Trimmed Surfaces Resulting in Naked Edges

I am working on this model and repeatedly running into this issue with naked edges that I do not fully understand. Here is my overall approach to constructing this:

I’ve attached pictures of linework, surfaces, and the resulting naked edges after joining and the rhino file.

Any help understanding where my approach is going wrong would be greatly appreciated. My work around of repeatedly extending and retrimming surfaces is getting pretty frustrating.


Hi James - I think I’d build that something like this -


Keep the surfaces nice and simple.

Transition_maybe.3dm (417.4 KB)


Assuming that you have followed through with a minimal number of control points for the Profile Curves, few things that I have noticed:

The outer Stem profile seems to be intersecting and crossing through the cylindrical part of the model.
Simply trimming and developing a new surface wouldn’t give up a clean set of “Joined” polysurfaces.

What I have done is take up the Isocurves in the vertical direction and trim a substantial portion from the top to create curves that follow the cylindrical surface👇. Used Blend Curve instead of Fillet.

Then Created a Sweep 2 using the 2 curves in RED

I was almost able to recreate what you have made, unfortunately, I have to run for work.

Regardless here’s some tip

Your method should work as long as you start using the Surace Edges and Isocurves instead of the original to create surfaces once your primary surface is constructed. Rhino sometimes approximates a kind of loose surface creation. (Somebody correct me if I am wrong)

And I also noticed that you have a very high absolute tolerance.

Sometimes used NetworkSurface when Sweep 2 didn’t work.

Let me know if it works for you. :slight_smile:


That looks very clean Pascal. Could you describe your approach to creating that transition?

Hi James - here’s what I’d do -

  1. Be careful about the curves - here, I’ve taken the arc-like portions of the curves and rebuilt them as degree 5, 8 point curves - 6 points makes a good approximation of an arc up tp 90 degrees but the curves you have include extentions to the arcs, so I added a couple more points in the rebuild. The main thing here is that the curves have the same structure and closely approximate the arcs and extensions.

These curves are pulled (Pull command > Loose = Yes) to the slightly arced side surfaces.

The other arc=like curves are rebuilt to degree 5 with 6 points:

These four curves make an EdgeSrf - note opposing pairs of curves have the same simple structure - makes a clean and simple surface from this command.


These two are a Loft (EdgeSrf would also work)


Then MatchSrf the curvier surface to the straight one for tangency:

Trim the side surfaces.