The hydrostatics dialog, in the Data menu, will compute the upright hydrostatics at the design waterline. More sections are used for the computations as the precision is increased. As well as the normal hydrostatics, the righting moment at one degree is also given. This is computed as: GMt D sin(1°). The precision at which the calculations were done and the number of sections used are given in the last row.

To change the density or VCG, type in the new value and press tab or the recalculate button to refresh the data.

Note:

The wetted surface area displayed in this dialog is calculated using the same method as that used in the Calculate Areas dialog in the Data menu. This method is more accurate than that used in Hydromax; Maxsurf divides the surfaces into triangular elements to calculate the surface area, whereas Hydromax does a lengthwise integration of section girth.

When using the Calculate Hydrostatics dialog from the Data menu, Maxsurf displays the sections used to calculate the hydrostatic properties in the window in the background. You can move the hydrostatics dialog around on screen to view the sections to ensure that they are correct. Note that this dialog calculates based on your current settings of trimming, surface visibility and precision.

Note: Skin thickness and hydrostatic calculations

In Maxsurf skin thickness is used for creating the table of offsets. For hydrostatic calculation purposes, skin thickness is ignored. Hydromax can be used to calculate the effect of skin thickness on the vessel’s hydrostatics by selecting “include skin thickness” in the opening dialog.

This dialog is available in Maxsurf in the Data menu.

Default settings for coefficient length and LCB/LCF measurements

The first part of the dialog is used to define the length to be used for calculating Block, Prismatic and Waterplane Area coefficients; the same length may also be used to non-dimensionalise the LCB and LCF measurements. (In previous versions of Hydromax, the length had to be set before an analysis was carried out. In this version, the changes may be made at any time and the relevant results will update automatically without the need for redoing the analysis – this is the same behaviour as the Units options).

The second part of the dialog is used to define how LCB and LCF (but not LCG) measurements are presented. The range of origins for the measurements has been extended to include forward and aft perpendiculars. Also you may define whether positive values should be in the forward or aft direction (relative to the chosen origin); finally you may choose to non-dimensionalise the value by dividing by the coefficient length (chosen in the first part of the dialog) and displaying as a percentage.

These options are used in all Hydromax results and in the Maxsurf Hydrostatics dialog. The LCB options are not used in the Maxsurf Parametric Transformation dialog (though the coefficient length is used for the coefficients in this dialog).