Server....
Fascinating study !!!
I, too, take issue with the wording, "hard stop". As a lay person, my view of the "stop" at the end of the casting stroke involves various rates of rapid deceleration to an end point for many casts.
Some casters can make that deceleration in less time than others.
For some casts, there is no true, "stop", as I see it. The loop can form at the rod tip as long as there is sufficient deceleration of rod tip velocity that the moving fly line can overtake it. It appears to me that that usually occurs at the rod straight position even if the rod is straight for only a brief period in time.
To put it differently, the caster can make many different casts with no true stop of the hand and butt section of the rod.......but it does appear to be necessary to have that true stop......if for only an instant, for most efficient delivery of the fly line loop when competing for distance.
Gordy
From: Ssadik1@xxxxxxx
To: hillshead@xxxxxxx
Subject: High Speed Data for Straight Rod Tip Trajectory Cast
Date: Tue, 14 Mar 2006 02:20:14 EST
Hi Gordy,Hope all is well and you are enjoying your week of casting activities. These are the high frame rate data and below is some background information relative to the data.~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~Attached is a Powerpoint file (you'll need Powerpoint to view file) and a .jpg photo that contains the high speed record of myself casting. This is derived from data taken a while ago -- summer of 2004. To my knowledge it represents the first data of this form and has the capability to fully describe what is happening with both caster and fly rod. However the complete loop has not been closed at this time because the data can be further quantified to describe the human input kinematics as well as some aspects of the rod structural dynamics. However this record set vividly demonstrates the correct paradigm of casting and should correct a long standing misunderstanding of casting dynamics -- the, in my view, meaningless _expression_ "hard stop".
The parameters of the data collection technology are
- six high speed infrared cameras and illuminators
- reflective markers which are the only objects the cameras can record
- data at 200 records per second
- effective data capture within a volume in space - when markers are near the boundary or beyond it "data dropout" occurs and no subsequent image occurs
- on the data taken most of the markers were on my body - the rod had only 6 markers - the jpg file gives you an idea of the arrangement
Data was data on two occasions and some of the data involved expert casters for the purpose of evaluating special kinds of casts. I examined this data in summer 2005 and it turned out that almost all of these experiments experienced so much data drop-out that it wasn't possible to determine what the fly line would be doing. There were two good records and luckily one was of me so I can distribute the information. Two of the scenes in the file show the position of the markers at important points in time during a forward delivery cast - the type of cast being performed is a "baseball cast" as used for delivering long casts. Bear in mind that the physics of this type of cast requires that the rod hand should move at maintained//high velocity throughout the cast so there can no stopping while the rod is functioning. First position is end of preloading phase//start of cast phase where rod loading occurs. The next scene is the data record where maximum rod loading occurs. The fourth data display is one where all data from a number of frames are plotted and lines are drawn through the data points. The starting point is a time where I deemed significant rod loading (after start of phase 2) had occurred through the time where significant data drop-out had already occurred. Examining the tip trajectory shows that during the period where successful data capture occurred the tip moved in very nearly a straight line over a distance of around eight feet and extrapolating into the time after data drop-out there was probably a total of 10-11 feet of useful (nearly straight) rod tip motion. The final//last several feet of rod tip motion (about the last 2 feet before rod straight position) during rod unloading finds the rod tip dropping (moving in a nearly circular trajectory) and not accelerating the fly line because while the rod tip will be moving faster it is moving downward relative to the now flying flyline. Study of this image demonstrates that achieving a straight line tip travel depends entirely on rod rotation during the third phase (rod unloading phase). This brings me to my displeasure with the "hard stop" terminology. I used to wonder how this worked because when casting properly you do have the feeling as if you are "stopping hard", or at least something is happening but the explanations I have heard over time are so froth with error that it hardly makes sense to even try to discuss them. This data along with any other relevant data or understanding of the underlying physics straightforwardly demonstrates no cause-effect relationship exists. Simply stated when casting a graphite fly rod the casters main control over how the rod unloads is in controlling what is done to achieve peak rod load. Realistically in any given properly executed stroke you get one chance to load the rod and immediately afterward the rod unloads. That chance occurs during approximately the first half of wrist rotation and during the latter portion of wrist rotation the rod is unloading or counterflexing (I stole this term from Jeff Wagner - in structural dynamics we have no special term for free vibrations that fit well into the fly rod context -- so I like "counterflex" because it is highly descriptive). Taken literally the concept of "hard stop" would have the caster loading the rod, suddenly stopping it and unloading occurring after this stop. Neither the human body nor the graphite rod will allow you to do that -- roughly half the critical casting phases are actually decelerating the rod (rotational deceleration really). During part of that period positive work is done on the line to increase its speed and over the rest the caster has reversed the load and is performing negative work necessary to eliminate the free vibrations in the rod. Careful examination of the trace demonstrates that if you were able to stop the rod at peak load the tip would jump upward, and it is the rotation after peak loading that drags the tip downward and creates a straight rod tip motion ( not to mention the increase in line speed). An analogy (to wrist angular velocity) is the similarity to those ultimate performance tests of production hot-rods -- the test where you accelerate to 100 mph then come to a stop. Performance cars are more efficient in stopping than in accelerating but a human with a fly rod doesn't have this advantage to the same degree.
Best regards - Server
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