Airfoils and propellers are often defined with arcs at the leading or trailing edge. It would be great to be able to create spline that starts or ends tangent to a circle for such structures.
Problem Tangent.3dm.zip (22.9 KB)
Hi Miano, I always reverse the process.
With “ContinueInterpCrv” I extend the top and bottom curves. Click the curve, use the “EndTangent” option, click the end of the curve and continue the curve in a straight line.
With the “Circle” option to touch two curves and specifying a diameter ( see the icon below) you can place your leading edge. Select and trim the bits you don’t need and presto!
Max.
depends a bit of the desired workflow…
have a look at:
_blendCrv
(the curve can for example be further refined by _insertKnot, _changeDegree)
_match
_line (option tangent)
draw a helping / construction line, the second control point defines the direction of the curve at its start.
so make sure the first CV is identical to the Startpoint of the line, and the second lays on the line.
For CV edit - to keep this condition - _scale with the scale center being the startpoint.
_rotate
the first and second CV around the Circle will keep the tangent to Circle constraint.
for analysis
_curvatureGraph
_gCon
kind regards - tom
Yes, vanes and impellers used on things like centrifugal pumps or turbines are also usually defined in the same way.
The fillet command can get you pretty close just by eye-balling where the curves would be tangent. ~ Problem Tangentx.3dm (2.4 MB)
What I do is make the surfaces and then use FilletSrf command with history enabled to make the arc shaped edge. That makes it possible to then use a small amount of point editing of the surfaces to get the arcs positioned precisely where they are supposed to be. Unfortunately, the curve fillet command doesn’t have history so you can’t do that with curves.
The exact shape will not have a short arc at the leading edge. The arc radius specified indicates the curvature at the leading edge.
Tangency is not sufficient. The surface at the leading edge should have the same curvature as an arc of the specified radius.
The surface should be tangent to a vertical line at the leading edge.
I wish Rhino would help out here 