Analyzing tails

[victor]

I have just watched that clip again and I see no evidence of creep. if you time the end of the line passing the rod tip the pause on the back and forward strokes they are pretty similar.

Mike

[Magnus]

Mike the end of the line doesn't pass the rod tip on the back-cast after the tailing forward cast in the clip I have. We watching the same thing?

[victor]

Post 1, example. No creep, I see a proper pause,

Perplexed,

Mike

[Bernd]

Aitor, Magnus,
in the wonderful Mel Krieger book "The essience of fly casting" the reason for a tailing loop is shwon to be a concave path of the rod tip between RSP and RSP. It is shown to happen over the full distance between RSP and RSP.
I am teaching my students since a cuple of years that in truth the concave tip path mostly only happens in a short part of the arc.
So this is quiet normal to me. And here we have a perfect example of it.

To me the main help for a student would be to make him opening the arc a bit.
In long terms he will learn (by running good basement exercises) to go for a proper (smooth) acceleration anyway.
But in one short moment he could probably not optimize his power application that well.

What I still don't understand Magnus, is why can't I see the overpowering in the graph of the butt rotation (short before max peak)?
Can you really see it there? Please mark it to me!
I am not used to work with the CA. But the graph should show a sudden overpowering or not?

Greets
Bernd

[Magnus]

Hi Bernd

What would overpowering look like on a graph? The max angular velocity would be high - significantly higher than a 'good' cast throwing the same length of line in the same conditions - and the peak would be relatively narrow - ie over a short time, aka abrupt or sudden.
As I have pointed out several times, the maximum angular velocity in the tailing loop stroke is double that Bruce uses in the tight loop - and the length of line in both cases looks at least similar.

With due respect to Mel Krieger, one of the more common causes of tailing loops is Creep and increasing the arc by altering the stop is NOT the cure for Creep. I'm sure Mel does not say that.

For a forward cast, the most common advice to address Creep is to learn to drift the rod back before the forward stroke. That's really a patch - it makes damned sure the rod is not moving forwards slowly, eating into the arc, during the pause.
Just as easy and possibly better in terms of learning controlled short line casting, is to hold the rod in position for the start of the arc.

Bruce drifts his rod back a few degrees before this forward stroke. More to the point look at the backcast - lower max angular velocity - slightly slower rate of acceleration up to MAV - similarly abrupt stop - and NO tailing loop.

[Bernd]

Ah ok. Thanks for your help in understanding the graph better.
I should have used the CA more often. Just was using it once yet.
I am pretty much sure without the graph here we would have been in one line very fast.
To understand the graph perfectly it needs more experience with it than I have yet!
The pure video told me about a small amount of "creep" in the beginning of the stroke and a little high power add in the end around max butt rotation.

To me the concave tip path isn't the reason for a tailing anyway .
The concave tip path is what happens after "whatever the caster did to create it"... And there is the key to find. Creep is one common example, yes .

Good night,
Bernd

[Tom]

Hi Bernd.
What if we used a much stiffer rod,and still have
the same input?

Tom.

[Tom]

Come to think of it.No need to make it more difficult than necessary.
Who doesn`t remember Mel Krieger saying;flycasting is a feeling of
applying power and slinging the line out as in trying to throw an apple
stuck on a willow stick.
Start slow,sling it out - think oily.

Tom.

[gordonjudd]

Do we agree to that the reason for this is power application?
How do we,(and can we) read this from the curve?

Tom,
I am not sure if the jump in the angular acceleration curve is enough to shock the rod and cause the dip in the tip path, but there is a big change in the acceleration at around 9.4 seconds on the graph.

I cannot get the download from You-tube to play on a frame by frame basis, so it is difficult to tell whether or not there is a time offset between the video and the plot of the CA data. Probably not, since Noel came up with a clever use of a laser diode to produce a blink of light that was detected by the high speed Casio EX-F1 camera. With that process he could synchronize the video to the data from the CA to within 1 sample point of the analyzer.

The resolution on the plot is not great, but is good enough to see more detail if you expand the scales. I just digitized the data that was plotted by CA in his video, so it could be analyzed a bit more.

Here is a plot of the digitized data for the forward cast portion of the data.


You can see that there is a decrease in the slope of the angular velocity curve followed by a sharp increase in the rotation rate at around 9.4 seconds.

Those kind of discontinuities can have a big impact on the acceleration as shown here for just the portion of the cast up to max rod flex (MRF) that had the red overlay on the previous plot. The green curve is for the angular velocity with the scales on the right and the blue curve is the smoothed derivative of that curve and uses the scales on the left of the plot. Even with smoothing there is quite a bit of ripple in the acceleration curve, but I think it shows what was happening to increase the bend in the rod.



You can see there is an abrupt jump in the acceleration (blue curve) at around 9.42 seconds of over 1000 deg/sec.^2. That large increase in acceleration continues up just before the max angular velocity point. I would expect this added increase in acceleration would result in more and more bend in the rod, although there would be some time lag due to the spring constant of the rod.

Because of the unknown time alignment and difficulty in playing the video on a frame by frame basis it is hard to say that this is the cause of the dip in the tip path.

Gordy

[Tom]

Hi Gordy.
Nice.This is interesting.
Do we all agree to,that if the cast was done with a
stiffer rod,or with less energy (half the peak speed),
we would not get a dip or a tailing loop?

Tom.

[victor]

Oops, deleted

[gordonjudd]

Do we all agree to,that if the cast was done with a
stiffer rod,or with less energy (half the peak speed),
we would not get a dip or a tailing loop?

Tom,

I don't think there is such a thing on Sexyloops as "we all agree", but certainly a stiffer rod would bend less for a given amount of angular acceleration.

Also rotating the rod Bruce used with less angular acceleration would have caused less of a dip in the tip travel for this cast. Less acceleration as he approached MRF would have produced smaller angular velocity as well, so I would agree with your two points.

The hand path also enters into this as well. In the first part of this video Lefty Kreh demonstrates a tailing loop by lowering his hand coming forward and then raises it as the rod unloads to produce a concave tip path that will produce a tail. This is one method he uses even though he often says, “Tailing loops have nothing to do with a concave tip path.”

Gordy

[Tom]

Hmmm.Gordy.
I wonder why he says that the concave tip path has nothing to do with a
tailing loop.

Tom.

[Aitor]

Hmmm.Gordy.
I wonder why he says that the concave tip path has nothing to do with a
tailing loop.

Tom.

Lefty actually doesn't say that.

From his Casting With Lefty Kreh (2008), page 405:
"If the rod tip travels in a concave manner, you'll get a tailing loop, but this is because you drove the rod handle straight forward."

And on the same page:
"Some common explanations for tailing loops range from shocking the rod during the forward cast, to beginning the forward cast too soon or too late, to moving the rod tip in a concave manner. If you shock the rod with the tip stopping straight ahead, you will get a tailing loop. Shock the rod with the tip descending on the stop, and there will be no tailing loop, no matter how hard you shock the rod."

[gordonjudd]

Lefty actually doesn't say that.

Aitor,

Thanks for that input and I am glad to see that Lefty is more careful in what he writes than what he says while giving a demonstration.

I am glad to be corrected because I think the fundamental in producing a tailing loop is a concave tip path. I also think Lefty is a great caster, but do not agree with everything he says while giving a casting demo.

There are many ways to produce the concave path, but I would be surprised to see a tailing loop when the line was following a convex tip path.

Gordy