My previous post, Part 1: The Mechanics Of A Fly Cast In One Word, describes the fly cast as a rotation of the rod. As such, the velocity ratio (how much the rod tip moves compared to the rod butt) increases as the center of the rod’s rotation approaches the caster’s hand.
If you haven’t read that post, the significance of this discussion may be harder to understand.
For the purposes of this post, we will now consider three joints to help rotate the fly rod: the wrist, the elbow and the shoulder. As we compare these different centers of rotation, please keep in mind that the context is for casts up to 80 feet, and not distance casting.
The Wrist
Each of our wrists is slightly different, but a typical range might be 140 degrees from flexion to extension. For perspective, one clock hour is 30 degrees, and a cast from 10 to 2 o’clock is 120 degrees.
When our forearm is vertical, most of this range can theoretically be used to rotate the rod. However, as the forearm becomes more horizontal (eg. towards the end of a front cast), the range of useful motion to rotate the rod decreases significantly.
The wrist is naturally very close to our casting hand throughout the cast. As a result, it is capable of producing one of the largest velocity ratios at any time during the cast. But, because the wrist is the weakest (but fastest) of the three joints capable of rotating the rod, its role and timing in the cast depend on the load and trajectory of the cast.
When the line outside the rod is long, the wrist is best used with a stronger joint that has started the fly rod’s rotation. When the line outside the rod is short, however, it may initiate the rotation of the rod and it my be the primary engine for rotation.
The Elbow
A typical range of motion for the elbow might be 150 degrees from flexion to extension.
When the upper arm assumes a horizontal position, most of this range could be used to rotate the rod – depending on the wrist position. When the upper arm is vertical, hanging down from the shoulder, the range of useful motion for casting is reduced by approximately 90 degrees.
The elbow is a fixed distance from the casting hand, and as a result, it’s velocity ratio is fairly constant when the wrist is locked and the elbow does not translate forward.
The Shoulder
The shoulder has the largest range of motion of all three joints with approximately 230 degrees of motion from flexion to extension. The range that is useful for casting depends on the positions of the elbow and wrist.
Unlike the other two joints, the shoulder’s velocity ratio is variable. When the casting hand is close to the shoulder (eg. at the beginning of a roll cast or a front cast), the shoulder has a velocity ratio similar to the wrist – very large.
However, as the casting arm extends out from the body, the shoulder’s velocity ratio decreases: first below that of the wrist, and then, that of the elbow.
Table 1: Summary of each joint for rotating the fly rod
How Should We Make A Front Cast?
The shoulder is the strongest of the three joints for most casters. Because the caster’s hand starts a front cast in close proximity to the shoulder, it makes sense that we should use our shoulder to start rotating the rod.
When the shoulder rotates the rod with the casting hand in close proximity, the shoulder offers an unbeatable combination of range, strength, speed and velocity ratio of any of the three joints – especially at the beginning of a cast when we need a large force to move a body at rest.
During the shoulder rotation, if we start rotating the rod with our elbow too early, the arm becomes extended. As the arm extends, the shoulder’s velocity ratio decreases significantly. We might accept a decreasing velocity ratio of the shoulder if the elbow’s velocity ratio increased in compensation, but the elbow’s velocity ratio remains fairly constant.
So, with our casting hand near our shoulder, we should start rotating the shoulder down with gravity. As the shoulder approaches the end of its rotation, begin rotating the forearm down (again, assisted with gravity) using our elbow joint. Just before the abrupt stop of all joints and the rod, a wrist flick could be initiated.
At the end of the cast, the arm isn’t extended because we’ve tried to maintain the velocity ratio of the shoulder.
This is arguably the most efficient way to perform a front cast.
“We should use our shoulder to start rotating the rod.”
For comparison, find some roll casting videos online. A roll cast is essentially a front cast without the line aerialized.
Many of the videos that you will find start with a casting hand near the shoulder. Regrettably, most casters do not start with a downward rotation of the shoulder. Instead, many of the videos show a caster extending the casting arm out so that the hand travels horizontally forward. Two joints create this movement: the opening of the elbow and the upward rotation of the shoulder.
Opening the elbow rotates the rod forward. Fine.
However, the upward rotation of the shoulder has a “net effect” of pushing the rod forward, because the rotation of the upper arm (from a vertical position to a horizontal one) moves the elbow forward.
The result is a tiny contribution to the rod tip speed, but at a huge cost. Rotating the shoulder upwards (to make the elbow rise) expends much energy because the exerted force must be greater than that of gravity on an extending arm.
For many different reasons, this method of casting is utterly inefficient.
What About The Back Cast?
The back cast requires more force than the front cast because the back cast is made with an upwards trajectory – against gravity – whereas the front cast is made with a downwards trajectory – with gravity.
The following discussion assumes that the front cast has ended with an efficient front cast – not with the arm extended.
When we start the back cast, the shoulder and elbow joints are almost equidistant from our casting hand. The weakness of the wrist (despite its high velocity ratio) and the distance of the remaining two joints to our casting hand does not make any single joint ideal to use to start the rod’s rotation.
As a result, there are two legitimate choices for rotating the rod tip up and back during the power stroke: (1) use the elbow and shoulder together, or (2) use the elbow, shoulder and wrist together. Regardless of which option we use, we would still need to maintain a straight rod tip path, and we might use a quick or quicker wrist flick at the end to give the rod and line a little more zip.
Epilogue
Steve Rajeff doesn’t use much shoulder when he casts, but Steve is a Casting God – an immortal. His arm strength is superhuman, and most of the time, he doesn’t need to use his shoulder.
For the rest of us mortals, our arm strength is such that we must take advantage of our shoulder. It offers a combination of range, strength, speed and velocity ratio that is unrivaled for beginning the front cast.
And when all of the rotational forces are abruptly stopped at the end of a front cast, or when we start rotating the rod up to launch a back cast, there is a huge load directed downwards below the caster’s hand. This is why placing a foot under (or at least in proximity of) the casting hand is so critical in our stance.
When we start to realize that an efficient casting motion is an up and down rotation of our shoulder, elbow and wrist joints to make our line go forward and back, we have made a major breakthrough.