Hi Gordy,
Aitor is correct, peak load doesn't necessarily equate to bend because of the
angles involved.
I have a quick comment about RSP and loop formation, I think this is only
true on non-hauled casts. With hauled casts I have seen frames of loop formation
translating back to pre-RSP commencing at conclusion of the haul - with
significant bend in the rod. Lasse showed this a few years ago on the 170 cast.
I can never find this thread on the SL board however, so maybe Lasse knows?
With regards the "stopless" cast, it is certainly not necessary for the rod
to be stopped for it to unload. I believe that all is required is a deceleration
of the rod butt.
In putting those two bits of information together, it is my contention that
with a non-hauled cast a stop is desirable for a crisp loop and for hauled cast
a "stopless" cast is desirable for a smooth loop.
A friend of mine - Jon Allen - once came to a casting weekend with an extra
rod handle which he linked in parallel to the rod, giving us two rod handles.
When holding the second handle while the caster led with the rod you could feel
a defined stop without a haul. When the caster hauled the feeling of the stop
disappeared. It would be interesting to put the analyser on both casts.
Cheers, Paul
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Paul...
Hauling makes a huge difference. One must
then concider a whole range of complications including the influence of a
seperate application of force and its timing including its own accelertion,
start point and stop or release point.
Bruce Richards and Noel Perkins are now working
on a "Haul Analyzer ". I can only imagine the complexity of combining this
with the Casting Analyzer !
Gordy
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From Bill Kiester :
Gordy,
What do we mean by constant acceleration? How do we measure it?
I think of it as the acceleration experienced at the rod tip. We know
that acceleration is mathematically associated with force. The force is
applied rotationally and longitudinally at the rod handle
.. For that force to get to the rod tip it must be transmitted
through a fly rod that bends to varying amounts based on the angle between
the rod's axis at the handle and the trajectory of the fly
line. Varying angles create varying rod deflections. This means
that there is not a direct relationship between rod rotation and rod tip
movement.
I think that we can say with certainty that forces must increase throughout
the cast to overcome air friction as the speed of the fly line
increases. And, air friction does not go up linearly.
The ability to measure results of these variables presents a difficult
problem. The CASTING ANALYZER is a valuable tool because it provides a
repeatable set of measurements that allow us to make judgements about casting
ability. While it is indicative of acceleration I don't think it really
measures acceleration of the fly line. I would think the only
practical way to measure acceleration would be with time stamped high speed
imagery that would allow accurate measurement of rod tip travel.
And, when hauling a spot on the fly line.
Bill Keister
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Bill,
The Casting Analyzer is taking its measurements at the
rod butt.... so it isn't measuring what is happening at the tip. Also, we
must remember that it shows translation only as an increment of time.
Translation itself isn't measurerd.
Gordy
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Tony Loader weighs in :
Hi Gordy,
In relation to acceleration, Aitor describes
an experiment and mentions "force applied to the rod tip" then reaches a
conclusion about "force applied to the rod" (butt). Begs the question, are
we discussing acceleration of the rod butt or of the rod tip? If the latter,
then does not maximum acceleration occur after the caster
commences applying negative acceleration at the rod butt i.e. after the
"stop"?
Regards,
Tony.
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Tony,
After the "stop" and just
prior to RSP, we've pointed out that the rod tip is moving at its fastest
rate. It is my understanding that during this approximately 0.1 second,
the rod TIP is still accelerating but at a lower rate. This is largely due
to the spring effect of the rod straightening and releasing latent energy as
kinetic energy.
Gordy
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From Mike Heritage
:
Sorry Gordy, this still has me thinking, 14.) You are given a series of pictures of the caster and
fly rod taken as multiple frames shot as the cast is made. You are asked
to pick out the one which demonstrates the point of maximum acceleration.
How do you choose it ?
I know you don't mention the haul in the question and it does beg the
question, what are we accelerating. My answer to that would be the line. Many of
us don't start the haul until butt stop, ie, into an unloading rod, that is
still accelerating, it must be if the tip is moving fastest a fraction prior to
RSP. Add to that the acceleration added by the haul so, to my mind, max
acceleration must be just prior to RSP. If you had asked which photo shows
maximum leverage I would be happy to accept the one that shows the biggest
bend.
Mike
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Mike...
You may be right about that
! Also, we still have the question on the
table : If we have constant acceleration,
then can we even have maximum acceleration ? G.
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Dennis Grant answers David Lambert's message
with his pictures from Lovoll's study :
Hi Gordy
(DAVID) Darker
line is rod tip path from small illumination at rod tip.The lighter line
is the fly line.
My computer might make a different display of the
pictures than others. The rod tip path is the brighter line on my
pictures and the darker (less visible) is the fly line. I would expect that the
key point here is when the line path crosses the rod tip path. The line is
being pulled by the rod and the line is falling. The second that the rod
tip path drops below the line path the loop must begin to form. The line
cannot climb over the rod tip, the rod tip has to drop below the line path for
the loop to take over. The cross over appears to be happening at the ceiling
light which should put the loop formation slightly prior to or at
RSP.
This appears in the first photo. The cross
over point is consistent in all 3 photos.
All the best,
Dennis
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Dennis...
A point I had not considered.
Fits with the fact that if the rod tip does not dip even the least bit that the
line will collide with it. G.
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From Guy Manning
:
Good morning Gordy,
Peter wrote:
I teach my students that the "stop" is a
sequence of events that begins at peak load and ends at RSP.
Peter
-------------------------------
My
question is: Define peak load and when does it occur?
To
me, it is when the rod is bent farthest down the blank? closest to the cork.
Guy
Manning
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Some deep thinking by Walter Simberski
:
(I placed his detailed message in an
attachment.)
Hi Gordy,
I know we are getting to the point where many
people are probably getting bored with the physics discussion
but I've attached some of my latest ramblings.
Hopefully the use of an attachment makes it easier to avoid
for those who would rather not get bogged
down.
Cheers!
Walter