The Last Great Mystery
Once more I am pondering the qualities of a loop. Yeah, I know, get a life. Up until this moment one of the corner stones of my instructing is (or has been) the creation of an efficient loop and how a fly cast is totally shite without one. I have attributed all sorts of things to the loop from it’s sheer beauty to it’s dynamic abilities. One of the first things I do in either instructing or presenting is to snapcast twenty or thirty feet of line, create the loop and then point out how that loop propagates down the line and turns over the line and leader with hardly any effort, provided I have formed the loop. In that context I am attributing all sorts of (erroneous?) properties just to the loop.
In fact there are arguments as to whether the loop pulls the fly leg or the fly leg pushes into the loop. In the paragraph above I think I suggest the loop pulls the fly leg and logic tells me that can’t be the case (but then my logic may be different from yours). Force has been applied to the rod leg, not the loop. The fly leg has the momentum, not the loop. The loop is formed as a reaction to the line dividing at the stop. It’s just natures way of keeping things connected. It has to be there whether we want it or not. It’s very useful from a fishing point of view in that in turning over it carries the fly out to where we want it. We know a narrow loop is more efficient than a wide loop, but why is that? Yes, I know about drag on a wider loop face and that does come into it, but I think the main reason is that we didn’t accelerate the line in a straight line. The momentum in the line is through a curved path subjecting it to deceleration forces greater than if it had been straighter. The width of the loop is indicative of the straightness of the force applied to the line.
So now I am coming round to the fly leg pushing into the loop…or am I? I don’t know, these are just thoughts!
The loop can obviously be efficient or inefficient, it does make a difference to the outcome of a cast, so it would appear the loop does have a dynamic to it that can make or break a cast. So what is it? There is obviously tension in the loop, if there wasn’t it wouldn’t have shape, or at least not an even one that would allow the fly leg to push into it. I am now thinking that we are now creating a pulley effect in the loop. Carl Hutchinson hypothesised about this years ago but I wasn’t ready for it then. Lets take a look at pullback. Pullback is a subtle against the direction of the line tug mostly performed at the stop. It’s visual effect is to speed up the loop. However there is a correlation between line speed and loop speed. If loop speed is faster then so is line speed (by twice, as loop speed is half line speed) then perhaps pullback hasn’t affected the loop so much as accelerated the line behind it by using the loop as a pulley and a faster line speed has to create a faster loop otherwise the fly leg would overtake the loop, which isn’t very likely. Although having said that I have seen the fly leg carry on and straighten after the loop has run out of steam when casting distance which re-enforces my thinking that it is the momentum in the fly leg and it’s straightness that drives the cast, not the loop. If we go back to my presentation snapcast; How does it work? Paul Arden has argued that it’s because we shorten the fly leg when we make the snap. I now think that it’s because as we create the loop we create a pulley and directly accelerate the fly leg via the pulley. The loop, no matter how beautiful, enchanting and apparently mysterious is just the pulley the fly line has to go around to get the fly from way back there to just in front of that bloody fish.
Lots of bones to pick over.