CON & NA-NOV-2020

Q1. With regard to ship construction details for transverse watertight bulkheads: - A. State the purpose of this type of bulkhead; B. State how the bulkheads are tested for water tightness; C. If it is necessary to penetrate the bulkhead, precaution must be taken to ensure that the watertight integrity and the strength of the bulkhead are maintained. With this in mind, describe, using simple sketches, how the following pass through bulkheads: – i. Main transmission shaft; ii. Electrical cables; iii. Fuel oil transfer pipes; iv. Air and sounding pipes.

Q2. With reference to dry docking, define the responsibility of the 2nd engineer; A. Prior to docking; B. Whilst the vessel is in dry dock; C. Prior to flooding and leaving the dock..

Q3. Explain what is meant by "Dynamical Stability"; Explain how the area under the GZ curve represents dynamical stability for a ship;

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. Give a reasoned opinion as to the validity of the following assertions concerning ship structure: A. Crack propagation in propeller shaft ‘A’ brackets or spectacles frames is indicative of inadequate scantlings and strength; B. The adequate provision of freeing ports is as critical to seaworthiness as watertight integrity.

Q6. 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.
 

Q7. (a) Describe how bulkheads are tested. (b) A double bottom tank containing seawater is 6m long, 12m wide and 1m deep. The inlet pipe from the pump has its center 75mm above the outer bottom. The pump has a pressure of 70 kN/m2 and is left running indefinitely. calculate the load on the tank top: (i) If there is no outlet. (ii) If the overflow pipe extends 5m above the tank top.

Q8. 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.

 

Q9. A. Describe measures which may be taken to improve the stability or trim of a damaged ship. 

B. A ship 85m long displaces 8100 tonne when floating in seawater at draughts of 5.25m forward and 5.55m aft. TPC 9.0, GML 96m, LCF 2m aft of midships. It is decided to introduce water ballast to completely submerge the propeller and a draught aft of 5.85m is required. A ballast tank 33m aft of midships is available. Find the least amount of water required and the final draught forward.

Q10. A. Explain what is meant by singing of propeller. 

B. A propeller 6m diameter has a pitch ratio of 0.9, BAR 0.48 and, when turning at 110 rev/min, has a real slip of 25% and wake faction 10.30. If the propeller delivers a thrust of 300 KN and the propeller efficiency is 0.65 calculate - i Blade area; ii Ship speed; iii. Thrust power; iv Shaft power v. Torque.