DieselShip's Online Content Library

Q1. a) Define hogging and sagging with the help of neat sketches. Explain the causes of these structural conditions and when they are most likely to occur during a voyage. (8)

b) Discuss the effects of hogging and sagging on a ship’s structural integrity. What measures are taken in design, loading, and operation to minimize their impact? (8)

Q2. a) Define the term angle of loll. Explain the conditions under which it occurs and support your answer with a diagram showing the stability curve and ship’s position at the angle of loll. (8)

b) Describe the actions to be taken to correct the angle of loll and restore positive stability. What precautions must be taken during the corrective process to avoid worsening the situation? (8)

Q3. 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. (6)

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. (5)

c) State the Second Engineer’s responsibilities for the engine room gantry crane. (5)

Q4. With reference to Underwater Inspection in lieu of Dry docking (UWILD)

A. Explain in detail, how an underwater survey is carried out. (6)

B. State the requirements to be fulfilled before an underwater survey is acceptable to the survey authority. (5)

C. Construct a list of the items in order of importance that the underwater survey authority should include. (5)

Q5. Describe the effect of the following on the ship’s stability. (16)

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.

Q6. A. Describe the stability requirements of a ship for dry-docking.

B. A ship of 8000 tonne displacement, 110m long, floats in sea water of 1.024t/m3 at draughts of 6m forward and 6.3 m aft. The TPC is 16, LCB 0.6 m aft of midships, LCF 3m aft of midships and MCT1cm 65 tonne m, the vessel now moves into fresh water of 1.000t/m3. Calculate the distance a mass of 50 tonne must be moved to bring the vessel to an even keel and determine the final draught.

Q7. a) Describe the effect of cavitations on the propeller blades. (6)

b) 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 2550 Kw. Calculate: (10)

(i) Indicated power

(ii) Effective power

(iii) Ship speed.

Q8. a) With respect to Buoyancy of a vessel:

What do you understand by reserve buoyancy what happen if the lost buoyancy is greater than the reserve buoyancy? (6)

b) A forward deep tank 12 m long extends from a longitudinal bulkhead to the ship’s side. The widths of the tank surface measured from the longitudinal bulkhead at regular intervals are 10, 9, 7, 4 and 1 m. Calculate the second moment of area of the tank surface about a longitudinal axis passing through its centroid. (10)

Q9. (a) Define longitudinal centre of gravity (LCG) and longitudinal centre of buoyancy (LCB). (6)

(b) The immersed cross-sectional areas 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. (10)

Q10. A. What is the effect on fuel consumption per unit time, if the ship’s speed is outside its operation range?

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.