Designing hulls in Rhinos

Discussion in 'Software' started by pamarine, Oct 16, 2009.

  1. pamarine
    Joined: Sep 2009
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    pamarine Marine Electrician

    I have been using Solidworks for two years now to design boats for a local builder. I also have Rhino 4 with RhinoMarine to run hydrostatics and performance calculations.

    I haven't quite figured out how to use Rhino to design the hulls and was wondering if you folks had tips or new of good tutorials to designing and fairing hulls in Rhino.
     
  2. a78
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    a78 Junior Member

  3. pamarine
    Joined: Sep 2009
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    pamarine Marine Electrician

    what tutorial?
     
  4. duluthboats
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    duluthboats Senior Dreamer

    I like using Rhino for modeling hulls. Of course small boats and canoes are easier than big boats and ships. The key is to work with the minimum amount of points and lines. As you edit those lines make sure you fair and rebuild as you go along. The stem is easy to start with because its 2D. I rough in the transom with lines to start. I draw a shear from the transom edge to the top of the stem. This is the shear and I will pull it in 3D until I like it. The shear is the hardest and it defines the boat, remember fair and rebuild. You want the minimum points that will define the shear. Once you have got the lines looking good save them then save them again under a different name. Now add some surface to the curves. Analyze, fair and rebuild the surface. Delete the old curves and get new ones from the surface edge. Delete the surface and start working the curves again. I go around and around., it really can go fast. Use lots of layers so you can turn them on and off to keep the table clean. And remember you only need to work one side of the hull. There are many tuts out there and I will try to dig some up. My advice is if you know what you want start learning the million tools that Rhino offers. I had 10 years in 2D CAD/CAM before I went to 3D. Working in 3D is different but so much better. Rhino has a big support group and there are a lot of us here as well so feel free to ask.
    Hey Rhino do I get V5 free now ;-)
     
  5. Joe Petrich
    Joined: Jun 2008
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    Joe Petrich Designer

    Working with curves as duluthboats does is one method which works. Another way, which I use, is to create a rectangular surface with about 5x5, or 7x7 control points. Then rotate the fwd set of control points into a vertical line and elevate the outboard set of points to form the sheer. From there it is a matter of tweaking the control points until you have the shape you want, remembering to check your displacement, centers, coefficients, etc as you go. If you have a set of sections already drawn in 2D you can place them in the model to work to as well. Once you have the base model where you want it you can judiciously add additional rows or columns of control poits for very localized tweaking or for adding bulbous bows etc. Keels and/or skegs are added later, as are raised bulwarks etc. remember to keep things simple as duluthboats said. When you add too many control points you end up with surfaces which are hard to fair. Don't be afraid to move your control points to suit the surface. These methods work for small boats or large ships. There are many little tricks which would take too much time to discuss here. You will discover them as you go.

    I have included an image of a 200 ft vessel I designed with the methods mentioned here as an example of what can be done with Rhino.
     

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  6. pamarine
    Joined: Sep 2009
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    pamarine Marine Electrician

    Yea, I guess I really need to just dive in and start experimenting. Rigth now what I do is draw out a Top view and Side view on a 2-d grid, then project the chine and sheer into 3D Space using a point cloud, then connect the points using splines. I then create planes at each section to draw the section profile, and lastly loft the surfaces between the sections.

    Where i run into issues is fairing. I have really messed up some hulls trying to manipulate control points. I tend to use simple hull shapes that really don't require any fairing on the computer so it hasn't been an issue. But i want to start doing stuff on the side for myself and this will be a skill I'll probably need.
     
  7. bhnautika
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    bhnautika Senior Member

  8. Tcubed
    Joined: Sep 2008
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    Tcubed Boat Designer

    Here is one method;
    Draw the sheerline in profile view using curve.
    Drraw the sheerline in plan view using curve.
    Hit record history.
    Then crv2view slect the first two curves two get the sheerline itself.
    Draw the keel line.
    Draw a midsection with osnap on 'near'.
    Copy this twice forward and twice aft. So you now have 5 sections.
    Modify these with control points on till they intersect the sheer and keel lines.
    Loft with record history on.
    Now you can move the section control points and the hull skin will adjust in real time.
    Turn on curvature analysis and adjust the numbers so you get a good range of colors (as small as possible, like -0.1 to 0.1, depending on your shape)
    Keep on tweaking.
    The bow is often easier to make too long and trim later using its own mirror.

    This method usually allows me to create a pretty fair hull quickly.
     
  9. Joe Petrich
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    Joe Petrich Designer

    TTT, yes, that is a good method for chined hull forms. I cannot emphasise enough the importance of using as few control points as possible on the curves to maintain fairness. I like to use 5 or 6 points per curve; any more and you start to induce deflections. Asa I mentioned before you can carefully add points after you have a fair basic surface to tweak it if needed.
     
  10. bhnautika
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    bhnautika Senior Member

    You can also add more sections and waterlines to the surface after, using the project to surface command with the history turned on.
     
  11. duluthboats
    Joined: Mar 2002
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    duluthboats Senior Dreamer

    Ditto per Joe, rebuild those curves and reduce the point count as much as possible until you are happy than add any extras you need.
     

  12. Tcubed
    Joined: Sep 2008
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    Tcubed Boat Designer

    Yes few control points to start with.
    Often Rhino will insert more points than you want when you modify a curve.
    Fitcrv sometimes works, otherwise keep checking how many control points there are and manually delete them.

    For hard chined shapes i usually draw the chine lines and then use sweep2 with record history.
    Then when it's getting pretty close I delete these surfaces or move them into another layer and then loft a developable surface.
    If it's a fairly tolerant material i compare the exploded shapes to my swept shapes using smash. Depending on just how close these are i can determine whether i'm attempting to torture the panels too much- i'm specifically refering to plywood which will tolerate a certain amount of torturing, so i do not have to rigidly adhere to a strictly developable surface.
     
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