DieselShip's Online Content Library

Q1) A ship of length 140 m displaces 13492 tonne when floating in sea water of density 1025kg/m³ .

The centre of gravity is 4.0 m above the centre of buoyancy an the waterplane is defined by the following equidistant half-ordinates given in Table Q1:

Calculate EACH of the following:

(a) the area of the waterplane; (3)

(b) the position of the centroid of the waterplane from midships; (3)

(c) the second moment of area of the waterplane about a transverse axis through the centroid; (5)

(d) the moment to change trim one centimetre (MCT 1cm). (5)

Q2. Table Q2 gives values of righting levers (GZ) relating to a ship of 10500 tonne displacement in a particular load condition:

In the above condition the ship has 315 tonne of fuel stored in a double bottom tank which has to be emptied for survey. The oil is transferred to a wing deep tank, through a transverse distance of 5 m and a vertical height of 4 m.

(a) Draw the amended curve of statical stability, neglecting the effects of free surface. (12)

(b) Determine EACH of the following from the curve drawn in Q2(a):

(i) the angle to which the ship will list; (1)

(ii) the range of stability. (1)

(c) Calculate the righting moment at an angle of 25^o. (2)

Q4. A vessel of constant rectangular section 80 m long and 12 m wide has a KG of 3.93 m and floats on an even keel draught of 5 m in water of density 1025 kg/m³ . The vessel is fitted with a transverse watertight bulkhead 10 m from the forward end.

The compartment forward of the transverse bulkhead, which has a permeability of 75 %, is now damaged and laid open to the sea.

Calculate the new end draughts of the vessel. (16)

Q5. The hull of a box shaped vessel is 80 m long and has a mass of 800 tonne uniformly distributed over its length. Machinery of mass 200 tonne extends uniformly over the middle 20 m length of the vessel.

Two holds extending over the extreme forward and aft 20 m lengths of the vessel, each have 240 tonne of cargo stowed uniformly over their lengths.

(a) Construct curves of EACH of the following:

(i) load per metre; (8)

(ii) shearing force. (4)

(b) Calculate the value of the maximum bending moment. (4)

Q7) A ship consumes an average of 70 tonne of fuel per day on main engines at a speed of 17 knots. The fuel consumption for auxiliary purposes is 8 tonne per day.

When 800 nautical miles from port it is found that 140 tonne of fuel remains on board and this will be insufficient to reach port at the normal speed.

Using a graphical solution, determine the speed at which the ship should travel to complete the voyage with 20 tonne of fuel remaining. (16)

Q9. (a) The residuary resistance of a 1/25 scale model of a ship is 6.35 N when tested at 1.543 m/s in fresh water of density 1000 kg/m³.

The frictional resistance of the ship at 12 knots in sea water of density 1025 kg/m³ is 145 kN. Frictional resistance can be assumed to vary with speed to the power 1.825.

Calculate the effective power (naked) for the ship at the speed corresponding to the model test.

(b) The following additional data apply to the ship operating in service at the corresponding speed Calculated in Q6 (a) with a propeller having a pitch of 4.6 m.

Appendage and weather allowance = 22%

Quasi-propulsive coefficient (QPC) = 0.7

Propeller speed = 1.75 rev/s

Taylor wake fraction = 0.32

Propeller thrust = 565 kN

Calculate EACH of the following:

(i) The torque delivered to the propeller;

(ii) The propeller efficiency;

(iii) The real slip ratio.

Q9) (a) Explain the meaning of the term propeller cavitation. (6)

(b) Describe with reasons, the areas on a propeller blade that are more susceptiable to cavitation. (5)

(c) State how face cavitation may occur. (2)

(d) Explain why cavitation on a propeller is not steady and the consequence of this. (3)