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Walter & Group....
From Mark Surtees. (I added references to "effective rod length") *:
Hi Gordy
I’m back…sorry about the delay, there were places to see, people to meet and fish to catch… J
I’ve Just picked out a couple of interesting points from Mark and Alan's replies on questions three and four.
MM The constant force is applied longer, the longer it is applied the faster the rod travels and the tip speed would be faster even if the “rotation speed” were identical because butt speed would be added to tip speed.
AK The tip speed is a result of the rotation and translation. This assumes that the rotational force is the same and the translation adds force and therefore tip speed to the cast.
The force is applied over the same angle but translation co-occurs, that is, the rod is translated and rotated at the same time. So, the second cast has a duration that is the same as the first not longer. The tip, however, has moved over a greater distance in the same time as the first cast and has therefore travelled faster.
What this means in practice is that the caster can reduce the force used to rotate the rod through a particular angle by adding translation and still achieve a particular tip speed. A cast with a reduced force will take a little longer to complete for a given tip speed but this is because, by adding translation, we are able to accelerate over the same angle at a reduced rate….this can be a very good thing for casters that habitually use too much “oomph”.
MM Generally more force produces more bend but the more direct relationship is between tip speed and bend thus equal force would produce dramatically different bends when comparing translation (less bend) to rotation (more bend).
The bend in a rod is a function of its material properties and the net force applied to it. Were we to be inclined to measure these things…which I’m not by the way….equal forces applied steadily would generate the same “amount” of bend in the rod. With translation on its own there is no change of angle so the bend remains more or less uniform….(though no-one casts like this for obvious reasons so it’s a bit of an academic point). With rotation, however, the angle between the rod and the line it is pulling along behind it changes, so while you continue to apply force to the rod, the bend changes shape and displaces first down the rod and then back upwards as a result of the change in this angle.
That there is a relationship between tip speed and the bendiness of the rod there is no doubt. When the rod bends the tip lags behind the rest of the rod speed wise and the bend takes the bumps out of our commonly less than perfect application of force like the springs of a car smooth the ride on a rough road. When the rod unbends it delivers a smooth increase in tip speed at a rate that we the caster would be unlikely to achieve by hand alone, the rate at which it does this is dependent on the restoring force in the rod. Basically, in the simplest possible terms, it takes some speed out at the start whilst it is bending and gives some back at the end whilst it is unbending.
The concept that more bend = more speed misses the bullseye here. More force, or alternatively the same force but over a greater distance = more speed, bend is merely a byproduct of force and the properties of the rod. You can control the bend by controlling the force and, as we have seen above, we can reduce the force by adding translation. So, we can reduce the bend by adding translation and yet still achieve the same tip speed. There are many benefits to reducing the bend with respect to tip path, not least in the matter of controlling the gap between rod leg and fly leg and definitely in dealing with tailing loops.
There is a reason why expert single handed distance casters tend to use rods that bend less for a high force. Again, simplifying enormously, bendy rods reduce the effective length of the rod as a lever, as a speed magnifier, so the more it bends the less speed you will generate at the tip through rotation.* Plus, a bendy rod most often has a lower restoring force than a stiff one so, if it’s extremely high tip speed that you want, then a bendy rod is most likely not going to be the tool for you…and a stiff rod has sports suspension, if it’s a nice soft and forgiving ride you are after then go for bendy.
There are a couple of potentially knotty issues arising from Lyths answers too.
LH The casting angle when adjusted properly (lesser angle for short line and greater angle for long line will maintain a straight line path of the rod tip.
Opening the angle during the stop phase of a casting stroke is a very effective way of dealing with some casting problems, this I completely accept. But, for a given force, we almost universally use a combination of hand path, (that curvilinear translation that you are now trying to get to grips with Lyth), and, to a much lesser extent, Casting Angle, to maintain SLP. It is the confusion between the meanings of, and relationship between, rotation and curvilinear translation during the period when we are applying force in a casting stroke that has lead us to the claim that Casting Angle alone is the sole moderating influence on tip path…it isn’t…controversy may ensue… J
LH Less force, less bend, more force more bend
Yes…bang on but….
LH The bend in the rod is what allows us to get the straight line path of the rod tip when the rod moves with an arc or angle. More bend requires more arc to maintain a straight line path of the rod tip, less bend requires less arc to maintain a straight line path of the rod tip.
9. When the rod bends it helps to smooth out the bumps not only in our force application but also the consequent variation in tip path that would have arisen from those bumps and the convexity produced by our need to rotate the rod through an angle.
What seems like a very long time ago now I delivered a lesson to a guy and said to him that we “match the arc to the bend in the rod to get a SLP of the tip” and I suppose in a very long roundabout indirect sort of way we sometimes kinda do..the trouble is it’s not the only thing we do…anyway...he promptly, and quite reasonably in my opinion, asked me “How ?” and I was flummoxed.
So, I’m now going to ask you the same questions, Lyth,…to anyone in fact…How do we match the casting arc/angle to the bend in the rod?. Do we make this casting decision during the casting stroke or before we start? Which comes first, the angle or the bend?. Do we ever manage angle alone to control the tip path ?
