Huidplaten van een schip worden uitgezet als raaklijnen in het netwerk ipv dat deze door de controlpoints van het netwerk lopen

DELFTship forum Hull modeling Huidplaten van een schip worden uitgezet als raaklijnen in het netwerk ipv dat deze door de controlpoints van het netwerk lopen

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    • #37520
      Stefan Schreuders
      Participant

      Sinds kort gebruiker van Delftship en gebruik dit om uitslagen te maken van knikspanten en platbodems. Nu kwam ik achter een elementaire fout in het programma tijdens het opzetten van mijn eerste romp op basis van een spantenlijst.

      Ik gebruik de waarden uit de spantenlijst om de xyz waarden van de controlpoints in het netwerk te bepalen. Echter wanneer ik nu plaatvelden toe ga wijzen, blijkt dat de platen zelf niet door deze controlpoints lopen. In plaats daarvan wordt de bocht “afgesneden” en wordt de lijn tussen 2 controlpoints gezien als raaklijn. Hierdoor kom je met name bij sterke buiging behoorlijk wat ware lengte te kort op de uitslag.

      Hier valt omheen te werken door extra hulpspanten toe te voegen, echter het blijft dan een benadering. Bovendien is dit extra werk voor de gebruiker, wat volgens mij niet de bedoeling is van dit progrmma.

      Is het mogelijk om in plaats het netwerk te zien als raaklijnen, de huidplaten werkelijk door de controlpoints te laten lopen?
      (zoals bij de “spline” functie in autocad”)

    • #37521
      Marven
      Keymaster

      Dear reddoor_nl,
      Will you please post your message in English next time so that other users can learn from posts as well?

      You’re correct, the control points which are used to model the surface are almost always located outside the hull surface. This is certainly not a bug, it is related to the mathematical formulation of the surfaces. This property (also known as the convex hull property) ensures that no undesired inflection points are introduced into the surfaces. Most surface modelers have this feature, and this is something one gets used to quite quickly.

    • #37524
      Stefan Schreuders
      Participant

      Hereby the English translation of my question:

      Since a few days user of Delftship Professional. So far great program except for one issue.. I’m going to use this program for making “fold-outs” of shiphulls of existing ships. I’m used to drawing ships from “coordinate tables” (Spantlijsten). While using Delftship I found an elementary mistake in the method hullmodeling was programmed. I expected the control points of the “network” to be exact intersections of plate-edges and ordinates. Sadly this isn’t the case and it seems that corners are being cut. Especially at locations with sharp bends in the hull this will result in a substantial difference in size of the foldout plates.

      There is a possibility to work around this problem by adding extra ordinates, but this will be a lot of unnecessary effort and in the end it will always result in an approximate hull form and never the exact one.

      Is there a possibility to make the hullplates go exactly through the controlpoints (like the “Spline” Function in Autocad).

      The Answer given above will not satisfy me because I will not get used to a program that doesn’t draw the ship I’m trying to draw.

      I’m absolutely sure this problem is mathematically solvable and will result in a better Delftship as you will be able to exactly control the hull-form instead of approximately.

      Also see atachments for better explaination

      Attachments:
    • #37530
      Denis Pratt
      Participant

      Many years ago I had the same thoughts, my previous experience with Autoship was holding me back.
      In my view the program is a winner as it is. Does all the things I need to design a hull shape and produce the form needed, and so inexpensive that any criticism is not acceptable.
      How do they do it for the money??
      If one wishes to reproduce existing ship forms then perhaps better to use 3D cad package you are used to, save file as IGES and import to DS Pro and go from there.
      With more use and navigation around DS Pro the benefits will appear.

      Keep experimenting and trying the “what ifs” and the frustrations will stop.

      Kind regards,

      denisp

    • #37532
      Stefan Schreuders
      Participant

      I’m willing to admid Delftship does a great job for it’s price. Especially when it comes to fairing.
      Also the program is not that hard to learn if you have any experience with any kind of 3d cad drawing.

      So, yes, it is great value for the money.

      (on topic): Only wouldn’t it be nice to have the option to make the hull follow the outside of the network, rather than the inside?
      Maybe an idea for the developers to add this feature in future versions.

      By making this an option, old models will keep working while adding extra possibilities to the program. By doing this, one will be able to create a vessel from offset tables more precisely.

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