

(e) The amount of fuel required for the voyage at the reduced speed.

Q1. A RO-RO ferry of length 80 m has a displacement of 3800 tonne in sea water of density 1025 kg/m3 with BM = 3.4 m. The breadth of the ship at the waterline, between sections 3 and 7 is constant at 13 m. To increase stability, sponsons, 1.8 m deep and of constant plan area are to be fitted as shown in Fig Q1.

The sponsons extend over the midships length between sections 3 and 7, with sponson widths as shown in Table Q1.

For the new condition, there is no change in draught and the load waterline is at mid-depth of the sponson. Calculate the increase in BM due to the sponsons.

Q6. A. What factors influence the frictional resistance of a ship and what formula is used to calculate the resistance? B. A ship of 12000 tonne displacement has a rudder 15m2 in area, whose centre is 5m below the waterline.  The metacentric height of the ship is 0.3m and the centre of buoyancy is 3.3m below the waterline.  When travelling at 20 knots the rudder is turned through 30 .  Find the initial angle of heel if the force Fn perpendicular to the plane of the rudder is given by:  Fn=577 Av2 sin  N, Allow 20% for the race effect.

Q6. A propeller has a pitch of 4.57m. At 100rev/min the real slip is 20 percent and wake speed is I knot.  Calculate the apparent slip percentage

Q8. A. Explain the use of KN curves.

B. The half breadths of the load waterplane of a ship 150 m long commencing from aft, are 0.3. 3.8. 6.0, 7.7, 8.3.9.0,8.4.7.8, 6.9.4.7 and 0 m respectively. Calculate: (a) area of waterplane (b) distance of centroid from amidships (c) second moment of area about a transverse axis through centroid.

Q9. A. Explain the term volumetric heeling moments.

B. A ship 85m long displaces 8100 tonne when floating in seawater at draughts of 5.25m forward and 5.55m aft. TPC 9.0, GML 96m, LCF 2m aft of midships. It is decided to introduce water ballast to completely submerge the propeller and a draught aft of 5.85m is required. A ballast tank 33m aft of midships is available. Find the least amount of water required and the final draught forward.

Q9. A ship of 6000 tonne displacement has a wetted surface area of 2500 m2 and a speed of 15 knots.  Calculate the corresponding speed and wetted surface area of as similar ship of 2000 tonne displacement. (i) If the ship resistance is of the form R=0.45 S V1.83 N; find the resistance of the 6000 tonne Ship.

Q9: A. Explain how trim occurs, and explain the effect of trim on tank soundings. B. A ship 150 metres long arrives at the mouth of a river with drafts 5.5m.  F and 6.3m A MCT 1 cm. 200 tonnes-m.  TPC 15 tonnes.  Centre of flotation is 1.5m. aft of amidships.  The ship has then to proceed up the river where the maximum draft permissible is 6.2m.  It is decided that SW ballast will be run into the forepeak tank to reduce the draft aft to 6.2m.  If the canter of gravity of the forepeak tank is 60 metres forward of the center of flotation, find the minimum amount of water which must be run in and also find the final draft forward.

Q8. (a) Explain what is meant by left and right handed propellers, and also explain the rotation of propellers in a twin-screw ship.

b) A ship 120m long displaces 8000 tonne, GML is 102m, TPC 17.5 and LCF 2m aft of midships. It arrives in port with draughts of 6.3m forward and 6.6m aft.

During the voyage the following changes in loading have taken place:

Fuel used          200 tonne         18m forward of midships

Water used        100 tonne         3m aft of midships

Stores used        10 tonne           9m aft of midships

Ballast added     300 tonne         24m forward of midships

Calculate the original draughts. (10)

Q10. A. What is back emf? Derive the relation for the back emf and the supplied voltage in terms of armature resistance. (6)

B. Find the synchronous impedance reactance of an alternator in which a given field current produces an armature current of 200 A on short circuit and a generated e.m.f. of 50V on open circuit. The armature resistance is 0.1 ohm. To what induced voltage must the alternator be excited if it is to deliver a load of 100A at a p.f of 0.8 lagging, with a terminal voltage of 200V. (10)

Q6. a) Define centre of buoyancy and show with the aid of sketches how a vessel which is Stable will return to the upright after being heeled by an external force (6)

b) A ship of 15000 tonne displacement has an Admiralty Coefficient, based on shaft power, of 420. The mechanical efficiency of the machinery is 83%, shaft losses 6%, propeller efficiency 65% and QPC 0.71. At a particular speed the thrust power is 2550 kW. (10)

Calculate:

(i) Indicated power

(ii) Effective power

(iii) Ship speed.