Hydromax works by applying trapezoidal integration to data calculated from a series of cross sections taken through the Maxsurf model surfaces. Hydromax will automatically form these sections, called “Hydromax sections”, “hydrostatic sections” or just “sections”.  Hydromax deals only with sections that are completely closed, or can be unambiguously closed. This section outlines the section forming process in Hydromax and may be helpful whilst preparing a Maxsurf design for Hydromax. Whilst it is always preferable to give Hydromax a completely closed model with no ambiguities, Hydromax will try to resolve any problems with the model definition in the manner outlined in the following sections.

The following cases can occur:

·  Single surface

·  Multiple surface, closed section lines; e.g. via bonded edges, compacted control points, trimming etc

·  Multiple surface, small gaps within tolerance

·  Multiple surface, one opening per surface

·  Multiple surface, multiple openings per surface

Where a hull consists of an open shell (e.g. a hull surface with no deck), Hydromax will automatically close the section with a straight line connecting the opening ends.

If, however, the section is made up of two line segments, (e.g. having both a gap at the centreline as well as an open deck), an ambiguity exists as to how the two line segments will be connected. This is not an acceptable shape.

In the example above, if either the top or bottom gap had been closed in Maxsurf the design would cease to be ambiguous.

Multiple surfaces that are trimmed correctly, bonded together or use compacted control points will not cause any problems when opened in Hydromax. Hydromax will form a closed section through multiple surfaces by linking the curve segments together.

Hydromax will link curve segments together if they are only separated by a small amount. The user cannot change these tolerances, because there are too many dependencies in the program.

Each surface will be closed by a straight line linking the ends of the opening.

Where surfaces intersect, each surface will be closed before being intersected with another. The excess portions of the curve will be trimmed off to form a single continuous contour.

Hydromax first closes the individual surfaces

Hydromax closes the outside contour and trims remnants

Same as for a single surface, Hydromax deals only with sections that are completely closed, or can be unambiguously closed.

A common example of ambiguous sections is a model with multiple decks. Hydromax will have difficulties distinguishing the intended main deck.

The example above has bulwarks; generally these will be treated correctly by Hydromax and trimmed off, depending on the height of the bulwark relative to the rest of the section. To prevent ambiguities it is recommended to trim the bulwark in Maxsurf. If the bulwark’s volume is expected to influence the hydrostatic calculations, the bulwark’s volume has to be properly modelled in Maxsurf.