The centre of gravity of a ship of 5000 tonne displacement is 6 m above the keel and 1.5 m forward of midships. Calculate the new position of the centre of gravity if 500 tonne of cargo are placed in the 'tween decks 10 m above the keel and 36 m aft of midships.

The centre of gravity of a ship of 5000 tonne displacement is 6 m above the keel and 1.5 m forward of midships. Calculate the new position of the centre of gravity if 500 tonne of cargo are placed in the 'tween decks 10 m above the keel and 36 m aft of midships.

Reference: REED'S NAVAL ARCHITECTURE FOR MARINE ENGINEERS (4^th edition), Exercise – 4.2

 

Solution:

Mass (ton)	KG (m)	LCG (m)	Moment (keel)	Moment(midship)
5000	6	-1.5	30000	-7500
500	10	+3.6	5000	+18000
∑ = 5500			∑ = 35000	∑ = 10500

 

New KG = moment/mass

               = 35000/5500

               = 6.364 m above the keel

New LCG = moment/mass

                 = 10500/5500

                 = 1.909 m AFT