Hi Barrie - it often happens if you try to build a single surface that has a lot of shape change in a small constrained area (in this case the bend in your leading edge) that you'll get that type of effect. The change condensed down tends to result in a type of bump which if narrow enough will look like a hard edge.

Then also things that collapse down to a single point can also be tricky as well. With a wingtip you have both of these things happening at the same time so it can be a difficult thing in general.

You can get a more gradual shape transition by using the "Loose" option in loft but that will come at the expense of accuracy because the generated surface will only be generally guided by the curves rather than going directly through each section.

I would probably attempt to do a sweep or network and see if that behaves any better, they can sometimes be better for things that collapse down to a point.

- Michael