Cannot finish a loft to a curve

Discussion created by John Clayton on Jun 9, 2009
Latest reply on Jun 11, 2009 by Anna Wood

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I teach CAD as part of a robotics class, and am having trouble finishing out a project I would like the class to do. We are creating a rudder for a sailboat, with an NACA0012 airfoil section. We've put the outline of the rudder on the right plane and put the airfoil sketches on a sequence of planes offset from the front plane. We can loft among the sections, but cannot figure out a way to complete the loft on the left side of the part so that it smoothly merges with the outline spline on the right plane. Attached is the part. Other than putting another tiny airfoil section on a plane very near the tip, is there a better way?
Thanks,
John Clayton

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10 Lofted.zip152.2 KB

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Matt Lombard Jun 9, 2009 3:25 PM
You can't do that in Sw. There is a whole field of study for capping off shapes like that. I did a little event on my blog for propellers. Check it out.

http://www.dezignstuff.com/blog/?paged=3
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- Charles Culp @ Matt Lombard on Jun 9, 2009 7:04 PM
  John,
  
  You can just create a separate face for that, just make sure that the transition is curvature continuous. I would actually do it with two faces, one on top and one on bottom.
  
  I don't know how to create a proper transition to the end, every airfoil I have created ends at a blunt edge (they have all been blower fans and propellers, so they have matched the interior of the housing). Depending on what speed air is going to be flowing by this thing, it may not matter, and you can just do a filled surface, using the edge as a constraint curve. I was going to upload an example of this, but your Sketch1 in the file you uploaded does not match perfectly with the surface. If you have trouble with this method create the sketch that you want to be the leading/trailing edge (make sure it is coincident with the surface model), and I can provide an example.
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Rick McWilliams Jun 10, 2009 4:25 PM
I find that wing shapes with lightly twisted airfoils work best as a sweep. The profile needs to have splines tangent driving, proportional, and then pierce at leading and trailing edge. The path is usually a straight line and the leading edge and trailing edges are guide curves.

An alternative method is to use a boundary surface. I usually use a half airfoil at the root, leading edge boundary, trailing edge boundary. The boundary surface is much better than a loft as solidworks loft does not always hit the sections and can do unsightly bulges.

These methods have the tip integral to the main shape and give perfect planform control.
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- Anna Wood @ Rick McWilliams on Jun 10, 2009 6:18 PM
  Rick,
  
  Any chance you could post an example file with your technique?
  
  Thanks,
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  - Rick McWilliams @ Anna Wood on Jun 10, 2009 8:09 PM
    I have attached a simple wing sweep. I have also attached an easm of the conceptual airplane that uses the wing. I am using SW2007.
    
    Anna,
    I am just beginning to fly IAC aerobatics in my Zlin 242L. I flew in primary and placed 3rd. I was happy with my flying. The box is at a funny angle relative to the runways at PRB.
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    Wing sweep and Zplane.zip941.9 KB
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    - Anna Wood @ Rick McWilliams on Jun 11, 2009 2:24 AM
      Rick,
      
      A Zlin 242L, very cool...... :-)
      
      You have the bug now. Competition aerobatics is a blast. Yes, the box being not aligned to the runways or streets can be a big challenge.
      
      My fiance, Len, will be heading to England (Silverstone) for a month later this summer for the World Aerobatic Championships. He will be the Team Mechanic for the U.S. Areobatic Team.
      
      Thanks for posting your files, it is a great way for me to learn more surfacing techniques from you guys who are experts. I am so out of touch with surfacing techniques since I left the mid-west and the automotive industry behind.
      
      Cheers,
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Charles Culp Jun 10, 2009 6:56 PM
Anna,

He posted an entry in Matt's blog about propellers: http://www.dezignstuff.com/blog/?p=2023

http://www.dezignstuff.com/swparts/proprickmc.SLDPRT
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Cannot finish a loft to a curve

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