How do you create a sketch where a loft intersects a plane?

I am creating a tapered wing section and need tapered ribs.   To do that I create a sketch of the root rib, then create offset planes where each of the other ribs go.  On the last plane I create the tip rib.  I then create a loft section between root and tip.  Each of my ribs is the intersection of the loft and each plane.  But.... when I create a sketch on the plane and tell it to USE what looks like the intersection line, it pulls the line from the root and the tip... How do I get it to only use the intersection of the loft and the plane??  Also is there an easy way to tell it to use all the intersect points instead of having to click on each segment?