Counterflex in relation to max rod bend

[Bernd Ziesche]

https://vimeo.com/146253349

Hi everyone,
Tobias Hinzman (the author of the video above) told me that counterflex doesn't play a significant roll in the loop shape. This would be because the caster could just avoid counterflex nearly at all. Therefore to prove his point he published the video above.

Personally I yet have to see a first fly cast free of counterflex. I always saw the level of counterflex being dependend on the amount of max rod bend during acceleration in the first place.
Of course there are other factors like the line weight inside the rings and just outside the rod (overhang). That's why I was asking Tobias about the fly line he was using.

Anyway Tobias came up with a 10% number for counterflex based rod bend in relation to max rod bend during acceleration. Is this representative for most of our casting?
Thanks
Bernd

[Lasse Karlsson]

Would love to see the same measurements done in plane with the rod, and with high speed camera, angles cheat alot!

Cheers
Lasse

[Jason Borger]

Would love to see the same measurements done in plane with the rod, and with high speed camera, angles cheat alot!

Cheers
Lasse

Yes, be very careful on camera angles! That's what I love motion capture so much. That tech really takes any BS (and potentially bad camera angles) out of things.

Was actually told once that a side-arm cast that was videotaped from the side showed "perfect" SLP (and very tight loops, too!). Too bad that was actually tracking, not SLP....

[Lasse Karlsson]

Yup

Motion capture, that would be great!

Cheers
Lasse

[Bernd Ziesche]

Hi Lasse,
pretty much the same I thought. I told Tobias that sometimes even 250fps are not enough and we will see additional details when watching 500fps or more.
I remember a fine drawing you published long time ago. It showed the fly-leg mainly presenting the tip path prior the stop, the loop front presenting mainly tip path during the stop and the rod-leg mainly presenting tip path post the stop.
Now we both know that this can't be seen black/white when going into the details. But still I like that drawing for and easy an correct understanding of shaping (better reading) the loop.
Avoiding counterflex would draw a remarkable carry for the 170 MED distance casting, I think. The bouncing bomb hurts us quite significant as far as I can see it. Cutting it out...
Cheers
Bernd

[Merlin]

Hi Bernd

Counter flex is highly influenced by the caster, and here we have an example of a forward / upward thrust which is a mean to fight against it. Is that motion really effective, I am doubtful in terms of distance; there is some kind of attraction for “watch my competition casting style”. I am not sure about the angle measured, we cannot see exactly where the tip goes, it could be a higher angle than 7 degrees, but this is not my point. Coming back to the physics of the cast, the rule of the thumb is that the counter flex can be about the same size of the maximum bend if there was no damping. It depends first of the kinetic energy captured by the rod. More precisely, there is a concentration of the kinetic energy of the rod in the tip by about 80%, the rest is used to decelerate the rod butt and a possible limited transfer to the line. This allows the tip to get speed while the butt slows down, so necessarily, the higher the tip speed is, the larger the energy that has to be dissipated during counter flex is. As usual, using a single cast to try demonstrating something is misleading. Try a slow rod, take off the line and you will see a huge counter flex as you “cast” the rod and stop it abruptly, without any lift at the end. The rod is important too, I do not know about this one but it is a fast one, something like a Sage One.

Merlin

[Bernd Ziesche]

Hi Merlin,
thanks a lot for your answer. That makes sense to me.
How about the line weight inside the rings and the overhang?
I think using a thin monofilament as a shooting line and adding significant overhang reduces cf a lot? At least that's what I kept in mind from watching some of Lasse's slo-mos as well as some Aitor made of me casting a shooting head.
An average WF line easily could mean to have several additional gramm supporting to cflex the tip down!?
Regards
Bernd

[Merlin]

Hi Bernd

The line in the guides contributes to the equivalent mass at tip for about a quarter of its value. Suppose you have 2 m line in the guides, weighting 1 g/m, then you have an extra of 0.25*2 = 0.5 grams at tip level. This is something like the weight of the tip top guide itself. So yes, that increases counteflex, and this is why the CF can be larger for a DT by comparison to a running line. A typical equivalent mass for a rod is 3 grams (9 foot #5).

Merlin

[easterncaster]

Merlin,
Thanks so much for your clear descriptions!

Craig

[gordonjudd]

I am not sure about the angle measured, we cannot see exactly where the tip goes,

Merlin,
I don't think that the deflection in the rod should be measured by angle as that has nothing to do with the spring constant of the rod.

As Grunde has shown the way to measure deflection is the perpendicular distance from the tip to broomstick line that extends the angle of the butt of the rod. That corresponds to the "D" distance shown below.

That distance has a direct correlation with the pull force on the tip and the non-linear spring constant of the rod.

Try a slow rod, take off the line and you will see a huge counter flex as you “cast” the rod and stop it abruptly, without any lift at the end.

When I did that inertial bending test the counterflex deflection was bigger than the deflection due to the positive acceleration as shown in the red deflection line below.


Gordy