Question

(a) How the distribution of mass within the ship affects the rolling period? (6)

(b) A ship of 14000 tonne displacement is 125 m long and floats at draughts of 7.9 m forward and 8.5 m aft. The TPC is 19, GM. 120 m and LCF 3 m forward of midships. It is required to bring the vessel to an even keel draught of 8.5 m. Calculate the mass which should be added and the distance of the centre of the mass from midships. (10)

Answer 1

Part (a)

The rolling period is influenced by the ship's metacentric height (GM) and radius of gyration (K), which are determined by the location of the masses onboard.

Masses at the bottom:

The centre of gravity (G) moves down.
Metacentric height (GM) increases, resulting in greater stability.
Rolling period decreases.

Masses at the top:

The centre of gravity (G) moves up.
Metacentric height (GM) decreases, reducing stability.
Rolling period increases.

Masses concentrated at the centre:

The radius of gyration (K) decreases.
Rolling period decreases.

Masses distributed away from the centre:

The radius of gyration (K) increases.
Rolling period increases.

✓ Verified Model Answer (Text Solution)

The rolling period is influenced by the ship's metacentric height (GM) and radius of gyration (K), which are determined by the location of the masses onboard.