Simple Ship Bow Section using X-Topology

This tutorial goes through the process of creating a simple surface representing the bow of a ship.

1. Using a X-Topolology curve, create a midship section. In addition to the ends include two control points for bilge radius..

2. Apply a Blended Segment constraint to the two control points on the bilge radius.

3. Accuratley place the control points so that the curve will form a vessel with 20.0m breadth, 12.5m depth and 2.0m bilge radius. These dimensions are the same as used in the midship section tutorial.

4. Apply a X-plane Locations surface, moving the midship section curve location to X=50.0m.

5. Now rotate the view and add the centreline curve. Start at the midship section and work forward adding two points for the stem forefoot and one point at the top.

6. Select and edit the centreline curve. Apply a Blended Segment constraint to the internal two points forming the forefoot.

7. Using the attributes, update the location of the control points so that they follow accurately on from the shape of the midship section curve.

8. Starting at the midship section, draw a deckline curve.

9. Use four internal control points and finish up by connecting to the point a the top of the stem.

10. Select and edit the control points of the deckline curve to improve the shape if necessary. Apply a Straight Segment contraint to the first and second control points of the curve leading out from the midship section curve.

11. The coordinates of the deckline curve control points used in this example are shown below.

12. Rotate the view around and create a flat of side curve. Start the curve at the top of the bilge radius on the midship section, with two internal control points, finishing up on the deck

13. Select and edit the curve to improve the shape if necessary.

14. Create the flat of bottom curve starting from the bottom of the bilge radius on the midship section curve.

15. Create three internal control points before finishing the curve at the bottom of the forefoot radius.

16. If the control points do not create a fair shaped curve, select and edit to update curve shape.

17. Select the midship section and apply the 'X' Ribbon surface tangent for force curves to intersect it longitudinally. Both the Flat of Side and Flat of Bottom curves should have 'Parallel to Curve' Ribbon tangent so that any reference curves are set to be tangential to the flat of side or flat of bottom planes.

Curve which have Surface ribbon tangents are indicated in the graphics window by short lines indicating tangent direction.

18. Add a waterline curve near the deck line curve with five control points from the flat of side curve to the stem. Apply a 'Z' plane location surface.

19. Once the curve has been added, edit the control points of the curve if necessary...

...if the initial control points were not in a good position.

20. Add a further waterline, beneath the last with the same number of control points.

21. Apply a 'Z' plane Location Surface.

22. Update the curve once it has been added to place the control points in the best positions.

23. Add a final waterline curve from the midship section to the control point at the top of the forefoot radius on the stem. The same number of control points should be added. As this curve is slightly inclined a location surface will not be necessary. Update the control points, if necessary, after the curve has been added.

24. At this point some section curves are requrired. First create a section curve, attaching it to the control point where the middle waterline curve intersects with the flat of side curve. Attach this curve to the lower waterline, before finishing at the flat of bottom curve.

25. Apply and 'X' plane location surface to the curve.

The curve will not indicate section shape in that area of the hull.

26. Add another section curve forward of the flat of side curve. Start it at the deck line curve, attach it to the three waterline curves before finishing at the flat of bottom curve.

27. Apply an 'X' plane location surface to the section curve.

The curve will now indicate section shape in its area of the hull.

28. Using the plane location coordinate, move the section aft to allow another section to be added to the hull definition forward of the curve just added. (The location of the plan can be moved interactively by clicking on the black bar between the two arrow buttons and dragging the mouse up or down to change the value).

This will move the curve longitudinally up and down the hull definition curves.

29. Add a final section curve, starting at the lower point of the forefoot radius which should also be the location where the flat of bottom curve attaches to the stem.

30. Apply an 'X' plane location surface to the latest section curve added to the definition.

It is likely that the section curves added at this point may be unfair but the hull shape will be updated subsequently.

31. Select all the curves and from the Right Click menu, create an X-Topology Surface, (Right-Click -> Multiple Selection -> Create XTSurface Group).

32. Hull surfaces may have holes after it has first been created as some of the default options have yet to be completed. Changing the surface options will allow the holes to be filled.

33. Change the patch type to a Cubic Coons Bezier.

34. In the Custom Surface Patch Options, in attributes panel, remove the 'Use Irregular Subdivision' option.

The hole will now be filled in but the quality of the result may depend on the shape of the result.

35. The problem of filling odd shaped holes can be resolved manually if the software is incomplete in these areas. Subdivide the flat of bottom area of the surface by extending the section curves so that they attach to the centre line. Press and hold down 'A' while ediing to add a point to the curve (See Curve Tutorial).

36. Extend the other section curve.

37. If there are problems filling in the odd shaped faces on the flat of side, extend the aft section up to the deck line.

38. Once the holes have been filled, add contours.

39. Select and edit the waterlines, adding further control points or curves until a satifactory shape has been achieved.

40. The completed surface.

41. The complete surface can also be reviewed by rendering or displaying surface curvature or reflection lines.

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