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Some thoughts on Bernd's thoughts on stretch in fly lines

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Paul Arden
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Re: Some thoughts on Bernd's thoughts on stretch in fly lines

#51

Post by Paul Arden » Fri Oct 22, 2021 8:00 am

Hi Gary,

there are several Snakehead eats. Certainly there is the one that east and dives towards you and then (if it’s off babies) turns slowly around and swims back. Often they launch themselves out the water while engulfing the fly. With these fish I find what feels like an incredibly long wait is required. If I strike or strip to connect, the hook-up rate is very low.

But there are also fish that eat at an angle, in fact I’m making a video this week which explains that this is the angle I try to position the boat for, ie 30-60 degrees retrieve angle away from the fish direction. These fish are always easier to hook and you can set on them, but still it’s better to let them eat properly.

But this is not very different for me when compared to fishing for stillwater trout. I’ve often fished surface muddlers for trout (it was a major tactic for me) and the answer to hooking up is to let them hook themselves up, ie rod tip down, just keep doing what you are doing when they ate, which for me is normally a fast figure-of-8. When fishing a floating fry static (trout on reservoirs have a feeding behaviour where they bash into fry to stun them and then return to sip them off the surface, often working in packs) then the delay is long - can be 10 seconds - followed by lifting with the rod strike.

So I see that as quite similar. The difference with Snakehead is that I’m usually stripping and if I keep stripping I can often strip the fly right out of its mouth – like an early strike. I’ve been training myself for a number of years now to let the fish eat by releasing the line during the strip, which I have found incredibly difficult to do. But if you think about it, when they engulf a real fish or flog, it just sits in the mouth; they have it. No need to really clamp down on it. I think the game is they have it, they turn, they expel water from the gills and now is the time to tighten/or set.

I’m sure that these buoyant flies sit in the roof of the mouth, which is also a problem. Which is why I experimented with the pencil popper you told me about. This was perfect for Ladyfish by the way! But with Snakehead, I haven’t got it right yet because the fly doesn’t land as soft as I need and also, because it’s more aerodynamic, I have a harder time making small adjustments when positioning the cast. In other words it turns over too fast. But I might be able to solve that with a smaller hook and more feathers.

With streamers on rivers and trout, I keep the rod tip down, pointing down the line, and I keep doing whatever I was doing to get the eat to set the hook. If it’s swinging I just keep everything tight. If I’m slowly stripping I slowly strip until everything is tight. This is also good practise because if the fish misses the fly it will often eat again but if you have struck all you have ended up doing is pulling the fly far away from the fish. It’s very much easier than what I’m doing at the moment I know that! But I never had problems hooking trout on streamers. Lifting the rod early will cause the hook to miss, but that was never a problem of mine. Starting out reservoir fishing with streamers, which was what almost everyone did in those days, means that I learned not to strike right from the outset. It’s was only when I started imitating insects with static or slow presentations, did I learn to strike. So that’s all second nature.

I haven’t really fished for Salmon but I know there are some anglers who swing the fly with a loop of slack line trapped beneath the finger that they release when the fish “eats”. This is more like what I’m trying to do with Snakehead…

I have another complicated problem that’s started to appear and I’m finding very interesting. A few months ago I started tying my poppers with defined frogs legs, they are mobile and kick enticingly. The idea was to try to turn more of the chasers into takers, which it most certainly has! But something else interesting has also occurred. I’m now actually getting the Snakehead to eat the fly static (sometimes). And I have not worked out how to hook them yet :D I’ve been making the delay longer and longer, but I still haven’t successfully set on one yet.

Those Snook sound fascinating. If you drop the popper where they can hear it land, do they come over and investigate? Do they ever eat it static? Is it a fast running away strips or is it bloops with long pauses?

Cheers, Paul
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Merlin
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Re: Some thoughts on Bernd's thoughts on stretch in fly lines

#52

Post by Merlin » Sat Oct 23, 2021 6:18 pm

Gordy

I'm sure we are not using the same input for the spring&marble model.
Let's have a look outside of the Board.

