PHYSICS OF FLY CASTING

Casting â 2008

I apologize up-front for any editing errors â I notice missed errors every time I proof read but want to get this material out. OK, I havenât posted in a while - probably as long as 24 months ago. However I see that commentary Iâve passed along in the past are now becoming obscure so itâs well overdo to review the fundamentals of casting physics that I have discussed in the past. This document is more of a treatise on casting mechanics and physics than a rambling collection of odds and ends. It tries to address those aspects of casting physics//mechanics that I feel are fundamental and universal. Also I think they are proven (I can prove them â they can be proven on paper based on physics or examining casting data without need for on-the-ground âground-truthingâ and they can also obviously be proven by âground-truthingâ, especially with instrumented rods or photography) and based on fundamental considerations from physics and engineering. Since they are largely at odds with a lot//most of recent commentary they should be reviewed thoroughly if you have a strong interest in understanding casting. Basically it is not possible to reconcile a lot of what has been posted about casting in the past several months or so â especially remarks addressing âfundamentalsâ and âprinciplesâ. If you do this review then you can agree, disagree and explain/ask, or perhaps not understand the substance or implications. If you decide to make complaints or ask questions please abide by the need for specificity (to the degree you can). The items Iâll be discussing include things like the absolute facts that 1) there is no âhard stopâ in casting (that any caster makes at any time), especially in the sense that this term has been classically applied in casting discussions (you could conjure up something else for the meaning of âhard stopâ because at some point various movements do decrease and stop but that would be contrary to the accepted meaning//spirit//a dishonest application of the term), 2) âkickbackâ as I described on this board several years ago is the primary cause behind tailing loopsand leads right into the subject of âpreloadâ which I introduced several years ago, 3) the subject of âtranslation and rotationâ in casting is now an often written about familiar subject, however it is much better reframed into a subject where the subject matter is a sequential execution of âpreloadingâ then âcastingâ the rod, 4) mechanics necessary to achieve a long segment of straight rod tip trajectory in situations where large rod deflections have been produced, 5) when using conventionally engineered fly rods, based on the best reasonable data available the fly rod elastically stored energy is the primary provider when large line velocities are generated, 6) thankfully I examined the ACA web page and examined video sequences there demonstrating very large rod butt rotation rates (peaks might be as high as high as 1500 degrees/s) which show that with extremely stiff rods and casters who can rotate the rod butt that fast, that very large line velocity can be generated by âswingâ, 7) not surprisingly to me, I hear nothing on line reversal loading which is a useful concept to understand and consciously apply if wanting to improve your own or some elseâs casting mechanics//performance, 8) the several paradigms of casting that encapsulate most casting variations within straight line casting, 9) not understanding the role of slack and fly line tension in legitimate straight line casting, 10) what you can feel//sense when casting and what you canât, and 11) Slide Loading . I felt, as if for the most part, in the past I had written about many of the underpinnings of casting and there was enough explanation to put things on somewhat of a solid footing. Iâve been trying to skim the postings over the past 2 years (especially if it doesnât require too much time and if it is directed to something that deals with the process//mechanics or physics of casting) and I canât recall much substantive commentary on the mechanics of casting and now some especially questionable statements are being propagated and echoed. Iâll go through this stuff as well as other subjects related to what I think are the substantive elements in fly casting that in total comprise a fairly complete picture (at least as well as I can remember right now).

First summary comments on the important fundamentals of casting (with some elaboration later since I havenât seen any of this [the technical basis behind the real fundamentals] included in any recent board discussions)

1) Long time readers know that I have provided mathematical proof that the idea of a âhard stopâ is basically faulty (faulty at its roots). I guess itâs time to repeat it â nothing like a hard stop ever occurs in any casting that I have ever personally observed. This is simply a physical fact. A caster initiated âstopâ will not ever begin, providing the cast is reasonably smooth, before the start of counter flex when casts are made using the usual practices â how soon stopping is initiated during//after counterflex and other nuances controlling rod behavior after counterflex depend on the skill of the caster. What you do after counterflex isnât that important since the line is in âfree flightâ anyway. Recall that the notion of âhard stopâ is that caster initiated stopping occurs around peak rod load and somehow then contributes to how the rod unloads â I am saying that generally no attempts at stopping occur until rod unloading is complete which is quite a different story. In fact the caster starting to restrain the rod during counterflex is an involuntary act anyway since it has to be done to continue holding onto the rod. Ideas like â âwell you canât stop all at once but you start to stop after maximum rod loadingâ, âitâs necessary to start stopping the rod so it can unloadâ, etc. are all basically statements without any physical merit. I now have an alternate observation (that doesnât depend on knowledge of particle dynamics or calculus) that can be applied since it is unfair to expect the typical reader to scrutinize a statement requiring a working knowledge of college level science/engineering and I will discuss this now. The moment//torque applied by the caster on the fly rod is directly related to (alternate words are âcan be determined fromâ) the curvature (i.e., take it as âbendâ) of the rod at the top of the rod grip//adjacent to the casters hand. Even if the applied torque were being varied fairly rapidly (say reversed every millisecond) the curvature/bend near the location of torque application would continue to track the applied torque but the curvature at distant points would be doing its own thing (that is the rod would be shaking if the torque were being reversed rapidly) â you can see from your own everyday experience that the human caster for the most part does not (cannot) induce this type of rod input (as in reversing/cycling inputs ever millisecond). So the point is if you understand the bend of the rod next to the casters hand then you also know the moment//torque being applied to the rod by the caster (Iâm going to try and drop the âmomentâ terminology because most readers probably arenât familiar with it in preference to âtorqueâ but it is a hard habit to break because in teaching Engineering Mechanics the term moment is employed almost universally). Next related point is with the rod in the hand of a human caster the curvature along the rod is normally of the same sign//sense along the whole rod â that is the bend of the rod is smooth progressing from its value near the grip to different values as you move toward the tip â an important feature is that the sign//sense of the curvature will be the same (normally) along the entire rod. (It does not necessarily have to be that way â simply throw your rod up in the air and hit it with a hammer near the ferrule and youâll see the rod shake as I described several sentences earlier if the grip torque were being reversed every millisecond). When your hand is actually making the rod move it is likely the curvature will have the same sign//sense along the rodâs entire length. So if you were trying to stop the rod (even in the slightest amount) that would be reflected in the rod butt curvature reversing direction. The data always shows (best and most accessible data is strain gage data due to Perkins/Richards and I assume everyone has this information available to them â however I have seen other data some of which I was involved in generating which is also consistent) that this curvature changes sign whenever the rod fully unloads. That unequivocally says that most casters will//do first begin stopping the rod at the time of complete rod unloading because that is when a torque in the opposite direction is first applied by the casterâs hand. This has little to do with caster intentions (explained later) â in fact I donât think the caster can help himself. Such is the symbiotic relationship between caster and his fly rod in most casting situations. More detail on this later but this interaction between caster and rod is totally contrary to the âhard stopâ terminology typically employed and hoped I had put to bed and sleep several years ago. In fact all the time the rod is unloading the caster is placing forces and torques//moments in the same direction as applied when the rod was being loaded!! And, of course this is required if the system linear and angular momentums are to increase during rod unloading.

