Getting a Crack on a Fly Rod When There's Nothing on Your Line?

You can get a crack behind your head at the point where you're turning around, and you hear it when there's nothing on your line. The equation is one half coeficiont of drag cross sectional area times velocity square. Ands min o, the tuitive read would be its way down to the point of nothing, like there us no resistance back there. Feels weyh different. You also have body drag on the line, which is a weird thing i don't understand, and i'm probably about to have to learn that with this paper we're working on. I sort of think about these things while i'm fishing. You definitely think about your caste and