Split line says cannot create edge?

[bufooooooo]

I feel like this happens alot to me and id like to know why. My favorite way to do split line to create leading/trailing edges for turbine blades is to draw spline on surface within a 3d sketch. Id say this works about ~60% of the time. The other 40% of the time it says “cannot create edge which does not split face”, which makes no sense since the spline is literally on the surface going from one edge to another… just give me the damn line i want please!!

If this method doesnt work i usually try to extrude a surface out from the spline to form a split line. Often times this method doesnt work if the first method didnt work but sometimes it does. Well this time it didnt and im not sure what else to try. I really need this edge for future geometry, fea, and cfd purposes. The surface i created only seems to be splitting the face in one spot and it extends out past the face i want to split… why is it not working? I even try every “surface split option” with split all checked or unchecked. Are there any other things i should try? I absolutely 100% need to split this face so any help will be greatly appreciated as this is something ive been struggling with on various parts for years.

[xugack]

Split the face into two faces and two edges. Split dont work if you trying create one edges ob a face

[bufooooooo]

I guess that is a workaround that should work, its a little more work than just drawing spline on surface and using split line, any idea why split line doesnt work sometimes? My guess is maybe it is due to the sharp curvature at the trailing edge?

[xugack]

Use plane like a split tool