2 and 3) The terminology of translation/rotation is potentially useful but mildly unfortunate. Although it could be more useful or improved if used in a way which explains the casting process. I suspect that some readers have a subconscious understanding of whatâs going on but difficulty cutting through the clutter. Troy had indicated he applied it on Guy Manningâs web page//bulletin board some years back. I also was and am part of that bulletin board. While I donât recall the details of that I trust Troy in what he is saying. Bruce also has used the terminology in fruitful ways. But I am pretty sure that itâs legitimate//real and most important role in casting was not discussed although I have always assumed that subconsciously this role led to the introduction of the phrase. Several years ago I did introduce the role of a âcasting phaseâ within a casting sequence process which addresses the significance of what âtranslationâ should be more appropriately called â this is the notion of ârod preloadâ which itself is strongly connected to the rod structural dynamics notion of upper rod âkickbackâ. As some of the past posts have identified, you donât really translate the butt of the rod (unless the caster uses special combinations of rotations at the various joints so the rod butt does not rotate for a portion of total stroke â I personally try to do this sometimes because of theoretical advantages but doing this is really a physical challenge for me) but that is no big deal in my mind if your true mission is create a description of a two phase process. In slicing through the insignificant, the important thing to realize is that the caster must not have the rod tip kick-back (or equivalently, slow down excessively) when maximum torques are applied by the caster (I like to call this phase, the time of maximum caster applied torques, the actual action of âcastingâ â I use this terminology because it implies that without it the angler really isnât âcastingâ but merely âwavingâ the rod). Also well for you to know is that maximum applied torque usually means maximum rod loading//deflections. Obviously having maximum rod loading without the rod tip in intimate contact with the fly line does not lead to favorable results (that is, kickback or slow down creates fly line slack in the vicinity of rod tip just as the rod begins unloading). Another consideration is that rod unloading immediately follows max loading so that rod unloading starts with guaranteed slack owing to the kickback. So kickback is not normally a good thing and in most casting needs to be avoided. Preventing âkickbackâ is accomplished by having the rod pre-loaded adequately prior to trying to achieve peak rod loading (I call the achievement of peak rod loading the âcastâ phase and others call it the âpower snapâ and probably other terms as well.). Adequately (for preload) means that if greater peak torque is to be applied at the âcastâ then a greater amount of preload is required in order to prevent kickback or excessive slowing of the rod tip. While other discussions have talked about âtranslationâ eliminating slack (is this a failed cast, or what? â many//most good casts do not//should not have appreciable slack) or other benefits (which I am also not sure actually exist) they have not been discussing the relation between preload and kickback. Itâs not likely youâll make a nice longer distance cast without preload â without adequate preload a flaky tailing loop is guaranteed. As Iâve discussed in the past the first milestone of a caster is to learn to stop âwavingâ the rod. Many/most competent fly fisher persons I see on the streams/lakes can do this on their forward cast while a significant proportion continue to wave on the backcast. The next milestone, which many casters never achieve, is to develop a controlled preloading phase in the casting stroke prior to the action I refer to as the âcastâ. This is a much more sophisticated physical activity and many never get there. It is especially difficult to learn for the back cast which I assume is caused by the way our bodies are built. (Some almost get there, false casting with adequate preload and then generating significant kickback only on the final forward cast perhaps because of increased applied torques or perhaps because they are applying the cast too early.) Forget about translation//rotation unless you are analyzing (mathematically) the detailed kinematics of the casting hand//rod butt (because academically//scientifically the terminology only makes sense if you are decomposing rigid body motion into those components and they are occurring simultaneously rather than separately) and think in terms of casting phases â a (i) preload phase ( containing both rod butt translation and rotation) precedes the (ii) primary/peak rod loading phase (the âcastâ) which in turn precedes (iii) rod unloading and rod straight position which in turn precedes (iv) counter flex phase, rebound, etc. I personally donât have any real disagreement with using the translation/rotation terminology because I immediately visualize the speaker/writer trying to describe the real process involving preload (âtranslationâ) of rod followed by achievement of peak rod loads (the âcastâ or ârotationâ) but not aware of precisely what he is trying to describe or the terminology that best suits the job.

The attachments show plots of strain gage histories of an MSU student (Alex) and myself â see if you can see what produces the tailing loops on Alexâs forward casts (forward cast yield negative strains because of the manner in which the gage was mounted). Also you see that the line does not have to be engaged to generate rod loading. The other file has plots of casting 60 ft of line and you can see the additional rod loading required.

4) I preface these comments by saying they apply most strongly to situations where considerable rod deflections occur â Iâm no entirely sure today but I do not think they apply as strongly to situations like the Korich and Rajeff videos of distance casts on the ACA web site where the casts feature smaller rod defections and much larger peak caster input angular velocities. Not having a âhard stopâ is paramount to achieving straighter rod tip motion in situations where rod loading//unloading are strong contributors to line speed. These considerations results from the geometry changes associated with rod unloading. (This is not related to the discussion in #1 which only depends on the caster continuing to hold the rod.) Certain things can and are done to improve linearity//straightness of tip motion but none of them can be associated with âstopping hardâ. Some of these adaptations are sophisticated and might be done without the caster even knowing he is doing them â not totally surprising these actions arenât generally appreciated//understood since the idea you are stopping the rod is very popular but is in direct contradiction to actual physical activity (what the caster and the rod are actually doing as described in the prior paragraphs). I have in the past I posted detailed graphically presented data on the mechanics of achieving a long span of straight rod tip motion (stereoscopic 200 fps video records) and this data shows how essential it is to continue applying moments//torque while the rod unloads and continuing to rotate the rod butt. Stopping the rod// rod butt rotation would ruin the cast (not to mention the rod shaking it would create). Pictures from the data also demonstrate that the rod tip completes unloading (RSP) several feet after maximum line speeds are achieved (another equivalent statement is that loop initiation for a long cast occurs several feet before RSP). That is to say that while rod straight position will be when the rod tip is moving fastest, the gross (majority of) fly line gained no kinetic energy during the last several feet of tip motion approaching rod straight position. This is an issue related to the vector qualities of the velocity vector and it is necessary to think in terms of 2 rather than 1 dimension. The essence of the cast is over several feet before RSP and thereafter the bulk of the fly line is in free flight.

5) The relationship between rod stored energy and energy directly from motion derived from human boundary conditions (rod butt rotation, say) will be discussed because recent discussions about this are at odds with what I believe and the relevant data that is available. Basically you can always reduce the contribution on the rod stored energy

a) by minimizing the load on the rod, or b) using a rod which is stiff enough that rod deflections are significantly reduced (this, I think, is the case with the Korich and Rajeff examples shown on the ACA site). For example, reduce the acceleration inputs to the rod handle (go into more of a âwavingâ mode â if the pictures presented in the Lovoll//Borger article are representative it appears that is the situation with their data along with what I regard as unusual mathematics for their metric of elastic return contribution), use a very stiff rod to reduce rod deflections, or use a shorter length of fly line. However, that said I would assume the real question is how much does the rod contribute in a real fishing situation where greater (rather than minimum) performance is sought/achieved. Good photographic records allow you to estimate this. A special tribute to Perkins/Richards (our frequent contributor Bruce) for providing high quality data and analyzing the data. The Perkins/Richards data shows that about 80% of the final energy is attributable to the rod in their testing with casts of only 35 ft of fly line. Also special thanks and tribute to Guy Manning for expending the effort to achieve some of best photography showing other instances with high performance casts. Guyâs photography allows us to estimate what happens in the high performance casts that Guy photographed. Guyâs photography also illuminates what I call the 2^nd paradigm of high performance casting which is discussed separately below.

