It’s called Tension and has been source of endless Sexyloops discussions since the very beginning of the BoardI believe the rod-leg applies a force to the fly-leg.
I’m happy to continue calling curved rod and loop planes “planes” and not surfaces while I assess how you handle referring to them both as “surfaces”. For consistency you are going to have to stop referring to loop planes for most casts and start referring to loop surfaces as well. Once I’ve seen how much simpler and clearer your discussions become, then I’ll make an assessment between the two.The point is, that the "vertical rod plane" is a flat surface in vertical orientation per definition. That is not my definition, but the by far most common one in physics and math.
If you move your rod along a vertical, but curved surface, I get that very easily and it's precise.
Who is "it", when you are able to make it travel flat enough? The loop?
“It” refers to loop plane (loop surface for you) which is horizontal enough to overpower horizontally and curve the presentation. It’s not fully flat as you point out as a result of rod bending/unbending, so it’s certainly not a loop “plane” for you, but as a loop “surface” it is sufficiently angled to hook the presentation.