I’ve noticed when giving casting lessons that certain people respond better to different teaching techniques. While watching an example of a cast may be more helpful to one person, learning the science behind what is happening during the cast resinates with some people better. I promise I am not trying to get high school physics class on you here but some scientific minded people may find it helpful to understand the physics behind the fly cast to properly learn it.
Most all of us fly fishermen started fishing with some sort of conventional fishing pole. Here you were using the weight of the lure/bobber to cast. In fly fishing, it is the weight of the line that we use to cast. Those long rods that we use serve as a lever to generate line speed. Line speed is the name of the game here and we need to use our lever to increase the line speed.
I am sure most all of you have at some point or another heard a fly cast be described as the arms on a clock, with your forward cast ideally stopping at the 10 o’clock position, the backcast at the 2 o’clock position. As you move your rod between the 10 and 2 positions, you want your lever to accelerate smoothy before coming to a sudden stop. When the rod comes to that stop, the energy that was created by accelerating the rod, gets transferred to the line (using your lever to generate line speed).
A smooth acceleration followed by the sudden stop is key here. This allows the rod to flex (load) which essentially stores more energy in your lever (rod). As you want to increase your casting distance, you need more energy stored in your lever. Increasing the line speed is how you will increase the flex in your rod and therefore the energy stored in it.
I hope this helps give a solid foundation to the physics behind the fly cast. Remember that you spent a lot of money on that fly rod, let it do its job! You don’t want to be breaking a sweat trying to double haul. You want to use the flex and energy developed in the rod from the line speed. This means you can use less effort to cast further.
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