Another subject in this general area is the simple classic test that probably has been done numerous times. I read in Vincent Marinaroâs âIn the Ring of the Riseâ about his experience with this test and his conclusion that rod swing was in some way necessary without being specific how but yet I think implying the energy associated with swing was important. Gordy mentioned another source who had also concluded something similar from his experience with this or perhaps a similar test. I personally am not satisfied with these results and have made an obscure note somewhere in my piles to try a test which has a chance of success. At least in Marinaroâs case, the rod tip is pulled back with the rod at a vertical orientation and therein lays the problem. To perform a more meaningful test you will need a helper (which is the reason I havenât done the test myself â never having another person interested in fly casting around when I think of this item). What you want to do is load with rod with a stationary butt but the orientation should be maybe 60 degrees from the vertical. So have your helper stationed on his knees (to bring the tip lower) and hold the rod vertical while you grasp the fly line//leader end (say 40 ft of fly line beyond tip) and walk backward far enough to say yield 6 ft of rod deflection. Then have the person rotate the rod 60 degrees forward as you move forward (probably have to move forward about 6 ft for a 9 ft rod) to preserve the rod deflection. Then you let go of the end of the leader and see what happens. Since I have thought of this but havenât done it I can only use intuition to predict that the line will turn over reasonably well. I anticipate that the problems in what Marinaro describes come from using a vertical rod orientation.

6) --- see item 8) below

7) Line reversal loading is a third key concept to understanding how casting works (the mechanics of casting) in many situations, especially our typical fishing situations. This is basically a statement of Newtonâs Law applied to the rod-fly line system. From a practical standpoint it implies that sooner will be better than later in most casting as will be discussed later. It runs counter to the commonly quoted advice of allowing a false cast to fully extend before initiating the next cast. Casting can be (and for most of us often is) basically a momentum limited activity. The momentum of the fly line at the end of a cast is a physically small quantity and line momentum change is a primary resource in developing rod load. You want to use whatever methods are available to maximize the momentum change that can be converted into rod loading. Finding additional momentum should in most situations lead to increased rod loading.

8) The several paradigms of high performance casting I am familiar with are discussed next. Since examining the ACA videos I have to expand by adding a 3^rd paradigm that more closely describes the significant features of the Rajeff and Korich examples â this paradigm is essentially what one can anticipate by theory as providing the largest âswingâ contribution. 1^st paradigm is cast mechanics which depend highly upon angular accelerations produced by rotations produced at wrist joint in order to load the rod and where subsequent unloading causes major line speed increases. This is personally how I cast and thought was generally universal â it is perhaps more universal for, shall I say, real fishing situations with fishing style rods. This paradigm counts on preloading the rod, saving wrist rotation until the total stroke is well along, bracing your body muscles to support elevated (exertive) wrist rotations while producing the main rod butt rotation, and then allowing the cast to unfold. As discussed below under âvery tight loopsâ sophisticated rod adjustments during COUNTERFLEX/REBOUND can be added to reduce the size of the loop, especially the early-on loop size. In no way is intentional ârod stopâ necessary or executed. Guy Manningâs sequence of photos of Jay Clark seems to illustrate this paradigm. Why? Because you will note that the casterâs arm is nearly straight horizontal when the wrist rotation is applied and when rod unloading occurs. Thus hand translation velocity will be small during rod unloading when peak line speeds are developed. Guy also has a photo of Steve R. casting a continuous fly line in a very similar pose (all the other photos discussed here involve casting a distance shooting head and it appears that Rajeff uses a different casting technique for distance heads than for continuous fly lines). The second paradigm is that shown on Guy Manningâs video photos of Rene G. where rotations coming through the shoulder (and show-up as forearm rotations) become more important in loading the rod - the wrist is rotated near the end of the cast while the rod is already unloading. Also it appears a base velocity is maintained by moving the hand forward while the rod is unloading. You can look at the hand motion and wrist rotation as performing work during rod unloading and adding to the energy in the system during unloading (i.e., energy added during unloading is the sum of rod unloading plus additional work done via wrist rotation). So additional final line energy is achieved. One difference between the 1^st and 2^nd paradigms is the significance of shoulder rotations - the first paradigm uses them in generating preload and relies on wrist rotation to generate peak rod loading while the 2^nd paradigm uses shoulder rotation as a//the primary mechanism for generating peak rod loading. Both of the two examples above generate much higher angular velocities without using the wrist than I thought were possible. This is interesting to me because 15 years ago or so I tested myself in an effort to determine how best to generate rod butt angular accelerations/velocities by making 60 degree rod butt excursions back and forth in a fixed period of time. I found that I was much quicker with my wrist than with my shoulder so I concluded that wrist rotation would be the primary source of rod loading accelerations (as well as tip speed induced by rod âswingâ) as opposed to shoulder based rotations. I now see that the test is flawed because use of the shoulder involves what I calling âbracingâ (muscular bracing) where muscles in areas outside of the shoulder must be contracted (like back, bicep, triceps, and legs) in association with performing a rapid shoulder rotation. In performing the test all this contraction with the shoulder movements reduces the rate at which the cyclic movements are made so misleading results are developed. The third paradigm is described by video images at the ACA site where Video of Steve Rajeff and Chris Korich are shown. Assuming that the camera recording rate is accurately estimated at 30 fps (I am assuming that it is reasonable to assume 1s/30 elapses between frames) you can see some of the effects that are employed â rod unloading is not nearly as important on the total effect especially for Rajeff, base motion (translation of hand) is much more important by observing that other events correspond with times of high hand speed so high hand speed adds directly to line velocity. One of these events is rod butt rotation, butt rotations possibly as large as 50 degrees per frame are shown (in engineering units, 26 radians/s implying tip speeds, assuming an arc length of 7.5 feet which allows loss of 1 ft length due to rod deflection, of 200 ft/s due to âswingâ contribution of cast), note that the haul occurs in two frames (1s/15) and might be about 4 ft in length with average velocity about 60 ft second, in that same two frames the hand translates about the length of Rajeffâs arm so about two ft contributing 30ft/s of average speed to the line. In theory this is the best way to achieve maximum âswingâ contribution (superimposing rotational contributions from shoulder and wrist rather than separating them, and simultaneously combining with peak haul speed and peak hand translation speed and if the rod is unloading during this instant so much the better)â without the contribution of rod unloading being added to the picture we are in the area of 300 ft/s of line velocity. It is interesting to me that Clark and Gillebert show more rod deflection than Rajeff and Korich. This is surprising because there is some universality in rods employed for this type of casting because the ACA makes available rod blanks (~$200/blank) to their members especially built for purposes of distance casts with shooting heads. I personally have a rod built from the blank circa 1990 and I can tell you it is very stiff. It is a paradox that in the photos Rajeff appears to produce less rod deflection than Rene G. (assuming everyone is using the same basic rod model). So you see that rod performance can be substantially eliminated from determining cast results but you personally may be limited by your athletic abilities as well as the utility of casting a head in typical fishing situations.

I have to wonder about use of the 3^rd paradigm in many fishing//casting situations. While I do not have proof for this today I suspect that the 3^rd paradigm is strongly related to casting a shooting head configuration and that the paradigm isnât as suitable for false casting typical floating fly lines. More thought is required on this. In fact I think the same individuals casting continuous fly lines revert back to paradigm 1 when casting standard fly lines. Guy Manning took a photo of Steve R. which seems to show him using Paradigm 1 (I ran into this photo at an internet site Steve Rajeff maintained at the time).

