Archive for the ‘English’ Category

practicing with ultra soft fly rods

Montag, Juli 31st, 2017

This article was also published in The Loop Magazine, April to July edition (page 13 and 14):

practicing with ultra soft fly rods

Near the end of the year 2007 I took a private fly casting course with Uwe Rieder from Austria. After seeing my cast he stated that I could improve it by practicing with soft fly rods without double hauling. I agreed to try this of course. Uwe then provided me not with a soft fly rod but with an ultra soft one from Vision (I don‘t remember the name exactly, but I guess it was a „mirage“ – due to its softness it was not available commercially). This fly rod was so soft, that the tip of the fly rod could almost be deflected towards its grip („grip action“ – see picture with Uwe). My first casts with this fly rod were lousy, since my motions were used to much stiffer rods, but as time went by I was able to adjust my motions and I elongated my casting path. This longer casting path enabled a slow and continuous increase of the deflection of the fly rod that is vital for softer fly rods and my results steadily improved. My preferred way to cast with an almost „closed wrist“ helped me a lot during these exercises. By the way, as with other superb casters, Uwe uses very little wrist actively.

Uwe made the following comment, “Tobias, there are a lot of superb casters out there that have problems casting a longer fly line with a soft fly rod. The soft fly rod indicates who can cast really well. The soft rod separates the wheat from the chaff.“

Shortly after returning to Berlin I snapped the softest fly rod I had (which I was going to sell before I finished my course with Uwe) but exercised with this very soft rod periodically for about one year.

My practice sessions with the soft rod always started by putting the fly line stretched on the meadow. As Uwe showed me I started my casting motion from my upper body followed by the shoulder and the upper arm last. The elbow always precedes the cast, which causes a significant translatory motion. When I wasn’t able to move my elbow further, the rotary motion started to prevail.

My first time practicing this was hard. I often started the rotary motion too early, which caused vibration in my soft fly rod leading to waves in the fly line. This especially happened on my forward cast. As I understood that on the one hand my elbow didn’t precede long enough and on the other hand I forced the rotary motion too much, my casting with this soft fly rod improved more and more.

After a couple of these training sessions I felt the highest effort I needed to apply into the grip was for a very short moment around the vertical position of the grip. During the rotatory motion between the vertical position and the end position of the grip I was able to reduce my pressure on the grip since the fly rod has a kind of “self dynamic” – which means that though the upper mass elements are still gaining velocity less effort at the grip is needed.

I‘m convinced that these exercises improved my casting stroke and I found it much easier to use stiffer fly rods after making these adjustments.

Thanks to Walter Simbirski for optimizing my english.

The above descibed practicing with ultra soft fly rods is useful to trigger the redistribution properties shown with short words in the following video:

wait, wait, wait, … rotate !

Montag, Juli 10th, 2017

Being asked about the right time the caster should rotate the fly rod I don’t have to think long. My answer will be that the rotation should be strongly delayed. This holds true for longer fly casts, but I personally prefer a later rotation even for medium fly casts. I’m convinced that on the one hand a later rotation is a good medicine to avoid a lot of casting faults and on the other hand it benefits an efficient, power minimized fly cast.

To understand this context a closer look on the effects is useful. Looking on some fly casting videos of me and other caters it can be observed that the deflection of the fly rod tends to be bigger and deeper the later the fly rod is rotated. This deflection causes basically a significant

  1. shortening of the lever arm (projection of the fly rod),
  2. storing of some energy (potential ‘spring’ energy) as well as
  3. redistribution of some energy into the tip of the fly rod (the angular momentum in association with the modification of the moment of inertia).

All enumerated effects interrelate in a complex way, but here I would like to focus on the relation between the lever arm (a) and the two further properties (b and c).

