Whip effect

[VGB]

or does the whip effect result in a higher tip (and hence line) velocity).

Sorry Gordy but I can’t follow the comparison that you are trying to make. What do you think the whip powered tip velocity is higher than?

Are there any videos of this “whip effect” in a cast?

Vince

[hshl]

In annex 3 of my investigations there are some explanations about the whip effect by Franz Josef. The whip effect works "in" the system fly rod concentrating some KE into the tip. Since the tip propels the fly line its velocity should benefit from this effect too - but how the energy transfer tip / fly line works in detail I can't tell. As far as I know this is very hard to model.

I tried to explain the energy transfer along the fly rod shaft ("whip effect" as a part of the "redistribution effect") with various videos. What about this one or this one?

TL, Tobias

[VGB]

Thank you Tobias, I think there are several interpretations in the various threads. For me, the inertial effect and whip effect are not necessarily the same thing. For the leader only casts with a small dry fly, if I cast my heavy tipped slow action cane rod, my tip is primarily travelling under its own inertia once I start to decelerate, there’s a little contribution from strain energy in the rod. If I cast my fast action stiff tipped carbon fibre rod, strain energy becomes dominant and the tip is being driven by the whip effect.

Regards

Vince

[gordonjudd]

Tobias,
I don't know how the variation in the rotation center in a cast would impact your concept, but I don't think the actual rotation center of the butt is at the intersection of the extensions of the butt angles you inferred in your diagram.

https://imageshack.com/a/img923/451/8Ft463.jpg

Rather the rotation center changes throughout out the cast as shown here on a cast made by Chris Korich.
https://vimeo.com/18686774

I have found that the rotation center of the butt for most single handed casts is near the elbow as shown below in that cast by Chris, and thus is at a much different location that you would get assuming is is on an extension of the butt orientation.


Furthermore I would expect the rotation center for a section of the rod near the tip would have a much different flow and position than the rotation center for the butt and as you say would have a much different angular velocity profile as well.

Gordy

[Torsten]

Hi Gordy,

What is the mechanism for the energy transfer from the rod to the line?

This is something that we have to analyze. There is a very interesting page about this topic.

See http://whip.creatingspeed.com/

There is the chain reaction hypothesis "a chain reaction of levers and blocks" proposed.
You can see there a simulations of fishing rods / whips.

I'll try to put a simulation model together. But first I'd like to see my fly line simulation running again, needs a few weeks.

Is there an actual transfer of energy from one medium to another as there would be for a transverse wave in a string with two different impedances or does the whip effect result in a higher tip (and hence line) velocity).
Since the impedance of the rod is so much different than the line I don't see how there could be much direct transfer of energy from the rod to the line as there would be in a transmission line having a smaller impedance discontinuity.

Well, it's maybe possible to describe loop propagation and rod unloading as some kind of nonlinear wave. But that's not like a transverse wave on a string. The above chain reaction model seems to be better suited to explain these phenomens.

Maybe Daniel could explain in detail how he derived the energy shares and how his model works.

Thanks,
Torsten

[VGB]

Great link Torsten

Data for casting with a fishing rod are difficult to obtain. The world distance record in casting is 286.6 meter. The release speed (computed as √g⋅distance) must then have been at least 53 m/S (191 km/h, 118 mph) (this computation disregards air resistance, which in practice would require a higher speed). Golf champion Fred Couples and casting champion Steve Rajeff once competed in a promotional event. Couples, being a long driving golf champion, but not a long driving champion hit the ball 999 feet. Rajeff won the event by casting a ball 1011 feet. So on this occasion, performance was similar for casting and golf, with casting having the edge by 1%. One would assume a golf long driving champion would have hit the ball further.

