There are several important checks that must be carried out in Maxsurf before opening a design in Hydromax:

§   Setting the Zero Point

§   Setting the Frame of Reference

§   Surface Use

§   Skin Thickness

§   Outside Arrows

§   Trimming

§   Coherence of the Maxsurf surface model

Ensure that the zero point is correctly setup in Maxsurf. A consistent zero point and frame of reference should be used for the model throughout the Maxsurf suite. In Hydromax you have the option of displaying longitudinal measurements such as LCB or LCF from the model zero point or amidships.

It is vital that the Frame of Reference is correctly setup in Maxsurf before attempting to analyse the model in Hydromax. The Frame of reference should not be changed in Hydromax. The frame of reference defines the fore and aft perpendiculars, the baseline and the datum waterline; midships is automatically defined midway between the perpendiculars. By convention, in the profile and plan views, the vessel’s bow is on the right.

The perpendiculars define the longitudinal positions of the vessel’s draft marks and cannot be coincident. The base line is the datum from which the drafts and KG are measured.

In Maxsurf you can choose between two types of surface use

Hull

Hull surfaces are used to define the watertight envelope of the hull.

Internal structure

Internal structure surfaces are used for all other surfaces (any surfaces which do not make up the watertight envelope) and also surfaces which are to be used in Hydromax to define the boundaries of tanks and compartments that have complex shapes.

The following table describes the difference between each surface use in Hydromax:

Verify that all surfaces that are to be used as tank/compartment boundaries are defined as Internal Structure. If a surface is defined as internal structure, it is not included as part of the hull shell by Hydromax, i.e. internal surfaces will be ignored in the forming of hydrostatic sections.

If skin thickness is to be used in hydrostatic calculations, ensure that the thickness and projection direction have been specified for the hull shell surfaces. Thickness can be specified differently for each hull surface, resulting in more accurate hydrostatics. To activate skin thickness in Hydromax ensure that the “Include Skin Thickness” option is selected when reading the file or calculating the hull sections.

Note

Tank boundaries made from internal structures surfaces do not have skin thickness. To include skin thickness, the internal structure surface should be placed to model the inside of the tank if the tank wall has significant thickness.

Skin thickness for hull surfaces will be treated so that the hull sections go to the outside of the plate whilst any tanks are trimmed to the inside of the plate.

The surfaces’ outside arrows define the orientation of the surfaces. Ensure that you have used the Outside Arrows command from the Display menu to tell Maxsurf which direction points outwards (towards the seawater) for each surface. The surface direction may then be flipped by clicking on the end of the arrow.

Ensure that all surfaces are trimmed correctly. You should have completely closed transverse sections or sections with at most one opening.

Correct Section with no opening.

Correct section with one opening: this section will be closed across the top.

Also see:

Hydromax Sections Forming on page 25

Checking the Hydromax model on page 29

Hydromax will generally have no problem correctly interpreting your design as long as the following requirements for the Maxsurf model are observed:

§   Make sure that each surface touches its adjacent surfaces at its edge, preferably by bonding the edges together

§   Where surfaces intersect, trim away the excess regions of the surface; e.g. the part of the keel that is inside the hull and the part of the hull that is inside the keel

§   Do not have surfaces that cannot be closed in an unambiguous fashion, i.e. a maximum of one gap in a transverse section through the hull.

§   Remember that the inner portions of each intersecting contour will be trimmed off

§   Check surface use; internal structure surfaces are ignored when forming the hull sections in Hydromax

Note:

For internal structure surfaces that will be used to define tank (or compartment boundaries) the same requirements apply.

Also see:

Checking the Hydromax model on page 29.