DieselShip's Online Content Library

Q8. A. List the variables which affect the force on a rudder. B. A propeller of 4m pitch has an efficiency of 67%.  When turning at 125 rev/min the real slip is 36% and the delivered power 2800Kw.Calculate the thrust of the propeller.

Q6. A. Explain why the bilging of empty double-bottom or deep tanks below the waterline leads to an increase in GM.

B. the immersed cross-sectional area of a ship 120m long, commencing from aft are 2,40,79,100,103,104,104,103,97,58 and 0m^2 calculate - (i) Displacement; (ii) Longitudinal position of the centre of buoyancy.

Q10. A) Define torque and explain how it is developed in a D.C. Motor. Drive from first principles an expression for the torque developed in a D.C. Motor. (6)

(b) A diode valve, having the following characteristic is connected in series with a resistor of 10,000 ohm to a 240 V d.c. supply. If a resistor of 40,000 ohms is connected between the anode and cathode, determine the current through the diode.

Q6. A. With reference to dynamical stability, describe the effect of an increase in wind pressure when a vessel is at its maximum angle of roll to windward.

B. An oil tanker 160m long and 22m beam floats at a draught of 9m in seawater. Cw is 0.865. The midships section is in the form of a rectangle with 1.2m radius at the bilges. A midships tank 10.5m long has twin longitudinal bulkheads and contains oil of 1.4 m3/t to a depth of 11.5m. The tank is holed to the sea for the whole of its transverse section.  Find the new draught.

Q6. A box-shaped pontoon is 36 meters long, 4 meters wide and floats in salt water at drafts F-2.00m, A-4.00m. Find the new drafts if the pontoon now passes into fresh water.

Q9. A. Describe how the distribution of mass within the ship affects the rolling period;

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.

Q9. A. What are the factors which determine the synchronous speed of a motor? (6)

B. A 72 KVA transformer supplies a heating and lighting load of 12 KW at unity power factor and a motor load of 70 kVA at 0.766 (lagging) power factor; Calculate the minimum rating of the power-factor improvement capacitors which must be connected in the circuit the ensure that the transformer does not become overloaded. (10)

Q7. a) Describe how water tightness is maintained where bulkheads are pierced by longitudinal beams or pipes. (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.

Q10. a) Explain the concept of dynamical stability. (6)

b) A ship of length 140m, Breadth of 18.5m, draught of 8.1m and a displacement of 17,025 tonnes in sea water, has a face pitch ratio of 0.673. The diameter of the Propeller is 4.8m. The results of the speed trial show that true slip may be regarded as constant over a range of 9 to 13 knots and is 30%, w = 0.5CB-0.05. If fuel used is 20t/day at 13 knots and fuel consumption/day varies as cube of speed of ship, determine the fuel consumption, when propeller runs at 110 rpm. (10)

Q9. A ship 120 meters long at the waterline has equidistantly spaced half-ordinates commencing from forward as follows 0,3.7,5.9,7.6,7.5,4.6, and 0.1 meters respectively. Find the area of the waterplane using Simpson’s Second rule and the TPC at this draft, Water density is 1.025 t/m3. (16)

Q9. a) Draw a metacentric diagram for a vessel of constant triangle cross-section (6)

b) A block of wood of uniform density has a constant cross-section in the form of a triangle, apex down. The width is 0.5 m and the depth 0.5 m. It floats at a draught of 0.45 m. Calculate the metacentric height (10)

Q7. a) What is the difference between a DC Generator and a DC motor? (6)

b) A 4-pole, 32 conductor, Lap-wound DC shunt generator with terminal voltage of 200 V delivering 12 A to the load has ra = 2 and field circuit resistance of 200 Ω. It is driven at 1000 RPM .

a) Calculate the flux per pole in the machine. (6)

b) If the machine has to be run as a motor with the same terminal voltage and drawing 5 A from mains, maintaining the same magnetic field, find the speed of the machine. (10)