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Lift force acting on a fly line

Moderator: Torsten

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Walter
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Re: Lift force acting on a fly line

#291

Post by Walter » Tue Jul 16, 2019 12:55 pm

After 30 pages on the subject I wonder if anybody has read this:

https://paperplanemafia.com/how-do-paper-airplanes-fly/
"There can be only one." - The Highlander. :pirate:

PS. I have a flying tank. Your argument is irrelevant.

PSS. How to generate a climbing loop through control of the casting stroke is left as a (considerable) exercise to the reader.

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Walter
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Re: Lift force acting on a fly line

#292

Post by Walter » Tue Jul 16, 2019 1:24 pm

Walter wrote:
Tue Jul 16, 2019 12:55 pm
After 30 pages on the subject I wonder if anybody has read this:

https://paperplanemafia.com/how-do-paper-airplanes-fly/
Or this:

https://en.m.wikipedia.org/wiki/Lift_(force)

I especially like this bit:

How simpler explanations fall short

Producing a lift force requires both downward turning of the flow and changes in flow speed consistent with Bernoulli's principle. “
"There can be only one." - The Highlander. :pirate:

PS. I have a flying tank. Your argument is irrelevant.

PSS. How to generate a climbing loop through control of the casting stroke is left as a (considerable) exercise to the reader.

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Graeme H
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Re: Lift force acting on a fly line

#293

Post by Graeme H » Wed Jul 17, 2019 9:21 pm

Hi Gordy,

In your last few posts, there is no mention of aerodynamic lift associated with an inclined line. The thread is about that concept and it's this lift I'm seeking to eliminate with this experiment. Without the lift, the rod leg should sag according to the numeric modelling, correct?

So when I cast 15 metres of chain simultaneously with 15m of fly line, the chain will droop and the fly line will not, according to the premise of this thread.

After all, there have been various estimations of lift forces of between 2% and 1500% the force of gravity on an inclined section of line. Without the lift from form drag, we will see significant differences, won't we?

If we won't see differences, then we can probably stop talking about aerodynamic lift.

So please help me design an experiment that will prove this lift exists. If momentum flux is now the only important thing, let's shut this thread down until someone completes Torsten's road map.

Cheers,
Graeme
FFi CCI

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Paul Arden
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Re: Lift force acting on a fly line

#294

Post by Paul Arden » Thu Jul 18, 2019 1:38 pm

Hi Gordy,
As has been mentioned (but probably not understood) the fly leg will reach a steady state tilt angle where the upward force from form drag will balance the downward force of gravity just as it does in the line wind gauge experiment
I don’t really see this. I think that’s why we need to see a set of videos produced from different backcast angles. I think virtually all the videos I’ve seen have come from a low backcast angle. We really need to get some accuracy loops as thrown by the likes of Steve Rajeff to eliminate this upward angle effect. I will try my best when Graeme is over. Certainly when I cast at a close front target or into the wind my backcast angle straightens above the horizontal.

As an instructor I think many of the videos we are analysing with low backcasts are in fact faulty :D These low backcast, canted loops look pretty but the fish aren’t in the trees, they’re in the water and apart from distance that - or just above - is where the fly should be aiming :laugh: I’ve been guilty of it too, and you can see examples around Sexyloops but high trajectory backcasts are the real deal for me.

I genuinely can’t say if loops have lift or not. And I would like to find out. For me it’s not a given either way.

Cheers, Paul
It's an exploration; bring a flyrod.

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Graeme H
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Re: Lift force acting on a fly line

#295

Post by Graeme H » Fri Jul 19, 2019 1:49 pm

As mentioned in another thread, an idea of casting something with huge amounts of drag should be attempted to see if any lift can be found.

I lashed 3.5 metres of wool to a 10 weight line and cast it. The amount of drag in the wool made casting a very difficult thing to do. The fly leg very rapidly lost its momentum to skin drag and the taper and leader (without the drag) tried to overtake the line with wool lashed to it. I had to apply large amounts of pullback to even form a loop.

