| Fwd | Aft | |
| Drafts | 9.42m | 10.88m |
| DWA | -0.09m | -0.09m |
| 9.33m | 10.79m | |
| -0.047m | +0.043m | |
| 9.283m | 10.833 |
Therefore, Trim now = 1.55m
Now P = (trim ⨯ MCTC)/d
= 155 ⨯ 252.76/112.5
= 348.25
MCTC in 1.020 = 252.76
We know that –
GG1 = P ⨯ KM/W
= 0.185m,
Old GM = (KM – KG)
= (10.2 – 9.4)m
= 0.8m
Virtual GM = (0.8 – 0.185) m
= 0.615m
-
A vessel of displacement 6220t, length 144m, CF 2m abaft midships, KM 6.9m, MCTC = 150, TPC = 17t, KG 6.2m at a draft of F 4.10m, A 6.20m, is floating in a dry dock were the depth of water is 7.0m above the top of the blocks. Calculate her virtual GM (i) when the level is lowered by 1.5m, (ii) when the water level is lowered a further 1 m.
Solution –
Draft fwd = 4.10m, draft aft = 6.20m,
Trim = 2.10m
Corn to aft draft = 2.10 ⨯ 70/144
= 1.021m
Hydrostatic draft = (6.20 – 1.021)m
= 5.179m
