Paul Arden wrote:Hi Graeme,
1 So the overhead cast is a "transverse wave" and the roll cast a "surface wave". Aren't surface waves seismic?
Surface waves occur when the medium "rolls" and returns to its starting point. It can be any medium, but the ones in an earthquake are the deadly ones. The requirement is that the
medium starts at one point, pulls backwards, then upwards, then forward and finally down to return to its starting point.
A roll cast starts with the line on the dangle, rod near the water surface and pointing at the fly. The line just outside the tip is pulled back towards the caster with the rod, a D-loop is formed as the medium (fly line) is first lifted and then begins its forward motion and finally the stops back where it started, just above the water pointing at the fly. (The same motion could be described for the fly as the wave reaches the end of the line.)
That's a surface wave.
2) The fact that "ballistic trajectory" travels in the direction of the loop does not necessarily mean that gravity is making it do this - it could be the loop. After all the same phenomena applies when casting a loop in the horizontal plane. There is a cast where we false cast horizontally to the bank and then on the final forward cast change angle to deliver across the stream.
Ballistic motion simply means the object is following the path a ball would take if it was thrown (or a bullet, if you like). It largely follows the path of a parabola minus the effect of air drag.
Any marker placed on the line will follow this same ballistic trajectory. Merlin has a
really good graphic example derived from one of Lasse's casts.
If someone says the loop is pulling the fly leg, ask them what is pushing on the loop to make it do that? It's not the rod leg because string doesn't offer compressive strength. Besides, we can demonstrate that the rod leg is under tension and we can demonstrate that the line continues ballistically if the loop is destroyed (by crashing into a wall.)
Even in a side cast, each element in the fly leg is falling as it travels forward. Gravity NEVER stops pulling an object down when there is nothing to hold it up. What force is lifting the line just before it hits a loop? Don't say "the loop", because a sideways loop example kills that argument. And besides, ask yourself what is holding the loop up if the loop is supporting the fly leg? (To paraphrase Newton's 3rd Law: for every action, there is an equal and opposite reaction.)
3) It's been shown that a loop in horizontal trajectory stays aloft longer than a line in free-fall. I agree that there is some dispute around this.
And I'll bet good beer money that the fly leg was thrown with an ever-so-slight upwards vector. Did the back cast end just a little below the rod tip, or even at the same level? In other words, was the line hanging just a little below the level of the tip before or during the front cast?
The reason we need to increase the tempo on the sideways casting task in the CCI/MCI exam is because we need to give the line less time in free fall between each stroke. We can't aim it obviously upwards or we'll fail the task, but a subtle amount is very hard to see with the naked eye - unless you look for it. So we reduce the time it has available to drop with high velocity and cast with a much flatter trajectory. It looks so close to horizontal that we don't see it real time. Got any slo-mo footage?
However if I was to take your logic then a high backcast should result in turn with a forward cast that doesn't counteract gravity and instead falls faster. This is obviously not the case and you can prove this to yourself by throwing a higher backcast!
Where is the line at the start of the next forward cast? If it's above the SLP, then it definitely will fall faster because we'd be adding downwards component on top of the force of gravity.
If the line has dropped to the level of the SLP and we are adding only horizontal force, it will fall as if it were to continue falling (i.e. no upwards or downwards vector).
If the line has dropped below the SLP, we're going to need to add some height to the cast and it will stay in the air longer after our cast.
I can see this causing apoplexy, but I can't help that.
Please don't ask me where the longitudinal waves in the cast are. These are too hard to see in a normal cast, although I did capture one in some footage of a dud cast. It looked very cool travelling from the fly to the tip as the loop went the other way! It did some weird shit to the loop as it passed through it.
Cheers,
Graeme