please somebody help to rhino offset

Discussion in 'Software' started by metin_mehel, Oct 11, 2011.

  1. metin_mehel
    Joined: Jul 2009
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    metin_mehel mech.eng.

    Can somebody offset this hull 10mm to inside and trim its extensions? then please send to me? I think it is imposible. :eek:
     

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  2. DCockey
    Joined: Oct 2009
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    DCockey Senior Member

    The boat is only 7.50 millimeters long in your model. You have units set to millimeters. Offsetting by 10mm is meaningless.

    I assume you intended for it to be 7.5 meters long. That may be the cause of your problems
     
  3. metin_mehel
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    metin_mehel mech.eng.

    what should I do? could you please write to me?
    Thanks
     
  4. Olav
    Joined: Dec 2003
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    Olav naval architect

    Hope this works for you...

    I used Rhino to make a solid from both the hull and the cabin, saved each of it as a STEP 214 file, opened them in SolidWorks and made the 10 mm wall thickness thing there (since I'm much more comfortable with SW than with Rhino). After that I re-exported the models via IGES back to Rhino and saved them as the attached *.3dm file.

    Edit: David Cockey is right, the boat's length is only 7.5 mm, so the 10 mm offset is actually 0.01 mm. However, it shouldn't be a problem to scale the model in Rhino by a factor of 1000 using the "scale 3D" command.
     

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  5. metin_mehel
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    metin_mehel mech.eng.

    Olav,I want it to make with Rhino. I think this should be easy. I corrected the units. however it sometimes trim and sometimes not trim and I dont understan why. I also extend the surface but unfortunately...
     
  6. metin_mehel
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    metin_mehel mech.eng.

    I made `extend trimmed surface` and it worked
     
  7. metin_mehel
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    metin_mehel mech.eng.

    no sorry, it trimmed but it disturbed the shape
     
  8. DCockey
    Joined: Oct 2009
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    DCockey Senior Member

    Use Untrim followed by ExtendSrf instead
     
  9. gwboats
    Joined: Sep 2005
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    gwboats Naval Architect

    Inside Surfaces

    metin_mehel,

    A method I have used for flat panels in the past is:
    Offset your surfaces - check offset arrows and flip the right way if needed.
    Go to Curve>Curve from Objects>Intersection.
    Create new curves at all inner surface intersections and sheer.
    Use Sweep 2 Rails using the longitudinal curves as rails and the end intersections as cross section curves.

    Hope this helps.
    Regards,
    Graham
     
  10. metin_mehel
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    metin_mehel mech.eng.

    gwboats it is a good idea I think. Do you think the curves are generated properly in my model?
     
  11. gwboats
    Joined: Sep 2005
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    gwboats Naval Architect

    Inside Surfaces

    metin_mehel,

    Your surfaces look OK. Not too many control points and reasonable spacing.

    For the curves generated in my previous method, it can help to:
    Select curve
    Go to Edit>Rebuild
    Set Point Count to say 8 and Degree to say 3
    Click Preview (not OK) and the maximum deviation from original will be displayed
    If this is acceptable then Click OK, otherwise increase Point Count slightly to get acceptable value
    Use rebuilt curves to generate surfaces as before.

    Cheers,
    Graham
     
  12. metin_mehel
    Joined: Jul 2009
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    metin_mehel mech.eng.

    how do you know that "Your surfaces look OK. Not too many control points and reasonable spacing." which command?
    I have another question. This model was builded by me with delftship. I want to produce this boat and sell. In order to reduce machining job (actually beveling), I made this hull straight. Do you think this boat is aesthetic?
    Do you create hull by rhino? Or exporting from any shipdesign program. My version of Rhino does not calculate me Cp value... Can you model this kind of boat in Rhino too?
     
  13. gwboats
    Joined: Sep 2005
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    gwboats Naval Architect

    Inside Surfaces

    metin_mehel,

    From your questions I think it is time for you to do a few Rhino tutorials. There are plenty around including marine ones, try a Google search. These will help you with the more common commands and show you what Rhino can do.
    For now, to see the Control Points for a surface:
    Highlight the surface
    Go to Edit>Control Points>Control Points On
    You should then see a mesh with Control Points which will indicate the complexity of your surface. As for Curves you can rebuild surfaces but take note of the maximum deviation as you did for the Curves. Alternatively you can push and pull Control Points for fine adjustment.

    Your boat looks OK to me but it is not the sort of style I really get involved in. Maybe you should do some market research and see what potential customers like.

    For small craft I use Maxsurf for hull design as it is fairly quick to get a reasonable shape and includes hydostatics. For Rhino there are add-ins such as Rhinomarine (obsolete but still around and useful) or Orca 3D which will probably answer your form questions.

    Cheers,
    Graham
     
  14. DCockey
    Joined: Oct 2009
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    DCockey Senior Member

    Cp can be quickly calculated using several Rhino commands.

    Remeber the definition of Cp

    Cp = Immersed Volume / (LWL x Largest Immersed Cross-sectional Area)

    Hydrostatics command provides immersed volume and LWL

    For largest immersed cross-sectional area:
    Create a cross-section of the hull outer surface at the appropriate location.
    Trim the cross-section at the waterline height.
    Close the top of the closed cross-section with a straight line and join the cross-section curves into a single polyline.
    Use Area command to calculate the area.

    Calculate Cp using the immersed volume, LWL and Area

    Remember that an exact value of Cp is not critical. Many other factors will affect performance more than a difference in Cp of .001. Check that Cp is within .01 or the desired value.
     

  15. metin_mehel
    Joined: Jul 2009
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    metin_mehel mech.eng.

    Thank you very much guys for these informations.
    I have principle of yatch design book. It says use cp .56 and lcb -3.4%. But correcting the shape and recalculating cp is hard work.
    Thanks again
     
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