This example shows that a force is needed on the rod leg of the loop to maintain the change in momentum of the fly leg. That momentum change will provide an acceleration force on the fly leg that helps to offset the deceleration of the fly leg produced by drag effects on the line and loop.
This hand casting example used a piece of fluffy yarn with length=2.5 m, diameter=7.6 mm, and a linear mass density of only .00076 Kg/m. This diameter and low linear mass density makes the yarn very sensitive to drag effects.
It was difficult to cast the yarn outside, so I used my garage to get as much protection from the wind as possible. The wind was very light, but still had an effect, so I was casting into it, to show that was possible with tension in the loop, but not when there was no loop propagation.