Fly line loop formation / Counterflex & rebound / tension

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Attached file will open with Windows Media or you can place into Power Point etc. Its an attempt to illustrate how a fly line, travelling at its max velocity passes the fly rod and show how the line shape nearest the rod tip will during its slack period as the fly line passes be altered by the rod counter flex until the mass of the fly line overtakes and starts to change the loop shape – or morph as they say. Shooting heads I suggest make tighter loops because the running line puts fewer impediments on the fly line as tension increases. Comments?

Best wishes,

Ally Gowans

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Comments: Note the diagrams in Ally's attachment. I think this is a very clear depiction of what happens with straight line casting.

My own take is that the dip in the rod leg of the loop does have a lot to do with counterflex. I think that a combination of forces result in what Paul Arden referred to as, "sucking it up" as the rod leg began to straighten. Seems to me that rebound after counterflex would aid in this ....plus the tension created between the traveling loop and the rod tip which would differ depending upon whether or not the line is shot in which cast the rod leg would have velocity and (since it also has mass), inertia.

Gordy

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More on this from Ally:

Hi Gordy,

Just a comment on Paul talking about the line being sucked out as the loop travels. It’s the line that has the energy and the loop is the result of retardation of the line by tension from the rod tip. The loop does not pull the fly line forward, it holds it back and by doing so prevents the line becoming disorganised – as you found happened when you cut the backing and let go completely. The rod leg of the line has no velocity it comes to a standstill as the line travelling forward turns over but it has tension. The fly leg has velocity and experiences the same tension via the loop. Loop shape is a function of the line velocity and material and the position of the rod tip in relation to the line velocity. I think!

The shooting line the rod leg has velocity after line is released (shot) and that should be after the line loop has formed because by then we would have tension enough to pull out the running line and the heavy running line can indeed have sufficient kinetic energy to pull it a long way. If line is released during the period when the tension has disappeared immediately after the rod tip max velocity, either a poor or no line loop results - we have all seen this early release too often!

Best wishes,

Ally Gowans

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Ally.... I'll have to think a bit longer on your statement, "The loop does not pull the fly line forward, it holds it back....."

If I cut the fly line at its connection with the backing, the loop travels a long way forward and carries what is left of the rod leg of the line along with it. Either that, or the entire fly line / loop / fly leg & cut rod leg all function as a unit moving against atmospheric resistance. The fact that the loop doesn't unroll much in that situation, suggests that this is because the tension between the moving loop and the stationary rod tip has been eliminated.

I'll not comment further on that concept until I given it more consideration.

Gordy

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