wrist based rotation

[Merlin]

If the "hit" is an impulse applied to the rod, is the haul an impulse applied to the line?

Hi Gary

To me an impulse is something lasting less than 50 ms. A haul lasts approximately 300 ms to 400 ms, so I would not classify it as an impulse. I cannot figure out what a “hit” can be, if it consists in wrist rotation only or something different.

Merlin

[John Waters]

Hi John

I specifically mentioned assessment tasks and fishing casts, rather than competition casting by expert casters exhibiting fine control. Side casting requires comparatively high line speed at short distances, as does leader only casts. In both these cases we need to increase the range of movement and preferably our base of stability to achieve the objective.

When I cast dry fly based accuracy events using my standard over-the-shoulder stroke, my COM does not translate.

Any movement of body mass such as the arm will shift the CoM unless we compensate by postural adjustment. At about 1:00 in this clip, there’s CoM shift going on:



Regards

Vince

Hi Vince,

That's what I said, it's an option not an essential, you can move the COM in the direction of the cast, or not. The clip does show COM movement forward and back as the result of rocking the upper body, with some weight transfer. You can see that at the end of the video when the rocking motion is visible from the shot of the feet. High line speed at short distances can be achieved without increasing range of movement, just movement speed.

Good video, a lot of COM movement in the direction of the cast, in the distance stroke shown.

John

[VGB]

Hi John

I understand your intent now.

High line speed at short distances can be achieved without increasing range of movement, just movement speed

Depends on the constraints such as the ones I mentioned in my earlier post.

Regards

Vince

[Mangrove Cuckoo]

If the "hit" is an impulse applied to the rod, is the haul an impulse applied to the line?

Hi Gary

To me an impulse is something lasting less than 50 ms. A haul lasts approximately 300 ms to 400 ms, so I would not classify it as an impulse. I cannot figure out what a “hit” can be, if it consists in wrist rotation only or something different.

Merlin

Thanks!

I am guessing but 50 ms sound like it is pretty fast... but maybe not so quick as the time it takes to snap one's fingers?

At 1/6 to 1/8 of a haul, it probably is longer than that? But, still damn quick.

And, if that is the case, is it humanly possible to apply an impulse into a fly cast stroke at any point?

Does anybody know how long it takes to throw a short jab-like punch?

Sorry for the goofy questions, but evaluating my own casting I find that I cannot move a flyrod backwards as fast as I can move it forward. And I definitely cannot seem to include a very short burst into the backcast no matter how I try.

[John Waters]

Well John, you've chosen a hell of a field to earn a Ph.D. in! I studied isolated molecules and am now feeling like I took the easy route. You've got a metric ton of interconnected degrees of freedom to juggle.

Since most joints are built for rotation, it's quite amazing that we manage to generate any linear motion at all.

Thoughts on directly comparing rotation angles or rotation rates at the wrist vs. elbow? Can we really get away with direct comparisons without some way of adjusting for the difference between the induced rod motions?

Few

Hi Matt,

The more I do and learn about casting, the simpler it is to me. At 73 I think my casting days are behind me, but I now realise what I did for years was performance limiting. You can generate linear motion in the direction of the cast, which I understand is described as translation in the casting world, but IMHO, the driver is rotation range and separation.

Of course all that could be absolute BS but then again .......

John

Apologies Matt, I did not understand what you meant by "Thoughts on directly comparing rotation angles or rotation rates at the wrist vs. elbow? Can we really get away with direct comparisons without some way of adjusting for the difference between the induced rod motions?" I'm not sure what adjustments you are referring to.

Thanks,

John

[gordonjudd]

Probably I have a misunderstanding in reading the graph.

Bernd,
The error in reading the plot was mine not yours. I was just eye balling peaks and did not take into account the rapid fall of the elbow rotation rate that occurred just before MAV. Your estimate of a 50:50 contribution from the elbow and wrist rotation rates at MAV is correct.
Gordy

[Merlin]

Gary

As an example, a wrist input lasts typically between 100 ms and 200 ms. I do not think one can include a 50 ms rotation input into a cast which can last from 350 ms (competition) to 500 ms (fishing). A short translation maybe.

Merlin

[Few]

"I'm not sure what adjustments you are referring to."

Sorry John, I wasn't clear--too concerned about not being verbose!

First, my mention of the motion of the center of mass was only to clarify that in simpler (non-casting) contexts, the degrees of freedom of a body can be separated into vibrations, rotations, and translations. Vibrational and rotational modes of motion are defined so that they involve zero motion of the center of mass (COM). All motion of the COM is lumped under translation, which need not be linear. Such simplicity is not available when analyzing fly casting, of course, but that background is what triggered my question about "rotation" about the elbow axis and "rotation" about the wrist axis.

I've read a lot of discussion of when to include rotation in the stroke, and it seems to me that rotation about the elbow yields quite different rod motion than does rotation about the wrist. I'm guessing there's little argument about that. So when analyzing graphs of angular acceleration about the elbow vs. angular rotation about the wrist, a straight numerical comparison of numerical values (perhaps expressed in rad\(\cdot\)s\(^{-2}\)) may not capture what's going on. I would expect some factor that captures the difference in the geometries to be necessary--something like the distance between the axis of rotation and some reference point on the rod. This is probably now more long-winded than the point justifies, but I hope it's less confusing than my previous post.

And my hat is off to you for pursuing an advanced degree later in life! I'm in the education business and it gets disheartening dealing with students (or parents!) more focused on what the diploma will buy them after graduation than on the learning process. More power to you!

Few

[Paul Arden]

Haha you fit right in here Matt

[Bernd Ziesche]

As an example, a wrist input lasts typically between 100 ms and 200 ms. I do not think one can include a 50 ms rotation input into a cast which can last from 350 ms (competition) to 500 ms (fishing). A short translation maybe.

Paul,
Is there still the video of Frank Lopresti casting a 100' with pure rotation as he called it? I remember, that we didn't disagree with his video. I think that cast may have come close to what might be called an impulse. That aside, I dont like the term "hit" for exactly the reasons Merlin highlighted here.
Cheers
B