a cusp between two sides

DELFTship forum Hull modeling a cusp between two sides

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    • #44164
      iggi
      Participant

      Hi all,

      I am having a problem of a cusp being visible on the decks of my model.

      What is the most efficient way to make it all smooth?
      I tried introducing a second set of closely located points at exactly same height, but it doesn’t help too much.

      Thanks a lot in advance,

      • This topic was modified 3 months, 3 weeks ago by iggi.
    • #44166
      Terrance Egolf
      Participant

      Hi Iggy.

      The ridge or cusp you see is the result of the crease edge at the centerline of the model. It is almost impossible to create a smooth tangent at the crease edge with viewing the model with Both Sides selected in Hull Display.

      If having a smooth foredeck is important, I suggest building the entire deck as a non-symmetrical object on its own layer. That way you can eliminate the crease edge along the centerline.

      To avoid rebuilding the right side of the deck, you can use the program’s Mirror feature:

      1. Select all the faces that make up the deck and assign them to a new layer in the Layers Menu Group on the Home Ribbon. I suggest renaming the new layer “Deck” or something meaningful to you.
      2. In the Layers Edit window, first uncheck the Hydrostatics check box for the Deck layer, then uncheck its Symmetric checkbox. Then click Accept.
      3. Turn off the visibility of all layers other than the Deck layer in the Layers dropdown list.
      4. With the Control Net visible, select the entire deck object so that everything is highlighted yellow.
      5. Switch to the Tools Ribbon, then click on Mirror in the Transform Menu Group. A dialog box will appear.
      6. In the 3D Mirror plane section of the dialog box, click on the Vertical Plane radio button. This mirrors an object across the vertical longitudinal plane. Verify the (offset) Distance is 0.0, and the “Connect to existing points” checkbox is checked.
      7. Click OK to create the right side of the deck.

      Most of the time this will create the right side of the object connected to the original left side. However, if there is some extra edges that weren’t connected properly in the original object, then the two sides won’t be connected along the centerline. If that happens, you will have to delete faces (one at a time is best) at the centerline and then manually connect the adjoining faces to obtain an interior edge along the centerline.

      When the two sides have been joined properly, the deck surface should form a smooth camber from side to side.

      I used this technique to create a smooth elliptical coamings for my model of a c. 1905 naphtha launch. The hull is on a symmetrical layer while the coamings are not.

      Hope this helps.

      Terry

       

      • This reply was modified 3 months, 3 weeks ago by Terrance Egolf. Reason: Image didn't attach
      • #44169
        iggi
        Participant

        Hi Terrance,

        Thanks a lot for your very detailed explanation. It is indeed very difficult to create a smooth tangent. Following your instructions, I did make a smooth surface of entire deck.

        But now, an inverse question arises… Can you divide this smooth (non-symmetric) surface into two halves in such a way that the tangents stay smooth?
        (in my case it is desirable to be able to use both half-models and full ones)

        Many thanks once again,
        and best regards,

        • This reply was modified 3 months, 3 weeks ago by iggi.
    • #44168
      Terrance Egolf
      Participant

      And, as usual, the image file didn’t attach…

    • #44171
      Terrance Egolf
      Participant

      Iggy wrote:

      But now, an inverse question arises… Can you divide this smooth (non-symmetric) surface into two halves in such a way that the tangents stay smooth?

      The short answer is ‘no.’ The program is not able to simply “disappear” the right half of a nonsymmetrical object in either the viewport or in the lines plan. If you try to split the nonsymmetric deck object in half, you reintroduce the centerline crease edge, and then you are back to where you started. Crease edges always create tangent-discontinuous surfaces, no matter where they are located (page 19 of Manual_13_mc0.pdf).

      I would suggest just living with the deck and any other objects that need to be ‘nonsymmetrical,’ then deal with them in the lines plan when it comes time to create your half-hull plans.

      The lines plan can be exported as a 2D DXF file. Most modern 2D CAD programs can import these DXF files as vector polylines. (I use CorelDraw.) With care, you can delete the unwanted far side of the nonsymmetric objects when cleaning up the plan image.

      Hope this helps. If anyone reading this can add to or correct this response, please do!

      Terry

      • #44172
        iggi
        Participant

        yes, that’s exactly what I am doing currently – cutting half in the SketchUP which I use for 3D visualisation.

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