CON & NA-JAN-2021

Q1. With reference to International Load Line Statutory Certification,

A. State the reasons for the freeboard requirements;

B. (i) Explain the term conditions of assignments

(ii) List the items that may be examined during a related survey after major repairs in the drydock.

Q2. A. Sketch a transverse section through the hold space of a container ship hull; 

B. Referring to the sketch in (A) describe how adequate structural strength is built into the hull.

Q3. A. Describe the arrangement made in a main structural bulkhead for a watertight door aperture; 

B. Explain a procedure for ensuring that sliding watertight doors are operated safely. 

C. Differentiate between the categories of watertight door and state the regulation pertaining each type.

Q4. Describe the effect of the following on the ship’s stability; A. Ice formation on superstructures B. Effects of wind and waves C. Changes that takes place during the ships voyage D. Bilging of a compartment E. While water is being pumped out from the dry dock.

Q5. A. Explain in detail, how an underwater survey is carried out;

B. State the requirements to be fulfilled before an underwater survey is acceptable to the surveying authority;

C. Construct a list of the items in order of importance that the underwater survey authority should include.

Q6. A. Describe stability requirement for dry-docking.

B. A ship of 8000 tonne displacement floats upright in seawater. KG = 7.6m and GM = 0.5m. A tank, KG is 0.6m above the keel and 3.5m from the centreline, contains 100 tonne of water ballast. Neglecting the free surface effect, calculate the angle which the ship will heel, when the ballast water is pumped out.

 

Q7. 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.

 

Q8. The breadth of the upper edge of a deep tank bulkhead is 12 metres. The vertical heights of the bulkhead at equidistant intervals across it are 0.3, 5, 6, 5, 3 and 0 metres respectively. Find the depth of the centre of pressure below the waterline when the tank is filled to a head of 2 metres above the top of the tank.

Q9. A propeller has a pitch ratio of 0.95. When turning at 120 rev/min the real slip is 30%, the wake fraction

0.28 and the ship speed 16 knots. The thrust is found to be 400 KN, the torque 270 KN-m and the QPC 0.67.

Calculate:

i. The propeller diameter;

ii. The shaft power;

iii the propeller efficiency;

iv. The thrust deduction factor.

Q10. A. List the precautions necessary before an inclining experiment is carried out.

B. A box shaped vessel, 50 metres long × 10 metres wide, floats in salt water on an even keel at a draft of 4 metres. A centre line longitudinal watertight bulkhead extends from end to end and for the full depth of the vessel. A compartment amidships on the starboard side is 15 metres long and contains cargo with permeability 30%. Calculate the list if this compartment is bilged. KG = 3 metres.