Inclining Test
It is easy to check the weight of a vessel by reading draughts and comparing with the known properties. It is not as easy to check the position of the vertical centre of gravity (VCG) and yet this dominates stability. The VCG position can be estimated by moving a weight to produce a known overturning moment. Knowing the restoring properties (buoyancy) of the vessel from its dimensions and floating position and measuring the equilibrium angle that the vessel lies at, the VCG position can be calculated. This is an Inclining Test and it is usually done inshore in still water and free of mooring restraints to achieve accuracy. Inclinings can be performed in service by meaning out the effects of motions caused by waves. Again, the weight shifts have to be known and the angles of tilt measured. The effects of the moorings can be calculated and deducted. A series of weight (usually ballast) movements are used to obtain an average and variance for GM.
