I've been working on the question about how a taper can be utilised to both dissipate and increase the velocity of the fly within the same line by modifying the tension in the rod leg.
James got me thinking about angular momentum so I analysed a few of my videos with that concept in mind, seeing if I can work out why sometimes the fly can accelerate beyond the breaking strain of the tippet, while at other times it can be placed most delicately on the water surface. During casting, I've noticed:
- Rapidly pulling the line as the loop approaches the leader can cause a "crack of the whip", especially if there is no fly attached to the tippet. (Velocity increased)
- Lowering the rod tip as the loop approaches the leader can let the fly touch softly down (Velocity dissipated)
I don't know exactly why that's happening, but if the answer is "angular momentum", then it might be explained by the amount of line following a curved path as it enters the loop. If more line is subject to angular momentum, perhaps more accelerative force from that line is applied to the fly leg? If that's the case, then pullback at the right time can crack a whip, and with the same line, we can also wipe off speed by dipping the rod tip at the right time.
If the line in the rod leg is stationary, about a quarter of an oval is occupied:
If the line in the rod leg slides forward, less of the fly leg is pulled into an oval shaped path:
If the rod leg is pulled back during the cast, nearly half an oval is occupied:
In the snap cast, we have a LOT of line moving rapidly in a curved path. If angular momentum in a fly line is real, there is a lot of it in a snap cast, and we also see the fly leg accelerate markedly in the snap cast. We can enhance turnover in a failing cast by pulling back on the rod leg near the end of the cast.
In a delicate cast, we can soften the impact by pushing the rod tip forward, inhibiting turnover.
As I say, I don't know if this is the answer to Will's question, but it's something that's working for me right now. I'll keep thinking on it.
Cheers,
Graeme