Catenary curve / "HANG TIME"

Walter & Group...

Walter Simberski had mentioned the catenary curve formed by the fly line after completion of the stroke as we discussed the effects of this line supported by the rod tip on one end and unsuported at the other.  My question was this:

Walter....

 

Isn't a catenary curve that made by suspending a flexible line (cable/chain, etc.) from TWO points not located on the same vertical axis ?

 

(I've forgotten the equation.)

 

Gordy

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Gordy

 

You are correct. The basic equation is y = a * cos(x/a).

 

The equation gets more complex when one end of the line is higher than the other or when

the line touches the ground.  I don't have those readily available and while I thoroughly enjoyed

the calculus of variations course where we studied this in university I'm not sure I want to

revisit that at this time.

 

I suspect things get more complex in our case because the loop is also moving in the x and

y directions. We also see some interesting things happening with the line as it falls because

form drag as the line falls is very significant. I believe Noel calculated or measured

the terminal velocity of a horizontal piece of floating fly line as just under 4 m/s and this is

for a piece of line falling horizonally. As you know a long falling line does not just fall as one

horizontal stretch. A line that forms a loop shape as it falls will have a higher terminal velocity

and the tighter the loop the higher the terminal velocity. This is also good confirmation that

tight loops are more energy efficient for casting purposes.

 

Couple that with the idea that for an underpowered cast the fly leg often remains horizontal

and continues to unroll while the rod leg is sagging in to a loop shape.

 

It would be interesting to see a computer simulation of this stuff.

 

Thanks

 

Walter

 

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Walter....   Thanks.  I couldn't remember the equation.   Would make better sense to all if plotted against  X - Y vertical & horizontal axises, I guess.

 

Also:  The question has been raised as to just how you define the term HANG TIME ?  (We've both been using that term.)

My description (I hesitate to call it a "definition") is that it is the time interval between RSP/loop formation and the start of rod movement in the direction of the next cast.

Some activity can and often does take place during that interval including things such as "layback", line shoot, drift, repositioning of the casting hand and the unrolling of the loop.

As you point out, this can get complicated.  We could simplify it by referring to the cast which ends with RSP with no line shoot, layback, drift, etc. I suppose.

Even if we do that, however, questions will be raised such as:  How would line shoot affect line fall ? and how would drift affect it ?

Questions on the table:

1. How can we define HANG TIME ?

2. Does line shoot during hang time affect the rate of line fall ?

3.) Does drift affect the rate of line fall ?

Gordy