The javelin thrower simulation looks interesting

[hshl]

Gordy,

I don't know how the variation in the rotation center in a cast would impact your concept, but I don't think the actual rotation center of the butt is at the intersection of the extensions of the butt angles you inferred in your diagram. Rather the rotation center changes throughout out the cast as shown here on a cast made by Chris Korich.
https://vimeo.com/18686774

The caster rotates the fly rod near the butt and this "rotation center" you refer to will not move upwards since it is hold by a constrain - like the grip of a whip. I refer to a "center of the rotating mass" as the center of all mass elements, which contribute to the angular momentum. This "center of the rotating mass" model tries to face the whole redistribution effect (containing the moment of inertia, the angular momentum and other possible interrelating effects) taking place during the fly cast.

The video "Contribution of angular momentum in fly casting" is just another view on the redistribution of angular momentum. It tries to clarify, that in contrast to a rigid fly rod the lower mass elements of a flexible fly rod have a significant higher angular velocity ω than the upper ones during the early phase of the cast, rotation respectively. This leads to a „butt dominated distribution“ of angular momentum L (L = J * ω; J = moment of inertia). Since this angular momentum distributed along the lower mass elements just can’t disappear due to the energy conservation theorem, it must be transferred towards the upper mass elements during the later phase of the fly cast (energy transfer / redistribution effect).

For a rigid fly rod this "center of the rotation mass" and the "rotation center" near the butt are supposed to fall together. But as shown in this video for a flexible fly rod it could be different (at 2:18 the "center of the rotating mass" is described).

There are already some essays about this phenomenon.This one uses the whip effect to clarify the difference between the "rotation center" and the "center of the rotating mass".


Cheers, Tobias

[Merlin]

The story of the inertial effect is given in the “Physics of the overhead fly cast” which can be downloaded from SL
here

I used my 2D casting model to run two cases with different rods and hopefully get a better idea of the energy split in between mechanisms (inertia, spring, and lever). There is no hauled used, the stroke is varied with the amount of carry, and this is rather approximate, since there is no exact law to define that (casting arc vs carry).

Here is the process is different from the one I posted before. I came back to basic equations to try making something mechanically sound. There are two kinds of forces working to accelerate the line: one due to inertia and the other one due to spring. Isolating the stored elastic energy is arbitrary; the spring is working all along the stroke. Common wisdom says that since that energy is captured by the line the shortcut is acceptable, this is all right for the large majority of cases, but there are exceptions where the stored elastic energy can be higher than the line kinetic energy (the catapult effect for very slow rods)!

Isolating the lever energy is also arbitrary, since you do not know what is happening to this energy during the stroke. Here the energy due to the lever is calculated at the maximum rotation speed of the stroke, and for the actual lever arm of the bended rod at that time. In terms of timing it happens much before the line maximum energy. Using the rigid lever arm can give inconsistent results, which is illustrated in one of the graphics.

There is an irreducible combined share of lever and spring once the stored elastic energy and the lever arm energy are discounted.
I could split energies like this:
• Inertial energy by difference in the model (with or without)
• Stored elastic energy: it is given by the model, there is a slight effect of the inertia on this energy, a few %
• Lever energy by using the actual arm lever of the bended rod, and I added the same for the rigid rod case to show the difference (dotted line).
• Combined spring and lever contribution: this is the difference in between the total energy provided by the moving spring, from which the stored elastic energy and the lever energy as defined above are discounted.

And now the two graphics:

Amazing, isn’t it? If I had chosen a different casting arc / carry relationship, I could have found something nearly constant for all cases. It shows the difficulty of comparing things in a very variable situation. Pick up other assumptions and you might be able to get what your intuition tells you.

Merlin

[hshl]

Hi Daniel,
the value behind the "100% of energy" should depend on the amount of line carry, so for a longer line carry the total amount of energy behind the 100 % is higher than for a shorter line carry... So what I can see is a trend that for medium fly rods the contribution of the "whip / spring" energy tends to be unchanged for different line carries, for faster fly rods both tends to decrease... Indeed amazing, thanks for sharing

Cheers, Tobias

[hshl]

... and I didn't expect that for a longer line carry the contribution of the lever arm decreases faster for a modern fly rod than for a medium one...