Fly rod deflection

[Lasse Karlsson]

Hi Bernd

Tobias claimed I was using a wrong (non representative) angle (line to rod) for that test. The results would be very differnt when positioning the rod more into the direction of the cast before letting the line go. He also claimed: "Up to now I'm still missing any physical law, which helps the rigid fly rod to transmit the energy feeded in the grip into the tip."

I've seen Tobias' clip with the rod positioned at a more forward angle, and a huge bend. Fact is, not even in my longest casts, do I have such a bend at that angle, and in Tobias big load clip, the line went only a little over a third as far, as it does in my longest cast....

Cheers
Lasse

[Bernd Ziesche]

Exactly my point, Lasse. I saw his video as well but couldn't find it anymore now. Glad you keep such things in mind as well.
Some years ago I got a paper presenting a calculation made by Noel Perkins and Bruce Richards presenting (if I remember correct) upto ca. 70% of increase in line speed when using a very soft fly rod happening during straightening (after max rod load). The number was based on a pretty long caclculation which I never fully understood. It was that number which first put my nose into this topic. I went out and broke my rod when sticking the fighting butt into a pipe to pull in some bend being big enough to really speed up my line (it was a medium line length). Still nothing we'd call a cast happened.
You made a very good point. Even though we see pictures showing huge rod bend in distance casting - the amount of energy being stored in that bend is (I think) nothing compared to what it takes to hit those distances we hit in such extreme casts. But for an average cast we both know with how little rod bend the fly can be put to the fish.
Cheers
Bernd

[hshl]

The video Lasse refers to was taken during my studies for my „Experimental investigations on the fly rod deflection“. It should give me an idea of the “pure loading property” of the fly rod. Yes, the deflection is high which favour the result, but not unrealistic (see e.g. the “Meadow cast”). On the other side Bernd’s video handicaps the “pure loading property” since the fly rod is fixed vertical. Who ends the rotary motion at the vertical position for a normal fly cast ? The “message” is clear, but Bernds video …. well. My video is still on youtube, it could be found easily under my account.

However, no one disagree that it isn’t the “pure loading property” which propel the tip and the fly line. But just as little as a “pure loading property” isn’t efficient on the one side, on the other side the “pure leverage property” isn’t efficient too. That’s my point, Lasse.

Bernd claims the pure leverage property of the fly rod beeing the key for an efficient fly cast. This is how a broomstick basically works. And that's not applicable. To me it became evident seeing the similarity between a broomstick and a plunger rod (see section F3). The broomstick as well as the plunger rod transfer the energy only “one by one” from its one end towards its other end. That’s all.

Moreover if Bernd’s view would strike it would mean that the two further properties the flexible fly rod provides – 1. the caching of energy (“loading” / spring energy) as well as 2. the redistribution effect (impact of angular momentum / inertia, see section F1 and annex 2) - won’t benefit the energy transmission. This doesn’t match physical relations showing by my investigations as well as modelling.

The feel in casting isn’t part of your own calculation for a significant more than two and a half times higher efficiency for the flexible rod. You left the feel out of this calculation, not me

Of course I let feelings out. I’m looking forward to see some calculations of Bernd including his feelings.

Hi Bernd, No way, the broomstick cannot be better than the flexible rod.

A very clear statement I agree with.

Tobias

[Bernd Ziesche]

On the other side Bernd’s video handicaps the “pure loading property” since the fly rod is fixed vertical. Who ends the rotary motion at the vertical position for a normal fly cast ?

Hi Tobias.
In my fly casting trajectory is among the most three important key factors. The line end in that video obviously was held significant below the rod tip. Thus trajectory for that forward cast was aimed upwards. When casting such a short length of line upwards in my forward cast 12/2 (for the whole casting arc) is an appropriate arc in my experience. In addition this video was about to show what happens by unloading not rotating the rod.
At what position would you want to see max rod bend to happen? In my experience there is always a part of arc left for the deceleration. That means for a normal fly cast with an upward trajectory (line clearly tilted downwards in the back cast) - even if you finally have stopped the rod behind the vertical, max bend (starting point to unload) was probably around the vertical. Obviously you instead would have thought to better position the arc for a horizontal cast. That would have been inappropriate (not matching) for that back cast. Still you miss the point that we stored much more energy in the cast as would have been there in a true cast for that length of line.
Let's assume I would fix the rod at 11 and then of course lift the end of the line in the back. What difference would that make? None....
Ok, for maybe 100 years fly casting was about loading and unloading the rod - so it seems to be fair to wait for another 50 years before everyone may understand this to have been a wrong concept for 95% of our fly casting.
Cheers
Bernd

[Bernd Ziesche]

Bernd claims the pure leverage property of the fly rod beeing the key for an efficient fly cast.

Again no one ever was saying the broomstick would be anything like a valuable tool for fly fishing. All we said was that fly casting mainly is not about loading and unloading the rod, but rotating the rod in order to create the desired speed instead. The broomstick was a proper tool to prove this point. I think Grunde did a fantastic job here to highlight this - as did Alejandro in saying "rod bend is a consequence of our main purpose to rotate the rod".

In addition I have listed a lot of aspects why we need a flexible fly rod from the casting perspective. Not sure you read them?

Sorry Tobias, I have no clue how to make this more clear for you.

I never said (nore did everyone else) the pure leverage to be the the key for fly casting. All I said is that fly casting is MAINLY* about rotating the rod - not loading and unloading the rod.

