DieselShip's Online Content Library

Q8. With the aid of sketches:
a. Explain various lines plan.
b. The half -breadths of waterplane of a ship of 120m length ad 15m breadth are given below:

Calculate i) Water plane area ii) TPC in salt water iii) Cw iv) LCF from Mid-ship

Q10. A ship of 10000 tonne displacement floats in sea water of density 1025 kg/m3 at a draught of 6m. A rectangular tank 10m long and 8m wide is partially full of oil fuel of density 900 kg/m3. In this condition, the KG of the ship is 6.25m.

Other hydrostatic data for the above condition are:

Centre of buoyancy above the keel (KB) = 3.325m

Transverse metacentre above the centre of buoyancy (BM) = 4.865m

Tonnes per centimetre immersion (TPC) = 20.5

Calculate the change in effective metacentric height when a rectangular tank 12m long, 10m wide and 6m deep, with its base 1 m above the keel, is filled to a depth of 5m with sea water ballast.

NOTE: Assume the ship to be wa11sided over the affected range of draught

Q7. A. Explain how to distinguish between list and loll and describe how to return the ship to the upright in each case. B. A ship 120m long has a light displacement of 4000 tonne and LCG in this condition 2.5m aft of midships.  The following items are then added:

Using the following hydrostatic data, calculate the fine draughts:

Q10. A. Explain how to distinguish between list and loll and describe how to return the ship to the upright in each case. (6)

B. A ship of 5000 tonne displacement has a double bottom tank 12m long. The ½ breadths of the top of the tank are 5, 4 and 2m respectively. The tank has a watertight centreline division. Calculate the free surface effect if the tank is partially full of fresh water on one side only. (10)

Q6. Explain why the bilging of empty double-bottom or deep tanks below the waterline leads to an increase in GM. B. A ship of 10,000 tonnes displacement has GM=0.5 metres. The period of roll in still water is 20 seconds. Find the new period of roll if a mass of 50 tonnes is discharged from a position 14 metres above the centre of gravity.

Q8. A. List the factors that determine the starting torque of the three-phase induction motor. How does this torque generally compare with the value of the rated torque? (6)

B. A three phase induction motor is wound for four poles and is supplied from a 50 Hz system. Calculate.

i. The synchronous speed.

ii. The speed of the rotor when the slip is 4 per cent.

iii. The rotor frequency when the speed of the rotor is 600 r.p.m. (10)

Q4. A. Explain why the GM must remain positive until the critical instant at which the ship takes the blocks overall. B. A Ship of 5000 tonnes displacement enters a dry dock 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.

Q7. A 3-phase slip ring induction motor gives a reading of 60V across the slip rings on open circuit, when at rest with normal stator voltage supplied. the motor is star connected and has an impedance of 0.6 + j6 ohms/phase. find the rotor current and its power factor when the machine is 1. At standstill with slip-rings joined to a star connected starter with a phase impedance of 5+j4 ohm 2. Running normally with a 4% slip.

Q7.A. Explain how to distinguish between list and loll and describe how to return the ship to the upright in each case.

b) A ship of 12000 tonne displacement has a rudder 15 m2 in area, whose centre is 5 m below the waterline. The metacentric height of the ship is 0.3 m and the centre of buoyancy is 3.3 m below the waterline. When travelling at 20 knots the rudder is turned through 30 degree. Find the initial angle of heel if the force Fr perpendicular to the plane of the rudder is given by:

Fr=577Av2 Sin  a N

Allow 20% for the race effect. (10)

Q7. a) Describe the stability requirements of a ship for dry-docking. (6)

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. (10)

Q7. A resistor of ohm value 3 ohms is connected in series with a coil of inductance 0.1 H and resistance 1 ohm. If 100 V at a frequency of 50 Hz is applied to the circuit find the current flowing.

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)