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Shooted cast

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Merlin
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Shooted cast

#1

Post by Merlin » Tue Sep 01, 2020 1:10 pm

I can run the Tension model for untethered casts, and now the running line is on board. Of course, the situation is simplified, the line is still a level one, the loop a half circle and the legs are parallel, the fly is a given, etc. By the way, given the necessity to recalculate continuously the drag force on a loop with variable taper, I am not at the eve to have a “taper” Tension model I think. Excel files are not well adapted to such calculation.

I gave a look at a few parameters like the weight of the head (9 m long), the density of the running line, its size (diameter), and the timing of an early release. That point is very, very discernible. I am using a more realistic skin drag coefficient now, taken from the only specifically fishing oriented experiment including front drag coefficient for some flies. (L. Gaddis, Clemson University, “Axial fluid drag on slender cylinders and terminal objects” late 90s I think).

The extra shooting distance reduces drastically as the line release is delayed, it is extremely sensible (100 ms).So it seems mandatory to anticipate the release of the line and maybe someone can confirm that trend and explain how he tunes the release. Since such timing corresponds to the end of a haul that does not appear to be simple for an average caster like me. There is a physoliogical reaction time to anticipate. I imagine this contributes to the variability of casting distance significantly.

Running line: thin and light, that is the recipe. The weight is more important (detrimental) for thicker lines, for thin running lines it seems to be more marginal. So maybe someone uses “heavy” running lines against wind, if that thing exists.

Line weight: no surprise if I say that the best performance is obtained with the heaviest head although the difference in distance achieved is not that big on the paper. I know, the cast is supposed to be horizontal so the ballistic effect of a tilted cast is not included.

Another information: the tension at ends of the loop varies with its tangent/rotation velocity, so the tension at the bottom is higher during an acceleration phase and it is the reverse in a deceleration phase of that speed.

Merlin
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Re: Shooted cast

#2

Post by Mangrove Cuckoo » Tue Sep 01, 2020 2:05 pm

Merlin,

Very cool!

The fact that you are doing this type of stuff with Excel is impressive.

Out of curiosity... since release time is critical, do you have parameters for haul length and haul speed???
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Paul Arden
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Re: Shooted cast

#3

Post by Paul Arden » Tue Sep 01, 2020 4:49 pm

Hi Merlin,

With a shooting head I think so and I release earlier (before the haul stops). With something like a MED it makes a difference but I don’t find it anything like as critical and I’m happy to release at haul stop. I know others who might disagree.

Are you modelling counterflex and RSP2? I would be very interested to understand what happens in terms of line tension during RSP1-2. Certainly I don’t feel much tension until after the loop is properly in flight. If I start the up part of the haul too early/quickly I create slack, but that may have to do with the greater friction of the running line compared to shooting line.

Incidentally why is the cast supposed to be horizontal? My trajectory is about 30 degrees above the horizontal. This way I find it flies further after loop straight. (In to the wind is different of course)

Thanks Merlin!

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Lasse Karlsson
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Re: Shooted cast

#4

Post by Lasse Karlsson » Tue Sep 01, 2020 7:15 pm

Paul, please show us a pic of your 30 degree up trajectory 😉 until then, I call bollocks....


And horizontal makes sense, I only go above in a good backwind, and rarely more than a few degrees...

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Lasse
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Paul Arden
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Re: Shooted cast

#5

Post by Paul Arden » Tue Sep 01, 2020 9:13 pm

Of course!
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Re: Shooted cast

#6

Post by Michal Duzynski » Tue Sep 01, 2020 9:53 pm

Hi Merlin
I like it, it might help with the seatrout distance.
Here is a cast I am very happy with, but now when I red it I think it could go even further, because of the release.
I watched it again I think I maybe released it too late.
Have a look, there is slow mo of the delivery and release, let me know what you think.


Shooting line is 0.37mm

cheers
mike

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Re: Shooted cast

#7

Post by Michal Duzynski » Wed Sep 02, 2020 12:41 am

Here is another video, and in the slo mo part of the delivery cast you can see that my hand opens/releases the line behing my butt cheek😎.
Now I start to think about it.
Could you use my video, or something simalr and mark wher the release position should be for the best result?
During fals casting there was not too much overhang- just right, and the loop was under an awesome tension- no wiggles and waves in a loop.
cheers
mike


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Lasse Karlsson
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Re: Shooted cast

#8

Post by Lasse Karlsson » Wed Sep 02, 2020 3:40 am

Paul Arden wrote:
Tue Sep 01, 2020 9:13 pm
Of course!
Thats app 8 degrees dude, far from 30... don't measure the angle of first psrt of the rod leg ;)

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Paul Arden
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Re: Shooted cast

#9

Post by Paul Arden » Wed Sep 02, 2020 3:47 am

You think the bottom part of the rod leg is pulling the fly leg? Anyway I agree it’s not 30. Let me see if my phone has a protractor...
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Re: Shooted cast

#10

Post by Paul Arden » Wed Sep 02, 2020 4:12 am

Typically 15 degrees. (I knew it was a dissection :D). It can be more but I’ll do some tests and will measure every time I throw now.

It’s quite easy to do this with the measurer app. Just stick a bit of tape either side of the phone where the measuring lines are on the app and line up the two tape points to your target.

When casting I pick a higher and higher target until the loop tails and then lower the target slightly. So with this it will be very easy to measure trajectory in different conditions.

Of course the rod tip to target angle is going to be different. Not much I can do about that :D

Cheers, Paul
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