Walter & Group...........
This is an important, "heads up" message on fly casting mechanics.
During the past few weeks we've been doing some FFF committee work which has brought to the forefront some new information derived from the study of findings using the Casting Analyzer by Bruce Richards and Noel Perkins (Engineering Dept. U. of Mich.)
Before being enlightened by this along with information gained from Server Sadiki & Walter Simberski of our Group and other engineers and physicists with whom I've spoken, I and most others were teaching that acceleration had to increase during the casting stroke for most efficient casts and best loops. As you know, I even used the term, "accelerated acceleration" to make the point. I was wrong.
We also taught that acceleration should be greatest near the end of the stroke. Many, including me, had a sketchy understanding of the differences betwen, "speed", "velocity" and "acceleration" often mixing up these terms as we taught.
As I understand it, new information includes the fact that an efficient cast with good loop control is best achieved with SMOOTH, CONSTANT ACCELERATION THROUGHOUT THE ENTIRE CASTING STROKE.
This does not change the observation that rod tip speed increases near the conclusion of the stroke and is maximal betwen the stop (or max deceleration) of the hand/rod butt and the rod straight position (RSP) at which point the fly line can overtake the rod tip yielding loop formation.
The acceleration of the rod tip during the rotational phase near the end of the stroke is responsible for the greatest tip travel during the stroke in a given period of time and so accounts for the increase in tip speed during that interval.
Acceleration during this rotational phase can be considered as change in angular velocity of the rod despite the fact that the acceleration itself has been constant throughout the stroke including the preceeding translational phase. Its measurement would be that of rate of change of angular velocity.
One observation has been that the translational phase has as one major objective, the taking up of slack thus making the rotational phase more efficient.
As Bruce Richards has analyzed these elements, he's found that the best loops for distance casting have been achieved with:
1.) Smooth, constant acceleration through the entire stroke.
2.) Longer translational phase to delay the rotational phase, thus placing rotation closer to the end of the stroke.
From a practical teaching standpoint, he has found that the loops improve quickly when he has taught to delay the rotational phase. Since learning that, I've found the same thing.
All this, I feel, can dovetail very well with the simplistic concepts of, "start slow and end fast" and, "loading move followed by power snap", "Pop-stop", "speed-up-and-stop" which are easy for our students to understand.
Bruce will probably write an article for the LOOP on this subject. We'll also start to disseminate this information at our Continued Education Courses the first of which will be at the Marlboro Mass. Fly Show in January.
Gordy