9) Iâve seen discussion in various forms regarding differences in elliptical and regular casting motions. It is difficult to reconcile what is being stated. Some basic facts havenât been emphasized including that the nature of the line system being used is very important â probably the most important. The mass flow rate through the loop leading edge (along with vector velocity change between top and bottom legs of loop adjacent to leading edge) effects the momentum changes occurring from the bottom to the top leg which determines the difference in tension internal to the fly line between those two locations. Several years ago on Guyâs site I gave a laymanâs blow by blow extended description of what happens here under something titled like âfly line dynamicsâ. From basic casting experience we probably all know the if you are using a shooting head and start the next cast before the head reaches the leading edge that it is like grabbing air. I would think//assume for the elliptical cast to work smoothly you need a fly line with either a very long head or one which is all head (like a DT) so that this situation is not encountered. Then because of line reversal loading any time the rod is moved in the cast direction tension is elevated throughout the line due both to accelerating the bottom leg as well as increasing the tension jump at the leading edge due to line reversal loading. I donât think you would want to employ elliptical inputs if you are using bass bug taper (short head). When the line belly is in the leading edge any decent cast âelliptical or otherwise - will cause a tension jump across the leading edge. Line tension along the bottom is increased by accelerating the bottom leg â presumably this occurs earlier in time with elliptical casts and may result in reduced peak values because the total momentum changes are spread across a longer time duration. It is hard for me to see what huge fundamental differences occur in the two casts â perhaps one could impart a significant vertical wave in the fly line on back casting to help elevate the line in the backcast? It would be interesting to explore the elliptical cast in more detail because at a Conclave in the early 2000âs I saw someone from Scandinavia or Austria (probably by virtue of casterâs name) demonstrating and I was amazed at the cast â canât describe what was done exactly but was totally surprised.

10) Several years ago I tried to start a thread regarding what casters can feel//sense when casting. The basic intent of the line of inquiry would have been to pursue what our senses tell us when casting and how the information can be used. However I could see from the scant responses that the remarks were not headed in the directions I had hoped for and dropped any follow-up. In general I think your senses are misleading you part of the time â why else you even begin to believe you are trying to stop the rod when you are actually doing all you can to accelerate it. As far as I can tell the basic senses available to you are tactile sense in your hand and feeling the muscle contractions that you as the caster are executing. The dominate hand tactile sensing is through pressure applied on the rod handle. It would be nice if, as humans with normal abilities, we could reduce this data. However when I rotate a rod with my wrist I am aware I press on the top on the grip with my thumb and with my little finger at the bottom to generate forward torque. But I have the rod in such a strong grip for higher performance casts that the overall gripping pressure overwhelms the additional pressures which cause angular acceleration. Similarly with angular rotations of the forearm, muscular contractions obscure sensory feedback from the hand (I donât think that the arm muscles will help you sense what angular acceleration is being generated in the forearm). It is these broad muscular contractions that are the most readily detected and give the strongest sensory signals (that is, you sense Ã âyes, my arm muscles are contractedâ). For my own purposes I gave this overall effect the name of âbracingâ because that is the role of these muscular activities where they help to create a total human/rod/fly line system which can act most responsively when cast. I discussed this with another faculty member at MSU whose specialty is physiology and human performance and asked what terminology professionals might using in describing this lemma (Dr. Mike Hahn). He thought they would call it âco-contractionâ which is very descriptive because I presume the term to identify when opposing muscles are contracted simultaneous not to perform work but to stiffen (hence brace) a bodily span. A laymanâs description might go like this; imagine a fly rod to which is strapped a flexible plastic ruler and you grasp the ruler and rotate it to cast the rod. Poor results are predictable. Now suppose rather than the plastic ruler a titanium tube is fit tightly over the handle and the tube is rotated. The later system does not introduce significant flexibility and is a good brace. The same thing has to be done by the body if motion (particularly accelerations) is to be imparted â the wrist needs good bracing if it is rotate the rod butt with large angular rotations and similarly if one is to produce large forearm angular accelerations then bracing is required throughout most of the body. Hence you see extreme casts being made with various sets of movements up to the time of casts with maximal possible contractions over broad areas of the body. From some of the photos itâs not that hard to imagine that muscle contractions for the purpose of stiffening the body and transferring loads to the ground are occurring. From the discipline of Structural Dynamics it would be presumed that flexible (soft) regions reduce the natural frequency of the fundamental structural vibration mode and lead to slower development of loads (which means reduced performance if the rod is being used as the prime contributor to performance) as well as reduced rod butt angular velocities. In just having picked-up a rod and mock casted it I am becoming firmer in the feeling that most feedback is coming during counterflex when the torque has to be reversed to maintain control of the rod. If this is true then you do not so much feel the rod load or unload as knowing it did unload from the reversed torque applied during counterflex. Of course this is a perfectly valid feedback mechanism.

By the way I think we have no, or very weak sensing ability to sense angular acceleration â it would be necessary to be able to process the net forces at the top and bottom of the hand and compute their difference. I doubt this can be done. What this points to is the benefit of technology that something like the Casting Analyzer would provide. It seems like this would allow a caster to experiment while knowing what changes in turn are produced in terms of rod butt angular velocity and acceleration. You would have no other direct way of knowing angular velocity//acceleration excursions for your cast.

11) Slide Loading â I think slide loading can be a real effect. Jeff Wagner has written to me and indicated he uses a form of slide loading on his final back cast in his maximum distance casts. I donât remember exactly which of Lefty Kreyâs publications or presentations addresses it but I recall him identifying the technique. As indicated in other posts, others have also described slide loading. I will describe my version of it with the nuance I think that produces results for me. For me this is a cast that is fun because of the results it produces. This cast is made using a Bass Bug type fly line (short belly floating line) with only the head outside the tip top. On the last false back cast the fly line is released and shortly after the rod is moved relatively quickly forward. The line slides through the guides while the rod deflects (self loading and kickback) and begins moving forward. At some point in here (after a short translation and rotation of the rod butt) the rod tip is moving with significant speed in the forward direction and the fly line belly is moving back ward. The fly line is suddenly grasped so it can no longer slide through the guides. Now the lower leg of the fly line and the tip of the rod must have the same//compatible velocities. The fly line lower leg is reversed and speeded-up and the rod tip experiences a sudden rise in lateral//loading force. Since the momentum of the line and rod were in opposite vector directions a considerable amount of momentum exchange occurs in a short time period. Iâm not sure what the total effects are but it is clear from the results that rod loading is heightened. Impressive amounts of line shoot occur when the timing is good and the line is efficiently grasped. I think that this can be done (for people who have greater skill) with longer lengths of line but for me things get dicey in particular because I have lots of trouble grabbing the line. I wouldnât be surprised if good timing is also more difficult to achieve because the rod loads up quickly and when it does it will immediately begin unloading. The fly line needs to be straight at this instant. There is probably little tolerance for sagging or slack line because a fast moving rod tip and large velocity difference is desirable when the tip and the line engage one another. Itâs a fun cast on a lawn but it becomes boring after a few cycles because so much time is spent retrieving fly line for the next cast. Iâll have to measure accurately next summer but I think placing the leader end about 90 feet out occurs when starting with around 30 feet of line beyond the tip. On the surface this almost seems like a violation of the requirements associated with rod tip kick back. However rod tip kickback is not on issue provided the line and rod tip due not engage one another until the rod tip is moving smartly in the direction of the cast. The principle points here are that the tip should be moving forward rapidly, the fly line should be moving backward without slack and have only a limited amount of line in the top leg, and foremost the caster must be able to solidly clamp the fly line when a haul motion is initiated.

