Constrained spline becomes unconstrained after mirror

[TheModelBoatGuy]

Hi, please forgive me if this is an elementary question. I'm still a Fusion 360 Newbie!

In the attached screencast, you will see a sketch which I need to make symmetrical about a vertical "centre line". All of the curves, including the spline in the top-left are black, so fully constrained. 

After I use the Mirror command to mirror all the objects, the spline (both original and mirrored) turn blue, indicating that they are unconstrained.

Can anyone please explain why this is happening and suggest a solution.

Thanks

[g-andresen]

Hi,

1. Screencast missing

2. please share the file

günther

[TheModelBoatGuy]

Sorry about that!

File attached.

Screencast:

https://autode.sk/3lfvAbA

The affected sketch is listed under Sketches as "T New".

[g-andresen · Accepted solution]

Hi,

I noticed that the sketch was not fully defined even after the mirror had been removed.
From my point of view this is also not really possible with Fit Point Splines.
This type of spline needs the position of the tangent in addition to the coordinates of the control point.
I have determined this with tangent length and inclination angle.
Nevertheless the spline was not "black" and therefore it is not fully determined.
On the right side I have created a control point spline with 3 points and dimensions of the X/Y coordinates of the middle point. You can see the result in the screencast.
Basically I am no friend of attempts to determine splines by dimensions.

günther

Screencast

[davebYYPCU]

Can’t explain why it does that.  

Generally

if you need a mirrored sketch, you should make the half part and mirror the part/Body.  

too many spline points? check Curvature Comb, less is better.

Might help....