3 Replies Latest reply on Dec 22, 2012 1:57 PM by Rick McWilliams

    Sailing Yacht Hull, Help getting right please

    Niall Mitchell



      Im trying to reproduce in Solidworks a scale AC45 catamaran although I hope to be able transfer the same principle to other boats I have plans for.


      So I started off by inserting the plans in scetches on the top and right planes. Then inserting 20 planes along the hull length at 50mm intervals and placing the hull cross sections on each of the planes. Finally I drew 4 3d splines along the length of the hull to use as guides.


      My problems are that when I try and loft the hull is that the hull doesent come out looking all that smooth. Ive tried that a couple of times before and have tried manipulating the handles that are created with a varying drgree of success but still not anything like as smooth a transition I would like or occur naturally.


      I then tried using the Boundry Surface Command which I find works better than the Lofted Boss/Base Command to produce the hull. However the results are still the same and not nearly as good as what I was hoping for.


      Ive attached some screen shots and the model.


      Would really appreciate some help with this , I have looked at the other posts and tutorials but they dont seam to cover what im trying to achieve. Im resonably skilled using the solidworks but have done very little in the past when it comes to surfacing.

        • Re: Sailing Yacht Hull, Help getting right please
          Jerry Steiger



          I didn't open up your model, but looking athe isometric view, I would suggest that "less is more" when it comes to surfacing. You are usually better off when you have the least possible number of profiles and the least possible number of points in your splines. You might also find that it is better to split your hull into two or more surfaces, say one at the front, where it changes fairly quickly, and one at the back, where it changes much more slowly. Boundary Surfaces give you more control than Lofts.


          Jerry S.

          • Re: Sailing Yacht Hull, Help getting right please
            John Burrill

            Niall, your hull surface is rippling and buckling for a couple of reasons.

            First what Jerry said: you've got too many cross sections and minor irregularities from eye-ball tracing the sections and a general lack of control over the spline weighting is producing surfaces with a lot of inflection points where the curvature changes from concave to convex.  My suggestion is that you start with two sections and try to tweak your guide-curves by dragging the tangency handles and by adding curvature pionts (not spline points) to make guides that match your nautical lines.

            Second, you want to use boundary surfaces between the bulkheads and fill surfaces at the ends.  Boundary surfaces and lofts that have to collapse to points, develop singularities and produce unexpected results when thickened.  When you're building your fill surfaces, use the edges of your boundary surfaces as tangent curves and then you can set them curve continuous.

            Third: if you're hull is symetric about a plane, only model half of it and then mirror it.  This requires that you set up tangent controls for your profiles at the plane of symmetry and that you have a guide curve on it.

            • Re: Sailing Yacht Hull, Help getting right please
              Rick McWilliams

              Boundary surface does very poorly with many sections. Try to use two edges and a guide curve or two and two sections. Use curvature display and zebra stripes to find imperfections. It is best to think of all surfaces at having four edges. Singular points cause trouble. Beware of projecting two planar curves that share a point. The resulting curve will not go all of the way to the point. A fine old bug from 2003.


              I am designing airplane fuselage shapes. I get excellent surfaces using the GW3D add in from cadcamcomponents.com. They have an excellent controllable conic surface that will give you a beautiful fair shape. There is also a geodesic mapping feature that will generate a flat pattern with minimum distortion. This is good for cutting a core material for composite construction.


              When you look closely, almost all Solidworks surfaces have defects; butt cracks, hogbacks, ripples, curls, tits, wrinkles and gaps. These cause trouble down the line when surfaces are thickened or manipulated.