C L DUBEY – EXERCISE – 08 (DRY DOCKING)

GG₁ = P ⨯ KM/W
= 0.199m

21. Calculate the GM taking the blocks overall when drydocking a (damaged) vessel, given W 43200 tonnes, LBP 210m, LCF 5m abaft of amidships and draughts F 13.14m A 9.84m. KG 8.60m, km9.00m, TPC 36, MCTC 350 t-m.

Solution –

Change in trim = 3.3m
P = 3.3 ⨯ 350 ⨯ 100/110
= 1050 tonnes

GG₁ = P ⨯ KM/W
= 1050 ⨯ 9/43200
= 0.218m

New virtual GM = (0.40 – 0.48)m
                            = 0.182m

22. A ship LBP 180m, W 18000 tonnes is damaged forward and trimmed by the head. Calculate the maximum allowable trim by thr head to ensure that there is a positive GM of 0.15m when taking the blocks overall given that the blocks have a run down (towards the gate) of 10cm per 100m and that the ship is being docked bow in. KG 7.20, KM 7.56m, MCTC 210 t-m and LCF 8m abaft of amidaships.

Solution –

Present GM = 0.36
Required = 0.15m

GG₁ = 0.21m
0.21 = P ⨯ KM/W
P = 500 tonnes

Now, P ⨯ d = trim ⨯ MCTC
Trim = 500 ⨯ 98/210 ⨯ 100
Run down = 0.1m per 100m will provide 0.18m trip