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...
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?
Scott Swartz
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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.
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.
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.
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.
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.)
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.
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.
Gordy