How to draw arc tan at end of line D and near to A and B?

Item I have photomodelled, traced and sectioned offers me a challenge, it has an arcing surface mesh sections at B,
It has to come down to be tangent at C onto line D, else a slight drop made up with weld.

Is there a command start tan at C (on line D) and run through B and get near to A ?

What is best way ?
arc ABCD fit.3dm (178.4 KB)


Hi Steve - I do not see a single arc that is tangent to ytour line D at C being anywhere near those points - use Arc > Extension to see. ArcBlend may get you something closer, with two arcs.


Use either the approach that @pascal mentioned above, or “Circle tangent to 3 curves” ( ! _Circle _Tangent ), though in this case you have to snap the circle to the middle of the line between C and D. Then you can split the circle via the existing small arc and the line.

You can’t in this case

You will never be able to pass an arc through those points starting at point C, because the ‘arc of points’ curves too sharply to the left on the lower end… You could run a blend curve which has sharper curvature on the lower end which would catch most of the points (except on the lower end), or you would need to change the position of “C” to be able to make a nice arc that hits most of the points.

Or maybe you should do it like this:

Hi, that is what happened, I re-measured, (about the fifth time) and solved it with a revision of C.

Uploading: arc ABCD fit remeasure and solve.3dm…
something dug from the ground and not made to perfection originally can throw such problems as well as allow some movement to solve them !