Creating the defining curves using the half siding approach

The half siding approach is a means of defining the shape of the end surface using a knuckle curve called a half siding knuckle, which the user creates and manipulates.

The half siding approach is based on the principle of fitting the waterlines to a knuckle curve that is parallel to the profile curve in a buttock view. This means that each waterline ends with a knuckle point followed by a straight segment that meets the profile curve. The final shape of the waterline ending is defined by a circular or elliptical arc whose center lies on the centerline, and that is tangent to the waterline at two points (where the straight segment meets the centerline, and at some point on the curved portion of the waterline the other side of the intersection with the half siding curve). This is illustrated in Figure 3:93 below, Top: The half siding knuckle is a 3d curve that the waterlines are fitted to. Bottom: How the final shape of a waterline ending is derived from the half siding.

Figure 3:93. Explanation of the half siding principle.

The user controls the shape of the end surface through the shape of the half siding knuckle, since the shape of the radii curve and (optionally) eccentricity curve are determined by it.

Note: The half siding approach will only work for stem or stern profiles that are single-valued in the direction of the z axis. This prevents the approach from being used with hull models that have with gooseneck bulbous bows.

Create an end-surface using the half siding approach in PACE

1. Create a half siding knuckle curve. The curve should be kept parallel (or approximately parallel) to the profile curve in a buttock view. Frequent refitting of the waterlines to the knuckle curve is a good way to judge its developing shape.

2. Refit the waterlines to the half siding knuckle curve.

3. Open the End Surface Options dialog (END SURFACES \ OPTIONS... ), and select the End Surface Creation page.

4. Check the Use Half Siding Curve box.

5. Select the half siding knuckle curve from the Half siding Knuckle drop-down list.

6. Check Create Normal Eccentricity Curve if you want the shape of the end-surface to be approximately circular in a plane that is normal to the profile curve (this will cause any existing eccentricity curve to be overwritten).

7. Click OK to close the End Surface Options dialog.

8. Regenerate the end surface (END SURFACES \ GENERATE END SURFACE). This triggers the creation of the radii curve and eccentricity curve (if Check Create Normal Eccentricity Curve was checked) from the half siding knuckle curve, and then automatically regenerates the end surface and tangent curve from them.

9. Repeat steps 1 - 8 until the end surface is the correct shape. The shapes that the waterlines endings will be can be previewed by selecting DISPLAY \ PATCH \ CUT CURVES. This displays a planar slice through the end surface at each waterline height. Alternatively, the shape of the end surface may be adjusted by manually editing the defining curves in the ways described in the previous section.