Tearing down the wall - The inclining experiment

It is a well-known fact that the current method for calculating a ship's vertical centre of gravity (VCG) following inclining experiments is limited when considering magnitude of applied heel angle and accuracy achieved for certain hull-forms due to the assumption of unchanged metacentre position when the vessel is heeled. New methods for calculating the VCG have been proposed, notably the Generalised and the Graphical methods. This paper aims to test these methods on a range of vessels, as well as present and contrast a new method named, the Polar method. The test will establish the error potential for each method using a purely technical software-simulated inclining experiment. Using the established error potential, a corrected VCG is calculated from actual inclining VCG values, which have been evaluated against the loading conditions for each vessel to see if the stability margins have been compromised. The study confirms the Classical method's dependency on applied heel angle magnitude, the change in waterplane area and that it compromises safety in some cases. The other methods, especially the Generalised and the Polar, produce very accurate results for any floating position of the vessel, highlighting the need to tear down the wall-sided assumption implicit in the Classical method and replace it with the better and more flexible methods.