Loop width control is a recurrent topic in casting instruction. Several aspects govern loop width, but “matching casting arc to rod bend” is what instructors use the most; so “if your loops are too wide narrow your casting arc” is the usual fix we offer.
Let’s say that I am bass fishing with a popper knotted to a short, stout leader, followed by a bass taper #7 weight line. I want to cover a very promising spot, just a small hole among low hanging branches, which asks for a side cast with a narrow loop.
First try my line crashes against a branch: I need to narrow the loop considerably. So keeping everything equal I decrease my stroke angle… and the loop fails to straighten, for same acceleration along a smaller angle gives, obviously, less line speed.
So keeping the same stroke angle I increase the force applied to the rod to gain that lost line speed. But, hold on one second! More force applied results in more rod bend, and a basic principle of casting mechanics says that we have to match casting arc to rod load! So this time I must increase the stroke angle! Now I widen the angle applying more force at the same time… and my popper curves to the left hooking a branch, as a result of an overpowered cast.
Reducing casting stroke angle to narrow your loops doesn’t work in isolation. No wonder that beginners have a hard time in controlling loop width, as it is a question of very fine-tuned adjustments, more than just varying “casting arc”.
Playing with loops by changing the casting stroke angle is fine; play with force and stroke length as well just to see what happens.