Page 431 - statbility for masters and mates

Specimen examination papers 419
SHIP CONSTRUCTION AND STABILITY
Attempt ALL questions
Marks for each question are shown in brackets
1. A vessel of 5200 tonne displacement has a KG of 4.32 m and is listed 2.5 to starboard. KM 5.50 m (assumed constant).
The following cargo operations take place:
Load: 125 tonne Kg 2.45 m and 4.85 m to starboard of centreline. Discharge: 280 tonne Kg 3.55 m and 1.50 m to starboard of centreline.
Calculate EACH of the following:
(a) the resulting angle of list; (25)
(b) the angle of list if a slack tank containing salt water and with a fresh water free surface moment of 900 t m is also considered. (10)
2. A ship is ¯oating at drafts 7.25 m forward and 8.45 m aft and has to pass with an underkeel clearance of 0.5 m over a bar with a depth of 8.5 m.
The following hydrostatic particulars apply:
Length BP: 180 m
LCF: 3 m aft of amidships
MCTC: 200
After peak tank: Lcg 2 m aft of AP Fore peak tank: Lcg 173 m for'd of AP
Calculate EACH of the following:
(a) the amount of water ballast to transfer from the after peak to the fore peak to enable the bar to be crossed with minimum clear- ance; (25)
(b) the ®nal drafts forward and aft. (10)
3. A rectangular shaped vessel of length 50 m and breadth 8 m ¯oats on an even keel draft of 1.50 m in salt water at a KG of 2.50 m.
500 tonne is now loaded at Kg 2.20 m.
Calculate the vessel's righting moment at 5 heel for the loaded condition. (35)
4. Explain, with the aid of sketches, how the stability of a vessel is affected by an increase in EACH of the following:
(a) KG; (15) (b) Freeboard. (20)
5. (a) `When a ship is ¯oating out of design trim, the true mean draft (or draft at the centre of ¯otation) and not the arithmetic mean draft (or draft at amidships), must be used with the hydrostatic data in order to obtain the correct displacement.'
For a ship ¯oating with a trim by the stern and LCF abaft amidships, explain, with reference to a sketch EACH of the following: