Bad join, not sure why

I am trying to create a “lip” for reinforcement along an edge but keep getting a bad join as seen in the picture. What I am trying to do should be apparent in the attached Rhino file.

I duplicate the edge and then modify the curve to create my second rail. I create a cross section profile and then Sweep 2 to a point on each side of the profile curve. All seems to go fine until I join the surfaces. I have fiddled with the tolerance and tried every option in the Sweep2 dialogue but nothing seems to help. Insight into what is going on would be much appreciated and/or an alternate approach.

Sample.3dm (351.7 KB)

Hi Ashley - one way out is to split the vertical surface (Isocurve option) at the ends of the sweep-

When you Join it all up the meshing works out better.


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Yes, that totally worked. Thank you!

It does point up a ‘weirdness’ in the render meshing, I’ll put the example on the developer’s list for a look.


So it’s only a display error. I did it again as originally posted without splitting the sides and exported to an STL and Netfabb says it’s a valid mesh. Exporting to an STP and then opening again in Rhino retains the weirdness though.