Walter & Group.......
Take plenty of time to read this one from Eric Cook:-
Gordy,
I agree with what Paul, Mac and others are saying about when and magnitude of power applied has a great influence in determining the shape of the loop. Along these lines, isn’t the thrust nothing more than additional acceleration at the end of the stroke? This past summer, Mac got me experimenting with later and later rotation. Prior to that, I was consistently having climbing loops and even had side arm casts (loops in the horizontal plane) that would be climbing perpendicularly to the loop (climbing in the vertical plane). As my rotation was delayed ever closer to the end of the stroke, the more the loops started to take on a wedge shape. Also, in order to get that rotation later, I had to forget about any kind of stop and to essentially stop when I ran out of arm (in the case of distance casting). I was thinking that this " casting stroke til I ran out of arm" was doing both; a) allowing me to accelerate longer through the stroke and b) creating high jerk for transference of energy (more background on jerk later).
I had concluded that a wedge shaped loop is created when the greatest amount of casting energy is concentrated, in the direction of the cast, at the moment of RSP (loop formation). In the case of a morphing loop, I assume that the point on the fly line that coincides with the rod tip at RSP is still accelerating well beyond loop formation. Is this possible? Does this violate what we accept in loop speed is ½ the fly leg line speed or ½ the sum of the fly leg and rod leg speeds? Can this one point on the fly line still be accelerating even when the rest of the fly line may be at constant velocity? For this last question, I think this would have to be true for the loop to change shape.
When I wrote to you about jerk, I failed to give an example for better understanding. I also forgot to mention that I believe the English refer to it as jolt. Jerk applies to both acceleration and deceleration. Currently, I deal with jerk in industrial robotics and CNC controls. We have one particular CNC routing machine that we cut plastics with at a rate of 1200 inches per minute. The CNC can accelerate from a stop to this 1200 ipm in about 1 second (without jerk inhibited) as well as decelerate to a stop in about 1 second. The jerk parameter in the control is dealt with in percentages, so if I were to adjust the jerk parameter to 50%, the acceleration on this machine to 1200 ipm would double to 2 seconds. Remember, jerk is not a percentage (it is the time rate of change of acceleration), that is just how this particular control inhibits it. Related to fly casting; as you can see from the CNC machine example, if a caster where to possess a high tolerance for jerk (strength to decelerate the rod rapidly, or run out of arm) they would be able to accelerate longer into the casting stroke.
Eric