A ship is floating at drafts of 6.1 metres F and 6.7 metres A. The following cargo is then loaded: 20 tonnes in a position whose centre of gravity is 30 metres forward of amidships. 45 tonnes in a position whose centre of gravity is 25 metres forward of amidships. 60 tonnes in a position whose centre of gravity is 15 metres aft of amidships. 30 tonnes in a position whose centre of gravity is 3 metres aft of amidships. The centre of flotation is amidships, MCT 1cm 200 tonnes m and TPC 35 tonnes. Find the new drafts forward and aft.

A ship is floating at drafts of 6.1 metres F and 6.7 metres A. The following cargo is then loaded:

20 tonnes in a position whose centre of gravity is 30 metres forward of amidships.

45 tonnes in a position whose centre of gravity is 25 metres forward of amidships.

60 tonnes in a position whose centre of gravity is 15 metres aft of amidships.

30 tonnes in a position whose centre of gravity is 3 metres aft of amidships.

The centre of flotation is amidships, MCT 1cm 200 tonnes m and TPC 35 tonnes. Find the new drafts forward and aft.

Reference: Ship Stability for Masters & Mates (6^th edition), Exercise – 16.4

Solution:

Change in trim = trimming moment/MCTC

= -735/200

= 3.675 cm by the head

Sinkage = w/TPC

= 20+45+60+30/35

= 4.4 cm

x/t = l/L

=> x/3.675 = ½

=> x = 1.8375 cm

y/t = L-l/L

=> y/3.675 = ½

=> y = 1.8375 cm

New draft AFT = 6.7 + 0.044 – 0.018 = 6.726 m

New draft FOR = 6.1 + 0.044 + 0.018 = 6.162 m

Md. Tawhid Hassan