For the fly rod on the one end of the lever arm the tip is located, on the other end there is the grip. The lever arm property of the fly rod is vital for generating tip speed especially as it is rotated. The longer the lever arm is, the higher the tip speed could be. Tip speed is a kinetic energy which can be transferred from the grip. The more energy should be put into the tip, the more energy at the grip is needed. This is an advantage of the fly rod as for a stiff lever arm the ratio of the output and input energy (synonymous with efficiency) remains always unchanged as it works similar a ‘plunger rod’.

For shorter lever arms the tip speed, tip energy respectively will decrease as well as the introduced energy at the grip. But in terms of the fly rod the shortening of the lever arm is accompanied by the deflection, which means that the two further properties (b and c) are correlated ! As shown in my “Experimental investigations on the fly rod deflection” (rev. 2.0, 11/2014) on the one hand the shortened lever arm might cause a reduced tip speed (see section F3), but coincidently on the other hand the effort the caster has to apply decreases significantly and the tip gains additional speed upon rotation of the fly rod by efficient redistribution of energy.

Up to a limit, which is basically determined by the softness of the fly rod, the disadvantage of the initially decreasing tip speed will be significant smaller than the advantage both the storing and the redistribution of energy are providing ! So what the caster could gain is a much higher efficiency (ratio of the output and input energy) by ‘loosing’ a bit effectiveness (output energy, the tip speed is all what counts).

Caster who generate a smaller deflection are getting a longer lever arm. That might be useful especially in situations where effectiveness could be the key for success, e.g. tournament distance casting. They often prefer to rotate earlier or ‘through the casting stroke’. So in terms to their aim those casters ‘rotate at the right time’ too.

For the common fishing situations my aim is to cast as efficient as possible. Hence to me ‘Wait, wait, wait … rotate’ is a good phrasing to clarify the right time the rotation should take place.



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angular velocities of the mass elements on the fly rod shaft

Mittwoch, Juni 28th, 2017

Playing with the GIMP tool (GNU Image Manipulation Program) I superimposed some pictures taken out of a casting sequence of me. I liked the result since it visualizes how the angular velocities of the mass elements on the fly rod shaft vary over the entire casting stroke.
The angular velocity ω is determined by the angle φ divided by time t (ω = φ / t).
Due to the deflection of the fly rod during the earlier phase of rotation (shown by the violet lettering) the lower mass elements are covering a larger angle than the upper ones (see picture 1). According to the relationship shown above they have the highest angular velocity ω.


During the later phase of rotation it is the other way round (shown by the red lettering). Now the upper mass elements are covering a larger angle (see picture 2), for which reason they have got the highest angular velocity ω.


So what can be detected is a shift of the highest angular velocity from the lower mass elements towards the upper ones over the duration of the fly cast (see picture 3 – visualized by the black arrow), which correspond to the varying contribution of the angular velocities.

The angular velocity (ω) multiplied by the moment of inertia (I) leads to the angular momentum (L). L = I * ω. Taking the modification of the moment of inertia caused by the deflection into account, this relationship points to a contribution of angular momentum, which shifts towards the upper mass elements like the angular velocities.
The towards the tip of the fly rod shifting contribution of angular momentum equals the shift of the center of the rotating mass shown in my “Experimental investigations on the fly rod deflection” (rev. 2.0, November 2014 – section F1) and indicates, that some kinetic energy could climb up along the fly rod shaft towards the tip. This behavior benefits an efficient fly cast (ratio of the output and input energy).
It is obvious that the energy transfer from the grip towards the tip of the fly rod depends on the way the fly rod is deflected. The varying contribution of the angular velocities of the mass elements is a good indicator for that.
The pictures above are taken out of a video, which I produced in order to explain what I wrote before:


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fly rod deflection and rotation

Sonntag, März 12th, 2017

Looking through fly fishing forums I often read a statement like this: „we rotate the fly rod and as the inevitable consequence it deflects“ (and again recently “rod bend is a consequence of our main purpose to rotate the rod”).

