If your are applying a transverse wave equation to a fly loop and using the wiggle cast as a reference, then the wave length is the combined height of the loops on forward and backcast.
Not quite. In the wiggle cast analogy, the tension vector that allows those wiggles to propagate is
away from us towards the fly leg. It stretches the wave in that direction. In a cast, the tension vector is usually down, collapsing the apparent wavelength we can observe. Rather than moving away from us as it did in the wiggle cast, the wave moves towards us (downwards) as shown in that
first wavey rod video. That was a "vertical wiggle cast" with tension supplied by gravity instead of a fly leg. We always need to cast with
some vertical line tension (or even upward projection) to counteract the constant gravitational shortening of the wavelength we see.
The height of the loops is not a valid measure because a horizontal loop has no effective height itself. However, the fly leg still must be aimed as appropriate for any projectile. Down or level for short casts, higher for longer casts.
I'd say the wave length may be calculated from the period of the return of any given point in the system to the same point in the previous cycle, e.g. the fly reaches the end of the front cast again or the tip crosses the vertical on the back cast again. The height the fly falls* in that total time (minus the stroke times) can be calculated from a
formula. We can observe the time it's airborne, so we can calculate how far it has "fallen". If a total cast cycle is 2.2 seconds, and the strokes totalled 0.7 seconds, the fly "fell" for 0.75 seconds during each phase of the cycle. Using those numbers, the fly in my image from a few pages back "fell" 5.5 metres, so that was the wavelength for that cast cycle. This is not something we can photograph and measure: we need to measure times and back-calculate distances according to common physics equations.
Please note, I made some errors in my calculations a few pages back, combining the total time instead of splitting it into two separate phases of roughly equal flight duration and allowing for stroke time. Mia culpa.
We know that the fly leg acts in accordance with standard projectile motion physics (or at least, I know this) because it receives no vertical supporting force after RSP. From that point until the fly lands or begins its next phase of the cast,
each little piece of the fly leg will be under the influence of gravity and air drag until it hits the rod leg. When the tension falls away from that too, the whole line falls as one.
The further we want to cast, the higher our aim must be on each phase or the fly will land before we can begin the next one. That's the same as if we were throwing a ball: aim higher (within reason) to throw further. But for us, we pull the ball back on our string before it lands and fling it the other direction. If it's not below our rod tip when we fling it the other direction, it's not going very far because we can't aim it upwards. Standing proud on a cliff would be great because we can let the fly drop below the level of our feet and aim higher on the next cast.
The higher aim means longer wavelength (it rises and falls more) and longer period between the start of each cycle (length of pause).
I believe it enjoys being
all of a full one even more than all of a half one. In an overhead cast, the front cast is usually preceded by a back cast. ALD doesn't work too well without a PU ...
Cheers,
Graeme
* I put "fall" in quotation marks because it is still being pulled down by gravity even if it's going up at or after RSP. If gravity was not pulling it down, it would reach 5.5 metres total height in the 1.5 seconds it was aloft.
