Concavity? Not So Much


A “concave rod tip path” during the casting stroke is what lies behind the problem; at least, that is the most popular explanation about the tailing loop issue. Being a simplified view it may work at a basic level, reality is a bit different though.

Short cast/short stroke, long cast/long stroke; a very popular expression that makes a lot of sense. To send our fly to the target we must impart some speed to the fly line. For that we apply force to the rod butt, accelerating it along a given length.
As when driving our car, to get a relatively low speed we only need to accelerate along a short distance; to get a higher speed we must accelerate along a longer distance. The same happens when casting a fly line: as our target gets farther away our casting stroke gets bigger, both in length and in angle. That is the case as well when throwing a ball at different distances. So the use of a variable length acceleration lane is somewhat ingrained in our brains as a natural motion.

By applying force to the butt the rod gets some flexion, and the higher the acceleration the bigger that flexion is. That results —when casting with the rod upright— in the rod tip moving downward in the vertical plane. That motion is a double-edged sword, though: on the one hand it is the main element of casting efficiency, as it allows for a curving motion of the rod butt to turn into a —close to— straight one of the rod tip; but, on the other hand, if that downward motion isn’t properly executed it causes problems, i.e. tailing loops.

That is the case on this demo of a tail due to a too narrow casting angle performed by Paul Arden. Notice that it shows a somewhat concave tip path —similar to the cross section of a bowl— as rod tip concave trajectories has been traditionally understood:

So, how is it possible to sustain that concave, bowl shaped rod trajectories, aren’t actually seen in the real world of tailing loops, as I suggested at the start of this article?

As stated before, increasing the casting stroke as we increase the casting distance is an intuitive response. But look at Paul’s rod position when it gets straight at the end of the forward cast: it is very close to the vertical! I have never seen anybody stopping the rod so high in real casting; in fact what is common place is the opposite: too wide casting arcs resulting in big, rounded, inefficient loops.

In my experience ultra-narrow casting angles only occur in casting demos. I know instructors who claim they have had students showing tails due to excessively narrow casting angles, but I doubt that they were as extreme; and without an extremely small casting angle you can’t get that bowl shaped trajectory of the tip during the whole stroke seen in many illustrations depicting taling loop causes. In my view, if super narrow casting angles belong to the demos realm only, so do concave tip paths.

So, how is the rod tip path that generates a tailing loop? Well, it normally is a small anomaly breaking the slightly convex line drawn by the rod tip during the stroke; something like a dent, with the rod tip going down and then up again, more a check mark than a bowl. The reason? A sudden peak in the force applied by the caster. There are a couple of causes for that, and one is… too narrow a casting angle! An extremely narrow angle makes impossible to avoid a tailing loop: we have to attain the line speed needed to get the fly to the target; if the available acceleration lane is too short the only solution is a very high acceleration, i.e. bigger force, so the rod tip is forced sharply downwards… and it can’t help but draw that close to ideal concave path shown on the video above.

The following shows Paul demonstrating a tailing loop due to creep. Notice how a wider —although still purposefully decreased— casting angle fails in producing a bowl shaped tip path, making a sort of dent in the rod tip trajectory instead. Notice as well, how Paul not only decreases his casting angle at the start of the forward stroke —the creeping problem proper— but also at the end, stopping the rod earlier than in the previous cast. When you know how to accelerate properly it is difficult to do it badly even when creeping; by robbing yourself of part of the angle in front, you can tail more comfortably. But when showing tails due to creeping that is cheating, isn’t it?

If  casting angle width were the main source of tails, these would be much easier to solve.
However —after shooting and studying many slo-mo videos— what I see as the most common source of tailing loops is a faulty acceleration of the rod, an increase in the speed applied to the rod butt that isn’t progressive enough; that means that, at some point, there is a sudden peak in force that drives the tip momentarily down. That produces a tailing loop whatever the width of the casting angle we are using.

Here is an example of a pretty wide casting angle resulting in a huge tail, and showing just a dent in the rod tip path. This is a real tailing loop, not one made on purpose:

Tailing loop path

Experimenting with tailing loops is always interesting. I am of the opinion that all of us have a preferred casting stroke that works for most of the usual fishing situations we face; so if you are accustomed to 9’ long rods take a short one, let’s say a 7’6”, for a casting session. Most probably you will cast tail after tail till you are able to adjust to the unfamiliar rod. Take the same cast to put your fly at the same distance and see how the same casting stroke doesn’t work for all rod lengths. But this is stuff for another article.

The following picture shows the result of one of the firts casts with a 7’6” rod after  years of fishing with nine footers:

Mysterious creature

Final note:
Tailing loop have nothing to do with “overpowering”: we can cast a good shaped loop with very different speeds, from slow to fast. For instance, when casting against the wind we have to “overpower” compared to the same cast in calm conditions, are we doomed to tail in that scenario?
It isn’t about the amount of line speed, it is about how we get that speed.

7 comments on “Concavity? Not So Much

  1. paracaddis says:

    Nice explanation.. I think we are all guilty of “cheating” when demonstrating tails.. 😦

    Liked by 1 person

    • Aitor says:

      Yes, most of the tailing loop demos have little to do with real cases. I have studied many videos and found some cheating even in commercial ones; once I shot a slo-mo video of my iPad screen while playing a video by a pro showing tailing loop causes: he cheated in all of them.
      It is hard to learn how to accelerate correctly, and equally hard how to unlearn it. 😉


      • Aitor says:

        In my view the most reliable way of demoing a tail without cheating is by using a brisk, forceful, ulnar/radial deviation of the wrist; it is a common fault in the real world also:

        Liked by 1 person

  2. Hi Aitor,
    Nice article. The tailing loop in fly casting history was defined to be a significant wave in the fly-leg crossing the rod-leg. Since that old definition managed to enter all fly casting instructor certification exams, candidates worked out the easiest ways to create such extreme waves. In my teaching reality instead I hardly ever see such extreme waves, but small waves being shaped into the fly-legs mostly not crossing the rod-leg (seen from the side view in of course usually average sized loops). Those smaller waves aren’t verd hard to be demonstrated in exactly the way students do this! In my experience, if I understand a cause, I usually can demonstrate it as well as helping my student to get rid of it in short time (minutes mostly). Key is in understanding the cause(s) AND the level of the cause(s). All else in your article I can’t agree more with. Regards Bernd

    Liked by 1 person

    • Aitor says:

      “The tailing loop in fly casting history was defined to be a significant wave in the fly-leg crossing the rod-leg.”

      Hmm, I think that there isn’t any official definition of tailing loops that focuses on the wave character of the issue. The FFI talks about crossing twice but no mention of waves.
      That is a problem because the main characteristic of a tail is that it is a transverse wave propagating down the line. If it crosses twice or doesn’t cross at all is just a question of quantity and not quality.
      Moreover, many times that crossing depends on the position of the viewer, so it isn’t a good element to use in a definition.

      Thanks for your comment!


  3. Agree. But having the fly-leg crossing the rod-leg twice, asks for a significant wave as far as I can tell. Add the typical small issue and you won’t get two crossings *tyoically seen from the side view). Oh, and you may fail the exam. 😉

    Liked by 1 person

  4. Aitor says:


    Even big tails can fail in the “crossing twice” department:


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