This statement left me unsatisfied. On the one hand I totally agree that the rotation of the fly rod is vital to generate a proper line speed to get the fly into the target. But on the other hand I was missing something. To me this statement felt uncomplete somehow, since in this view the meaning of the deflection tends to be a kind of byproduct of the rotation reduced to some geometrical advantages – basically to carry the tip of the fly rod on a straight path.

Since my „Experimental investigations on the fly rod deflection“ I can explain what I was missing: the meaning the deflection could have in terms of efficiency (ratio of output / input energy) !

As one conclusion of my investigations there is no doubt that the deflection of the fly rod enables a significant better energy transfer from the grip towards the tip. In comparison to a totally rigid fly rod – which provides basically leverage resulting from the translatory and the rotary motion – the flexible one provides two further transfer properties: 1.) the storage of energy (spring energy, the „load“) as well as 2.) the redistribution of angular momentum (associated with the modification of the moment of inertia – see section F1 and annex 2 of my investigations). Both further energy transfer properties interrelate and enable the caster to generate a proper line speed with less effort, if he deflects the fly rod in a proper manner ! Even if the rigid as well as the flexible fly rod could be massless – as investigated in my work – the flexible one has a significant better ability in energy transfer than the rigid one.

What is the insight ? The rotation in combination with the controlled deflection as well as the controlled counter deflection (reduced counterflex) is the key of an efficient fly cast ! In terms of efficiency a closer look on HOW the fly rod is deflected is important instead of THAT it just deflects as a consequence of rotation. The rotation is vital to achive this and it is always effective (“the aim is all”) somehow – but without a proper deflection the rotation alone is not efficient (1).



I produced some videos with should clarify what I’m talking about.

read on scribd
________________________

(1) Scientists would say, that for efficiency the rotation is a necessary, but sololy not a sufficient condition ! Both conditions are only met if the optimal deflection joins the casting stroke !

velocities of the mass elements of the fly rod

Donnerstag, Februar 23rd, 2017

In additional contemplation to my work “Experimental investigations on the fly rod deflection” I looked at the distribution of the velocities, which mass elements of the fly rod have. Over the duration of the cast it becomes clear, that the velocities of these mass elements vary significant to each other due to the deflection. Whereas the highest velocities are located at the middle mass elements at the beginning of the cast, the highest velocities are located at the upper mass elements at the end of the cast. So the highest velocity shifts towards the tip of the fly rod. This is another clear indication for the (“complex”) redistribution processes taking place in the fly rod.

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criticism on the advantages of flexible fly rods

Mittwoch, Januar 7th, 2015

In the following I take up the main criticism which were observed after the first publication of my “experimental investigation on the fly rod deflection” (in which I compare a flexible with a total rigid fly rod) in february 2014. In the revision 2.0 of my investigations, published in november 2014, all the criticism is considered. My comments refer to my revision 2.0. With pleasure I anticipate that all the criticism can’t question my investigations.

Criticism: “the mass of both fly rods was not considered. By considering the mass the calculated difference between the efficiencies of both fly rods will drop.”    

Without doubt the assumption of massless fly rods could influence my calculations most (see section A). With this assumption I kept the calculations simple in order to reach more people who are able to understand my investigations.

Because the mass of the fly rod is significant higher than the mass of the fly line the caster has to apply the most energy to accelerate the fly rod. But with my comparison calculations in annex 2 I show that my calculated difference of the efficiencies is influenced only insignificant by the mass of both fly rods. Further more the fabrication of a rigid fly rod needs more mass towards the direction of the tip, which effect an additional effort for the caster. So my calculated difference of ~2 (see section E) lies absolutely in the range of possibility.

Criticism: “there is no need to customize the fly line and the fly rod. With a stiff tarpon fly rod a class 5 fly line could be casted longer than a customized class 5 fly rod could do.”

I do not question that the tarpon fly rod could cast a class 5 fly line longer than a customized fly rod. But this fact alone doesn’t mean the tarpon fly rod is more efficient, because a look on the casters effort (“energy input”) is necessary too. This argumentation lacks this view, because there is only a look on the result and a look on the effort is missed. My following answers show, that the tarpon fly rod generates a higher effort to cast a fly line in relation to a customized fly rod.

