Page 261 - statbility for masters and mates

Or
Method (b)
Drydocking and grounding 249
Virtual loss of GM MM1 P KM W
Now consider the two parallel forces W and P in Figure 28.4. Their resultant(W P)actsdownwardsthroughG1suchthat:
W y P X
W GG1 siny P KG1 siny W GG1 P KG1
P KG GG1
P KG P GG1 W GG1 P GG1 P KG
GG1 W P P KG GG1 P KG
Therearenowtwoforcestoconsider:(W P)actingupwardsthrough M,and(W P)actingdownwardsthroughG1.Theseproducearighting moment of (W P) G1M siny.
The original metacentric height was GM but has now been reduced to G1M. Therefore GG1 is the virtual loss of metacentric height due to drydocking.
or
W P
Fig. 28.4