Walter & Group.......
This is Bruce Richards' answer to our last Group message. I've, again, placed Bruce's words in text in bold red italics prefaced in each case by ****.
A great deal to be learned from studying this despite its length !
From Scott Swartz :
Gordy,
Thanks for posing the question to Bruce. I think what he has to offer about
loop shapes makes perfect sense. I appreciate him, and everyone, for coming
in on this puzzle with some pieces. I have a much better understanding
thanks to the folks here.
I now have a tangential question based on Bruce's response. I don't want to
hijack my loop shape question (or any further answers) so feel free to wait
to post this or just give me your thoughts.
I understand SLP makes the tightest loops and according to Bruce and Noel's
work constant acceleration helps us best achieve the SLP.
Q. Why would it seem loops get tighter with the old "speed up and stop"
that was the mantra for so many years? I used Lefty's term but almost all
popular instructors of our time have a name for it...power
snap...micro-second wrist, ect... SS
I wonder if attempting to SUAS is simply a mind game that helps to maintain
acceleration and SLP or is there something "magic" about the last movements
of the cast before the stop. To quote Lefty again..the cast goes in the
direction of the speed up and stop. By example: a moderate length cast,
with a huge convex rod tip path, through a long wide arc, would normally
lead to a wide open loop but can be turned into a tighter loop with a
moment of exaggerated acceleration of the cast just before the stop. What
makes this work and why? Were we all mistaken in teaching students last
minute acceleration all these years? I believe there must be more influence
to the loop shape from the final moments of the stroke than there is from
all the rest. Could that be true? SS
Scott Swartz
*****All the historically popular terms for how we accelerate the rod can
be correct, but lack the specificity needed to truly understand how the rod
should accelerate to get the best result. Certainly a great cast is made by
speeding up and then stopping the rod, a motion that can also be accurately
described as a "power snap", which could be translated to Doug's "micro
secondwrist". If you think about it, the best casts are made with delayed
rotation that is then quite quick, which Doug thought was well described by
"microsecond wrist". But if you didn't already know precisely how the rod
should accelerate, none of those terms really tells you. "Speed up and
stop" could easily mean any sort of non-constant acceleration and include
big loops, tailing loops, etc. Although the terms seemingly work, I don't
think it is because they lead anyone to understand just how a rod should
accelerate for best results. Fly casting is one of those sports where most
people will eventually get the feel of how it should be, if you can get
them close enough to ideal to recognize it. For instructors and better
casters wanting to improve, I think it is very important that a higher
level of understanding is reached.
*If an instructor thinks that rod acceleration should be slow at first, then fast later, and students follow
that instruction, results will be disappointing at best, for everyone. * (Bruce)
*Note that Bruce didn't say, "rod speed", here. He stated, "rod acceleration". With smooth, constant acceleration, the rod speed is slow at first, then fast later. Still fits with the old dictum of, "start slow and end fast". G.
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From Gordy ~~~~~~
Scott: Let me jump in here with an answer to your question..... then
we'll ask for Bruce's critique.:
To some extent, the loop can be altered with what we do at the conclusion
of the stroke, as I see it.
I see nothing wrong with Lefty's, "speed-up-and-stop", Joan's,"Power-Snap"
or Doug Swisher's, "microsecond wrist". All these are discriptions which
were very good for getting the movements of making a tight loop into
students' brains without confusing them with more scientific terms. They
all worked, and still do.
Then Lefty added: " The size of the loop is determined by the distance
that you speed up and stop ". Many took umbrage with that statement, and I
did, too .... until I talked with Lefty and understood that what he meant
was that when you speed up (accelerate) to a stop over a long interval, you
usually dip the tip of the rod down and unload it way below the oncoming
line forming a wide loop. When you do it over a short interval you don't
dip the rod so far down below the oncoming line and you get a tight loop.
The former yields more convexity of the path of the rod tip than the latter
at the end of the stroke. G.