Criticism: „the angular momentum is only conservated in isolated energy systems. Because the fly rod doesn’t represent an isolated system the angular momentum can’t have a significant effect.”

That’s not correct. Surely the effect of the conservation of angular momentum is shown for isolated energy systems, because it could be watched clearly. In annex 3 Dr. Schmitt disproved his criticism. Due to the shift of the turning point (= center) of the rotation mass towards the tip the angular momentum with is present in the fly rod can’t disappear and must be conservated. This effect could also be called as redistribution of angular momentum. However, the angular momentum can provide positive effects in not isolated systems, like a fly rod represents, too.

Criticism: “Over the path of the retraction of the fly rod positive effects of the conservation of angular momentum will be eaten up, hence a positive effect can’t be left over the whole cast.”

The impact of the conservation of angular momentum could be watched on a figure skater, who runs a pirouette. As he is bringing in his arms, he shortens the radius between the rotating mass of his body and the rotation center so the rotation speed increases significantly. As he sticks out his arms, he decelerates the rotation speed of the pirouette.

Transferred on the fly cast it means, the conservation of angular momentum initiates an additional rotation speed into the tip of fly rod as long as its deflection increases. As the deflection decreases over the path of retraction the angular momentum causes a deceleration. This coherence I pointed out in figure XIII by the shifting turning point (= center) of the rotating mass.

But over the whole cast the deceleration can only eat up a little part of the advantage, the conservation of angular momentum provides in transmitting the energy significantly better. On the one hand the velocity of the tip of the fly rod is about 80% of its final value as the angular momentum starts to decelerate. That means the positive effects of the conservation of angular momentum are already within the most velocity of the tip as well as in the fly line. On the other hand the beginning conversion of the stored potential energy into kinetic prevents decelerating the tip immediately. Due to both effects the advantages coming from the angular momentum are still significant predominant. This is shown by the significant higher efficiency of the flexible fly rod.

Criticism: “the fly cast and the whip don’t have any parallelisms.”

In annex 3 Dr. Schmitt shows the effect of the conservation of angular momentum by pointing out some similarities between the deflected fly rod and a whip as they exist for my investigated cast.

For the whip the turning point of the rotating mass shifts into the loop, which appears right after the whip is lashed and which becomes faster and faster till it the end of the cord sounds. Similar to a whip the turning point of the rotating mass of the fly rod shifts into the “loop”, which lies in the area of the maximum deflection. As a difference to the whip the turning point of the rotating mass can’t shift completely into the tip of the fly rod (because the tip section can’t deflect as much as required to do so), but moves back towards the grip as the fly rod is retracting. For this reason the velocity of the tip of the fly rod doesn’t “run to infinite” like the end of the cord of the whip does, but it gains an additional, finite velocity. So the flexible fly could use a big part of the positive effects of the whip. Due to the lacking deflection the rigid fly rod can’t activate such positive effects at all. So there are obviously some parallelisms between a whip and the fly cast I investigated. Further more this comparison shows why the turning point of the rotation mass could leave the grip of the flexible fly rod (see section F1 and figure XIII) and why the efficiency depends on the shape of the deflection too (see section E4).

Criticism: “if the tip of a rigid fly rod is guided on a straight path, the rigid fly rod becomes significant more efficient.”

That’s not correct. Surely the horizontal velocity of its tip will increase, but on the other side a significant higher effort developes. In annex 1 I disprove this criticism by calculating this case (comparative calculation).

