Need help with a loft

[dwc]

I am a long time AD user, but have rarely needed to loft.
Well now I do and it is not going well.
Attached is the offending file.
It is the back of a viola which I need to get right, not just approximately.
I have put the topological map of the surface in sketches on planes at the correct heights.
Sketch1 is the complete topological map which I project to other sketches for use.
As long as I don't use sketch0.0, sketch3.5 and/or sketch4.5 it is well behaved.
The moment I add any of those three which include the cusped outline AD responds with one of a multitude of cryptic errors.
I assume it has something to do with the cusped outline and have tried just lofting small portions of the part at a time, but I have found no way.
I am hoping that one of you experts can lead me to a solution.
This is, of course, just the beginning as the inside surface must also be similarly formed, the same for the belly of the instrument.
Many thanks in advance for any advice you may have.
Don

 

[bigseb]

Looks like something better suited to a surface modeller. Got Moi/Rhino/Catia?

 

[JST]

You have essentially no control over what happens between he profiles or lines you establish, and often Alibre will bulge out or suck in those areas.

Loft is a great tool that almost works right.

 

[HaroldL]

It appears that between sketch 0.0 and 4.5 should jut be an Extrude Boss. Between 4.5 and 3.5 is a reverse (negative) curve. then from 3.5 to 5.2 it starts to bulge out the back on a positive curve.

You could try Guide Curves between all the sketches on the YZ and ZX planes, EXCEPT 0.0 and 4.5. Just extrude between them. The guide curves may give you just the control you need for this part.

 

[dwc]

Thanks for your tips.
Unfortunately I don't have or know a surface modeller. For the moment I am sticking with what I know.
I have found some problems in certain sketches and am now making the part in a way so the outer profile is not lofted and it is working.
Thanks again
Don