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Stiffness and Tip speed

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Paul Arden
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Stiffness and Tip speed

#21

Post by Paul Arden » Thu Jan 17, 2019 8:35 pm

I cast Joakim’s rod on the way up through Sweden. I think that’s the Animal we were throwing in Scotland. Or maybe the Animal plus 1! Great people. I’d move to Sweden if it wasn’t so cold (and had Snakehead).

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Stiffness and Tip speed

#22

Post by guest » Thu Jan 17, 2019 8:37 pm

So all of their usual rods were stiffer than the control rods. :pirate:
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Lasse Karlsson
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Stiffness and Tip speed

#23

Post by Lasse Karlsson » Thu Jan 17, 2019 9:43 pm

VGB wrote:So all of their usual rods were stiffer than the control rods. :pirate:
Yup!

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Stiffness and Tip speed

#24

Post by Lasse Karlsson » Thu Jan 17, 2019 9:45 pm

Paul Arden wrote:I cast Joakim’s rod on the way up through Sweden. I think that’s the Animal we were throwing in Scotland. Or maybe the Animal plus 1! Great people. I’d move to Sweden if it wasn’t so cold (and had Snakehead).

Cheers, Paul
If only you could actually remember things, this could be an interesting debate :D HT 4,6,8,10 and 12 and the same line, numbers would be much appreciated :p

Think Joakim was using a 12 for a short while, but that might have been for seatrout. ....

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Stiffness and Tip speed

#25

Post by Paul Arden » Thu Jan 17, 2019 9:56 pm

I’m far too old to remember things Lasse - I think it was an 11CTS. Wasn’t the study done before the general shift to stiffer rods?

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Merlin
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Stiffness and Tip speed

#26

Post by Merlin » Fri Jan 18, 2019 5:40 am

Hi Vince

The hand path is a long nearly horizontal translation, it includes the slide loading of the rod, and the rotation takes place pretty late. I use a video analyzis performed by Gordy.

The tip path is too much domed and I know where it comes from: my large deflection program, which lacks a suitable discretisation (too few elements). This is because the discetisation is currently tuned for frequencies. I should built another large deflection file with a large number of elements to get something better, focused on deflection. This is less troublesome for light line rods, but for stiff ones it does impact the results. For example I can mimick Matthias' cast tip path quite nicely.

I see people are still speaking of stiffness whislt it is a frequency issue (that comes from the differential equation), but we cannot avoid the natural trend for stiff rods to be faster, even loaded, and in particular when the step is 2 line size.

The graphic I posted gives trends, the order of magnitude for speed is correct, and such results are usable for comparison purposes. They are less usable for any kind of prediction about a specific cast and rod, unless a comparison with an actual cast can be made. It is unfortunately impossible to make such comparison, we do not have any tip path record for a #10 rod for example.

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Stiffness and Tip speed

#27

Post by Merlin » Fri Jan 18, 2019 5:43 am

Hi Bart

Thanks. The topic was covered two years ago, I just had to process existing data, add a few, and make the graphic.

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Stiffness and Tip speed

#28

Post by guest » Fri Jan 18, 2019 7:11 am

Hi Daniel

I don’t really get the horizontal translation and tend to see the paths that Dirk mapped some time ago:

https://thelimpcobra.com/tag/spline-mathematics/

I agree that stiffness is the wrong parameter and also think that maximum tip speed is not what we should be considering. Work done on the line may be more appropriate because it also involves distance (or tip path length). When we launch the line we want as much of the mass moving in the direction of the cast as possible and the tip path length gets the line straight and moving in the right direction. There’s also hints of the relationship between rod stiffness and haul timing that I think may be relevant but I haven’t got a handle on it yet.

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Vince
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Stiffness and Tip speed

#29

Post by Merlin » Fri Jan 18, 2019 10:40 am

Hi Vince

Below is an illustration of hand (rod butt) path for a couple of 170 casts. The scale is in meters.
170 hand path.JPG
170 hand path.JPG (24.01 KiB) Viewed 1076 times
I set the paths to start from the same point, for comparison. Pretty similar, isn't it (apart from the overall length)?

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Stiffness and Tip speed

#30

Post by Lasse Karlsson » Fri Jan 18, 2019 10:48 am

How did you measure them Daniel, and which clip are they taken from?

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