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Walter & Group...
[GH] I'LL BE AWAY FROM MY COMPUTER FOR THE NEXT SEVERAL DAYS..... IN SPOKANE, WA. ATTENDING THE FFF FAIR/CONCLAVE. BACK IN ABOUT 10 DAYS.
So many things happen at the same time or in overlapping sequence as we fly cast. One element may progressively overtake another as a transitional phase. An example is the cast which begins with translational movement combined with hardly any rotation followed by a transition during which rotation becomes predominant as translation takes second position.
The simplistic approach is to take each element of the cast.... one at a time, and try to relate it to other elements. This would seem to make the study of fly casting mechanics easier to understand.
An in depth understanding, however, must take into consideration the fact that there is a complex interrelationship such that a change in one element demands change in several others.
Mark Surtees come forth with these answers and comments as he explains some of the variables involved. As he does this, he makes us think as he elevates the scenarios beyond the simplistic level.
Gordy
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>From Mark Surtees:
Hi Gordy
I am fascinated…I’ve picked a couple of questions to comment on.
6.) Do translation and rotation occur separately? or as contiguous events when casting?
Translation and rotation of the rod can co-occur or occur separately when casting. During a Casting Stroke they almost always co-occur. It is very difficult to make one happen without the other in real time casting.
7.) When does the movement of the rod through the CASTING ANGLE begin and end?
It would conventionally be measured from RSP1 – RSP1. Bearing in mind RSP is a position which is fleetingly present, the beginning and end of Casting Angle is of absolutely no practical consequence whatsoever from a teaching perspective, when it starts and ends is only important if you are going to measure it. This is also true of Casting Stroke Length, or indeed Casting Stroke or any of the notional elements that go to make up a cast. If we are teaching, we use relative terms, higher, lower, more, less, longer, bigger, smaller, shorter, to change these things. We are not usually interested in the number of degrees or inches to the last dot and zero.
We have made a bit of a rod for our own backs by using the terms of measurement of rotation and translation to mean the actual process of rotating and translating. The terms serve their purpose but they promote and reinforce a way of thinking about the parts of a cast such that we need to have starts and ends of things with a hard boundary between the two. In the process of casting there are smooth transitions between the elements of a casting stroke where simple rotations and translations, accelerations and decelerations overlap and blend at the boundaries, these are not contiguous events.
8.) What relationship must exist between the ROD BEND and the CASTING ANGLE in order to achieve a straight line path of the rod tip when casting?
There is no direct, single relationship. In its simplest form, there is a three way relationship between force, rotation through casting angle and translation through hand path, bend is a function of net force and the material properties of the rod. The desired tip path is generated by a mix of the first three factors, not just one. In order to get a particular outcome, vary one and you have to vary one or, more probably, both, of the other two. The material properties of the rod and the biomechanical capacity of the caster are limiting on how this is achieved.
There is a misunderstanding about the enabling properties of curvilinear translation of the rod with respect to the management of both Casting Angle and the maximization of our biomechanical abilities. It is manifest in the insistence in some quarters that angle alone is the factor that you must control in the presence of bend to achieve a SLP which is why I am interested in answers to the unasked question.
“How do you match arc/angle to the bend in the rod”
If casting angle refers only to the angular change in position of the rod, then the only way to practically do this during a casting stroke is to use the wrist and permit no other movement of hand, arm or body. This cannot be how such a thing is done mainly because its barely physically possible, except perhaps at exceedingly short line lengths. Casters use predominantly hand path coupled with angle change to deal with the changing bend profile as it displaces up and down the rod just because it’s, physically, way easier.
Almost any casting video will demonstrate this so its puzzling to find any resistance to the idea when it’s evident in every cast we see. There must be a reason for this and so it is quite attractive to believe that when people refer to casting arc or angle in this particular context they are referring, not to a single term of angular measurement, but to the whole movement of the rod created by combining the rotation and translation that we use to achieve some change in value of that term. In which case we are talking about something different to just Casting Angle, the angle.
In the last set of questions we asked whether there are more than two ways to achieve a SLP of the rod tip and the general consensus seemed, correctly in my opinion, to be yes. Variation of the angle and variation of the hand path being evident in the answers.
So..consequently here’s a couple of thoughts on some other questions…
21.) What is likely to happen if we use lots of force and develop more rod bend without increasing our casting angle?
Depends on the amount of line you have out, bend is as a result of net force not just the force at the butt.
For a normal length of line, if it happens with an uneven application of force, a tail. However, applying high force over a small angle smoothly is biomechanically extremely hard to do so we will rarely see high force being applied over a narrow angle smoothly. The reason, therefore, that we need a bigger angle, is not principally so we can control the bend but so we can apply less force for longer over a greater distance and get it within our biomechanical capacity to deliver it evenly.
If we get less bend as a byproduct of the increased angle and the reduced force, this should mean, if the arc/bend matching theory holds up, that the casting angle should now be reduced to match the reduced bend...but we can’t… because we need it as a force mediator. Casting Angle alone can’t do these two things at once, we can’t increase the angle to help us reduce the force and make it easier to apply and simultaneously decrease the angle to match with the reduced bend to get a SLP. If we add translation in the form of a curvilinear hand path however, then we can keep the smooth application of force and still achieve the desired tip speeds and straight line path of the tip and that is exactly what we do, 99.9% of the time..
22.) What happens if we don't use enough force to develop sufficient rod bend for the amount of casting angle?
Again, it depends on the amount of line you have out. If you use low force and a big angle with a short line you will usually get a non loop or no loop at all. If you use low force and a big angle with lots of line out you will get a crossing loop or a loop which fails to propagate. If you use a low force and a big angle with a short line and compensate for the convexity of the tip path with your hand path, you will get a nice tight loop. It will have to be a pretty wild hand path though so in this case we increase the force and decrease the angle to reduce the drama at the hand end.
23.) Do you ever purposely perform the exercises in 21.) and 22.) as a demonstration to your casting students?
No, only to other instructors… J
Best
Mark
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From Rick Brown:
Gordy, back in 2009 when Al Crise had his study group, I asked, '' but why do you call it translational?'' At that time, translation meant from English to Spanish or similar.
The answer that I got came from Troy Miller and it is worth repeating.
''When something translates in scientific terms, it simply moves through 3-D space from point A to point B. While it's doing this, it may be rotating, it may be changing color, it may be laughing, it may be getting smaller. .. But it is moving through 3-D space. As in, its center of gravity has changed position. Many people think that translation implies linear movement, but it doesn't. You could move from A to B in an infinite number of paths, but there's only ONE linear path. In the grand scheme, that's the one that I'm trying to make my thumbnail (and the rod tip) imitate.''
Rick
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[GH] Didn't know that .... but I'm here to learn. Troy Miller is an engineer.... so best to take his word over mine.
Webster's Unabridged Dictionary:
Translation : 6. Mech. Motion in which all particles of a body move with the same velocity along a parallel path.
From the Farlex dictionary: Translation: 3. Physics Motion of a body in which every point of the body moves parallel to and the same distance as every other point of the body.
Or, from the Allwords English dictionary: Translation: (countable) (context, mathematics, physics) Motion of a body on a linear path, without deformation or rotation, i.e. such that every part of the body moves at the same speed and in the same direction.
Enough ! I'M OFF TO SPOKANE. HOPE TO SEE MANY OF YOU THERE.
Gordy
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