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Gordy,
If you could, ask Paul if it would be possible for him to dig out a photo of pre-RSP loop formation. I think it would be very helpful for every one to see what this looks like. A year or so ago I saw such a photo it was very interesting.
Chuck
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[GH] Paul Arden comes in with an answer before even seeing Chuck's question :
Hi Gordy/Aitor,
can't see the video for some reason, but I'm referring to some of Lasse's 170 videos shot a couple of years ago. The loop point translates to well before RSP.
Cheers, Paul
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[GH] From Jim Chestnut :
Hi Gordy,
I am really having trouble with this one.
If Paul would add "starts to" or "begins to" form, I would think that is
the best definition possible to come up with. It isn't very descriptive as
to the "when", or "where" during the cast, but I don't think that is going
to be possible to define.
If it were not for the haul, I would say that the loop begins to form the
instant the rod tip speed slows (relative to the trailing line's
direction) to below that of the trailing line.
However, throw in the haul during rotation, and the rod tip speed slows
to below below that of the trailing line speed (or the trailing line speed
exceeds the tip speed. But in either event, loop formation doesn't
begin..... so that doesn't work.
For some reason, I have trouble watching some of the vimeo videos, and
Aitor, unfortunately this one is one of them. My computer is approaching
its maximum carry, so I can't add any more load to it without risking a
crash. But I cannot imagine a loop starting to form before RSP unless the
rod were a very, very slow one or unless one were using a bouncing bomb
off a very high platform. I also think Paul may well have been thinking
"post-RSP" and wrote "Pre-RSP". I do that all the time. I would certainly
agree with "post-rsp" when hauling through counterflex as Paul and Steve
Rajeff often do.
Cheers,
Jim
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[GH] Jim... I was remiss in sending out Aitor's video link in the first place, since I failed to realize that this was from his private collection, so the link and password were meant for me alone. I have to be more careful about that in the future.
Suffice it to say that as far as I could see there was no inkling of loop formation despite the early completion of the haul.
Here is one often quoted description of the start of loop formation :
"The loop starts to form when the fly line overtakes the rod tip "
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[GH] Kudos to Mack Martin and his group at Atlanta ! They have done some additional studies on loop formation of which I was not aware :
Gordy:
The instant the fly lies reaches a speed that is in excess of the rod tip speed, the bottom loop forms and we have consistently found that this occurs within microseconds after RSP. This has been confirmed with new camera equipment that records at 1200 frames/second, but we have not perfected recording the speeds approaching and following RSP. This can be done as soon as I have some additional time. Excess time these days comes at a premium!
Mack Martin , MCCI
Atlanta Fly Fishing School
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[GH] John Symonds replies to my message of yesterday :
Hi Gordy,
In your reply to my previous email you made the statement.....
Peak velocity of the rod tip has been shown to occur during approximately one tenth of a second prior to RSP as the rod is decelerated (part of the stop sequence). That suggests to me that the peak acceleration of the haul might be most efficient when it coincides with the peak acceleration of the rod. This would fit well with your third paragraph
I can’t see how this can be. Firstly the unflexing time of a fly-rod depends on its natural frequency which varies from rod to rod and those with a slow recovery take longer, so the point in time at which maximum velocity of the rod-tip occurs cannot be generalised. Secondly, I would think that rotation of the fly-rod would have a greater influence on the rod-tip velocity than the unflexing of the rod and so the peak velocity will depend on when the maximum rotational velocity is applied (before, during or after RSP).
[GH] John adds :
Hi Gordy,
Thinking about my reply I was sloppy is saying “when maximum rotational velocity is applied”. What I should have said is that no matter how efficient the stop is there will always be some remnants of rotation which will decay as the rod is unflexing because it is physically impossible to stop the fly-rod dead. The peak rod-tip velocity will depend on the rate of decay and if this can be sustained it will add to the rod-tip velocity caused by unflexing and so the maximum rod-tip velocity can be anywhere between the stop and RSP, or even after RSP I believe. Modern double-handed casting employs block and stop which I think exploits the additional rod-tip velocity that can be created through post-stop rotation. In a similar manner the squeeze and release at the stop, with a single-handed fly-rod will have the same effect I think. The optimum rod-speed would be when the decay begins immediately after RSP but I would think that this would be almost impossible to control.
If maximum rod-tip velocity occurs at one tenth of a second before RSP or at any other time before RSP then what prevents in from occurring at RSP which must be the point of zero acceleration and peak rod-tip velocity – I would suggest the rotational component?
Best regards - John
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John,
That is why I said, "That suggests to me......."
I have no data to support my contention other than my interpretation of the acceleration curves produced by Bruce Richards with the CA (Casting Analyzer).
Perhaps you are correct about the rotation of the fly rod (by action of the caster) has a greater influence on the tip velocity than the straightening of the loaded fly rod. Studies showing this have been challenged as to the degree each exerts with the suggestion that it is a variable, highly dependent upon the caster, the cast, and the fly rod.
Some gain the false impression that a "hard stop" is something akin to instant cessation of motion which is, of course, not possible as we cast. You point this out clearly.
If we could achieve that, it would be as though we had struck a stationary object with the rod handle. This results in rod vibrations and a ruined cast with erratic layout.
Both the concepts ofd "block & stop" and "squeeze to a stop" make good sense to me.
(Reminds me of Charles Ritz' "Squeeze-Zic-Block" as part of his well known "HS/HL" (High speed/High line) casting technique taught in Europe in the 50's.) *
* A FLY FISHER'S LIFE The Art and Mechanics of Fly Fishing, by Charles Ritz, MJF books, English Translation, Reprint: Robert Hale, 1996, ISBN 1-56731-264-0, p. 41.
Gordy
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[GH] From Mark Surtees :
Hi Gordy
It’s interesting to see that a simple term like “Stop”, which has been used for so long in instructing, has so many possible different interpretations and this is why, perhaps, the definitions are important.
“The stop occurs at the end of rod-tip acceleration because after this point the fly-line is traveling faster than the rod-tip and so no more energy can be transferred to the fly-line, if hauling is discounted.”
“The stop also occurs at maximum rod-flex because up to this point the rod-tip is always accelerating and hence loading the fly-rod.”
The “Stop”, as I understand it, relates to a caster controlled change in the rate of angular acceleration at the rod butt.
For a long time I made the mistake of trying to teach a ”stop” by having the student look at the rod tip. It was always too late. Due to some gentle correction by wise old casting sages on this very group I now teach it by reference to the hand and it seems to work much better.
A “stop” as we commonly use it should really be interpreted as “a controlled deceleration at the rod butt” or something similar, and, on the basis that it is in our power to control it, it can happen whenever we want…or not at all.
With respect to Paul’s point on loop formation. In the context of a discussion on definitions we do not need to know when the loop is first formed at all, though you may want to know what a loop actually is. Generally speaking, starts and finishes are the basis for measuring conventions and that is all. They arise in these sorts of discussions as a result of a highly linear approach to cast analysis and the consequent need for hard boundaries between the components, this doesn’t work. In a more three dimensional model with soft boundaries the main components can transition smoothly from one to another, and, if there is a nice convenient boundary for a term, they can overlap.
Anyway, I am, in this context at least, an anti measurer…no-one teaches in measurements do they ? …..Blimey… I hope not…. J
Mark
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[GH] Mark,
I love the way you think "outside the box" with respect to our tendency to try to line things up in order, measure them, and see them as an orderly progression rather than overlapping ranges of events. I think this helps place us in the real World of fly casting.
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