Walter & Group........
Gordy,
You said,
"Noel and Bruce have shown that the rod tip is moving fastest between the STOP
and RSP." That’s not exactly correct. Let’s go back and re-examine
the research together.
Dr. Noel Perkins, Ph.D. Mechanical Engineering,
scientifically proved that the rod tip reached maximum velocity, or tip speed,
when the rod is at “zero deflection” (better known as Rod Straight Position or
RSP). Dr. Perkins’ study was done by carefully by measuring and plotting
the rod tip speed as a function of time and compared the data to corresponding
plot of the strain gauge voltage (and gyro voltage too). The intersection
of this “zero deflection” line and the strain gauge signal occur exactly at the
same time as the peaks in the tip speed. These results are pretty
convincing and should be, once and for all, accepted as fact by your Master
Study Group and Glossary Committee.
A closely related landmark study done
this year by Dr. Grunde Lovoll, Ph.D. Physics, and Jason Borger concluded that,
“The ‘stop’ (from the perspective of the caster) is not a single event in the
casting stroke, but consists of a sequence of slowdowns while the bent rod
unbends.” In other words, the ‘stop’ occurs dynamically (as opposed to a
“well-defined, even abrupt stop of the rod”) while the rod tip is still
accelerating, but at a slower rate, until it finally reaches RSP and then begins
to decelerate. The very moment the rod tip begins to decelerate, the fly
line overtakes the rod tip and the loop is formed. This happens just after
RSP!
A little food for thought during the Holidays.
Happy
Thanksgiving!
Your friend,
Peter Lami
FFF Master
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Peter.....
Technically, neither of us are 100% correct with our statements.
These messages speak to the various levels of understanding fly casting.
We both have agreed that despite the fact that the physics experts have found Paul Arden to be correct when he stated that there is no true absolute, "brick wall stop" it is still a good idea to teach the student that he/she should make the most sudden stop possible. At this student level, many of us also teach that when we stop that the bent rod straightens and when it does that the fly line can overtake the rod tip at which time a loop is formed.
This is overly simplistic and technically not completely true, but like many things we teach students, it gets into their brains at an, "entry level" and helps that student make a fly cast. To me that is what is important in the real world of teaching flycasting.
At the other end of the, "level" spectrum lies physics information that we don't yet have. Some examples include the challenge to the data presented by Dr. Lovoll et. al. on the basis that their conclusions were derived electronically and might not be fully supported by ultra high speed video techniques not as yet accomplished or at least unpublished. Also, the admission by Noel and Bruce that they have, as yet, not been able to precisely measure the exact intervals of slowing down of velocity of the rod tip.
I accept the concept of the STOP being an event which probably differs with each cast and each caster and that it is not ever a true instantaneous cessation of all motion, since it is clearly impossible for a human being to do that for a variety of reasons. In fact, we have demonstrated as did Dean Floyd, that when a true sudden stop of the rod butt is made by striking a metal bar that the cast is literally ruined as the harmonic vibrations of the fly rod introduce waves in the line. That simple experiment fits well with the sophisticated studies leading to Lovell et. al.'s data and conclusion.
You stated that the rod tip reached maximum velocity or tip speed when the rod is at "zero deflection", or RSP (rod straight position). Now it is my understanding that Noel and Bruce actually found that the tip speed decreased somewhere between 0.1 and .075 seconds prior to RSP. With their available equipment, they could not get closer than that.
It was this finding that prompted me to undertake the study to try to discover whether loop formation actually began during this interval prior to RSP, after RSP or exactly at RSP.
You will recall that we worked together along with Mack Martin, Scott Swartz, and David Diaz with high speed video taken while Scott and I cast. At 100 fpm, we could not be certain to separate the start of loop formation from RSP. Although their study was not designed with this object in mind, Lovoll's video rendition at 500 fpm appeared to yeild the same information. We all agreed, as we studied this frame by frame that neither study could yield a final conclusion because they could not break out that tiny (less than one tenth of a second) segment just prior to RSP sufficiently and that video with greater than 1000 fpm would probably be needed to do that.
It is for the above reasons that we do not accept the broad statement that the rod tip has reached maximum velocity exactly at RSP. Having said that, I feel that at a moderately advanced (sub scientific ) level of understanding, that it is sufficiently, "correct".
Gordy