The rigid fly rod works similar a connection rod. A connection rod transmits an energy feeded in the one end (grip) to the other end (tip) only “one by one”. For this reason it doesn’t matter on which angle / length / velocity and so on the rigid fly rod is moved. In the case of masslessness it can’t reach an efficiency higher than 1.0 (see section F3). On the other side the flexible fly rod could transmit the energy significant better, because it concentrates / “pumps” kinetic energy towards its tip. In the case of masslessness the flexible fly rod could lift up its efficiency significantly over 1.0 ! The difference of efficiencies could be proved by physical laws. Up to now I didn’t hear any physical law which helps the rigid fly rod transmitting the energy.

Further more the caster of the rigid fly rod must handle a vertical down- and upwards movement (“swing”) to keep the tip on a straight path. The longer the rigid fly rod and the casting arc become, the more this vertical down- an upwards movement restricts the caster. The caster must especially give up more and more the rotation movement the longer the rigid fly rod becomes. A common rigid two handed fly rod can’t be casted for this reason.

As the rigid fly rod is rotated, it can’t get rid of an important disadvantage: the part of a vertical movement ! A pure rotation movement at the grip (how I investigated in my paper) forces the tip to travel on a convex instead of a straight path, so the part of the vertical movement lies at the tip. To keep the tip on a straight path the part of the vertical movement lies at the grip (the down- and upwards movement, see figure XVI). Both parts of the vertical movement reduce the efficiency of the rigid fly rod. On the other side for the tip of the flexible fly rod there is no need to go through a vertical movement, for which reason the effort of the caster could be reduced significantly.

Criticism: “the rigid fly rod is intuitively casted by a movement, which benefits its rigid behavior. The movement the rigid fly rod is casted in my investigations is not optimal.”

That’s correct. With the rigid fly rod the caster is able to shape tight loops and he will automatically use a movement which is the best for the rigid behavior. But even the “optimized” movement can’t offer a better transmission of the energy to the rigid fly rod. The rigid fly rod doesn’t possess any movement, which improves to transmit the energy feeded into the grip up to the tip (see section F3). If every fly rod is casted under its best condition, the rigid fly rod will never reach a better transmission of energy (efficiency) than the flexible one !

Surely the shape of the loop could benefit on an optimized movement – but in relation to a flexible fly rod a higher effort and many other disadvantages must be borne (e.g. very high force to decelerate the fly rod, disharmonic distribution of the force the caster must apply, limited rotation arc). In the meaning of a ‘cost benefit analysis’ the rigid fly rod will never reach the possible value of the flexible fly rod.

It is important to say the efficiency of the flexible fly rod varies much on the amount and the shape of the deflection. On short casting distances there will be not a significant difference between the efficiencies of both fly rods.

Criticism: “due to the flexible behavior the fly rod can’t transmit the whole potential energy on the fly line and the loop widen.”

That’s correct. Experts estimate the flexible fly rod is not able to transfer about 1/3 of its potential energy to the fly line. Saying this sometimes it is overseen that the much higher part of the kinetic energy is transferred without a lost. Over the whole cast the part of the potential energy is about ¼ (see section D1), so the lost is small. It is 1/3 * 1/4 = 1/12 ~ 8% and lies below 10 %. Looking on all the advantages of the flexible fly rod this disadvantage could be neglected.

Due to the counterflex the loop widen a bit as the fly line begins to launch. Saying this the positive effect of the counterflex is often overseen: it damps the flexible fly rod significantly, so the caster could reduce his effort to decelerate. As the rigid fly rod doesn’t bend it can’t possess a damping effect at all. For this reason the caster needs to apply a high pulse of force to accelerate and decelerate the mass of the rigid fly rod (disharmonic behavior). On the energy equation “force = work(energy) / path(arc)” follows that the pulse of force becomes the higher the shorter the path of deceleration becomes. For a very short path of deceleration the force runs even to infinite. For this reason casters of rigid fly rods report of a “colored forearm” (see section F4). Healthy risks are included too by casting a rigid fly rod (see annex 2).

The caster of the flexible fly rod can avoid pulses of force. The potential forces enable a continuous rise and reduction of his effort (harmonic behavior).

