Walter & Group........
From Dermon Sox on the, "collapsing" shooting head when Spey casting :-
Simon,
Thanks for your reply to my inquiry. However, with all due respect to one whose mastery of the spey rod I am in awe of, I must disagree with you on several points. I am sorry that my reply is so long, but this is helping me tremendously as I work through these issues in preparation for taking my Masters test in a few weeks. Be assured that I present these arguments only in the interest of us ALL getting it right. And if I get shot down, so be it.
You write “[as] the 'shoot speed' starts to slow down, the heavier shooting head is being pulled down by gravity and the thin, light shooting line has no mass to hold it up. As a result, the line lands rear end first and loses distance.” I agree on the end result, that the shooting head lands rear end first, but I disagree on what causes it.
The rear end of the shooting head is the heaviest part of the system. It carries more kinetic energy than any other part of the system. Therefore it will be the last part of the system overcome by gravity. If you throw a golf ball and a ping pong ball at the same speed the one with the most mass, the golf ball, will carry the larger amount of kinetic energy and will stay airborne over a much greater distance. At RSP the running line and the shooting head are moving at the same speed as the loop begins to form. Now not only does the running line have much less mass, it also makes up the front of the loop and is encountering air friction, which the shooting head is not significantly encountering, since it is strung out straight behind the running line. If there is too much running line between the rod tip and the shooting head the running line is very quickly depleted of its kinetic energy and so begins to fall. And since it is attached to the shooting head it begins to pull the rear of the shooting head down. I can see absolutely no reason why the rear of the shooting head would begin to fall before the running line, since it has much more kinetic energy.
Actually you help me prove my point when you say, “If you attach a shooting head with a back taper to the same running line...the flight time is noticeably longer” What did you change to fix it? You did not change the shooting head, which you said was the problem, pulling down the running line. You changed the mass of the line running ahead of the butt end of the shooting head so that it had more mass, and therefore could stay airborne longer and not pull the butt end of the shooting head down. And the same is true, as you acknowledge a possibility that I am right, when you say, “Of course, you get less of an effect with a thicker shooting line, so one could argue that it is the shooting line, not the shooting head that is to blame!” Methinks you are beginning to see the light.
Then you state, “The energy from the fly rod will not transmit into the shooting head through a long, thin connection (the shooting line), or will that long thin connection have enough mass in itself to pass energy into the head.” I believe that this is totally wrong. I think there is a serious misunderstanding among many fly casting instructors as to where the energy is in a cast fly line. Your statements imply that you think that as the loop unrolls that energy is being transferred from the rod to the line, and therefore, since this running line has little mass, it cannot possibly carry the energy that it must transfer to the shooting head. But the truth is that at the end of the power part of the cast (at RSP) ALL of the energy that the shooting head is going to get is already in it. The rod tip has pulled that thin running line at an increasingly accelerated speed to the stop, and the unloading of the rod has increased that speed even more. The shooting head is attached behind that thin running line, and so has likewise been accelerated to that same speed. So all of the energy that the shooting head has was transferred to it through the thin running line; not through its mass, but simply because it is the connecting link between the rod tip and the shooting head. Now the mass/weight of the running line and shooting head moving at that speed are the total energy in the cast. Nothing will be significantly transferred from one part to another. If you could somehow magically snip the connection of the running line to the shooting head just at RSP the shooting head would go even further than it would have if it were still attached to the running line. It already has all of its energy right at RSP. If you could magically also snip the shooting head in half right at RSP the trailing half would not suddenly fall to the ground. It already has all of the energy it will get and will continue its flight right behind the leading half until its energy runs out.
So now we have a thin running line traveling ahead of a heavy shooting head. The running line runs out of kinetic energy and falls from the intended casting plane. Being attached to the heavy line which is not collapsing, it bends at the connection point. It looks like a hinge to me. I know it is different from when, for example, the coating on my fly line cracks right behind the nail knot attaching my leader, and it does not cast as well. But the issue there is the stiffness of the material through which the loop unrolls and not the difference in mass of the materials on either side of the hinge. When I have encountered the term “hinging” it has almost always had to do with having too much overhang when casting a shooting head or a weight forward line. Your definition of hinging – cutting a fly line in half and rejoining it with long braided loops – does not make a lot of sense to me unless the braided loops are so long that they become a kind of running line in the middle of the fly line and create the same problem we were dealing with above. The trailing part of the line still has all the mass it had before it was cut and has been given its own kinetic energy in the power part of the cast. It is not waiting to get energy from the line that is preceding it before it can continue. Yes, the braided loops will cause a glitch in the smooth turnover of the loop, but all the energy of the cast will not leak out so that it cannot continue past those braided loops. I need a clarified definition of “hinging”, and I suspect that I am not the only one.
I really would like to get some feedback on this from some of our Masters who are physicists or engineers as well as others who work with shooting heads.
Again, my apologies for the length of this, but thought it important to deal with all of the issues you raised.
Kindest regards,
Dermon
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Dermon.
I am not an expert on Spey casting. However, I see a lot of thought went into your message and I agree with many points raised. Just some brief comments:
First, I'll suggest that a good exercise to help prepare for your MCCI exam, would be to take your well thought out, "long answer", above, and contract it down to a, "short answer" with a minimum number of words.
1.) If you layout a fly line on the grass perfectly straight behind your rod tip, you can make a distance cast even if you have a long overhang. (length of thin running line between the rod tip and the head).
2.) The head will collapse if you don't apply sufficient energy at the correct time. It would seem that the reason for this collapse is that there wasn't enough energy imparted to the head to keep it in flight after which gravity took over.
3.) When roll casting (or Spey casting), you have either a static loop or an active loop (D-loop) behind you. If you have a sufficient length of thin running line making up most of this loop, you can't make a decent cast. The head collapses, rear end first.
The reason for this appears (to me) to be the fact that the thin running line could not transfer the energy applied by the movement inparted to the rod by the caster to the heavier head.
Putting it another way, when roll casting (or the Spey equivalent) it appears that you need heavier line transferring energy to the ever lighter line ahead of it in order to maintain good control, ergo a good cast.
You and Simon are both correct with respect to the result. (That the back of the head falls first.) Your thought that the running line can pull down the back of the head as its energy dissipates, may have merit. At the moment, I see this as a, "Gedenken" experiment without actual physical proof. In trying to keep an open mind on this, I have to consider that there may be other factors of which I'm not aware.
I'll leave the engineering / physics behind all this to those better versed in these disciplines in the hope that some of them will offer more scientific explanations.
Gordy