Methods Used

The majority of the calculations undertaken in Calc are concerned with the determination of particular areas, volumes and centroids. Before the existence of computers, it was not possible to calculate volumes by direct mathematical integration. Instead a series of approximate rules were devised to undertake this task. The most widely adopted method was Simpson's Rule which has been shown to provide acceptably accurate results on general hullforms providing there is sufficient coordinate data available. Many computer programs available today have merely encoded these same manually orientated processes, however, Calc utilizes a more rigorous approach to the calculation of volumes and volumetric properties.

The main hull and each compartment bounding surface are defined by a series of triangular facets. The greater the amount of curvature on a surface then the larger the number of facets that are used to represent that surface. The volumetric properties bounded by these facets are then determined by direct calculation and the overall properties obtained by simple integration.

It should be noted that the principle of lost buoyancy is used throughout Calc when assessments are made of the damage stability characteristics of a vessel. In using this approach not only are the effects of lost buoyancy of the hull taken into account, but so to are the changes to any applicable waterplane characteristics taken into the calculations.