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Q10. A ship 120m long displaces 12000 tonne. The following data are available from trial results:

V (knots) 10  11  12  13  14  15
sp (kw) 880  1155  1520  2010  2670  3600
(a) Draw the curve of admiralty coefficients on a base of speed

(b) Estimate the shaft power required for a similar ship 140m long at 14 knots.

Q9. A. Explain what is meant by: i. Wave making resistance; ii. Frictional resistance; iii. Eddy-making resistance (6)

B. When a ship is 800 nautical miles from port, its speed is reduced by 20%, thereby reducing the daily fuel consumption by 42 tonne and arriving in port with 50 tonne on board. If the fuel consumption in t/h is given by the expression (0.136+0.001 V3) where V is the speed in knots, estimate: (i) The reduced consumption per day; (ii) The amount of fuel on board when the speed was reduced; (iii) The percentage decrease in consumption for the latter part of the voyage; (iv) The percentage increases in time for this latter period. (10)

Q9. A. State what is meant by the term floodable length illustrating your answer by drawing a typical curve of floodable length of a ship. B. A vessel has a maximum allowable draught of 8.5m in fresh water and 8.25m in seawater of 1.025/m3, the TPC in the sweater being 27.5. The vessel is loaded in never water of 1.012 t/m2 to a draught of 8.44m. If it now moves into seawater, is it necessary to pump out any ballast and if 50, how much?

Q6. (a). Explain the significance of the root- mean- square value of an alternating current or voltage waveform; Define the form factor of such a wave form.

B. Draw the circuit of Half-wave rectifier and its output waveform. A diode whose internal resistance is 20𝛀 is to supply power to 1000 𝛀 load from 110 V (RMS) source. Calculate

(i) peak load current, (ii) DC load current, (iii) AC load current.

Q7. A ship of 2890 tonne displacement and speed of 14 knots has a machinery mass of 410 tonne. The mass of ship’s machinery is given by the formula: m=  V3 tonne;(i) Calculate the mass of the machinery of a similar ship of 3000 tonne displacement at the corresponding speed; (ii) if the 2890 tonne ship required 2920 Kw shaft power, calculate the shaft power required by the 3000 tonne ship.

Q7.A. By means of a schematic circuit diagram illustrate the peak rectifier. If the supply voltage is v(t) = Vra Sin wt, what is the voltage across the load resistor?

B. A d.c. motor takes an armature current of 110 A at 480 V. The resistance of the armature circuit is 0.2?. The machine has six poles and the armature is lap-connected with 864 conductors. The flux per pole is 0.05 Wb. Calculate;

(i) The speed;

(ii) The gross torque developed by the armature.

Q6. A. Describe how water tightness is maintained where bulkheads are pierced by longitudinal beams or pipes.

B. A propeller has a pitch ratio of 0.95. When turning at 120 rev/min the real slip is 30%, the wake fraction 0.28 and the ship speed 16 knots. The thrust is found to be 400 KN, the torque 270 KN-m and the QPC 0.67. Calculate:

i. The propeller diameter;

ii. The shaft power;

iii the propeller efficiency;

iv. The thrust deduction factor.

Q6. a) With respect to Buoyancy of a vessel:

What do you understand by reserve buoyancy what happen if the lost buoyancy is greater than the reserve buoyancy? (6)

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. (10)

Q6. A. Define following terms with reference to alternating currents - Cycle; Time-period; Frequency; Peak factor

B. A heater unit of inductance has a resistance of 6.5 ohms and is intended for use with 100V mains. For what 50Hz voltage would it be suitable when placed in series with an external apparatus, of negligible resistance, having an inductance of 0.01H. If the frequency rises by 5 per cent and this voltage remains constant, what constant, what would be the resulting change or voltage at the heater terminals?

Q7. (a) Explain clearly the meaning of the term ‘reserve buoyancy' (6)
(b) When a mass of 6 t is moved transversely through a certain distance on a ship of 4300 t displacement, the deflection of an 11 m pendulum is found to be 120 mm. The transverse meta-centre is 7.25 m above the keel and KG 5.46 m. Find the distance through which 6 t was moved (10)

Q6.  A double bottom tank is 1.2 m deep and has a sounding pipe extending 11 m above the tank top. The tank is filled with oil (rd 0.89) to the top of the sounding pipe. The double bottom floors are spaced 750 mm apart and are connected to the tank top by riveted angles, the rivets having a pitch of 7 diameters. If the maximum allowable stress in the rivets is 30 MN/m2, calculate the pressure in kN/m2 on the outer bottom and the diameter of the rivets. (16)

Q7. a) What is a right-handed and a left-handed propeller? (6)

b) The pitch angle, measured at a distance of 2 m from the centre of the boss, was found to be 21.5° calculate the pitch of the propeller. (10)