Path of the rod tip as it goes to basic loop forma

Stoatstail50 · Post by **Stoatstail50** » Tue Mar 01, 2011 3:03 pm

Hi Frank

Is there any part of the path of the rod tip that doesn't "go to basic loop formation" ?

Frank LoPresti · Post by **Frank LoPresti** » Tue Mar 01, 2011 3:05 pm

Yes, the translation aspect.

Stoatstail50 · Post by **Stoatstail50** » Tue Mar 01, 2011 3:07 pm

Which bit is that ?

Frank LoPresti · Post by **Frank LoPresti** » Tue Mar 01, 2011 3:10 pm

Looks to me like you've answered the question by simply asking it. Can you tell me what the translational path of the rod tip adds to basic loop formation. I can't

Stoatstail50 · Post by **Stoatstail50** » Tue Mar 01, 2011 3:14 pm

No, I know you can't....

Just as a matter of interest, lets say we managed to achieve a straight line path of the rod tip for a portion of our casting stroke, would the tip rotate along that straight line or translate along that straight line ?

Or both possibly...?

Frank LoPresti · Post by **Frank LoPresti** » Tue Mar 01, 2011 3:30 pm

I don't know bout the if part. What I do know is that the only time the rod tip comes straight is in relation to the rod butt as the tip passes over it, even then the path of the tip would be slightly convex for the narrowest possible loop.

Stoatstail50 · Post by **Stoatstail50** » Tue Mar 01, 2011 4:09 pm

Cool drawing Frank...

So, if the tip were to follow any of those three paths it would only rotate along those paths .... it wouldn't translate in any way at all ?.

If I get this right, in your view, there isn't any translation evident there and even if there were it wouldn't have any effect on loop formation whatsoever.

Frank LoPresti · Post by **Frank LoPresti** » Tue Mar 01, 2011 4:11 pm

Stoatstail50 wrote:Cool drawing Frank...

So, if the tip were to follow any of those three paths it would only rotate along those paths .... it wouldn't translate in any way at all ?.

If I get this right, in your view, there isn't any translation evident there and even if there were it wouldn't have any effect on loop formation whatsoever.

Have a look

Right, no I don't see how it could...

Frank LoPresti · Post by **Frank LoPresti** » Tue Mar 01, 2011 4:16 pm

Now take a look at what Stroke Length really constitutes...

Frank LoPresti · Post by **Frank LoPresti** » Tue Mar 01, 2011 4:18 pm

This is something I put together just for the fun of it...

Stoatstail50 · Post by **Stoatstail50** » Tue Mar 01, 2011 4:21 pm

Heyzoooos Christooo......its a total revelation Frank....I'm well impressed...

Hopefully a lot of prospective CIs and the like will be reading this because that drawing will help clear up a lot of things for sure..

Stoatstail50 · Post by **Stoatstail50** » Tue Mar 01, 2011 4:25 pm

How do the blue and green and puce lines and stuff get connected to the Casting Stroke ? is that by a hand path too ?

Frank LoPresti · Post by **Frank LoPresti** » Tue Mar 01, 2011 4:31 pm

They remain outside the actual casting stroke simply to offset and illustrate what motion goes to whatever it's tagged as.

No one has yet to see this so it's not an official anything. I'm still looking at ways to improve it. So anyone is free to add something if it fits and it's a logical extension of the model.

Frank

gordonjudd · Post by **gordonjudd** » Tue Mar 01, 2011 7:07 pm

Is there any part of the path of the rod tip that doesn't "go to basic loop formation" ?

Mark,
I do not know what "basic" would mean as it applies to loop formation as the Gatti-Bono paper shows the loop formation process is very complicated and I don't think any of us (that do not have a PhD in mechanical engineering at least) are going to be able to understand all of the effects that go into it.

However when you look at the diagram of the rod tip path Gatti-Bono included in the model she used to study loop formation you can see she considered the complete path from the start of the forward cast to MCF as being important to modeling the loop formation process.

Thus the short answer to your question is no.

I think our ego-driven assessment of the casting skill involved in making different loops clouds our understanding all the factors that actually go into making them.

We tend to think our expert manipulation of the butt, is going to have a direct impact on what is going on with the line. When I hear someone say they can "paint" different loop shapes by the way they stop or manipulate the rod, I simply ask them to demonstrate it and produce a pointed initial loop at MCF.

Alejandro met that challenge, but he had to use a broomstick rod with little or no counterflex to do it. I have yet to see anything other than an elliptically shaped loop at MCF in high speed videos, simply because that is the shape that the rod tends to produce because of the way it unloads and goes through counterflex.

Thus the caster is only one of the voting members that has an impact on loop formation. We provide the essential input to rotate and translate the butt and thus provide a driving force to the rod, but the characteristics of the rod and the line will also have a say in the ultimate loop that is produced for a given cast.

You only have to look at the huge amount of counterflex that resulted from the kinetic energy in the mass of the relatively soft fiberglass rod a champion distance caster produced in the 50's to see that regardless of skill you were not going to see a narrow loop produced in an energetic distance cast made with the heavy, noodle-rods that were available back in the day.

The bending stiffness of the line is also going to enter into the size of the loop that can be formed. Gatti-Bono discovered that line stiffness was an important factor to keep her program from blowing up as it stepped through the process to simulate a loop shape for a given tip path.

A good example of the importance of the line is shown the loop Paul produced with a pure linear acceleration and translation of the line in this video.

Since the line is so flexible, you might think that the linear path and sudden stop Paul produced with his "machine' would cause the line to just fold back upon itself and make the ultimate needle loop. However, as you can see below, the stiffness of the line causes a much wider loop to be formed. As a consequence you can probably assume that regardless of the stop, or tip path you provide; the bending stiffness of the line will not allow you to produce a loop that is much more narrow than the one shown here.

Gordy

Frank LoPresti · Post by **Frank LoPresti** » Tue Mar 01, 2011 7:37 pm

There's so much rotation behind Pauls motion that this hardly qualifies as anything except a cast that runs along a rail

try sticking a fly rod outside your car widow an accelerate as fast as you can in a straight line, slam on the breaks and see if a loop will form then

It's amazing what an outsized ego would like people to to believe versus what is taking place.

Looking at the Gotti diagram you would think that the tip path of the rod was entirely flat until the stop. I don't think it is, nor do I think it can be. Not even close...The tip path is primarily convex throughout the entire stroke. There is no escaping that fact. If you think the tip path flat then the world must be flat as well and we're all about to sail of the end of the world.

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Path of the rod tip as it goes to basic loop forma

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