Merlin
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Charles Ritz, A Flyfisher's Life

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Re: Some thoughts on Bernd's thoughts on stretch in fly lines

#53

Post by gordonjudd » Tue Oct 26, 2021 3:42 pm

I'm sure we are not using the same input for the spring&marble model.
Daniel,
That was the case and we were also using different criteria to determine the lag value.

Using your symmetrical acceleration and deceleration values I get this force vs time response for 10 meters of line with a spring constant of 161 N/m (1.1% elongation value) and a 5 Kg mass.

The lag time to get an arbitrary sticking force of 2 pounds from the stretched line was around 83 ms in that simulation. As you noted the time would be much longer if you raised the rod tip to set the hook as we tend to do in Trout fishing.
1p1%_force_equal_accel.jpg
1p1%_force_equal_accel.jpg (45.84 KiB) Viewed 321 times
Gordy

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Re: Some thoughts on Bernd's thoughts on stretch in fly lines

#54

Post by gordonjudd » Thu Oct 28, 2021 4:07 pm

The visco-elastic properties are described using something called the 'Loss Modulus'
James,
Have you been able to make any measurements on different lines with your Dynamic Mechanical Analysis test equipment?

I would be interested to see if the Loss Modulus of a line with a 5% elongation value is higher than a line with a 1% value for a 17.6 N load.

I have seen reports that good casters can get longer casting distances with low stretch lines and wonder if it is due to an internal energy loss mechanism. It would seem the tapering stretch in the line when casting would not produce much potential energy loss relative to its kinetic energy.

Gordy

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Re: Some thoughts on Bernd's thoughts on stretch in fly lines

#55

Post by James9118 » Fri Oct 29, 2021 9:08 am

Gordy,

I haven't been able to make any measurements yet. Lasse has kindly volunteered to send some line sections to me for Instron testing, at the same time I'll run some DMA tests. I don't routinely go into the lab these days as I'm easing myself into retirement, but I will go in at some point.

James.

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Re: Some thoughts on Bernd's thoughts on stretch in fly lines

#56

Post by Torsten » Thu Nov 04, 2021 7:49 pm

Hi,

I'm thinking also about a simple test without dedicated lab equipment, a static measurement is already easy just with some test weights and measuring the elongation of the samples. For a dynamic test I could imagine that free oscillations with a test weight should work, that means you would measure the step response and the decay of the amplitude to determine the loss or the damping coefficient for a simple mass-spring-damper model. I've tried a rough test with a bit of #30 runningline and attached a 500g weight - at least this system was not overdamped (I've seen a few oscillations after the first deflection).

Torsten.

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Re: Some thoughts on Bernd's thoughts on stretch in fly lines

#57

Post by gordonjudd » Fri Nov 05, 2021 6:01 pm

For a dynamic test I could imagine that free oscillations with a test weight should work,
Torsten,
Doing that test with different masses would also make it possible to fit the resulting frequency vs mass load test to get an estimate for the spring constant (k) and effective mass (mo) of the line as well. An experiment well worth doing.

I have seen some data that shows the maximum spring constant occurs with much larger loads than the 1.8 Kg mass used to get the elongation value in the German club evaluations. For a 30 lb test core material the maximum slope for the force vs deflection curve was for a load of around 80 N (8.1 Kg mass) and the roll off in the slope of the F/D curve started at around 120 N (12.2 Kg mass) So those frequency vs load tests could be done with very large loads and still remain in the elastic region of the line.

Gordy

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Re: Some thoughts on Bernd's thoughts on stretch in fly lines

#58

Post by Torsten » Sun Nov 14, 2021 8:08 pm

Hi,

I've created a topic in the physics section here:
https://www.sexyloops.co.uk/theboard/vi ... =11&t=3650
.. for measurements/equations/models etc.

Torsten.

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