I want to mention some good things I have seen on the message board. I liked Walterâs description of physics applicable to fly casting he posted several months ago. In particular paying attention to how mechanical work is performed is worthwhile because work = energy and the term âenergyâ seems to be frequently misapplied. Guy Manning has taken some amazing photographs that reveal details about casting. After reviewing his clear photos the photos on the ACA site can be approached with more confidence. These items were reviewed in some detail in #4 above. If you are interested in seeing his photograph sequences ask him for the web address where he has them available. Also Guy has a photograph of Steve Rajeff casting a continuous fly line which strongly implies he is using paradigm #1 â the photo shows him with a highly loaded rod (large rod deflections) applying wrist rotation while reaching almost full extension of his right arm. The difference with paradigm #3 is that 1) max wrist and forearm rotational velocities are not simultaneous and 2) high base linear velocity does not occur when peak tip velocity occurs. So this differs from the paradigm 3 cast because the base (hand) motion//velocity will be substantially reduced during wrist rotation and rod unloading. I found this picture several years ago on a web site that Rajeff was involved with but it no longer seems to be available. Guy mentioned to me that he thought he also took that photograph. Guy seems to have the touch in capturing these revealing photos. From further back is the very important article by Perkins/Richards where they using both the angular velocity gyro gauge and strain gauges â this article in my view is very important and I have examined it numerous times.

Additional discussion supporting main points follows. Some additional casting mechanics is described.

HARD STOP -- I had been wondering if the âhard stopâ phraseology would eventually creep back into the posts and it has (Troy explicitly used it not that long ago and I think Walter did also and even more recently several other posters and in November it was brought-in in the same fashion as in the old days â even some sort of a 5 part description of casting includes it and by the way the 5-parter really seems to say little about casting). Since I started writing this document it has been brought up any number of times and been elevated once again to the status of a âprincipleâ. Iâve tried to make a strong point of this in the past â itâs not a matter of the caster trying to stop the rod or a stopping activity requiring time to be accomplished. No; itâs a matter of actually trying to rotate the rod faster during the period/phase when the old explanations insisted the caster was performing his âhard stopâ. This means just the opposite is true. Also the sensation fooling you is the vast muscular contractions associated with performing a cast rather than actually being involved in any stopping activity â a lot of what does happen is a by-product of fly rod structural dynamics.

I provided a mathematic proof in the past. That proof is related to the fact the rod- fly line system has increasing angular momentum until rod straight position is achieved (remember this as the end of rod unloading). This means that external torques//moments associated with the casting direction are being applied â pure and simple â all the way from the start of a cast right up to the moment the rod is straight! Another separate proof comes from understanding how fly rods work; from acknowledging the nature of the rod bend/curvature just above the casting hand and understanding what this means about the torque applied to the rod. The torque applied to the rod is always in the same direction from initiation of a cast until the end of rod unloading â a simple fact. In order to say you are trying to stop something implies the direction of loading is reversed at the moment stopping is initiated (as in suddenly applying brakes in a car). In the case of a fishing rod this also means the curvature of the rod just above the casters hand has to be reversed when stopping is initiated due to reversing the direction of the torque. This event is not associated with passing the moment of peak rod loads. In casting this happens at and after rod straight position and it is more a function//property of rod structural dynamics (a by-product) than anything the caster does intentionally (meaning a human caster canât do anything about it provided he continues to hold the rod in his hand). I suppose this will not be easy for most readers to understand but during rod unloading the curvature in the rod is such that torques in the casting direction must be applied if the simple bent shape of the rod is to be maintained during rod unloading (the amplitude of the deflection profile â that is, the bent shape â decreases during unloading). The curvature of the rod next to the casterâs hand is related in a one-to-one manner to the torque applied by the casterâs hand â my meaning in this is that the instant the torque changes the curvature adjacent to the grip also changes. In engineering parlance you can say that the rod butt curvature (equivalently bending strains) tranduces the applied torque because of the close proximity of structure (dynamic âtransfer functionâ near 1.0) to the load application region. As stated in the preamble, such is the symbiotic relationship between caster and rod â violating it by actually introducing a stopping torque would yield a rod which feels like it is shaking in your hand (because it would) and the rod would no longer have a smooth deflected profile. So the bottom lines are that there is no hard stopping, the rod will unload when it sees fit to do so (provided the caster has actually loaded the rod â i.e., is not waving the rod) and the caster will continue applying positive casting (as opposed to retarding) torques until about the time counter flexing starts. The same is true for the net force applied to the rod because during rod unloading not only does the angular momentum increase but the linear momentum also increases.

By the way, the seminal Perkins-Richards article of several years ago very clearly shows a number of things that occur in casting and is wonderful information (especially related to the paradigms #1 and #2). This article showed how rod bending (plots of strain versus time) just above the grip changed with time and also the rod butt angular velocity as a function of time. Rod straight position occurs where the strain becomes zero. Rod unloading initiates when the strain hits its peak value (bend in the rod is the largest). The angular velocity of the rod butt is not directly related to angular momentum except at the instant when rod bending//deflection hits peak value â this is because at that instant the rod acts momentarily like a rigid body. A curious feature of the data shown in the article is the relationship between two very different physical quantities. These are the rod butt strain and the butt angular velocity. If you are familiar with the article (hopefully you saved it way back when it was published â also Bruce has posted these plots here several times I think) you may remember that the rod butt angular velocity and strain hit their peaks at very nearly the same time. Rod butt maximum strains occur when rod loading is at its peak so the data indicates that butt angular velocities peak when the rod deflection is largest. I am going to provide a structural dynamics analysis//explanation of what happens to the rod. In performing any type of analysis it is customary to list the assumptions under which the analysis holds so I do this now (Assumptions on rod behavior â the spirit of this is that if these assumptions are violated the analysis also becomes suspect)

1) In progressing from butt to tip, at all times, the lateral//side wards deflection and the slope continuously increases in moving toward the tip of rod (i.e., rod has a smooth deflection profile â those of you that have examined many photos of casting know that this is by and large true)

2) This means that angle of the tangent line to the rod (ârod slopeâ) continuously decreases (that is becomes more negative) in progressing from butt to tip (assuming CCW is positive rotation and that a forward cast is being considered)

3) Hence during rod loading you can conclude that rod angular velocities are negative along the entire rod with smaller magnitudes at the butt and the magnitudes become larger in moving toward the tip. The opposite occurs during rod unloading.

