In two previous posts (Part One and Part Two), we discussed how late acceleration of the rod can lead to the fly striking the water behind the caster in different ways.
In this post, I would like to explain another way that can cause the fly to hit the water behind the caster – without late acceleration. This is a problem that can mystify better casters making long casts.
One of the tenets of fly casting is that the trajectory of the back cast must be 180° away from the front cast. One of the reasons for this principle is that we do not want to create a vertical force vector.
Vertical forces open the loop, and they also rob the cast of distance.
Moreover, if the trajectory of the back cast is higher than the front cast, the fly will be pulled down towards the water. In Figure 1a, the back cast has straightened out with an upward trajectory. When the rod tip comes forward with a level trajectory (Figure 1b), it pulls the fly toward the rod tip. This force along the fly line is composed of a horizontal and vertical vector. See Figure 1c.
Although the rod tip comes forward with a level trajectory, the fly is pulled downward since the fly starts higher than the rod tip’s path. The fly will continue to be pulled downward until the fly becomes level with the rod tip. The downward momentum of the fly will cause the fly to continue travelling below the level of the rod tip. This downward momentum and the additional force of gravity on the fly (and line) will now be countered with an upward force vector while the fly (and line) remain below the rod tip.
The angle of the line (between the rod tip and the fly) in Figure 1c isn’t aimed at the water behind the caster. So, it’s less likely that the fly will slap the water behind the caster without one additional problem.
If the caster waits too long to come forward, and the line falls towards the water with gravity, now the line is more likely to strike the water behind the caster as the rod comes forward (Figure 1d).
The arrangement of the line is starting to resemble the first post in this series. That first video has a significant amount of line angled toward the water at the end of the back stroke. In addition, even though the caster isn’t waiting to come forward, the line falls because it takes so much time to remove the slack from the big loop.
If you are wading in deep water, and the fly hits the water behind you (not because you are driving the fly into the water), the instinct is to make the trajectory of the back cast higher. However, the higher you form the loop on the back cast, you create a larger force vector that pulls the fly down towards the water when you come forward.
There are various remedies. But, if the caster does not move to shallow water, if the caster doesn’t shorten the cast, and if the front cast trajectory remains level, then it is important not to allow the line to fall after it has straightened out and to lower the back cast trajectory so that it is also level.
In this case, the generation of a vertical force vector is not dependent on the size of the loop since it occurs after the line has straightened out.
Some might argue that waiting too long to start the front stroke is another example of late acceleration (coming forward). I wouldn’t disagree. But, the two previous posts discussed late acceleration DURING the stroke that led to the fly or line slapping the water behind the caster. This case involves a mismatch in front-back trajectories and a late INITIATION of the front cast.
There are many ways that the fly or line strikes the water behind the caster. To avoid the more common mistakes, it’s important to cast within your means so that you form reasonable loops that straighten out after the back cast; avoid wide loops and slack in the front cast that necessitate using much of the back stroke to eliminate the slack resulting in late acceleration that drives the back loop into the water; don’t let the line fall after the line has straightened for the back cast; and, make sure that the trajectories for the front and back casts are 180° apart.
Glen Ozawa, OD
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