Problem with sketch position. Help is wanted

[borei]

Hi All,
Im beginner with FreeCAD. First of all HUGE thank you for such product !
I've got some issue with sketch placement. Im trying to move my sketch to new position (using rotation around Y-axis), but freecad is shifting sketch a bit, so i can't apply it to generate final body. I have attached my mode model file.
There is side-rib-sketch, im trying to rotate it -12 deg around y-axis, after rotation is completed it's got shifted towards axis of rotation, but im expecting that it should be inside "segment-shell". Can't find where is the problem.

[Shalmeneser]

Beware, placement axis and general axis are not always the same.
Hand-drawing ?

[chrisb]

Confusion is sometimes caused by the fact, that the rotation is carried out first and then the translations in the new direction.

[kisolre]

What moves is not the sketch but its geometry. This happens because all of it is linked to projected external geometry points. They are always projected normal to the sketch so with the changing angle their projections move as well.

[GeneFC]

I believe the sketch is moving exactly as requested. Namely the rotation is occuring around the *origin* of the sketch.

The fact that all of the visible sketch details are well off-axis means that it will always appear there is translation in addition to rotation.

Think of an object on the rim of a wheel. If you rotate the entire wheel on its axle the object on the rim will undergo both rotation and translation.

Gene

[Shalmeneser]

Circles around the 3 axis.

[borei]

looks like i don't understand how does geom transformation works. On the following screenshot i created sketch on YZ plane and moving it in Y direction 450 mm, but it was moved in Z direction. Why ???

[borei]

Beware, placement axis and general axis are not always the same.
Hand-drawing ?

yep, it's hand-drawing. need to build "first approach" model, based only on the common sense.

[borei]

What moves is not the sketch but its geometry. This happens because all of it is linked to projected external geometry points. They are always projected normal to the sketch so with the changing angle their projections move as well.

so rotating 90 deg - will it disappear completely ?

[borei]

What moves is not the sketch but its geometry. This happens because all of it is linked to projected external geometry points. They are always projected normal to the sketch so with the changing angle their projections move as well.

looks like it's the reason.
Then question would be - how to rotate sketch with external geometry ?