Swing, Spring, Whip

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Swing, Spring, Whip

Post Number:#31  Postby Bernd Ziesche » Sat Feb 09, 2019 8:26 am

Merlin wrote:Hi Bernd

The model considers that the whole line has the same speed up to the launch point, it does not considers the shaping of the loop,


Hi Merlin,
Your "launch point" is the end of fraction 2 in my sketch?

Image

If so, how much percentage of the whip effect has taken place here?

The answer seems quite variable to me depending on how I perform the cast and what rod-line system I have in use.

I (think I) do understand, that the tapering of the fly rod would have a benefit to the speed up of the rod tip based on the conservation of energy/momentum principle. But yet I have no clue what this means in terms of helping me to bring my fly to the fish. If I would have to make a guess, I think it doesn't contribute much here in most of my casts.

The tapering of the fly line means: We increase surface and thus increase friction in relation to line mass. How is this with the tapered fly rod? Was this also taken into account?

Thanks
Bernd
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Post Number:#32  Postby Paul Arden » Sat Feb 09, 2019 10:35 am

The reason I thought a level rod would be better because it’s the propagation of a wave (which is why I asked the question to see if I understood the basic principle). But I’m not sure now :D

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Post Number:#33  Postby Merlin » Sat Feb 09, 2019 2:49 pm

Hi Bernd

First question: yes

Second question 75% typical in terms of speed at launch time, by comparison to absolute maximum speed. Launch time is considered as the moment when the tip begins to drop down. The gain at absolute maximum speed is higher, hence the 75%.

As stated in the article for a SH modern rod, the whip energy contribution is about 15%, but you can hardly detect it. If you want to have more chance to do so, take a tip heavy rod.

As also mentionned in the article, aerodynamics forces on the rod are not included in the energy evaluations (same for speeds).

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Post Number:#34  Postby Bernd Ziesche » Tue Feb 12, 2019 10:42 am

Thanks Merlin!
Are there any datas/ideas how the line length outside the tip effects the level of whip effect to the line speed up?
When I add high speed to a short line, I probably put an increased whip effect to the line since I store more energy in the rod in relation to line mass outside the tip. Casting a long line in lowest possible rod bend should be opposite though. Any idea how much of a range of increasing line speed by whip effect we may have?
Using a heavy rod means I can store more energy in the rod in relation to the line mass. Would this increase the level of whip effect? Regards Bernd
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Post Number:#35  Postby Merlin » Tue Feb 12, 2019 12:55 pm

Hi Bernd

Good questions indeed

The shorter the line is, the higher the relative speed improvement (percentage) is. Although there is some interference with stored elastic energy, the whip effect is a question of rod mass (and its location along the shaft), not of spring.

A heavier rod mass brings more speed increase in terms of percentage. For example, you may have 6% speed increase due to the whip effect for a graphite rod and 20% for a cane rod in similar conditions.

To give a broaded view, if I consider a graphite rod we may have from 8% to 4% increase in speed due to the whip effect, depending on carry, and from 25% to 18% for a cane rod.

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