Thanks Danny, that is really good advice and could well be part of the reason why I'm having problems getting a good surface and mesh from the wingtip. I think I'll rebuild those wingtip curves from scratch before applying the final surface.

This is the wing of a Bf109-F (WWII aircraft)

I thought I would post this problem here. I cannot create a wingtip that gives a smooth transition from the leading to trailing edge of the wing. Using the technique I've used (2 rail sweep and the scaling rail). It gives a bulged crimped wingtip.

As I suggested in another thread, perhaps if MoI had the ability of tweaking surfaces with point editing I could then tweak this wingtip to the correct shape as it is almost what I want.

Perhaps there is another way of approaching the modelling of the wing and wingtip so it gives the correct result, I am open to any suggestions help or advice ?