CON & NA-MAR-2020

Q1. Describe the relationship between frictional resistance and: (i) Ship’s speed; (ii) the wetted area; (iii) surface roughness; (iv) The length of the vessel.

Q2. Draw and Describe the construction of a forepeak tank. Explain How are the effects of panting and pounding taken care with help of neat sketches? 

Q3. Describe a method of the attachment of bilge keels; State THREE reasons for not extending bilge keels the entire length of the vessel; Explain TWO principles of roll damping those bilge keels exploit.

Q4. Discuss the need for adequate support of engine room gantry cranes, detailing the following (a) Sketch section through the engine room casing showing how the crane is supported by the ship structure; (b) State what restricts the forward and aft limits of the crane and what is fitted to prevent the crane damaging the forward and aft bulkheads or casing(c) State the Second Engineer’s responsibilities for the engine room gantry crane.

Q5.A. Explain what is meant by 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.

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 water plane area co-efficient is 0.83 and the difference between the TPC in sea water and the TPC in fresh water is 0.7. Determine the length of the ship and the TPC in fresh water.
 

Q8. With respect to Ship Propulsion: a. Explain the various efficiencies associated with propeller and shafting arrangement.

b. When a propeller of 4.8 m pitch turns at 110 rpm, the apparent slip is found to be —S % and the real slip is 1.5 S. If the wake speed is 25 % of the ship speed, calculate the ship speed, apparent slip and the real slip.
 


Q9. A ship 150 m in length, 24 m breadth, displaces 25000 tonne when floating at a draught of 9 m in sea water of density 1025 kg/m3. The ship’s propeller has a diameter of 5.8 m, a pitch ratio of 0.9 and a blade area ratio of 0.45. With the propeller operating at 2 rev/sec, the following results were recorded: Apparent slip ratio = 0.06 Thrust power = 3800 Kw Propeller efficiency = 64% The Taylor wake fraction is given by: WT = 0.5CB – 0.05 Calculate EACH of the following for the above condition: (a) The ship’s speed; (b) The real slip ratio; c) The thrust per unit area of blade surface; (d) The torque delivered to the propeller.

 

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.