I would like to draw an arc where the stroke thickness starts thin and grows wider round that arc.  This is for a control knob so as you have it low the line is thin, as you turn it up the line gets wider.

So far I have tried to use the eclipse tool with the start and end set to 120º and 60º which gives the correct arc.  To get the taper I am trying to use the Taper stroke path effect on this eclipse, which almost works.  When I use the Slice or Chord modes the taper works but has extra lines I don't want.  When I use Arc the taper effect doesn't work.

Ideally the inside diameter would remain constant and the line grow out but I am not overly fussy about that.

I have attached the taper settings, examples of the arcs with white fill and a red stroke for clarity of what's happening and also an example of what I am trying to do.  

Thanks for any help.

I believe the Pattern along Path effect will do what you want:

Or the path effect "Powerstroke":

Maybe this:

Thanks, the pattern on a path works perfectly!  It also made it easier to control the inside diameter (using the ellipse) and outside diameter (width of the pattern).