When rod unloading occurs the rod butt angular velocity wants to decrease because of the fly rod structural dynamics. You may be asking yourself âwhy is this true?â. It is because with rod unloading the rod bending is reduced along the entire rod and for a rod suspended in space this induces CCW rotations near the tip and CW rotations at the butt (such that angular momentum is unchanged for the suspended rod). This behavior is superimposed on the response to inputs the caster is making â these inputs are the continuing torques that were described in an earlier portion of this document. The continuing torques cause the total angular momentum to increase but these increases are overwhelmed by angular momentum increases from the rod unloading and from increasing fly line speed. Hence after the âtipping pointâ the rod butt angular velocity cannot be maintained and during rod unloading the rod butt angular velocity drops. Human physiology is no doubt also a factor in that body has been expending the rotational range it can apply to the rod butt. To maintain the rod butt angular velocity once rod unloading starts would require that the rod bending and thus torque applied by caster drop off much more slowly than typically occurs. This is fairly sophisticated structural dynamics. When examining Casting Analyzer data that shows the rod butt angular velocity peaking//dropping remember that this is also when the strain (rod bend) has its largest value. Thus the initiation of dropping butt angular velocities means that the rod is also starting to unload. Itâs really a good thing that Perkins/Richards took both gyro and strain gauge measurement because it would have been easy to think that the reduction in rod butt angular velocity was caused by retarding moments rather than as a by-product of rod structural dynamics.

I am changing the subject right now. In 2006 I had a short intersection with Noel Perkins while he was examining my results on the Casting Analyzer. To comply with his request I intentionally tightened my loop. The Analyzer clearly showed that I had briefly reversed the rotation of the rod butt. His interpretation may have been that this is a hard stop but what it is (in fact, easy to see on Analyzer outputs) is that during rod counterflex//rebound when the torque on the rod must be reversed the rod is rotated slightly in the direction of the torque (reverse direction). This raises the rod tip and brings the lower leg of the fly line closer to the top leg. (((The effects of doing the opposite came up in some resent posts involving M. Heritage and Bruce Richards referencing photo images credited to âvictorâ at âSexy Loopsâ. You can see how the main effect of continuing rotation after rod unloading is the initial positioning of the bottom leg. It is done while the rod is traveling from peak counterflex to the second straight position (for my casting, only minimal rod vibrations occur after this time))). I am guessing but I suspect that the misplaced use of âhard stopâ terminology is in part due to seeing the plots of angular velocity decrease after peak rod loading and assuming this is something the caster is intentionally invoking. This behavior (decreasing angular velocity of rod butt) cannot be altered by the caster because it is simply a consequence of rod unloading. Had âvictorâ been using the Casting Analyzer it would have shown the rod butt angular velocity decreasing in the same way during rod unloading (since he apparently was consciously trying not to stop the rod).

Obviously you canât be trying to stop a rod until you apply torques that resist the rotation. Resisting torques require the strain to first pass through zero and change sign (became negative).

Bruce has in the past posted typical records of Perkins-Richards data (perhaps the records used in the magazine articles?) which clearly/consistently demonstrates these features of fly rod response. If necessary perhaps he could post them once more. I provided mathematical proof that casting direction moments are applied during unloading and now offer readers the explanation based on observing the strain gauge records of Perkins-Richards. Bear in mind these are consistent with the commonly understood behavior of fly rods . Both explanations are somewhat technical but both are unequivocal. Rod unloading sees the rod unload while the caster continues to apply positive torques (not negative) which magically become zero at RSP and then apply negative torques (that is âstoppingâ type) during counter flex//rebound. And actually this is in part the casterâs reaction to what the rod is doing dynamically (for example if the caster were capable of releasing the rod at RSP the behavior of the rod would be considerably different and marked by what you might call âshakingâ). Also see the discussion below called âvery tight loopsâ because it deals with a related matter.

In summary, I see a lot of descriptions of casting that are inaccurate in the fundamentals and the conclusions drawn from them similarly lack merit. If you want your descriptions to have merit you need to eliminate âhard stopâ from your lexicon and describe what actually occurs.

PRELOAD is better than TRANSLATION -- Once a caster is at the position he can make a rudimentary cast â this means the caster has progressed beyond rod waving (waving = non-energized simultaneous rotation of wrist and forearm) and can successfully load the fly rod - then the next goal is to be able to produce rod preload in a controlled fashion. Readers who have been here for a long enough time will remember the simple demonstration I documented on tip kickback â place a sudden finite (meaning, apply suddenly) torque on a resting fly rod and the tip moves backwards. This results in several bad things when it occurs during actual casting -- the tip moves backwards and the tip moves through a convex trajectory. Because accelerations cannot be maintained the rod unloads early in the total motion of the caster. If you become skilled at observing you can directly observe casters executing this fault â the tip stops driving the line as it moves backwards then bangs into it and the tip trajectory as well as the action of the rod tip on the line (that is pulling the line near the rod tip downward initially and then eventually driving it forward and upward) automatically produces a tailing loop. The rod tip motion is the key to visualizing and understanding the consequences of this fault of experienced casters â understanding the vertical motions of the rod tip as well as the horizontal motions. With preload the disruptive vertical motions are eliminated as well as the reversal//slow down of the tip â both contribute to degrading the cast. This is the cause of a tailing loops â kickback because of inadequate preload in real casts (that is, I define any âreal castâ as one that actually produces significant rod load/bending â actions that are described as rod âwavingâ produce insignificant rod loading and do not qualify as a âreal castâ). Now test your rod with preload â have someone hold the tip for you while you preload then give it a sudden larger torque and pull/jerk it away from the person holding it. If the preload is sufficient it is doubtful you can make the tip slap your helper or make the tip move significantly downward before it begins moving forward (or rearward for a backcast). I find it surprising about some of Walterâs recent comments (the ones mentioning âstopsâ) because the way my original commentary on kickback came up on this bulletin board was in answering a question Walter had about why he was experiencing tailing loops he couldnât control. I subsequently met Walter that summer at the Conclave and confirmed to myself he was then prone to this situation (that was 2 Â years ago so it doesnât apply today). Also you may say to yourself that when done well it is hard to note two separate phases but the reality of separate phases comes into play when problems in casting mechanics arise and a solution is sought (to the problem of faults with the first phase). With an instrumented rod it is easier to observe the differences between a cast with proper preload and casts without proper preload. So I have posted strain gauge records that show the difference between proper preload and improper preload. The attached file shows strain gauge records by Alex â a past Engineering student of mine â and by me. The portions where the recorded strains are negative are the forward casts and see if you can identify why Alexâs forward casts consistently produced very strong tailing loops. By the way a few interesting bylines are that the snapback cast is an example of intentionally applying kickback, throwing the fly back to yourself by slapping the rod down is another example, and Paul Arden has a cast he calls âchange of directionâ which is a fairly sophisticated application of kickback in that he does the kickback after the cast has been initiated, if I remember right. I think from a face to face conversation with Paul (2006) that he does not accept that what is happening is a tip kickback. However the video he has posted on his web site leaves little doubt that kickback is employed in driving the cast backward â a very elegant but âdifferentâ type of cast in my mind. I still wonder where a person would use that cast â I couldnât tell the potential applications from the video â and perhaps Paul would give an explanation.

So in summary, while it is not totally apparent why the term translation/rotation was initially used, itâs not a bad way (inaccurate maybe, but not bad) of conveying the idea that things happen in several phases. These are the rod preload phase and the second phase is achieving maximum rod loading (again I call it âthe castâ and others use terms like âpower snapâ, etc., etc.). You can roughly associate âtranslationâ with preloading the rod and ârotationâ as the cast phase achieving maximum rod loading. At least, that is what came to my mind when I heard the phrase so I felt it had value in conveying those notions. None of the subsequent commentary has gone into substantial matters because that would require developing a more detailed understanding of preloadâs role and also the details associated with the cast phase. Iâve gone through these I believe â pure and simple, the phase before âthe castâ must develop a preloaded rod which is engaged with the fly line. Deficiencies in the first phase lead to problems in the next which lead to formation of a tailing loop in the third and fourth phases of rod unloading and fly line flight. By the way, I think it would be interesting to be able to cast with a pure translational phase followed by a rotational power application â this would allow you to start with the rod at a more vertical attitude and develop rod load in the preloading phase more efficiently, maybe. However this would require the caster to use reverse wrist rotations to counteract the rotation of the forearm which is a tricky movement. A possible advantage is that for the backcast you could have the line engage the rod through line reversal loading with the rod in a more vertical attitude and possibly generate greater preload in the back cast but these motions are a challenge.

