Create Clines

We should at this point have defined the profile curves, some control curves and preliminary set of section curves from the design data. We should now examine the design as a whole and identify zones on the surface where the orthogonal curves have similar shape and form and that could be classified as belonging to the same “family” of curves. The appropriate view, normally section, should be selected and Clines (2D construction curves) should be created in these identified areas.

To do this select the 2D construction icon , the 2D Construction dialog will be displayed on the screen. The default page is Cline and will be displayed automatically. Flat, Crank, or Parabolic Cline Curve type can be created either by entering the coordinate values into the relevant boxes or interactively by using the cursor. Curve and Knuckle Clines can only be input via the cursor.

Figure 3:19 2D Construction Dialog

Create Clines

1. Select Curve for the Curve type option and enter a Name for the Cline curve.

   The Cursor check box and other edit boxes will be greyed out.

2. Select the Create button.

   The cursor will change to a crosshair on the graphic screen and the status bar will ask the user to digitize points on the curve using the cursor.

3. After digitizing click the Right Mouse button to end and the system will automatically fit the points.

   The curve can then be faired and accepted as normal.

The user can create various types of Cline curves from the 2D Construction dialog by selecting the appropriate Curve type option. For details see 2D Construction Dialog.

When creating the initial Clines the user should note the areas of common curvature in the sections, (e.g. inflection points, points of maximum or minimum curvature) for the placement of the main Clines. To maintain the shape of the sections near the bilge radius, ensure that at least 3 to 5 Clines pass through that area. In general, 8 to 10 main Clines should be sufficient. The following figures show an example of a typical forebody and an example of an aft body for a container ship.

Figure 3:20 Typical Fore Body Cline Arrangement

Figure 3:21 Aft Body of Container Ship