Musing...

[Mangrove Cuckoo]

OK folks... help me out here. I am in over my head again (as usual).

I have a basic assumption and some questions. I am not considering tournament distance casts but rather minimally efficient fishing casts...

Assumption: Line speed is imparted to the line primarily by rod rotation and the lever arm length of the rod (mCL)… if there is no haul. When a haul is performed, some additional line speed is directly imparted to the line.

Questions:

In rough figures, what is the ratio of these two “line speed imparting” parameters?

Does the equation for work = force X distance apply to the haul? As in, does a longer haul add more line speed than a shorter haul? (All other parameters held constant)

In an easy cast, where the rod rotation speed is deliberately minimal, and some haul is required to make up the desired distance, can the haul actually become the major contributor of line speed?

And finally… for a rod with a less than extremely “fast” flex profile, does that minimal rod rotation speed cast (as above) effectively lengthen the mCL by not loading the rod so deeply?

Comments, references, even laughter would all be appreciated!

Thanks

Gary

[gordonjudd]

In rough figures, what is the ratio of these two “line speed imparting” parameters?

Gary,
The conditions governing loop formation are so complicated that I don't know if that question can be answered analytically with current models.

It might be possible to get an idea by casting two lines on the same rod as Lasse has done. One line would be taped to the rod and the other would be free to haul. The difference in the initial propagation velocity of the two loops could then be measured with tracker.

Does the equation for work = force X distance apply to the haul?

That simple W=F*d is only true when the force is constant over some distance. There is an integral relationship that must be worked out when the force is changing with distance as it does in a haul.

That said you should be imparting more energy into the line with the haul, and I would think it should increase the line velocity somehow.

But I also think that adding tension while the loop is being formed may result in a higher initial loop propagation speed as well since the propagation speed varies as the sqrt(tension). Gatti-Bono's equations for loop generation (6 equations with 6 unknowns) is well above any of us non-PHds being able to definitively say if there is something more going on in with the haul in increasing the loop propagation speed.

Good luck with the two lines / one rod experiment that I hope you will try.

Gordy

[Paul Arden]

In an easy cast, where the rod rotation speed is deliberately minimal, and some haul is required to make up the desired distance, can the haul actually become the major contributor of line speed?

Absolutely. On those rare occasions when I decide to burn my fingers with hand casting it’s virtually all haul and I see little difference when doing the same with the rod.

Cheers, Paul

[Merlin]

Hi Gary

For a (gentle) fishing cast I would say that the rod can generate 20 m/s to 25 m/s and a haul some 4 to 7 m/s (I don’t speak of distance here). So the rod dominates by a 4 to 5 ratio or something like that.

Haul speed is a question of distance over time and a short haul means a very short time to get speed. Long or short haul does matter if you consider tip path. Your interest is to limit the effect of the haul on rod deflection (potential tail if you make it too soon) and things go better with a long smooth late haul over a limited time.

You can reduce rod contribution to 5 m/s if you wish and contributions will be similar (cast, haul). It is always interesting to keep the tip of the rod moving as you haul, because you give more energy to the line (force over a longer distance) by doing so. Keep the rod tip moving a little bit, 100% haul is not comfortable for generating speed.

The minimum chord length does not correspond to maximum line speed, it is RSP which does. Focusing on the “lever arm” does not help to understand what is going on (swing, spring and whip), it is a kind of a myth. When you haul a slow moving rod, you can see the deflection induced by the force at tip which is due to the change in momentum of the line, but this deflection remains small and the chord has no influence on the resulting line speed.

Merlin

[Dirk le Roux]

For a (gentle) fishing cast I would say that the rod can generate 20 m/s to 25 m/s and a haul some 4 to 7 m/s (I don’t speak of distance here). So the rod dominates by a 4 to 5 ratio or something like that.

Hi Merlin

Here are measurements of casts by hand. As the fly with both casts was out of frame when hand top speed occurred, they are not much use for initial velocity. From where the fly reached me though, the evolution to and respective top speeds reached may be of interest.

With the non-hauled cast, the fly had to negotiate a dangle loop first.

Cheers,
Dirk