STRAIGHTER ROD TIP MOTION -- The third item I mention above deals with achieving straight rod tip motion. I see lot of mention of how straight rod tip motion is achievable but must dismiss most of it. Several times in the past high speed stereoscopic (that is 3-D) data has been transmitted to this bulletin board showing how a long segment of straight rod tip motion can be achieved under conditions where the rod is highly bent. This is achieved precisely by continuing to rotate the base of the rod so that as the rod straightens the tip motion remains in a straight line. Stopping rotation of the rod base directly after peak rod load would produce a very large tailing loop â for success in essence you have to rotate the rod fairly rapidly to not have the rod tip climb above the oncoming fly line. From the curvature of the rod near the rod butt it is obvious that torque is not reversed during this period. The graphics so clearly shows this that there is really no need for additional discussion of that portion of the subject.

VERY TIGHT LOOPS â (Some of this is essentially repetition of material above.) However the subject of absolutely minimizing the size of the loop goes a little bit beyond that above because it is necessary to account for behavior during rod counterflex. I think it was at the 2006 Conclave that I had an interesting brief interchange with Noel Perkins. He had me as the caster using the Casting Analyzer and him making remarks. He was looking for something on the plots which wasnât there and at the same time using the phrase âhard stopâ. He was looking for a tighter loop while I on the other hand was making typical fishing casts. So I said yes I can cast very tight loops if we want but normally I wouldnât do this except for special fishing conditions. So I adjusted the cast a little and delivered the very tight loops â not really a big deal for the short casts we were working with. Then in looking at the data from the casting analyzer Noel pointed to a feature in the data. The feature was that the rotational velocity direction was momentarily reversed (changed sign) and he said that feature was one they see with expert casters and may have inferred it was associated with a hard stop. He needed to get on to other Conclave attendees so we did not get to interpret the meaning further. However my conclusion, based in part to what I know I did in seeking in extra tight loop, is not that a hard stop was applied, but that once counterflex//rebound started I in essence went with it and reversed the rod rotation direction by exaggerating rebound. The effect of this is that normally in counterflex the rod tip dips downward and drags the anchor point for the bottom leg lower thus enlarging the loop. The rod tip does not normally rise to the elevation of the flying top leg of the fly line during counter flex +rebound. During rebound the tip rises once again and is what results in the propagation of the annoying line sag down the line which line tension will eventually smooth out. To reduce loop size then requires that the tip not fall so much during counterflex+rebound which can be impacted by subtle reversal of the rotation at the rod butt. In no way can this be construed as the mythical hard stop because this stuff is occurring subsequent to rod unloading. That was in 2006. In thinking about my own casting I realized I couldnât perform this same correction//action in my back casts and I wondered if some of the elite casters employ this tactic. I hadnât really observed anyone who did this (for example from watching Jeff Wagner and also Paul Arden they both throw very open loops on their backcasts and count on line energy to suck the legs of the line straight) for conventional overhead casts. Iâll make the note right now that thrust type casts need to be discussed separately. However at the 2007 Conclave I watched T. Rajeff demonstrate and he throws a very tight loop on his overhead backcasts. I was able to observe the subtle lifting of the rod tip â I couldnât really discern if it occurred during rod counterflex or rod rebound â but it counteracted the drop during counterflex and yielded very small backcast loops. So I consider this confirmed â it can be done .

Also discussed in the past is the physical conditions//point where the fly line accelerating portion of the cast ends. From the data//graphics I talked about earlier it is not difficult to see that the fly line reaches its peak speed in the direction of the cast well before rod straight position. After this point the rod tip continues to speed up but the rod tip velocity vector is directed at an increasingly vertical (rather than horizontal direction) and the horizontal velocity component of the tip stops increasing and thus the theoretical start of the loop is somewhere before RSP. No big deal but itâs true. I just mention this because so many board discussions throw in comments about RSP â RSP has these two fundamental properties Ã 1) it marks the transition from rod unloading phase to the counter flex phase of rod vibration//motion and 2) the speed of the tip has reached its highest speed although a major portion of that speed is directed at the ground (for example if RSP is at 45 degrees then the horizontal and vertical tip velocities are 70% of the tip speed). The second property affects the fly line in that it causes the loop to open up which is then further exacerbated during counter flex where further loop opening may also occur depending on how the caster handles rod motion after RSP. Walter S. recently posted a nice description of some fundamentals of physics with direct application to fly casting â a very nice service on his part and I encourage those without an academic background on the subjects to save and review it once in a while. I want Walter to consider me as a friend so I hope I am not injuring his feelings a lot but Walter occasionally mentions RSP as the very moment where the loop begins. This would be true if the rod tip moved in an absolutely straight line up to RSP. But the trajectory of the rod tip is not a straight line: it follows a 2-dimensional path especially as it approaches RSP. Accounting for the 2-dimensional motion of the rod tip explains why the bulk of the line has stopped accelerating while the tip is still increasing its speed slightly (and pulling the line closest to the tip downward). As Iâve said before this is no big deal because even the speed of the rod tip doesnât change much during the last 20% of travel (assuming a long cast is being made) and most of the change in the velocity vector is in vector direction (developing a significant downward velocity component) rather than in magnitude . So Walter may want to someday add to his valuable discussion of physics fundamentals by exploring the vector properties of velocity and the 2-dimensional character of rod tip (and therefore fly line) velocity.

Finally, several years ago I discussed the notion of line reversal loading and described why I believe it is fundamental to casting effectiveness (at least with the fly rods typically used in fishing). A major limitation in casting is limits on the amount of impulse (linear and angular) that can be achieved â for a given weight line, the more impulse the caster can exert on the rod the higher the potential performance during unloading. However there are only a few mechanisms that can be invoked to yield impulse//rod loading (in other words â no âmechanismsâ means you would effectively be using a rigid rod and waving the rod in casting). One mechanism is the inertia of the rod. In fact in âkickbackâ the loading must be due entirely to rod inertia because any tension in the fly line (and thus any coupling between rod tip and line) is being eliminated or reduced so the fly line does not participate in producing kickback. And from the data I have shown (Alexâs strain records), for normal fly rods, the impulse required to move just the rod itself can generate significant rod loading. So rod inertia is usually important. The other is the linear momentum of the fly line. Changes (rate of change is the concept but to keep the verbiage down with the non-technical audience I am using âchangeâ to mean rate of change - the key idea for achieving understanding) in the linear momentum of the fly line allow the line to load the rod. Anything the caster can do to increase the change in fly line linear momentum can potentially increase the peak rod loading. Thus, for example âhaulingâ can come into play because when it causes the bottom leg to move faster the jump (change) in line vector velocity causes a larger momentum change and raises the tension in the lower fly line leg. This results in additional rod deflection//loading which is your goal. Combined rod and hand motions are used as a primary method for causing linear momentum changes which load the rod. Being physically able to make speed changes more rapidly (athletic ability) is an important factor also. A profound leveraging mechanism for increasing rod loading potential is to increase the total change in fly line linear momentum and this is achieved through line reversal loading. Thus the caster uses rearward fly line momentum to increase the total momentum change to increase the rod loading. This is what I mean by âstarting earlierâ as stated above. Provided you have well formed loops start your forward and rearward movements earlier â well, well before the cast straightens. This is another of the old casting paradigms that needs to be erased â the paradigm that says the caster allows the cast in one direction to straighten before reversing direction. Interestingly (to me, anyway) is that I know I readily do this in one direction and not the other. In going from a back cast to forward cast I transition with lots of line in the top leg. On the other hand for whatever reason in transitioning from forward cast to back cast I apparently have a strong psychological need to watch the forward cast mostly straighten before starting the backcast. My attempts at training myself out of this have not been successful to date.

