SLP / convexity /Counterflex/ Loop size

Walter & Group.....

From Gary Eaton aprapos our discussions on the relationship between SLP of the rod tip, convexity of the tip path, counterflex and the formation of a large loop:-

Gordy,

I enjoyed an e-mail exchange with Jason Borger a few months ago

regarding the video source of these images. Comparison of a flexible

versus less-flexible rod provided visual evidence that the loop width

resulted from the acceleration phase combination of convexity above

SLP plus deviation below SLP plus "rebound" of the rod. I am familiar

with the concept of "suck-up" from SL and a great, long-cast video by

CBOG Lasse Karlsson from more than a year ago. I believe that

"suck-up" primarily only corrects the rebound component until the

front taper starts to become part of the loop. As the light front

taper enters the loop near terminus, the "rat snout" may appear and

the loop begins to represent the non-rebound loop size.

One of my students was at the test site that initiated Al's set of

questions. When he told me about the disagreement with the "convexity"

answer, I told him the best answer was becoming clarified. Thank you

and Bruce for addressing the issue. I suggested he was wise not to

aggressively defend his answer but that the combination of deviation

above and below SLP was essentially a "convex tip path" during

acceleration to the stop.

My student passed his CCI test. I may have another Master Study

participant for us!

Many Thanks,

Gary Eaton

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Gary ...    Agree.          Gordy

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

New message and new modification of diagram by Al Crise:-

(See his diagram in attachment)

Howdy Caster

 

 The June clinic has now been set for June 28 and 29 for CCI training.

 

Attached is a new mouse drawing from Al.

 

 Now this is from Gordy and he explains this loop formation and size Very Well:-

 

Al...

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Al...

 

You are correct in that the distance the rod tip is dropped below the initial SLP or straight line travel of the rod tip determines the size of the loop.  This is, however, convexity or increased rod arc just before RSP.  Not afterward.

 

Problem with the diagram is simple.

 

You show RSP (rod straight position) directly in line with the straight line path of the rod tip.  Loop formation starting at that point must do one of two things:-

 

1.) Form a very small, tight loop . (If there is a tiny bit of convexity to the final tip path)

 

                             OR

 

2.) If exactly as in your diagram, a collision of the oncoming line with the rod tip will occur.  Why ?   BECAUSE YOU SHOWED AN ABSOLUTELY STRAIGHT LINE PATH OF THAT ROD TIP all the way to RSP.

 

Years ago, that very thing was asked me by Bill Gammel and Tom Jindra as the second question on my Master oral exam ..... so I remember it well !!  (I didn't fall into that trap).

 

 

To make a loop which doesn't collide with the rod tip, you must have some downward deviation from the straight line path of the rod tip prior to RSP ..... not afterward.

 

That downward deviation just prior to RSP is slight convexity of the rod tip path thus unloading at RSP slightly below the oncoming line.

 

If that downward deviation (greater convexity or increased rod arc) just prior to RSP is greater, then you will unload a greater distance below the prior straight line path of the rod tip (way below the oncoming line).  THAT will yield a larger loop.

 

After RSP, counterflex occurs which will open the loop even more.  Some of that additional opening, due to lowering of the rod leg of the loop, will be what is, "sucked up" at least to some extent by the inertia / momentum of the forward traveling loop.

 

Gary Eaton, in today's message, pointed out that after counterflex, rebound will remove some of the sag temporarily formed by counterflex.   He's correct.

 

We must also remember, that after the STOP there are about 0.1 seconds or less to elapse before RSP.  I can't actually perceive that as I cast, so what I (and I think most casters do) is drop the rod down a bit as we make the stop......... a little increase in this rod arc for a tight loop, and a lot more for a controlled larger loop.

 

WE DON'T DO THAT AFTER RSP !

 

 

Gordy

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 

Al ...   The new diagram is much better.     One suggestion..........    We can make it more clear if we show RSP (rod straight position) as follows:

 

1.) As you have now shown it, with the rod tip at RSP just a bit below the prior SLP.  This represents a small addition of rod arc (convexity) which yields a small loop.

 

2.) A second RSP farther below the prior SLP.  This would represent a greater addition of rod arc (convexity) which would yield a larger loop.

 

3.) A third RSP way below the prior SLP.  This would represent an even greater addition of rod arc (convexity) yielding an even bigger loop.

 

OK to leave the depictions of counterflex in the diagram, however, at present they suggest that most of the determination of loop size is made during counterflex.  That simply isn't true.

 

By far the main thing determining the size of the loop is the convexity of the rod tip path before RSP .

 

Putting it in other words:    Convexity (additional rod arc) near the end of the stroke places RSP below the prior SLP and the oncoming line yielding a controlled wide loop.  Counterflex temporarily opens the loop further until the momentum of the forward moving loop combined with the effect of rebound minimize this effect.

 

The greater the distance between RSP and the oncoming line, the larger the loop.

 

A third, "word diagram" :  By using convexity of the rod tip path near the end of the stroke, we can place RSP at various levels below the SLP of the middle of that stroke which allows us to, "unload" at various distances below the oncoming line. The greater this distance, the larger the loop.

 

Gordy

 

 

 

 

Attachment: loop size 2.BMP
Description: Binary data