Hull Curves

It is customary in traditional shipbuilding to use sets of principal curves like frames, waterlines and buttocks. They play a less important role in today's AVEVA Marine when it is possible to refer directly to the surface and no predefined curves of these types actually are required. Anyhow, in most cases sets of such curves are created in the form data bank. These curves are always planar.

There is an additional type of hull curve that is essential for modelling of the shell plating, namely the seam/butt. Seams may be planar but may also have an arbitrary shape.

Common to the naming of all these curves is that they have composed names, that means, that they are identified and referred to by a number set by the designer. When the curves are stored in the data-bank their names are formed by concatenating a group name with the user given number.

The curve numbers should follow certain rules:

• They are normally positive (however, frame curves may have negative numbers).

• They must be smaller than 10000.

• Special for frames is that they should be in the interval [-899,2766] (at least if the numbers of the frame curves are used as number of frame positions as well).

The group names are individual to each type of curve and are registered in the Hull Reference object and set-up by a feature of the hull utility inithull. The following group names are recommended:

• AAX for frames

• AAY for buttocks

• AAZ for waterlines

• AAS for seams/butts

The group names will be extended by the surface suffix of the surface from which they are cut.

The hull curves (frames, waterlines, buttocks) are associated with co-ordinate tables that specify the x-, y- and z-co-ordinates, respectively, of each of the numbered curves. The names of these tables are defined and registered simultaneously with the group names and are suggested to be AAXTAB, AAYTAB and AAZTAB, respectively. These names should be extended by the surface suffix so that both the curves and the tables may be kept apart for curves from different surfaces (not yet implemented).

The seams/butts are instead associated with two co-ordinate limit tables that keep record of the extension along the x- and z-axes for each seam/butt. The names of these tables are recommended to be AASLIMX and AASLIMZ, respectively.

Note: If free naming of seams and shell profiles is activated, a seam may be given an arbitrary name.