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Covered topics /how it works

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Paul Arden
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Covered topics /how it works

#1

Post by Paul Arden » Sun Aug 02, 2020 3:58 pm

Hi guys,

I was reading Bernd’s FP last week about someone teaching that the double haul works because it increases rod bend on youtube, which is indeed what most instructors believed 20 plus years ago. I feel that there are many topics like this and while the information is available on the SL Board much of it is hard to find. For one thing you have to dig around and for another often there are differing opinions.

What I would like to try - and I have a brief go at it in the Check Haul topic, is for me or others to start a topic with a simple question such as:

Q How does the anchor work in Roll Casting? Does it load the rod?

A No. the purpose of the anchor is to stabilise the D-loop.

Q how does a fly rod function?

A it has three characteristics. Spring, Lever, Whip with corresponding explanations.

Q how does a fly loop unroll?
There might be two answers here-
A1 there is a force at the loop front from momentum change that pulls the line
A2 momentum of the fly leg is the driving force of the loop
(I think it’s probably both)

* the explanations need to be longer than the above of course but I’m hoping for either a short answer or a short answer and a longer explanation.

Anyway if there are two answers I will highlight both. I don’t wish to start any arguments :p I’m not looking for long and complex answers unless absolutely necessary.

Basic schoolboy stuff really. But I think done well it will be very useful digestible information that I can link to in the Sexyloops Glossary that I’m planning and it will definitely help people.

What do you think?

Thanks, Paul
by Paul Arden » Sun Aug 02, 2020 3:59 pm
And then I can highlight the corresponding answer/s like this!
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Re: Covered topics /how it works

#2

Post by Paul Arden » Sun Aug 02, 2020 3:59 pm

And then I can highlight the corresponding answer/s like this!
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Re: Covered topics /how it works

#3

Post by gordonjudd » Sun Aug 02, 2020 4:26 pm

A1 there is a force at the loop front from momentum change that pulls the line
A2 momentum of the fly leg is the driving force of the loop
(I think it’s probably both)
Paul,
Does that imply you think that momentum can be considered to be some kind of a force?

There is no momentum conservation going on with the roll out of the loop, and momentum is not a force.

I think that everyone agrees It takes a force to produce a momentum change as given by N1 that says F=dp/dt.

What is not agreed upon is that the momentum change of the line mass going around the loop (in this case the momentum change is due to a change in direction rather speed) can produce an internal tension in the line that helps to overcome the drag losses on the fly leg as given in A1.

Gordy

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Re: Covered topics /how it works

#4

Post by Paul Arden » Sun Aug 02, 2020 5:29 pm

By “driving force” I didn’t literally mean force, Gordy, but is the main component that is responsible for... :blush: However this is also why I’m not answering the questions :p

I realise that this one has potential to cause a problem. But since it is fundamental to fly casting then it has to be answered. Even if that means several opinions. Indeed I think if there is more than one viewpoint then it’s even more important that they are clearly described.

Cheers, Paul
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Re: Covered topics /how it works

#5

Post by Lasse Karlsson » Sun Aug 02, 2020 6:49 pm

Anchors in roll casting and speys are there to limit the amount the line slips towards the caster, ie. doesn't end up catching the bushes behind 🙂
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Re: Covered topics /how it works

#6

Post by Paul Arden » Mon Aug 03, 2020 4:46 am

In other words stabilises the D-loop :p
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Re: Covered topics /how it works

#7

Post by Lasse Karlsson » Mon Aug 03, 2020 1:04 pm

Paul Arden wrote:
Mon Aug 03, 2020 4:46 am
In other words stabilises the D-loop :p
In what way?
How does it do that?
Why does a loop need to be stabilised at the other end? Does it fall over? In a roll cast its just hanging line?

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Re: Covered topics /how it works

#8

Post by Paul Arden » Mon Aug 03, 2020 2:23 pm

It stabilises the D-loop by preventing the line slipping backwards. Might be a language thing. But for me they mean the same thing :D So while you are disagreeing with me I’m agreeing with you :D

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Re: Covered topics /how it works

#9

Post by gordonjudd » Mon Aug 03, 2020 4:34 pm

I realize that this one has potential to cause a problem. But since it is fundamental to fly casting then it has to be answered.
Paul,
And I think your A1 does just that. I think your addition of an A2 possibility just muddied the water. Momentum being some kind of a mystical force is widely believed however. Bruce Yeany even used it to explain the levitation of the line his clever string shooter experiment, and many people took that explaination as being gospel.

To get an idea of how well momentum will propel the fly leg try throwing a length of line as shown below.


I think that you will find that by itself momentum in a flexible piece of line cannot provide the tension (a force) needed to overcome drag forces. Consequently the line quickly turns into spaghetti and falls to the ground.

That idea that conservation of momentum is the driving force for the loop is in the same camp as the big spring theory for anyone that understands the basic physics of fly casting.

Gordy

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Re: Covered topics /how it works

#10

Post by Paul Arden » Mon Aug 03, 2020 6:43 pm

Hi Gordy,

Yep I realise that. However it’s not conservation of momentum. It’s just that the fly leg has momentum, it’s not conserved. And I think that’s why it (mostly) flies through the air.

However without some force coming from the loop front it will look like overcooked spaghetti! It will still fly through the air of course, but not as we know or want it.

So after years of reading these discussions I think that both are present. The momentum is the main thing perhaps - at least that’s the bit we first create - but without that bit of acceleration from the loop front it wont work as a loop.

Now I realise that I’m totally in danger of both sides of the argument beating me over the head with a fibreglass rod :D But that’s where I am with this. I think that both “camps” are right, and both are needed for the loop to unroll. As Frank would have said it’s a case of chicken AND egg :D

Anyway what I think is immaterial. What I would like to see is clear cut explanations of these things. I’m not capable of doing this - not like you guys, not by a long shot. And when there are two different and conflicting answers, then I will collate them and post them both together. At least then we will see where we all are. It’s not a conflict then, rather it’s more about what is/are the best explanation/s.

I think that this would really move us forwards and would help other readers to catch up too. I feel that we have been stuck over a very basic question which is “how does a loop unroll”? And short of calling it magic I think that we would be very well served with some precise explanations.

You know in the last 20 plus years we really have moved fly casting out of the dark ages. I think it’s now time to gather that information together in a digestible format. That’s something I would really like to see happen.

Thanks,
Paul
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