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Q: How does pull back work?

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Paul Arden
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Re: Q: How does pull back work?

#11

Post by Paul Arden » Sun Sep 19, 2021 5:09 am

Hi Graeme, I think it does, certainly there is a very visual line speed increase, but it’s difficult to isolate because other things are altered too. I’ll dig out a few videos.

Incidentally when I think of adding tension to the rod leg I think of little pixies pulling the fly leg!

Ok there is this one filmed in Australia https://www.sexyloops.com/movies/pullback.avi

1) standard. 2) pull-back.

And then there is this…



It’s difficult to isolate because are we applying a spike in force in the Casting direction before we pull back? Perhaps we are increasing the whip-effect, compound curvature, forced unloading and so on. Maybe it’s increased counterflex adding Tension. I don’t know. It’s probably all of them!

What would be interesting is to compare pull-back vs stop without a line. Maybe if would be possible to make measurements then.

Cheers, Paul
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Merlin
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Re: Q: How does pull back work?

#12

Post by Merlin » Sun Sep 19, 2021 7:19 am

Hi Paul

There are obvious differences in between the casts. The second one is made with a smaller angle (73 deg) than the first one (95 deg). That creates a smaller loop.
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You use a sharper acceleration from the wrist in the second cast, which generates a larger CF as you “check” the rod.

It is then not possible to compare them strictly and we have no idea of the tip top speed (maybe it is possible to track it to get an estimate, I do not know).

Check haul timing trend: the sooner you can make it, the higher the end line speed.

Merlin
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Re: Q: How does pull back work?

#13

Post by Paul Arden » Sun Sep 19, 2021 8:06 am

Thanks Merlin. I agree it makes them impossible to compare simply the effect of pull back isolated, because I don’t know how to isolate it. It might need a machine.

Talking of which Bruce and Noel’s casting robot had a two stage stop, which was created by feeding in Bruce’s analyser readout. The arm went bump-bump, bump-bump. Which I assume somehow is the hand absorbing the rod bounce. What was interesting was that they couldn’t program the robot to cast manually. I wonder if we could get Bruce to program the robot with a Pull-back reading. Let me drop him a line to see how he is!

Cheers, Paul
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Re: Q: How does pull back work?

#14

Post by Merlin » Mon Sep 20, 2021 7:53 am

Hi Paul

I used my casting model and looked after the difference with and without PB on a given cast. I found a marginal variation in tip speed and a larger CF. IMHO, the parameters of the cast (angle, timing), are much more influential than the PB itself and are the origin of the benefits you give to the PB.

A sharp PB makes the second frequency pop up and this explains the S shape in real life.

Casting robot: it is very difficult to mimic the auto adaptative damping possibilities of our arm/wrist. I don't expect such a machine to be able to cast properly.

Merlin
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Re: Q: How does pull back work?

#15

Post by Paul Arden » Mon Sep 20, 2021 8:13 am

The machine cast 30ft of flyline loops no problem. Nice controlled loops. They simply fed in Bruce’s stroke into the machine. What was fascinating is that the loop could start to fail after a while, and then start to recover until back to normal again and would go through this cycle. I had always assumed it would turn to spaghetti and not recover. But even after total failure it would eventually gather itself up again.

Interesting on pull-back. In that case it’s not so much what the rod is doing as much as what the caster is doing. I imagine that the tip path is considerably straighter as a result?

Thanks Daniel,
Paul
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Re: Q: How does pull back work?

#16

Post by Merlin » Mon Sep 20, 2021 10:08 am

Paul

The difference in tip trajectory is hardly visble, the PB option shortens it slightly just before MCF.
The estimate of the loop size is improved by 15% in that run of the model.

Merlin
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Re: Q: How does pull back work?

#17

Post by Paul Arden » Mon Sep 20, 2021 11:49 am

Thanks Daniel.

So probably then, Pull-back primarily works because it allows us to use a controlled, abrupt and increased force application at the end of the Casting Stroke. And the side benefit, which is less significant, is forced rod unloading resulting in slightly higher tip speed and a marginally straighter tip path?

Perhaps another difference, when compared to other “stops”, is because the force is reversed there is less effort being used to stop the rod. By this I mean if we are to try to make a “hard” stop in the casting direction, we use force to try to stop our hand/arm solidly, to prevent the rod from moving forward and opening the loop. However with pull-back we simply reverse the rod butt which takes less effort (in my opinion anyway). I think this is why the casting arcs vary so widely.

It’s interesting how different rods perform with pull-back. Some don’t like it at all. Rods that are very fast seem to give little benefit. Rods that are slow and tip heavy vibrate/bounce after the RSP.

Cheers, Paul
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Re: Q: How does pull back work?

#18

Post by Merlin » Tue Sep 21, 2021 9:04 am

Hi Paul

The way I see it with the info from the model and videos:
• You change casting parameters (arc, timing) to cope with the reverse motion. This is the main source of change in line speed (compact sharp stroke).
• Generally speaking torque is less without PB, but changes with casting parameters as well.
• PB needs a little bit more torque to reverse rod motion (side by side comparison with the no PB case).
• The PB itself helps in controlling loop size (smaller with a PB) and has a marginally negative effect on line speed. I guess this is a synch problem with the speed of the tackle. The reverse motion is sharp and can match the second mode of the rod (S shape).

Merlin
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