Arc with straight segments with loft

Kai_himself

Hey,

i would like to draw a arc with straight segments. Here is the link: https://cad.onshape.com/documents/b09e2546059a1c9df86d6cf9/w/6a3d3c8a830438bf837eb0fe/e/db58689cd6160d6ab6fb56da

I made three sketches:

1x Loft, i choose the Loft tool and select all intersections. The segment are not straight, they are bend.

1x Loft with Guides, i draw two outside outlines at every segment and choose them as guidelines. This wont work... i dont know why ?!

5x Loft, i make every segment with one loft, this works the segments are straight.

Is it possible to to it with only 1x Loft and right guidelines ?

Why are my guidelines are wrong ?

Best regards

Kai

NeilCooke

No, 5x is the way to go.

billy2

No, an arc to a line has an abrupt change in curvature at the end of the arc/line. Surfaces want/must try to smooth things out. 

It's the same reason you can't have a spline that makes a corner.

If you want straight lines, then change your arcs to ellipses and maintain tangency across the boundary. Or, connect the lines with splines and maintain curvature across boundaries.

Kai_himself

ok, Thank you very much and have a nice weekend

EvanReese

Rhino has an option in their loft tool for straight sections like this, and I've missed it from time to time. I've considered writing my own FS for this at some point, but it's not super high on the list.

steve_shubin

@Kai_himself

In the case of what you’re modeling, you could also use a sweep

https://cad.onshape.com/documents/997311fd7d7e6086696b41fb/w/5336c2235d0f4b15994bf969/e/4d8850db0ca83b8d9b5d1310

There’s two different parts studios in the doc

Look down in the lower left for the two tabs