Fishing Tips: Fundamentals of Loop Shape

Few images in sports are as captivating as an unrolling loop of fly line traveling over the water toward a target. Check out casting editor Jeff Wagner’s thoughts on the principles of good loop formation.

The line, leader and fly gently land on the water’s surface. Moments later there’s the gentle sip of a rising trout and the line goes tight. Similarly, few things cause more dismay and frustration to an angler than a cast gone wrong, whether it’s because of a tangle that forms in the air or a cast that lands many feet from the target, yet still scatters the fish.

Often at the heart of those aerial catastrophes is a poorly-formed loop. The loop is the shape of the fly line as it travels through the air. Interestingly, loop shape is not talked about to the extent you’d expect, given its importance. And whether casting a single-handed or two-handed rod the same principles apply.

Let’s start with the basics. What is the purpose of the fly rod? Why do we spend $1,000 or more for a fly rod? On its own it does one thing and one thing only: it stays straight. That’s it. But fly rods are designed to do so much more. They also bend, and the goal of fly casting is simply to bend, or load, the fly rod to get the fly line moving. The load comes from moving the rod through the air and dragging the weighted fly line behind it. That by itself is quite easy. The challenge in doing it efficiently, smoothly, consistently, and with the right amount of energy.

The bending of the rod can be explained by a number of principles and many writers before me have described their interpretations of what happens during the cast. For the purpose of this discussion, we can boil everything down to this: The fly line follows the path of the rod tip. This one statement has prompted a great deal of debate lately, some of it incredibly heated.

But this one statement is true. We could get into the physics of it all and I’m sure there’s an engineer somewhere who will spew out a plethora of equations that supposedly prove me wrong. But I can simply pick up my fly rod, (and I encourage you to do the same), and make a few casts. If I wiggle the tip of the rod the line wiggles with it. The distance that I move the rod right to left is mirrored in the fly line. Each move made that translates into rod-tip movement results in fly-line movement. The more extreme the movement of the rod tip, the greater the movement of the fly line.

This one principle will serve you well if you apply simple cause-and-effect. First, let’s talk about a good loop. Good loops are formed with a straight line path (SLP) of the rod tip. For you engineers, the tip’s path is not a perfectly straight line but more of an average, as the tip of the rod dips slightly at the end of the stroke to allow the oncoming loop to pass over it. But if the tip of the rod moves in a straight line the fly line will follow. The result is a straight-line cast.

So, how do we move the rod to cause SLP? When the rod is moved from the beginning to the end of the casting motion we call it the casting stroke, and it involves both angular or rotational movements – also called the arc – as well as linear movement. The arc is the angular change or change in degrees from the beginning to the end of the stroke. The linear movement can be considered the distance the hand moves along a straight line from the beginning of the stroke to the end. Combined they form the casting stroke. While it is possible to make a cast with only one of the motions it is most efficient to incorporate both.

Casting efficiently will serve you well, and efficient casting is achieved by focusing on two things:

  1. The cast from start to stop is a progressive speed-up, a smooth acceleration and then a stop. You start at zero mph, accelerate and end at maximum speed just before your hand stops. No herky-jerky movements – smooth is the word.
  2. When possible use the larger muscles of the arm, shoulder, back and even torso to make the cast. You can cast with small muscle groups in the wrist only, but this is not advised for long-term success and joint health.

For a specific length of line cast at a certain speed with a particular rod flex, the hand must move a particular distance with a particular arc and a certain amount of energy to create a straight-line path of the rod tip. When done correctly a classic U or V-shaped loop is produced as the line unrolls. From this we can bring to light a particularly good principle. That is, a longer cast requires a longer stroke. If you make a 20-foot cast, the arc, stroke length and energy used can all be minimal. But as the casting distance increases it is necessary to increase all of the components of the casting stroke. How do you know if you have done it correctly? By looking at the loop, of course.

The loop is an indicator of all things happening in your cast. A good loop – no matter what anyone says about casting style or the “proper way to cast” – is a good loop, and indicates a cast performed correctly. A loop with a distance of three feet or less between the top and bottom leg (fly leg and rod leg), and which is U-shaped or V-shaped, is considered a well-formed loop.

Of course there are times where you won’t want a loop that small and times when the loop changes shape unintentionally. Let’s consider a few of those.

  1. Wide Loops. These are loops wider than three feet, but which still have legs parallel to one another. They are formed because of a slightly arcing or domed path of the rod tip, or from dropping the tip of the rod too far at the end of the forward or backcast. Wide loops are great for casting heavy flies, multi-fly rigs, and casting with a tail-wind.
  2. Non-Loops. Often these are casts made by “wristing”or casting primarily with the wrist and not adding enough power and/or enough linear movement. Beginning fly casters are often prone to this problem. The result is that the rod is often “underloaded.” The tip of the rod moves in a pronounced arc or domed shape, and the legs of the loop are not parallel. This can be useful if performing a lob cast or casting very heavily-weighted flies or multi-fly rigs, but more often than not it is problematic.
  3. Tailing Loops. These are very common and often the nemesis of the intermediate caster. In this case the rod tip dips down during the casting stroke, causing the top leg of line to drop below the bottom leg. This can be caused by applying too much power, or power at the wrong time. Another cause may be the line touching the water during the casting stroke. Note where the tailing loop occurs, as this tells you where the dipping in the rod tip’s path occurred. If the loop tails near the tip of the rod, the dip happened early in the stroke. If the loop tails near the end of the fly line, the dip happened late in the stroke.
  4. Non-Parallel Legs: A loop with parallel legs has legs in the same plane no matter the orientation. This means that if you cast vertically the top leg should be directly over the bottom leg. If casting at 45 degrees to one side the loops should still be parallel, but tilted at 45 degrees. Legs out of parallel introduce slack that takes up precious casting stroke. Out-of-parallel loops also cause the line to move in opposing directions and can cause inaccuracy on delivery. But, there are times when having legs out of parallel is good. Continuous-tension casts that are made by swinging the line out and away from the caster on the backcast are good examples.
  5. Good Loops. A good loop is U or V-shaped, less than three feet in height, and is useful in many, but not all situations. A good loop is the result of a nearly straight-line path of the rod tip, smooth acceleration, and good stop of the rod.

Of course we could expound on casting loops for some time. But, these are the basics. By following these principles your next casting session will be more successful. Work to create good loops with as little energy as possible. Keep the legs of the loops parallel. And most importantly, have fun! If these things aren’t happening, think back to what a good loop is and how to create it.