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>From Peter Lami :
Gordy,
It is probably impossible for a human to make a cast with constant acceleration, nor a perfectly straight line path of the rod tip for that matter. But that missies the point, the closer you can to achieving constant acceleration ... the more efficient the cast. I'm with Bruce Richards on this one!
Peter
[GH] Bruce has made it clear that the accomplishment of "constant acceleration" is what really efficient casters strive to achieve ..... not something that is actually fully accomplished by strict physics definition. Putting it simply, the closer we get to that "ideal", the better the cast.
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>From Bill Kessler :
It is my understanding the the cast analyzer only measures rotational speed. Please correct my if I am wrong. I believe the key is maximum line speed and the size of the loop given the the line at both the tip of the rod and the end of the line and that they both are moving at nearly the same speed. Which in my mind is roughly straight line at that time with no slack. I believe that the maximum energy would be transferred to the line at that time and that resistance would be the next key in over coming distance. I my mind the resistance would be directly related to the size of the loop under a given set of circumstances. I know that this is roughly what the Federation has been teaching the whole time. It still makes sense to me. Please correct me as simply as possible, those of you who disagree.
Thanks,
Bill Kessler
[GH] Bill, I agree.
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Counterpoint re: CONSTANT acceleration, by Bryan Martin -
Gordy,
yes, for some time I’ve considered ‘constant acceleration’ to not be the optimum way to load, particularly for distance. Answering one of the comments, why can’t you have a rate of a rate, it’s just the next order derivative ?
Velocity is the rate of change of position and acceleration is the rate of change of velocity so acceleration is a rate of a rate etc.. In the study of dynamics, rate of change of acceleration is known as ‘jerk’ or ‘jolt’ which is the third order time derivative, d3x/dt3. ‘Jounce’ or ‘snap’ is rate of change of jerk but I guess this and further derivatives, other than being an academic exercise, are unlikely to contribute much to casting in practical terms.
For distance I aim for a smooth increase in acceleration, peaking at the point where the unloading sequence commences. Whether I can achieve the optimum of course is another matter.
Bryan
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[GH] Bryan,
As you know I am not a physicist, though I've studied and have been interested it the subject, especially as it applies to fly casting.
the concept you espouse has always made sense to me leading to my strictly unofficial and perhaps unscientific term, "accelerated acceleration".
To me, that still makes sense. Especially for distance casts. However, after studying the Casting Analyzer (CA) curves and discussions by Bruce Richards and physicist Noel Perkins, I have come to an unprofessional opinion that at least part of the acceleration curve on the CA readouts made from some of our best casts probably do indicate the straight line progression representative of "constant" change; ergo: constant acceleration. For the entire casting stroke ? NO.
Bruce has qualified some of this dilemma by stating that even he has never really seen a perfect straight line progression curve which indicates absolute constant acceleration achieved by any actual caster.
Like the STOP. A great teaching concept .... but something never actually achieved by the caster if we go by the definition of stop as instant cessation of all motion. It is apparent, however, that the closer the caster can get to this unattainable goal, the tighter the loop and the more efficient the cast.
Lastly; in the event the caster could "cross the line" and actually achieve a solid instant stop, the resulting rod vibrations would lead to a grossly inefficient cast with distance not achieved and an erratic layout.
Gordy
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>From Andrew Connell with a request reflected by many of us :
Have fun Gordy, I'd love to know where I can get Bruce Richards' book.
Andrew Connell
[GH] Bruce and I gave the Master's Prep Workshop last Friday at the Conclave. That was something all the participants wanted to know. No better writing for learning the basics and basic physics of fly line design.
The book: MODERN FLY LINES by Bruce Richards, Copyright 1994m Part of Lefty's Little Library Of Fly Fishing.
Bruce assured us that he had been working on this and that the copyright and other considerations had been largely addressed and problems solved. He informed us that the way has been paved for him to make some small additions and changes in the original text leading to a new edition and that he would be working on this.
Gordy
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