DieselShip's Online Content Library

Q10. A. Explain the considerations which govern the size and shape of a rudder. 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: Fa=577 Av2 sin  N, Allow 20% for the race effect.

Q7. A. Describe the ways in which an unstable ship can be made stable. (6)

B. When a mass of 25 tonnes is shifted 15m transversely across the deck of a ship of 8,000 tonnes displacement, it causes a deflection of 20cm in a plumb line 4 m long. If the KM = 7m, calculate the KG (10)

Q10. A) Describe measures which may be taken to improve the stability or trim of a damaged ship. (6)

B) A watertight bulkhead is 8m high and is supported by vertical stiffeners 700mm apart, connected at the tank top by brackets having 10 rivets 20mm diameter. The bulkhead is flooded to its top edge with sea water. Determine:

(a) Shearing force at top of stiffeners,

(b) Shear stress in the rivets,

(c) Position of zero shear. (10)

Q6. A ship 90 m long displaces 5200 tonne and floats at draughts of 4.95m forward and 5.35 m aft when in sea water of 1023 kg/m3. The water plane 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. Describe the effect of cavitation’s on the propeller blades.

b) A ship has a constant cross-section in the form of a triangle which floats apex down in sea water. The ship is 85 m tong, 12 m wide at the deck and has a depth from keel to deck of 9 m. Draw the displacement curve using 1.25 m Intervals of draught from the keel to the 7 .5m waterline. From this curve obtain the Displacement in fresh water at a draught of 6.50 m. (10)

Q9. A. Describe how the force on the ship’s bottom and the GM vary when grounding takes place.

B. A box barge 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 and 50 tonne is evenly distributed between them. Sketch the shear force diagram and give the maximum shear force.

Q10. The following data are available from the hydrostatic curves of a vessel.

Draught (m)
KB (m)

KM (m)
I (m4)
4.9
2.49

10.73
65250
5.2
2.61

10.79
68860
Calculate the TPC at a draught of 5.05m. (16)

Q9. A. Explain the effects on stability when a tank is partially filled with liquid. (6)

B) A box barge 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 and 50 tonne is evenly distributed between them. Sketch the shear force diagram and give the maximum shear force. (10)

Q6. (a) What is the significance of GM-GZ curve. (6)

(b) The pitch of a propeller is measured by means of a batten and cord. The horizontal ordinate is found to be 40 cm while the vertical ordinate 1.15 m at a distance of 2.6 m from the centre of the boss. Calculate the pitch of the propeller and the blade width at that point. (10)

Q9. A ship's speed is increased by 20% above normal for 8 hours, reduced by 10% below normal for 10 hours and for the remaining 6 hours of the day the speed is normal. Calculate the percentage variation in fuel consumption that day from normal.

Q8. (a) Compare Direct current with Alternating current. (6)

(b) A four-pole generator has a flux of 12 mWb/pole. Calculate the value of e.m.f. generated in one of the armature conductors, if the armature is driven at 900 rev/min. (10)

Q9. a) Sketch a schematic arrangement of a three-phase alternator with star connection. (6)

b) A 500V, 3-phase, star-connected alternator supplies a star-connected induction motor which develops 45kW. The efficiency of the motor is 88 percent and the power factor is 0.9 (lagging). The efficiency of the alternator at this load is 80 percent. Determine

a) the line current

b) the power output of the alternator

c) the output power of the prime-mover.  (10)