Incidentally I know some superb fly casters, who cast tight loops even though they use a high deflection. They have learned to control the damping of the flexible fly rod. So a tight loop is not only a result of stiff / rigid fly rods. And those tight loops require less effort and don’t cause a “colored forearm”.

Criticism: “the deflection of the fly rod doesn’t deepen till the beginning of retraction.”

This opinion might be true for some casts, but definitely not for the cast I investigated.

Criticism: “there is no exact moment for the ‘stop’, a clear separation between the phase of loading and unloading is not possible.”

I’m not going to contradict. But in the cast I investigated a separation is quite good to see, because the deflection clearly increases respectively redistributes till the retraction / unloading begins. This increasing / redistribution of the deflection causes the “kick” to the tip, which enables the fly line to sizzle away (see section D1 and F1).

Criticism: „my calculations and estimations are too simple, hence they can’t mimic the complex fly cast.”

More complex models need assumptions and estimations too in order to mimic the fly cast. Such a more complex model is a driven harmonic oszillator. This model needs differential equations and only a few people with a high scientific knowledge are able to calculate and to understand them. Because I wanted to open my investigations as much people as possible such a model was not an option to me – quite apart from the fact that first I had to renew my studies about differential equations. As even Dr. Schmitt as a physicist share the concept of my investigations they can’t be wrong. I refer to his nice preface.

As the result of differential equations varies much on the assumptions and estimations, they are not more exact in general. But I know that such a model certifies a significant higher efficiency for the flexible fly rod – even though this model refers to a smaller deflection than in my investigations and though it is one-dimensional. So the conclusions of my investigations are confirmed in general.

Because my conclusions are coherent and proven by physical laws I think over all this criticism is not applicable.

Criticism: “the meaning of the load of the fly rod is absolutely overrated.”

This is one of the oldest criticism. In fact the “load” of the fly rod in the meaning of the stored potential force doesn’t propel the fly line. It is just the conservation / redistribution of angular momentum, which is stimulated by the deflection of the fly rod (see section F1). For this reason I use (since my investigations) rather the term “deflection” instead of “load” in order to avoid misunderstandings. The deflection of the fly rod enables a significant better transmission of the energy from the grip towards the tip.

But it seems the potential energy gets an important meaning in relation to the casting movement: because over the path of retraction the turning point of the rotating mass runs back towards the grip (which equals a re-redistribution of the angular momentum – see figure XIII), the velocity of the tip should decelerate immediately – similar a figure skater who ends his pirouette by sticking out his arms. But over the path of retraction the velocity still increases a bit. This effect must (also) be caused by the transformation of the stored potential energy into kinetic.

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experimental investigations on the fly rod deflection

Montag, Mai 19th, 2014

(deutsche Version)

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update in november 2014 – the revision 2.0 is published ! The english translation is out now !

In the revision 2.0 I added some investigations – especially about the impact of the mass of both fly rods and about a casting movement that keep the tip of the rigid fly rod on a straight path. With pleasure I anticipate that all the criticism can’t question my investigations. The revision 2.0 is completing my investigations and all opened (“critical”) questions should be answered.

With this videos I try to explain the effect of the conservation of angular momentum in fly casting.

 

A more detailed physical explanation, why the flexible fly rod concentrates energy towards its tip, could be seen here:

 

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During the past year 2013 I occupied myself with the deflection of the fly rod. With a commercial digital camera, which takes a video by 30 frames per second, a casting sequence of me was catched and I pointed the video out frame by frame. I compared the conclusions of my casting sequence with the conclusions an absolutely stiff rod reveals under the same conditions. This comparison shows that the flexible fly rod possesses a lot of advantages. For example one advantage is the efficiency, which is more than double times higher in comparison with the absolutely stiff fly rod ! It would be a pleasure to me, if my investigations could help to understand the fly cast better.

My special thanks go to the physicist Dr. Franz- Josef Schmitt for his accurate translation, preface and support.

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My latest videos about the contribution of angular momentum:



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