Designing without curvature

Discussion in 'Boat Design' started by richardmg9, Dec 10, 2018.

  1. Angélique
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    Angélique aka Angel (only by name)

    Meaning something like these . . ?

    square sailing : venus : yacht design : steve jobs & philippe starck : feadship

    ‘‘ . . . . super angular design . . . . ’’

    [​IMG]

    [​IMG]

    [​IMG]

    Bolger design #630 Illinois

    [​IMG]

    [​IMG]
     
  2. Angélique
    Joined: Feb 2009
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    Location: Belgium ⇄ The Netherlands

    Angélique aka Angel (only by name)

    Last edited: Dec 13, 2018
  3. Rurudyne
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    Rurudyne Senior Member

    [​IMG]
    Also could double as a luxury flats boat in a pinch.

    That said, I believe the OP's question was already addressed with the earlier link to developable surfaces.
     
  4. richardmg9
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    richardmg9 Junior Member

    Compound curves. Anything that requires forming of plates.
     
  5. richardmg9
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    richardmg9 Junior Member

    Lol, those look fun, but I meant compound curves
     
  6. richardmg9
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    richardmg9 Junior Member

    lol
     
  7. richardmg9
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    richardmg9 Junior Member

    Thanks, this is the direction I was looking for.

    I am checking out Rabl's method, are there other similar methods you are aware of?

    Also, I suppose next time I should say "developable" to avoid the tables lol
     
  8. Wayne Grabow
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    Wayne Grabow Senior Member

    I have been playing with developable surface hull design for forty years. I am currently starting to build a new design. But, I don't use CAD, just some algebraic concepts and a basic calculator.

    Developable Surface Boat Designs: Hull design using simple mathematics https://developable-surface-boat-designs.blogspot.com/2008/12/question-of-how-to-create-more-than.html
     
  9. richardmg9
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    richardmg9 Junior Member

    Thanks Wayne!
     
  10. Mr Efficiency
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    Mr Efficiency Senior Member

    "Without curves", when you really meant "without compound curves" ? OK.
     
  11. richardmg9
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    richardmg9 Junior Member

    In my defense, I wrote "curvature" not "curves"
     
  12. Rurudyne
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    Rurudyne Senior Member

    If you use Delftship there's a pretty straight forward trick I've used to insure developed surfaces.

    The first thing I do is define a developed curve to approximate the desired waterline shape, letting the program work for me to produce a fair curve for a form in 3D.

    I make sure the curve has the correct beam by using three very close control points where the beam is supposed to be the widest at the waterline. I then usually have one control point at that beam between the widest point and the transom. I often did the same towards the bow ... though sometimes I added a second control point near the bow if I wanted a specific angle, which was useful if extending the bow reference line into negative offsets, the reason for which should soon be clear.

    Once that shape looks right you then move the upper or lower line defining the curve in or out in the Y plane, this gives you a reference shape that is developed. It may take some playing moving the placement of this reference curved panel to insure you end up with the correct beam at waterline, moving the whole in the Y axis.

    Y offsets for the sheer is derived by this method.

    That reference panel is one layer.

    Then you create at least two more layers, one for the sheer and one for the keel / hull lines.

    Once these look right you then make another layer, it isn't as much work as it sounds like, that is subdivided by numerable closely (within reason) spaced lines. You then use the intersect function to get Z axis offsets for your sheer etc.

    This lets you in turn make another set of layers (you can turn off visibility for layers you aren't using at the moment) which you use to intersect with the first reference layer.

    This gives you the offsets of a developed surface corresponding to the three curved layers you made earlier (if the boat doesn't have a flat bottom but has a V you can arbitrarily define a keel or you can use basic trig to calculate the offsets in the Z axis for the keel).

    As for the reason to have negative numbers for the bow, when you lean the thing this way or that and then you use it as I've described (I'm hoping I was clear) you may need extra to allow for the final shape of the bow.

    Again, it sounds like a lot of fussing but it really wasn't.
     
  13. tlouth7
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    tlouth7 Junior Member

    To achieve a developable hull shape in SolidWorks, consider what you want to control. Generally this is the shape and position of the chines. So create planes that the chines will lie on (these will probably not be parallel to the waterline). Then create splines on these planes. The minimum number of control points will give you the most fair curves (eg constrain the two ends and the maximum beam will give a true parabola).

    Then simply generate lofted surfaces between these curves to create a hull. You will need the same number of spline points on each curve to generate well behaved surfaces. Well designed constraints should allow you to adjust the various parameters quite easily.

    Hydrostatics are not as straightforward as in dedicated software, but can be found by generating solid volumes between the hull's surface and a waterline (optionally inclined) plane. The Mass tool in Evaluate tab will give CoG of this submerged volume which is the CoB.
     
  14. DCockey
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    DCockey Senior Member

    A simple lofted surface between two arbitrary curves will usually not be developable.
     

  15. Rurudyne
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    Rurudyne Senior Member

    When I first read the comment I thought he was just saying what I'd said but just much better than I'd done (to work with the intersections of a 2D curve extruded into 3D representing the sheer or the chine respectively with a third 3D developed surface so that, while individually these would be arbitrary enough, the resulting offsets from their intersections would still be developed). Which is to say I thought he was advising to start with the chine, extend a developed surface from it, and then subsequently use the program to find the intersections with the sheer profile.
     
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