In a previous post, I explained that the reel should be a counterbalance. And Kevin’s comments made me think that I gave an unconvincing explanation since the post was based mostly on what I feel. And so, I have spent a bit (a lot) of time thinking about the science of the cast.
I am not a physicist. My terminology or nomenclature may be incorrect, but I think that the ideas herein are worth considering.
The line speed that a fly rod can generate depends primarily on the caster’s ability to rotate the rod while keeping the path of the rod tip relatively straight.
Since high line speed is more important when making longer casts, the question is whether a reel-heavy outfit makes it easier than a balanced outfit to rotate a fly rod over a longer arc.
Initiating The Cast
At the beginning of a cast – whether it is a front cast or back cast – the reel is in a position to rotate downward with gravity. See figure below.
Initially, a reel-heavy outfit, compared to a balanced outfit, will place more force on the rod below the center of rotation causing the rod to bend and the tip to rotate eventually in the opposite direction faster.
In contrast, the mass above the center of rotation prevents a balanced reel from rotating downwards quickly. For the most part, the caster must initiate the stroke, and thus, the caster causes the rod to bend.
Acceleration During The Cast
On a front cast or back cast, if the center of rotation does not move, once the rod becomes vertical, the reel stops moving downwards and now starts moving upwards. See figure below.
Once the rod becomes vertical for an outfit with a heavier reel, the reel’s change in direction means that, instead of helping the rotation of the tip, the reel is now slowing it. The caster must apply force to the handle to maintain the rod’s initial acceleration. Timing and the magnitude of that force make fly casting – an already difficult task – even harder.
In contrast, a balanced reel doesn’t affect the rotation of the rod as much as a heavy reel when the reel’s path changes to an upward direction due to the distribution of mass along the rod. This allows the caster to apply a more uniform force throughout the stroke.
Movement Of The Rod’s Center of Rotation
Since the trajectory of the front cast for most fishing distances is downward, a rod’s center of rotation may move downward. Any downward movement of a rod’s center of rotation during the front cast extends the downward path of the reel and offsets some of the upward movement of the reel. See figure below.
Since a heavy reel causes the rod to bend more at the beginning of a stroke than a balanced reel, and if the reel falls over an extended path, less force may be needed to attain an adequate line speed to make the loop unroll completely.
However, such is not the case for the back cast.
In contrast, the back cast has an upward trajectory. To maintain an upward trajectory during the back cast, the fly line needs to be accelerated up – against gravity. Consequently, the force required to accomplish the rod rotation is much greater for the back cast than the front cast.
Moreover, to prevent the fly or line from slapping the water behind the caster for long casts, the reel must be lifted upward to extend the upward path of the rod tip.
The elevation of the rod’s center of rotation during the back cast has several consequences. First and foremost, the upward movement of the rod’s center of rotation makes the initial downward rotation of the reel shorter. In other words, the reel does not have much time to accelerate with gravity. See figure above.
And when the heavy reel must be rotated in earnest, it will be more difficult to rotate than a balanced reel due to its larger mass and the lack of mass above the center of rotation.
Lifting a heavy reel will also tire the caster faster than a balanced reel simply due to the heavier weigh of the outfit.
To state the above in slightly different terms, a balanced reel will be easier to rotate up against gravity compared to a heavy reel for two reasons: first, the balanced reel is lighter, and second, the mass of the upper parts of the rod help offset the force required to rotate the handle. In addition, a balanced reel will be easier to lift (against gravity) because the overall outfit is lighter.
Dampening
At the end of a long, powerful stroke, it is necessary to dampen the rod. Without any dampening, the counter-flex and subsequent flexes of the rod tip would introduce waves in the rod leg of the loop. Slack is the killer of line speed and distance because, when present, part of the stroke is needed to make the line tight instead of accelerating the line.
Reel mass helps to dampen the rod. One of the easiest ways to understand the explanation is with the concept of momentum. Momentum is determined by two variables: the product of mass and velocity.
When the upper parts of the rod (small mass) are moving at high velocity when the rod is accelerated to a stop, the counter-flex and subsequent flexes at the top of the rod cause the bottom parts of the rod (reel, blank, and handle) to move in the opposite direction. The resulting velocity of the reel will be much lower than the tip because the bottom parts of the rod are much heavier than the top parts.
Since the velocities of the tip and the reel occur over the same period, velocities can be converted to distance.
Essentially, the mass of the rod below the center of rotation determines the amplitude of these vibrations. During these post-cast vibrations, a heavy reel will move less than a balanced reel. As a result, the heavier reel will dampen a rod better than a balanced reel. This is the one true advantage of a heavy reel over a balanced reel.
Epilogue
A reel that it is too heavy or too light for an outfit is not the end of the world. The outfit will still cast.
If all else is equal, however, a balanced rod is easier to rotate than the same rod outfitted with a reel that is too heavy when the greatest force is needed: during the back cast. And, if you didn’t know, every good front cast needs a great back cast.
Knowing the science of the cast is not required to form a tight loop. But, most people can feel the difference between a reel-heavy outfit and a balanced one. A balanced reel will not initiate the cast. As a result, the caster rotates the rod and feels it bend.
I am always astonished by how much more I can feel the rod bend when I continue to cast a rod with the reel off the rod and in my pocket.
In my opinion, a balanced outfit provides more feel than a reel-heavy outfit. The combination of a heavy reel bending the rod and less of the caster’s force needed to attain an appropriate rod tip velocity for a given casting distance during the front stroke results in less feel.
The effect of the reel’s mass is typically more exaggerated during the front cast compared to the back cast due to the extended path downward in the front stroke.
And finally, we don’t normally use casting muscles in day-to-day activities. For most people, as a result, a light outfit that is balanced would be better than a heavier outfit that is also balanced. I think that this recommendation is particularly important for people of smaller stature since the reel needs to be rotated up and elevated against gravity during the back cast.
The one true advantage of a reel-heavy outfit is its ability to dampen. Since dampening becomes more critical with longer casts, I recommend a balanced outfit to learn how to make longer casts. Once you get good, you can alter your outfit to your liking – including the option to make it reel-heavy.
A word of caution: once you feel a good rod bending – whether it is stiff or soft, fast or slow – it is addicting. And then, there’s no turning back.
Glen Ozawa, OD
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