Hi Pilou, what you need to do is use this one you show here:



Extract the inner edge curve by selecting it and doing a Copy/Paste (Ctrl+C/Ctrl+V), then use Edit > Trim to cut the areas of self intersection away.

The regular offset command does this kind of trimming built in to it, but when you use sweep to generate the variable offset you will need to do the trimming yourself as an additional step.

- Michael