CON & NA-FEB-2021

Q1. With reference to Ship stability: a. With the help of a neat sketch explain the relevant features of a G-Z curve. b. What are the effects of the below-mentioned conditions on the G-Z curve: i. Increased freeboard, ii. Increased beam, and iii. Increased GM.

Q2. A. Explain what is meant by the permissible length of compartments in passenger ships; B. Describe how the position of bulkheads is determined. C. Describe briefly the significance of the factor of subdivision.

Q3. With the help of sketches explain the different types of strakes used in ship construction. What material is generally used for Hull plating and What are the tests carried out on Hull steel plating for certification as per class rules.

Q4. Describe the relationship between frictional resistance and: (i) Ship’s speed; (ii) the wetted area; (iii) surface roughness; (iv) The length of the vessel.

Q5. A palm of the rudder of a vessel requires extensive welding repairs and as a Chief Engineer you are requested to supervise; A. Suggest a suitable type of welding process; B. State with reasons FOUR common welding defects that can occur there; C. State what tests may be carried out before returning the rudder to service.

Q6. 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 2550kW. Calculate: (i) Indicated power; (ii) Effective power; (iii) Ship speed.

 

Q7. What is Prismatic Co-efficient (CP).a. Derive the formula CP =Cb/Cm, where Cb = Co-efficient of fineness and Cm = midship section area coefficient.

b. The length of a ship is 18 times the draught. while the breadth is 2.1 times the draught. At the load water plane, the waterplane area co-efficient is 0.83 and the difference between the TPC in seawater and the TPC in freshwater is 0.7. Determine the length of the ship and the TPC in freshwater.
 

Q8. A ship of length 140m, a Breadth of 18.5m, a draught of 8.1m and a displacement of 17,025 tonnes in seawater, 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 the cube of speed of a ship, Determine the fuel consumption, when the propeller runs at 110 rpm.
 

Q9. A. Define longitudinal centre of gravity (LCG) and longitudinal centre of buoyancy (LCB).

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 0 m2 calculate – (i) Displacement; (ii) Longitudinal position of the centre of buoyancy.

 

Q10. A ship 100 m long floats at a draught of 6 m and in this condition the immersed cross-sectional areas and water plane areas are as given below. The equivalent base area (Ab) is required because of the fineness of the bottom shell.

station AP 1 2 3 4 5 FP
X- area m2 12 30 65 80 70 50 0
Draft m 0 0.6 1.2 2.4 3.6 4.8 6.0
WP area m2 Ab 560 720 880 940 1000 1030
Calculate EACH of the following: (a) The equivalent base area value Ab(b) The longitudinal position of the center of buoyancy from midships (c) The vertical position of the centre of buoyancy above the base.