- When water level is further lowered by 1.0m
Level = 4.5m
Since water level < hydrostatic draft ship has taken over block over all.
Reduction in Hydrostatic draft = (5.063 – 4.5)m
= 0.563m
Or, 56.3 = P/15
Or, P = 844.5 tonnes
GG1 = P ⨯ KM/W
= 0.870m
Old GM = 0.6m
Therefore, New GM = (old GM – GG1 )
= -0.270m
-
A vessel of L = 145m, CF = 3 mts forder of *, MCTC = 150 mt TPC = 18 t, KM = 7.5m, KG = 6.9, w = 11200 at a draft of F = 3.72m, A = 5.70m is floating in a drydock where depth of water is 6.5m above the top of the blocks. Calculate the vessel’s residual GM and her draft’s F & A, when the W/T is lowered by 1.5m.
Solution –
When level is lowered by 1.5m then water level = 5.0m
Correction to aft draft =( trim ⨯ LCF)/ LBP
= 1.031m
Hydrostatic draft = 4.669m
Since water level is greater than 4.669m it means stern has taken to block while forward end is still afloat.
Reduction in aft draft = 70cm
Or, 70 = P/18 + P ⨯ 75.5/150 ⨯ 75.5/145
Or, P = 220.4 tonnes
GG1 = P ⨯ KM/W
= 0.147m
Virtual GM = (0.6 – 0.147)m
= 0.147m
Trim caused = Tc = 220.4 ⨯ 75.5/150
= 110.93
Or = 1.109m
Rise = 220.4/18 ⨯ 100
= 0.122m
Ta = 1.109 ⨯ 75.5/145
= 0.577m
