Some questions about Delayed Rotation/ rotational hit

[Paul Arden]

Hi Physics guys,

I have a few questions or at least ideas I would like to throw past you for some analysis.

So firstly I’ve often wondered if Rotation-only after MCL is preferable to Rotation with Translation because of increased air resistance on the rod tip with translation.

Certainly we have some very long casters who try to rotate-only after this point.

The other side of this equation however is that translation after MCL certainly increases haul speed.

Also I’m of the opinion that the Rotational “Hit” should occur late in the stroke, arguably as the rod is unloading.

Certainly a big punch at this position is highly detrimental to the cast. Perhaps it prevents unloading?

A couple of things in there might be out of left field but I would be very interested in your thoughts.

Thanks,
Paul

[Mangrove Cuckoo]

Paul,

I"m looking forward to this one!

While we are at it, to get things rolling, could you further define what you mean when you talk about the "hit"?

Above you seem to indicate it only has to do with rotation???

I've always had a hard time with this concept, or maybe its just that I don't think the word "hit" fits well with the idea of a rapid increase in rod butt rotation.

Personally, when I think of hitting anything when it comes to the casting stroke, I have found there is something much earlier in the stroke, when I am deliberately attempting to force a bend into the lower sections of the rod, and I sense some feedback as if I have found the rod's backbone (to use another squishy term).

From that point, since I cannot cause the rod to load any further, I think Server's SDM takes over, and my rotation and haul are simply my input to continue along with the ride.

And you think you are out in left field?

[John Waters]

May I suggest Torsten add a definition of impulse to the Glossary of Fly Casting terms.

It does not get the focus required,

John

[Paul Arden]

Yep Gary. I have some friends over this weekend and should be able to talk about this and upload. I’ll try to do a video on the launch with Nick and we will take it back from there. It may or may not make sense of my questions

Cheers, Paul

[Dirk le Roux]

Hi Paul

So firstly I’ve often wondered if Rotation-only after MCL is preferable to Rotation with Translation because of increased air resistance on the rod tip with translation.

Certainly we have some very long casters who try to rotate-only after this point.

It would help if you can clarify the point about which the rotation you speak of occurs. Feet, elbow, wrist, centre of butt rotation somewhere external to the caster's body? Do post that video illustrating what you mean.

The other side of this equation however is that translation after MCL certainly increases haul speed.

Also I’m of the opinion that the Rotational “Hit” should occur late in the stroke, arguably as the rod is unloading.

Certainly a big punch at this position is highly detrimental to the cast. Perhaps it prevents unloading?

You cannot prevent "unloading" unless the line or fly gets arrested behind. Delaying "unloading" is not necessarily detrimental. Hauling does that all the time.

All the best,
Dirk

[gordonjudd]

So firstly I’ve often wondered if Rotation-only after MCL is preferable to Rotation with Translation because of increased air resistance on the rod tip with translation.

Certainly we have some very long casters who try to rotate-only after this point.

Paul,
I would think that the bend of the rod is affected more by the angular acceleration of the butt of the rod as compared to the acceleration of the hand path. Consequently I would question the premise of your question.

The loaded frequency of the rod impacts the lag between the forcing acceleration at the butt and when MRF and MCL occur. In the Paradigm cast MCL was about 26 ms after MRF and MRF was reached about 34 ms after the maximum of the angular acceleration of the butt.

cord_len_defl.jpg (21.98 KiB) Viewed 1095 times

paradigm_smoothed_ang_accel.jpg (30.03 KiB) Viewed 1095 times

Because of the added line mass, the loaded rod frequency in a distance cast would be probably be lower the loaded frequency of the Paradigm cast. Thus these time lags would probably be a bit longer in a distance cast. However I would expect MCL to happen 80 ms or so after the maximum angular acceleration of the butt rotation was produced or about 50 ms after MAV. Measurements are in order to compute the actual values.

I have not measured the translation acceleration of the hand path but since the translation velocity of the hand is small compared to the tip velocity produced by the angular rotation velocity of the butt I would expect the translation acceleration would be much smaller than the tip acceleration related to the rod rotation as well. Thus translation effects on the bend of the rod are probably much smaller than rotation effects.

We need to get some measurements of the angular velocity of the rod rotation and the resulting cord length in a distance cast. I would expect that MCL happens after MAV not before as you imply in in your question.

Note the loaded frequency of the rod will smooth out the effects of sudden changes in the rod rotation, so a quick hit in the rotation of the rod will not produce a similar "hit" in the acceleration of the tip.

Gordy

[Paul Arden]

Hi folks,

I’ll try to explain it a bit better with regards how I hit a long distance forward or backcast. During the stroke I spike the force after the rod butt has passed the perpendicular to the line path trajectory and I play with later and later. This hit is predominately rotation/torque and while there will be follow-through and other things going on, there is a significant increase in casting distance as a result.

We filmed a lot of thing today but not this. I will tomorrow. Today wasn’t the right place.

Cheers, Paul

[Paul Arden]

Too cold! Ice everywhere. Let me get back to normal tropical temperatures and I’ll shoot an explanation video of the hit/launch.

Cheers, Paul

[Mangrove Cuckoo]

May I suggest Torsten add a definition of impulse to the Glossary of Fly Casting terms.

It does not get the focus required,

John

John,

Thanks for pointing out that rabbit hole to me. Like I needed another one to get lost in!

So... physics guys... please forgive me for asking about stuff that is way over my head, but...

... Back when we were discussing beams and their frequency response and nodes - wasn't there another rabbit hole about how they react significantly different when the load is applied quickly, in a manner that I'm guessing might fall under this idea of an impulse?

The example that stuck in my imagination was about maritime transport by the giant cargo ships, and that the boom that transferred the containers off the dock and onto the barge had to lift the loads smoothly. For if the load was snatched too quickly, the result could be dramatic - and not in a good way.

Can these concepts be mapped onto what happens with loading a flyrod?

[Paul Arden]

Can these concepts be mapped onto what happens with loading a flyrod?

And what happens when it’s applied during unloading (SDM)?

Nice post Gary!

Cheers, Paul