The loop didn't lift



The line without wool lashed to it falls at the same rate as that with wool attached.

Cheers,
Graeme
FFi CCI

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Graeme H
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Re: Excellent FP on modeling

#296

Post by Graeme H » Sat Jul 20, 2019 2:36 pm

A response from Vince who knows a lot about this stuff than I do:

DOG is another term for terminal velocity and occurs when the drag is sufficient that the net force on the falling body is zero.

The Gatti-Bono paper quoted drag induced lift which is peculiar to that paper and as Torsten observed, lift induced drag is the correct term but it is different to DOG

Lift induced drag is a product of increased form drag due to the lift generated by the turning of the airflow.

Cheers,
Graeme and Vince
FFi CCI

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gordonjudd
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Re: Excellent FP on modeling

#297

Post by gordonjudd » Sat Jul 20, 2019 3:01 pm

lift induced drag is the correct term but it is different to DOG
Graeme,
Could you (or Vince) explain why lift induced drag is the correct term and drag induced lift is wrong? At first glance that seemed to be a:
A Distinction without a Difference
A distinction without a difference is a type of logical fallacy where an author or speaker attempts to describe a distinction between two things where no discernible difference exists. It is particularly used when a word or phrase has connotations associated with it that one party to an argument prefers to avoid.
However, when I look at what is going on in the wind gauge experiment lift induced drag seems to be the wrong way to characterize what is causing what.

Form drag a piece of line that is exposed to a wind stream will cause the c.g. of the hanging line to lift. Are you saying it is actually the other way around and that the lift of the line produced the form drag? If so that makes no sense.

Gordy

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Walter
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Re: Excellent FP on modeling

#298

Post by Walter » Sat Jul 20, 2019 3:19 pm

gordonjudd wrote:
Sat Jul 20, 2019 3:01 pm
lift induced drag is the correct term but it is different to DOG
Graeme,
Could you (or Vince) explain why lift induced drag is the correct term and drag induced lift is wrong? At first glance that seemed to be a:
A Distinction without a Difference
A distinction without a difference is a type of logical fallacy where an author or speaker attempts to describe a distinction between two things where no discernible difference exists. It is particularly used when a word or phrase has connotations associated with it that one party to an argument prefers to avoid.
However, when I look at what is going on in the wind gauge experiment lift induced drag seems to be the wrong way to characterize what is causing what.

Form drag a piece of line that is exposed to a wind stream will cause the c.g. of the hanging line to lift. Are you saying it is actually the other way around and that the lift of the line produced the form drag? If so that makes no sense.

Gordy
Gordy,

I suggest you do a Google search for the two terms and let us know the results. You’ll find squillions of results for one and only one for the other.

Is there a distinction? Does mixing terms like force and power make a difference? Does reversing N2 make a difference? Does electricity flowing from negative to positive make a difference over flowing positive to negative?

The difference is that one follows centuries of standardization while the other leads to reinventing the field of study.
"There can be only one." - The Highlander. :pirate:

PS. I have a flying tank. Your argument is irrelevant.

PSS. How to generate a climbing loop through control of the casting stroke is left as a (considerable) exercise to the reader.

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gordonjudd
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Location: Southern California

Re: Excellent FP on modeling

#299

Post by gordonjudd » Sat Jul 20, 2019 3:25 pm

You’ll find squillions of results for one and only one for the other.
Walter,
If that is the case then explain to me how "lift induced drag" applies to the wind gauge experiment?

I don't even see how it applies to a dropped piece of line if that is one of the squillions of results you are talking about.

Gordy

Torsten
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Re: Excellent FP on modeling

#300

Post by Torsten » Sat Jul 20, 2019 3:35 pm

In the German language we know another term for this phenomenon, closest translation is something like "dynamic upthrust".

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