DieselShip's Online Content Library

Q1. Container ships have very large cargo hatch openings.

a) Describe how this ship type is susceptible to torsion and how the structure is designed to combat torsional stress.

b) Describe the problem created by discontinuities in longitudinal structure.

c) State THREE points of discontinuity, in any ship type, describing how the problems are overcome

Q2. (a) Define critical temperature and boiling point and hence show how some liquefied gases may be transported fully pressurized, whilst others need to be carried fully refrigerated.

(b) State the basic differences in construction of fully pressurized and fully refrigerated systems for the carriage of liquefied gas at sea.

(c) Compare the membrane tank and independent tank systems of construction.

(a) Define critical temperature and boiling point and hence show how some liquefied gases may be transported fully pressurized, whilst others need to be carried fully refrigerated.

Q3. a) Explain how a propeller blade may be eroded due to cavitation, describing the progressive nature of the damage.

b) Outline the design features that may be considered to minimise cavitation.

c) State FOUR detrimental effects of propeller cavitation.

Q4. a) Explain the procedure required to produce weight, buoyancy and load curves for a ship assumed to be floating in still water, stating any relevant features of the curves.

(b) Describe how shear force and bending moment curves are produced from a load diagram, explaining how the features of EACH curve are connected.

Q5.a) Explain how a force normal to the rudder is produced when the rudder is turned to a helm angle.

b) Define the term centre of effort as applied to a rudder.

c) Describe how the position of centre of effort changes as helm angle increases.

d) Explain the term balanced, describing the benefits of fitting a balanced rudder.

e) Describe, with the aid of a sketch, how an angle of heel is produced due to the force on the rudder.

Q6. (a) Describe the relationship between frictional resistance and

(i) Ship’s speed;

(ii) the wetted area;

(iii) surface roughness;

(iv) The length of the vessel.

b) A ship 150m long and 8.5m draught has a rudder whose area is one sixtieth of the middle-line plane and diameter of stock 320mm. Calculate the maximum speed at which the vessel may travel if the maximum allowable stress is 70 MN/m? the centre of stock 0.9m from the centre of effort and the maximum rudder angle is 35 degrees. (10)

Q7. a) Derive the Admiralty Coefficient formula and show how this may be modified to suit a fast ship. (6)

b) A 6m model of a ship has a wetted surface area of 7m2 and when towed in fresh water at

3knots has a total resistance of 35 N. Calculate the effective power of the ship, 120 m long, at its corresponding speed.

n=1.825. f from formula SCF=1.15 (10)

Q8. A. Describe how the force on the ship’s bottom and the GM vary when grounding takes place.

B) The ½ ordinates of a water plane at 15m intervals, commencing from aft, are 1, 7, 10.5, 11, 11, 10.5, 8, 4 and 0m. Calculate:

(a). TPC;

(b). Distance of the centre of flotation from midships.

(c). Second moment of area of the water plane about a transverse axis through the centre of flotation.

Q9. A) Define longitudinal centre of gravity (LCG) and longitudinal centre of buoyancy (LCB).(6) B) A vessel, when floating at a draught of 3.6 m has a displacement of 8172 tonne, KB 1.91 m and LCB 0.15 m aft of midships. From the following information, calculate the displacement, KB and position of the LCB for the vessel when floating at a draught of 1.2rn. (10)

Q10. A) Describe measures which may be taken to improve the stability or trim of a damaged ship. (6)

B) A watertight bulkhead is 8m high and is supported by vertical stiffeners 700mm apart, connected at the tank top by brackets having 10 rivets 20mm diameter. The bulkhead is flooded to its top edge with sea water. Determine:

(a) Shearing force at top of stiffeners,

(b) Shear stress in the rivets,

(c) Position of zero shear. (10)