How to create ribs

Can anyone suggest a method to create the ribs in the rudder illustrated in the attached image?

They are quite random in shape and while I dont’ need to create every last detail, I would like to represent them to some extent and I’m trying to find a way to do that.

Thanks (as always)


Hi Paul - here’s what comes to mind:

  • Have the ribs as curves.
  • Loft > StraightSections all the curves together.
  • Explode the result and ChangeDegree to 3 in the U direction.
  • Turn on points, and select the middle two rows of points on each surface.
  • MoveUVN inward/downward slightly.

@Paul_Adams - quick example attached. Ribs_PG.3dm (98.2 KB)


Thank you for the very fast response, Pascal, I’m working with that now.


When I explode the surface on my model, it spits into two sections, transverse to the ribs, even though I use the straight sections loft as you suggest. I will attach the model, can you see what I am doing wrong?

PaulElevator Ridge Test.3dm (1.5 MB)

Hi Paul - that is correct, you just need to finish - ChangeDegree to at least 2 but I used 3 in the U direction on the exploded surfaces - see my example file above. - oh - OK - I see - the ribs are all the same so Loft makes a single surface in U. Hold on a bit.

@Paul_Adams - in this case it will work out better if you first Rebuild the curves (degree3, 4 points should work) because they are made of two tangent segments which lets the loft explode in the long direction. Or use the Rebuild setting in Loft.

Since the curves make one straight section in this case, Split the result with the input curves and ShrinkTrimmedSrf on these then carry on as I suggested - ChangeDegree etc.
Elevator Ridge Test_PG.3dm (747.2 KB)