Moderators: Paul Arden, stesiik
ACW wrote:LorksGuys,
I am so pleased i can cast a fair line and catch the occaisional fish without having the faintest idea wtf you are on about!
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.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?
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.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.
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?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.
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.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!
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?
This can be done without any upward trajectory if the tip height is high enough so the line doesn't fall in the time allowed. Cast fast enough and the line won't drop enough to cause a problem. 
- but it would make an awesome slack line cast!As in a Spey cast? A roll cast is not a COD cast, right?Paul Arden wrote: 1. What if I make the roll cast with a change of direction? Which wave form does it take then?
That's a wonderful document on the drag forces on a line at the loop. However, I could never understand why people quoted that document as a reason for the loop to lift the line. Can someone point out how air drag lifts a falling object please?2. A loop is pulling and pushing - that's why you can speed the line up by increasing tension in the rod leg.
Forces on a loop: http://www.sexyloops.com/flycasting/loop%20dynamics.pdf
An aerial spey cast? The rod tip is propelling the fly leg across the river. The fly leg is the ballistic part of this. What is the objection here?3. Sorry you misunderstand me - I'm not arguing about gravity, I'm discussing the fact that your "ballistics" in this case are in line with the river bank, but the loop direction is cross-stream and that's where the fly ends up.
The fly leg is a projectile until it is stopped by the rod leg. Paraphrasing Newton's 1st Law: An object remains in a steady state of motion until acted upon by a force. The fly leg acts as a series of projectile elements (affected by air drag and gravity) until they hit the tethered rod leg. That's simple Newtonian physics, not some magical process.4? The line is not simply a projectile (apart from which you're calling it a transverse wave); it is a loop. Without the loop the fly would be at the wrong end
It is the contention that with enough speed the loop will actually lift. I actually have a problem with this paper however, but not because of loop lift, but because I don't see how that can lift the trailing line. I have however watched loops (possibly) lift and for the trailing line to collide or come through underneath.Skin friction reduces the downwards acceleration of the loop.
This reduction grows with the square of the speed of the upper leg. Thus, a loop traveling twice as fast generates four times the “lift” due to skin friction.
No, it doesn't need to return only to it's starting point to be a wave. An ocean swell moving towards shore does carry some of the medium (water) away from its starting point and towards the shore as the wave begins to deform, just before breaking. Eventually, the wave breaks when the top overtakes the base.1. well yes a Spey cast is a form of a roll cast - it's a Change of Direction Dynamic Roll Cast. You were saying that the line had to return to its starting point. How about if I shoot the line?
(All you've really done is add excess energy to the wave, but that won't work if the line wasn't lifted effectively.)Stating that with enough speed the loop will actually lift is like saying if I throw a ball down really, really fast to increase drag, it'll magically lift upwards. Drag can only ever slow things down, not provide a motivating force. (Before ANY lift can occur the line, by definition, must reverse its downward velocity to start going up. Between down and up, velocity = 0, so drag force = 0, so "lift" simply cannot happen.)It is the contention that with enough speed the loop will actually lift. I actually have a problem with this paper however, but not because of loop lift, but because I don't see how that can lift the trailing line. I have however watched loops (possibly) lift and for the trailing line to collide or come through underneath.
I'm following, but it's the fly leg that's falling, not necessarily the loop itself.3. Let's go back a step. You have explained in your video that the line has been given its set trajectory at around MCL and it's this upwards angle that allows it to counteract gravity. (You then use the paths to draw transverse waves). You also explain that the loop falls because of gravity and you draw this too. However I don't agree and I would argue that the tip path from MCL to RSP sets up the trajectory of the line and the rest of the line is pulled along this path.
To prove my point I pointed out that it's quite possible to completely change the direction of the line's "ballistic path" and we do this every time we execute a change of angle delivery cast across a river.
So while the angle the line is making with a low backcast/ high backcast/ D-loop is important, it's not the driving force to where ultimately the fly will end up. (The exception to this being when the carry is too long for the direction change).
Cheers, PaulA neat trick is the change of direction side cast. The way to achieve this is to perform the side cast as you normally would and then on the last forward cast just as the rod points in the direction you want to cast, rotate the wrist so that the reel points downwards. Many good stream anglers I know use this to good effect: they do a couple of false side casts to judge the right distance, and whack! change of direction, under the tree, dead on target.
Make sure that you point downwards with the rod tip on the final delivery, otherwise the line clashes with the rod...