*The word "mainly" indicates not only and it also doesn't mean "pure", but to a significant higher degree as the loading part of the cast. I have no clue why you don't get this. Obviously this misunderstanding was your point to start your investigation.

Cheers
Bernd

[Bernd Ziesche]

Hi Bernd, No way, the broomstick cannot be better than the flexible rod.

A very clear statement I agree with.

So do I.
In fact I wasn't referring about a broomstick but the theoretical construct of a weightless none flexible rod. That one wouldn't come with a massive reduction in torque, with a massive increase in air resistance. Also less of the arc would be needed to decelerate. Thus the cast would be a lot more successful = one would hit the desired speed on a small arc while having a perfect trajectory - set up high above the caster, a very tight loop and a pretty small line dangle.

Where exactly would be the big loss with such a tool?

Cheers
Bernd

[hshl]

In fact I wasn't referring about a broomstick but the theoretical construct of a weightless none flexible rod. That one wouldn't come with a massive reduction in torque, with a massive increase in air resistance. Also less of the arc would be needed to decelerate.

Even if we could have mass less rods, the flexible one would always beat the broomstick, because the flexible one can store extra energy which is released for the line

"Besides the very opposite results of Tobias his investigation I believe having a none flexible fly rod of the same length, same diameter and same weight distribution would be an impressive distance casting tool outperforming max possible distance of a typical flexible fly rod."
“The flexible rod being several times more efficient in energy transfer doesn’t feel right to me.”
“I tend to believe that the stiff rods are pretty efficient in energy transfer.”
“But leaving out weight here, I doubt that the effort and what you get is several times lower for the broomstick in general – no matter how and what for we use it.”

I'm used to missunderstand Bernd. Since the discussion is far from "technical analysis" I'm out ...

[crunch]

This is how I see a non hauled fly line cast using a flexible lever: If a casting session is done where using one, perhaps a #5 rod many different weight but same head length WF lines are cast and objectives are efficiency, max distance and rod bend behavior and its effect to line loop forming. Lightest WF1 line will produce a shortest cast. I believe line speed would become high but can't say it is higher than following heavier lines achieve but reason for the WF1 line short cast are low kinetic energy and very high relative drag against air and guides . Rod would bend the least and mostly because of the blank mass and second because of the blank air drag. I think line loop begins to form quite early because the rod tip velocity drops below the already achieved line velocity quite early when rod tip, which is not bent much, path turns down early and also because the line did reach its max velocity early. Also because of small rod bend the line path becomes concave which incease the rod tip path turning down slowing effect.

Then distances increase when line weight increase because the line kinetic energy increase and relative air and guides drag decrease. Also rod bends more.

Then when the rod bending and straightening cycle reach a point where the line loop "detach" length vise late WHEN the rod tip has traveled farthest WHEN the casting stroke comes to an end it is where the efficiency comes the best. So the rod straightening phase is well going on when the line loop begins to form but rod does not have to be fully strahtened. To make it possible for the rod tip travel farthest require ENOUGH rod bend so that the line path becomes straight enough. Rod counter flex should be also close the smallest because most of the straightening energy gets used to the line acceleration.

Yes, when using a stiff rod the line path can be made straighter changing the casting stroke path but eventually it decease efficiency elsewhere. The casting stroke best efficiency happens only to quite narrow distance with certain line head weight and rod combination. Now here when the max distance is a coal it might happen when a WF5 line is cast if this #5 rod is designed well for this used WF5 line. But when short casts are needed a heavier line keeps efficiency higher and when longer casts are needed a lighter line. Othervise when WF5 line is cast close a softer rod increase efficiency and when cast far a stiffer rod keeps efficiency better.

A hauled cast differs when the haul keeps accelerating the line velocity longer and line loop forming delays.

When a rod blank stiffness/weight ratio increase and the rod bends less because of its blank weight the efficiency can be increased significantly when a heavier line is cast.

When heavier lines are cast the distances still increase because the line kinetic energy increase and relative air and guides drags decrease but when line velocity drops the line needs to be launched to a higher trajectory. Efficiency drops because rod bends more and more because of the heavier line weight. When current technology rods bend backwards excessive bend delays line acceleration more than following slower straightening phase can gain back. Also IF such a casting stroke is used where the handle of an already excessive bent rod is continued to turn down the bent rod tip path turns length vise earlier down as well and it begins the line loop forming earlier because the rod tip and line velocity towards the wanted casting direction decelerates.

When still heavier lines are cast the distance finally begins to shorten because of the gravity when lower line velocity is not possible to compensate anymore casting line to a higher trajectory but perhaps this happens closer the WF15 line or perhaps the caster strength becomes the limiting factor?

Esa

[Bianchetti Ivan]

Io non sono un fisico,ma credo che se il lancio dipendesse dalla rotazione che si crea nella canna non ci sarebbe bisogno di mandare dietro la linea,credo anche che nello spostamento della massa in avanti la flessione sia importante semplicemente per permettere di aggiungere velocita in modo lineare ad un movimento che sarebbe circolare senza la flessione,non ho letto tutti i commenti perchè tradurre tutto è tropo difficile,potrei anche sbagliare.

and the imperfect Google translation.
I am not a physical, but believe that if the launch depended on the rotation that is created in the barrel there would be no need to send behind the line, I also believe that in the mass displacement in forward flexion is simply important to allow to add speed in linearly to a movement that would move without the fall, I have not read all the comments because it is difficult to translate everything trope, I could be wrong.