Bruce R. had objections to this idea of line reversal loading when I discussed it 2+ years ago and Iâm not sure I can vocalize exactly the nature of the objections. He suggested that there is lots of video which would help in understanding the situation. I think the availability of readily available video is questionable. However this year (with the purchase of a new video player where the frame by frame feature wasnât broken) I was able to examine as carefully as possible the VHS video âFly Casting with Lefty Kreyâ. I think I saw what I expected to see. For the most part in fly casting videos the viewer doesnât simultaneously see the caster, rod, and entire fly line in any frames. This is for the most part true in this video as well. But there are a couple of casting sequences where you can see Krey, the rod, and portions of the line simultaneously. In these shots I couldnât really see the fly line clearly but it appeared to me that the leader was flashing when he transitioned from back cast direction to forward cast. One would expect this because in transitioning from one cast direction to the next the leader can be caused to change speed or else straighten-out and perhaps produce a flash. I think I was able to see this â flashing of the leader. In transitioning from the back cast to the forward cast the leader flashed a little in front of Krey indicating the fly line end was near his head. This seemed to me to confirm the use of line reversal loading. These shots are at the end of the video where the credits begin. I suspect that other board participants have this video and I would ask that you review this portion of the video, and describe your impressions. I think this is the type of observation that Bruce was suggesting but the results appear in the affirmative to the significance of line reversal loading. After recognizing the physics involved in casting, the significance of line reversal loading should require no leap of faith â in fact to suggest it wouldnât be important requires explanation of the rationale. I see I havenât made a statement of the cause-effect which is that causing the line to reverse directions during the casting stroke increases the linear momentum change available for loading the rod. By all means examine the video I mention. Also if you have video that can be applied to this issue let me know so we can make arrangements for me to examine it personally.

Odds and Ends â one sees things (video records, casting demonstrations, data such as presented by Perkins/Richards) which open the possibility that common assumptions or preconceptions might not be universally valid. And the more that one sees these inconsistencies the more chance exists that important considerations have gone unobserved. As far as my own exposure goes to all the data which is no doubt out there in the world, it is very limited because there is lots out there I havenât seen. For example if I hadnât seen Guyâs photo sequences I wouldnât have believed it was possible to rotate the forearm as rapidly as was done in those photos. I thought his photos of R. G. showed the human limits of what is possible. The video on the ACA web site would not have been examined carefully if I hadnât reviewed Guyâs video images first. Those ACA videos seem to demonstrate even faster forearm rotations (I assume this means rotations are being produced primarily at the shoulder.) and very rapid haul movements. So without bumping into Guyâs video images I never would have suspected so much line speed could be produced before rod unloading is considered. If other board members have access to particularly enlightening photographic data I would appreciate hearing about it (ssadik1@xxxxxxx). Years ago I had access to a 2 hour video (from around 1990) of Steve Rajeff and Chris Korich casting (mainly continuous fly lines). My friend Dave Drennan had a copy of the tape but has since lost track of it. I would like to get a chance to review that tape now. I meet Floyd Dean several years ago at a conclave and he thinks he may have recorded the video â Iâll be sending him this write-up â perhaps it will jog his memory as to how a copy can be acquired. Iâd be interested in trying to evaluate how they generate line speed with continuous fly lines. By the way that video shows both casters with lower and upper fly line legs that cross during line travel. Some folks on this board call this a tailing loop but apparently it is acceptable in some corners. McCauley Lord calls it a âcrossoverâ as opposed to tailing loop. I am very sure these casts were all performed without rod kickback. Having the video available once again might make some interesting data available. And on the other hand members of this board might have access to lots of other data that would be equally informative and might even show other surprises. There have been several references to Dr. Al Kyteâs articles on casting. I did read these when they were published in the angling magazines but I couldnât identify what the message is. Iâll have to read them again to see if I can come away with anything that will be useful in further understanding casting (âwhat is being done, how, and whyâ).

There are certain areas that I feel are unexplored so passing mention is made to them. The area of sidearm casting especially as it relates to gravity is a dilemma to me. If you examine casting records with a time axis on them you will see that casts often involve about 1 second and a front cast âback cast sequence about 2 seconds. With gravity acting during that time there must be a vertical momentum change of 64 ft/s on the fly line. For overhead casting it is not difficult to see where the lifting occurs during the casts. When I cast sidearm I cannot see anywhere near the same amount lift occurring â it has to occur but when during the casting stroke?? All the angles appear to deviate only a small amount from horizontal providing only a small vertical component of impulse on the line? What is going on â what keeps the line from dragging across the lawn? Another area I have been meaning to examine is the area of aerodynamic resistance to fly line motion. As the loop propagates in a horizontal direction a form of aerodynamic drag referred to as âform dragâ acts on the projected face of the moving line. The magnitude of the force depends on relative speed of material pushed through the air and the frontal area. The effect of speed is very strong on form drag (square of speed) while line turnover provides a continuous force trying to drive the loop forward and increase its velocity. This is a scenario which makes you wonder if terminal velocity limits might come into play. Perhaps someone else has put the pieces together on this? An interesting feature can be discerned from Guyâs video sequence of Rene G. This is the Paradigm #2 mentioned earlier. You can see how straight the tip moves and you can see that wrist rotation and movement of the hand toward the flight line of the fly line occur simultaneously during rod unloading. This will produce a narrow loop. Turn this picture so that the cast is now a sidearm cast and the motion of the hand is backward and away from the caster during rod unloading. This may be the famous Lefty Krey backcast with the incredibly tight loops â load the rod using a rotation of the forearm (elbow close to waist) thus saving the wrist rotation and combine a limited wrist rotation with the hand motion away and backward and maybe the tip of the rod will travel straight backward as it does when Lefty casts. The energetics of the cast include the energy added by the wrist rotation while the rod is loaded/unloading (hand translation also contributes energy) and the combined wrist rotation with hand motion away from your body contribute to produce a straighter tip trajectory. When we get green grass here in Montana I look forward to seeing how closely I can mimic this motion in sidearm mode.

I conclude with the note that Iâve tried to put together many aspects of casting mechanics to provide a coherent picture. Those of you unfamiliar with physics, calculus, the engineering equations for beam types of structures, or structural dynamics of deformable bodies you may have to struggle to read it or find what you believe to be correct. That canât be helped but I have tried to form matters into non-mathematical explanations which can be interrogated and questioned more readily. If you have concerns or questions do the best you can in being specific â I am hoping it wonât be necessary to try to find old messages I posted (since this computer is only 18 months old and older posting may simply be gone).

Best regards â Server Sadik