Holes in Curved Panels

Holes in curved panels is a somewhat generalised concept. It includes closed contours corresponding to the normal understanding of an opening in the shell. However, a generalized hole may be an arbitrary open contour added as marking contour to a shell or intended to become part of the outer contour of shell plates.

In this way, shell plates with complex outer contours can be generated.

Thus, holes may be of the following types:

1. Ordinary standard holes

2. Arbitrary closed contours, treated as standard holes.

3. Holes, described as closed or open contours and located in space by a transformation matrix.

Holes of categories 1 and 2 must be located when set (by a line through the reference point along which the hole will be projected into the shell. The reference point is the origin in the local coordinate system in which the hole is described).

Holes of category 2 can be created in Drafting mode (around a local origin) and stored in the Hull Form databank (CGDB).

Holes of category 3 must be stored in the Form Data bank as a planar curve object with a transformation matrix. It can be arbitrarily located in space and will be projected along the normal (w-axis) of its local coordinate system. It can be created in Drafting mode in either a planar symbolic view or in a general 3D view perpendicular to a principal axis.

Holes will normally be truly developed, both when presented in views of the curved panel and when inserted in the developed shell plate.

However, for holes of categories 1 and 2 there is an option to insert the holes into the shell plate without development, for example, a round hole will still inserted in the plate in its original shape irrespective of the orientation of the line along which it is located in the shell.

The position of a hole of category 1 or 2 is calculated as the intersection between a line through the reference point of the hole and the surface. This line may be:

• A line parallel to a selected main axis of the ship coordinate system (through the reference point of the hole)

• A line through two point in space.

If the hole is not a round one an additional point may be given to orientate the u-axis of the hole. If the length of this point is <=1 it is interpreted as vector along the u-axis.

A hole of category 3 is positioned by its transformation matrix. If the hole when projected has several intersections with the curved panel, an approximate coordinate along an axis must be given to select the proper position.

A hole may be marked or burnt.

Hole crossmark (available in curved panel view) is created/updated/deleted along with the hole in Handle Holes dialog.

• Crossmark lines are positioned along u-axis and v-avis of the hole.

• Lines cross in mid points between u/v min and max coordinates.

• Lines extent to a physical part such as nearest seam, long/trans or planar panel.

Some other characteristics of this implementation:

• AVEVA Marine automatically identifies to which plates within the panel the hole belongs.

• Holes may cross plate boundaries.

• The hole contour is automatically added to the developed plate when transferred to the plate databank.

• The holes are visualized as part of a curved panel in any view, for example, 3D-views and shellx views.

• The weight and center of gravity calculation for a curved panel takes only burnt holes into account.

The Handle Holes button will bring up a form for setting the data required to create new holes, also to modify and delete existing holes.

Figure 2:14. Form for handling of holes in curved panels.

The New button: To create a new hole in the panel from an empty form.

The Copy button: Creates a new hole in the panel identical to the present one. Useful if only a few parameters should be changed (only when holes exist).

The Delete button: Deletes the current hole from the panel. (Ditto)

The Hole Number field: The number of the current hole in the panel.

The Select Hole button: Enables you to select any of the existing holes in the panel from a list (only in case when holes already exist).

The Next button: Moves to the next hole in the panel (only when holes exist).

The Previous button: Moves to the hole before the current hole. (Ditto)

The Designation field: The type of standard hole or name of a closed contour stored on SB_CGDB.

The Select Designation button: If a hole control file exists then you can choose a hole from the hole menu.

Hole to be: The check box Developed should be checked if a true intersection curve should be evaluated between the hole as a cylinder and the surface. If not checked the original shape of the hole will be retained.

The next field defines if the hole should be burnt or marked. The options for marking define the different combinations of marking of the hole center and marking of the outer contour of the hole. The outer contour can be either marked or not, and the center of the hole can be marked by a small cross-mark, a large cross-mark, a marking shaped like the digit 4 (‘special’), or not at all.

The Hole Along field offers three options for definition of the position of the hole (cf. above).

Axis means that the axis is along a selected main axis of the ship coordinate system. Selection is made via the Approximate Coordinate field.

In this case the two relevant coordinates of Point 1 should be given relevant values. In case of multiple intersections between the line and the surface an approximate coordinate should be given to select the proper intersection point.

In case of Hole Along Line two points in space should be given, defining the reference axis of the hole cylinder. Coordinates should be given in the fields Point 1 and Point 2 respectively.

(For holes of category 3 the alternative "As stored" should be used. It may be combined with an approximate position along a given axis. Otherwise, no location should be specified in this case.)

For Asymmetrical Holes the values of the Direction Point are used to specify a point on the u-axis of the hole co-ordinate system. Should be given only if the hole contour itself is asymmetric. Irrelevant for holes of category 3.

PS/SB specifies the symmetry of the hole. There are three options: As panel, PS, SB. for example, a hole for an otherwise symmetrical may be specified to be valid for PS only. Is "As panel" selected the hole will be valid in both the PS and SB version of the panel.

The Excess and Excess type are used to specify the excess along a hole. This excess affects the geometry only when accessed for nesting. - Excess is relevant only for holes that will become part of the outer contour, that means, not for closed holes in the interior of the plate and not for holes to be marked.

The Compensation field is used to define compensation (that means, "triangular" excess along a hole). It may be defined >0 or <0. The sign has the same meaning as when compensation is defined along the edges of the plate, that means, increasing "excess" as you go along the hole contour. The direction is the direction of the curve after insertion into the outer contour (that means, the original direction of the hole curve is irrelevant). - The compensation is not valid for closed holes in the interior of the plate.

Bevel may be defined for a hole. Two alternatives exist:

• Either an explicit bevel code may be defined in the field Bevel. The direction from which it is regarded may be defined via the field Bevel side. Any bevel gap will affect the geometry of the hole.

• As an alternative dotori bevel may be requested, that means, a bevel with continuously varying bevel angle. This is selected via the check box Dotori. In this case the Bevel set may be used to specify the set to be used for selection of the bevel type. If the set is undefined the default set for "bevel in holes" will be used.
  The dotori angle will be calculated relative to the cylinder along which the hole has been projected into the surface.

  The field Grinding may be used to specify that the hole should be ground (mainly for future use).

  Pressing Ok will bring the panel form back.

  Note: The accuracy of the developed hole (both in views and in the developed plate) is currently affected by a temporary environment variable SBH_HOLEMARK_PART that may be used to control the distance between points on the curve to be developed. By default this distance is 500 mm.

  This parameter is relevant only for non-straight parts of the curve and "fillets" (arcs with a center angle>30 degrees) will always be represented by at least three points independent of the partition.

  Reducing the distance may increase accuracy at the cost of performance.