More to the point, can you teach someone to match this angle to the bend in the rod during a casting stroke? Personally, I have never said those words in a lesson again because I haven’t been able to find an effective way that helps me actually teach someone how to do it. In fact, I’m prepared to bet one whole British penny that no one ever just uses Casting Angle alone, ie. rotation only, to maintain a SLP of the rod tip. Yes it is theoretically possible and of course I realize this is a fundamental tenet for many instructors but I’m afraid that I simply don’t believe that this is what we actually do. Needless to say I am expecting howls of rage from some quarters at this proposition, but I’m also expecting to keep my penny… J
The amount of force also changes the bend of the rod which then requires an adjustment in the arc to maintain a straight line path of the rod tip. More force equal more bend which requires more arc for a straight line path. Less force equals less bend which requires less arc for the straight line path of the rod tip.
Do you moderate your force to control your casting angle ? or moderate your force to control the bend ? Clearly you can do either, and you can, as we have seen, reduce bend or angle by adding translation and leaving force completely alone, so does more bend really require more casting angle to maintain a slp or could you maybe use your curved hand path to achieve the same thing ?
It is interesting to use a sort of mind experiment here to demonstrate the point, (you can actually go out and do this in the field too if you’re so inclined). It is perfectly possible to get a beautiful SLP of a rod tip with a rod that is absolutely rigid, i.e. it doesn’t bend. If we have to match the arc/angle to the bend to get a SLP how could such a thing be possible ? if small bend =small arc/angle then logically no bend would equal no arc/angle, which is absurd because we would lose the benefits of the rod as a lever if we didn’t rotate it to generate the required tip speed. In this extreme example SLP is achieved entirely by controlling hand path and I would personally contend that this is largely what we do with bendy rods too, we just do it less dramatically because the bend is working for us in order to suppress the need for extreme hand movement.
Hope this isn’t too confusing….and I would like to add that I do not teach like this, nor would I recommend anyone to even think about doing so.
I might have to do some real work in a minute which will be a shock to the system but keep the answers coming Gordy and I will do my best to add my thoughts as we go along.
Best
Mark
* THE TECHNOLOGY OF FLY RODS, by Don Phillips, 2000, pp. 44-46.
** " The measured chord that subtends the arc of the fully bent rod becomes the true casting or effective length. Accordingly, a nine-foot roe, under full bend may become a seven-foot rod. Another nine-foot rod, stiffer than the first nine-footer, may be eight feet in length. or, to put it another way, a stiff seven-footer may be effectively longer than a limber nine-footer."
IN THE RING OF THE RISE, by Vincent Marinaro, 1976, pp. 52-54.
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[GH] Let's add one more set of answers from Jim Chestnut:
Hi Gordy and group,
I am going to make two Casting Strokes. If I apply a force to the rod over
a Casting Angle of 45 degrees in the first and I apply force of the same
magnitude to the rod but continue through a Casting Angle of 60 degrees in
the second.
Will the second Casting Stroke generate a maximum tip speed which is:
faster slower or the same.
Assuming that the question means that throughout each cast the same
magnitude of force is being applied to each cast continuously throughout
the cast then:
Answer = the tip in the longer stroke is going faster than the shorter
stroke.
Reason: According to the “Given”, by definition it has to be going faster
since both casts start with zero velocity and each accelerates at the same
rate.
2. Will the second Casting Stroke have a duration which is :-
Answer: Longer than the first.
3. If I apply a force to the rod over a Casting Angle of 45 degrees in the
first Casting Stroke and I apply the same force to the rod over the same
Casting Angle but add 3’ of co-occurring Casting Stroke Length in the
second Casting Stroke.
Will the second Casting Stroke generate a maximum tip speed which is :-
a. Faster than the first? b. Slower than the first?
c. The same as the first?
Answer: I don't really understand the question. To "add" casting stroke
length through translation is to "add" force, and consequently the tip
speed would increase by the amount of the translation speed. But then you
are not applying the same casting force to the "rod" during the same
casting angle. The casting force on the "rod' is the sum of the
translational force and the rotational force.
Therefore, if my understanding of the question is correct, the tip speed
of the longer casting stroke would be faster by the amount of the
translational speed.
4. The second Casting Stroke would have a duration which is:
Ans: The same as the first if my understanding of the scenario is correct.
5. How does the Hand Path of the caster affect the path of the rod tip
? Ans: In all three dimensions.
6. How does the Casting Angle affect the path of the rod tip?
Ans: In combination with varying applied rotational force it can shorten
or lengthen the tip's distance from the rod hand.
7. What is the relationship between force and bend ?
Ans: All other things being equal, more force equals more bend.
8. How does the bend affect the tip path of the rod ?
Ans: Bend reduces the distance between tip and the caster's hand.
9. How does force have an effect on the tip path of the rod ?
Ans: It changes its velocity vector.
10. How could a curvilinear hand path help produce a linear tip path
during a Casting Stroke ?
Ans: If casting a very stiff rod with too light a line, one can use a
concave hand path to help counteract a convex tip path. The converse holds
true with a heavy line and an "underpowered" rod.
11. Using your answers above, if we want a Straight Line Path of the rod
tip during our Casting Stroke how many variables can we use to try to
achieve it ?
Ans: A great many. They would include casting angle, casting stroke
length, haul, haul timing, haul length, haul acceleration rate, amount of
force used in rotation, same for translation, when both are used, rate of
acceleration changes and when they occur, rod hand path, stance
adjustments.
12. Using your answers above, if we want a particular tip speed at the
end of our Casting Stroke how many options do we have available to achieve
it ?
Ans: Again many, All of those listed above can/will also affect tip speed
and line speed.
Cheers,
Jim
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