Q1. A vessel of SWATH (small waterplane area twin hull) design, has the following hydrostatic particulars when floating in water of density 1025 kg/m3:
Displacement = 1390 tonne
centre of buoyancy above the keel (KB) = 2.744 m
centre of gravity above the keel (KG) = 6.37 m
The distance between the centretines of each hull is 12 m and the half breadths of each hull, measured at equal intervals along the 72 m length of waterptane, are as shown in Table Q1.
Calculate the transverse metacentric height of the vessel in the above condition. (16)
Q4. A box shaped vessel is 100 m long, 20 m wide and floats at a draught of 5 m.
Due to a collision, a full width compartment 25 m long situated at midships, is bilged.
Calculate EACH of the following using the method:
(a) The permeability of the compartment if the final draught in the bilged condition is 5.85 m. (4)
(b) The change in transverse metacentric height due to bilging this compartment. (12)
Q3. The following particulars relate to a ship of length 220 m and breadth 36 m when fully loaded to an even keel draught of 12.4 m in sea water of density 1025 kg/m3.
Displacement = 85000 tonne
waterplane area coefficient (C„) = 0.82
longitudinal centre of flotation from midships (LCF) = 2 m aft
longitudinal metacentric height GML = 242 m
The ship may be considered to be wall sided in the region of the waterline.
Prior to the final loading operation, the draughts are 12.65 m aft and 11.00 m forward and the following two holds are available for the remaining cargo to be loaded:
No. 1 hold with lcg 60 m forward of midships
NO. 4 hold with lcg 35 m aft of midships
Calculate the masses of cargo to be loaded into the two holds to bring the ship to its fully
loaded even keel draught. (16)
Q5. A box barge of 88 m length, 12 m breadth and 6 m depth has a hull mass of 600 tonne evenly distributed throughout its length.
Bulkheads located 4 m from the barge ends, form peak tanks which may be used for ballast.
The remainder of the barge length is divided by 4 transverse bulkheads into 5 holds of equal length.
The holds are full of bulk cargo having a stowage rate 1.6 m3/tonne.
The peak tanks are empty.
(a) Calculate the midship bending moment during discharge when both end holds are half empty. (8)
(b) The midship bending moment is to be restricted to a maximum of 50 MNm (Sagging) during unloading.
Calculate the minimum depth of sea water ballast of density 1025 kg/m3, which must be added to the peak tanks to allow complete discharge of the end holds. (8)
Q8. The wetted surface area of a container ship is 7135 m2. When travelling at service speed, the shaft power required is 22500 kW when residuary resistance is 25% Of the total resistance and specific fuel consumption is 0.22 kg/kW hr. Propulsive coefficient, based upon shaft power is 0.6. Friction coefficient in sea water is 1.411 when speed is in m/s with speed index (n) 1.825.
(a) Calculate the service speed of the ship. (10)
(b) To conserve fuel the ship speed is reduced by 10%, the daily fuel consumption is then found to be 100 tonne.
The propulsive coefficient may be assumed constant at 0.6.
Calculate the percentage increase in specific fuel consumption when running at the reduced speed. (6)
Q5. With reference to the testing of a ship model in towing tank:
(a) define the term corresponding speed. (2)
(b) state Froude’s Law of Comparison. (2)
(c) explain how the effective power of a ship can be estimated from the model test. (12)
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