Uncertainty analysis procedure for the ship inclining experiment

The inclining experiment is typically performed for all new-build ships and after any major refit. The purpose of the inclining experiment is to establish the vertical distance of the centre-of-mass of the ship above its keel in the lightship condition. This value is then taken as the point of reference when loading the ship, for establishing the ‘in-service’ stability, throughout the life of the ship. Experimental uncertainty analysis is commonly utilised in hydrodynamic testing to establish the uncertainty in a result as a function of the input variables. This can in turn be utilised to establish an interval about the result that may be expected to encompass a large fraction of the distribution of values that could reasonably be attributed to the measurement. This paper provides a methodology for calculating a confidence interval for the location of the centre-of-mass of a ship from an inclining experiment; and ultimately, in any load condition. The uncertainty compared to an assumed metacentric height of 0.15m is provided for four classes of ship: buoy tender 0.15±0.15m (±100%); super yacht 0.150±0.033m (±22.0%); supply ship 0.150±0.047m (±31.3%), container ship 0.150±0.029m (±19.3%), ropax 0.150±0.077m (±100%). •Procedure for evaluating and reducing uncertainty in the inclining experiment.•For some ships, a substantial increase in the minimumGM¯ may be necessary.•A complete procedure for establishing the uncertainty in GM¯ for any load condition.