****Simply a matter of matching rod arc to rod bend. Most beginners throw
big loops because their rod arc is too big for rod bend. Shortening the
distance of acceleration is reducing the rod arc, and the loops will get
better. I don't like the wording, but it is hard to argue with the base
logic. (Bruce)
As I teach with Lefty, I am impressed with his way of using plain language
to get students to cast better even when the words are not strictly,
"correct" from a physics standpoint. As I watched Joan reap miracles with
her students, I'm equally impressed that her language works. G
****Hard to argue with their success, but no one method works with
everyone, and some instructors are pretty firmly locked into "their way" as
the best way, regardless of how the student learns. ( Bruce )
The concept that a convex path of the rod tip yields a wide loop whereas
the straight line path of the tip yields a tight loop, and a concave path
of the tip can yield a tailing loop is correct ..... but utterly
simplistic. We've come a long way from that as a final answer, especially
as we try to analyze complex casting problems. G.
*****True. Great instructors know precisely WHY the rod tip path was
concave, convex or straight and can simply explain it to any student in a
way they can understand. (Bruce)
One could say that failure to teach the concept of the straight line path
of the rod tip combined with smooth, CONSTANT, acceleraton was a flaw ......
but until recently, those physics parameters had not yet been worked out.
Never the less, those teachings worked ....because they got into student's
brains and casting arms with the use of plain language. Simply put, if I
tell a new student to use constant acceleration and to create a straight
line path of the rod tip, I've accomplished nothing .... because he won't
understand it. G.
*****A very good point Gordy. When we, as instructors, discuss casting
dynamics we use a lot of terms and I wouldn't consider using with a
student. Our discussions are to insure we all have the same basic
understanding of how casting works, and that can't be done in generic,
simplistic terms. The best instructors have an indepth and detailed
understanding of how casting REALLY works, but can convey that to any
student in a way that particular student can understand and respond to. It
makes no sense to me to try to explain "constant acceleration" to a student
when I can simply tell him/her to start accelerating a little bit later,
and faster than they are doing now. Start later, go faster, gets a much
better result. (Bruce)
I look at the "last minute acceleration" as no more than the logical
extension of constant acceleration .... not necessarily the increase in
rate of acceleration which the, "jerk" or "jolt" described by Eric Cook
represents. (I used to teach, "accelerated acceleration" until the
engineers and physicists shot me down in flames.) G.
*****In nearly every case of a good caster throwing less than perfect loops
the problem is acceleration that starts too early, and too slowly. Once a
caster gets beyond the big loop, tailing loop stage, that is the single
biggest flaw to fix, in my opinion. The fact that acceleration is slow
early means that it cannot be constant, that has been predetermined in the
first few fractions of a second of motion. I don't view late acceleration
as an extension of constant acceleration, but the only way to achieve
constant acceleration. Of course, how late can vary with the goal, for
maximum distance maximum rod bend is the goal and the later and more
powerfully the rod is accelerated, the more the rod bends. (Bruce)
I, too, thought that this was leading to the idea that what happens to the
rod tip path during the start and middle of the stroke wouldn't matter as
much as what happens at the end of it. Then I considered the fact that I
can change the effect of a convex tip path in the middle of the stroke only
to a very limited degree with what I do at the end. G.
****As you know, it is very easy to make a bad tailing loop by making the
tip path concave in the beginning, middle, or end of the tip path. Once the
rod tip speed goes above a certain threshold speed where it will throw the
line (about 10 m/sec.), the path affects directly the attitude of the top
leg. Remember, the tip path from about 10 m/sec. to RSP exactly draws the
attitude of the loop top leg. (Bruce)
Another example is that if I create a wide loop purposely to, "kite" with a
wind in the direction of my cast, I can do so by placing increased rod arc
(with convexity of rod tip path) right at the start of my cast followed by
a more straight line tip path for the rest of the stroke. That one, I
can't abort with anything I do at the end of the stroke.
Delaying rotation at the rod handle until later in the cast does not, I
feel, detract from the principle of constant acceleration to the most
complete stop the caster can make. Bruce has looked at that delay of
rotation with his Casting Analyzer and noted that when done it gave a
higher incidence of tight loops. G.
*****I hope I've made it clear that delaying rotation is what allows
constant acceleration. It is early, slow rotation that prevents it in most
casts.
Great discussion on a very important topic. This is the heart of good fly
casting and on which nearly all else we do depends.
Bruce
Gordy