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Lift force acting on a fly line

Moderator: Torsten

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gordonjudd
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Re: Lift force acting on a fly line

#311

Post by gordonjudd » Sun Jul 21, 2019 1:47 pm

The line without wool lashed to it falls at the same rate as that with wool attached.
Graeme,
If that is the case why does the wool section have a concave shape (i.e. higher in the middle) as the line falls in your video. Certainly you don't believe a piece of yarn having less mass and a larger diameter will free-fall at the same rate as a heavier, thinner piece of fly line do you?
Image

Gordy

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Graeme H
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Re: Excellent FP on modeling

#312

Post by Graeme H » Sun Jul 21, 2019 2:04 pm

Why doesn’t the line in the dangle rise at every opportunity then?
“ I see the cause as form drag and the effect as the lift of the line
.
And can you show us this effect please?
FFi CCI

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Graeme H
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Re: Lift force acting on a fly line

#313

Post by Graeme H » Sun Jul 21, 2019 2:17 pm

See the wave in the rod leg start at around 5 seconds. See the wave move to the right. See the wave stall in the wool section as the wool damps the motion of the wave. See the line all fall at nearly the same rate.

Gordy, you don’t seem to understand what is going on in that video. The wool is lashed to a 10wt line. It actually weighs a little more because the wool adds mass to the 10wt line. Yes, the drag is significantly more there than elsewhere but since the line doesn’t fall very far, it hasn’t built up a lot of falling speed. That means it falls pretty much the same everywhere. If the drop was from a great height, I’d expect a very different outcome.

If you really want to get pedantic, watch how much QUICKER that section falls between 22 and 33 seconds.
FFi CCI

Torsten
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Re: Lift force acting on a fly line

#314

Post by Torsten » Sun Jul 21, 2019 2:52 pm

I've moved lift related stuff from the modelling topic over here.

Graeme, great video, seems to me that the bow in the wool seems to indicate the drag force. The overall aerodynamic effect is difficult to isolate, because this loop has a complex compound shape - so we can't draw a conclusion.

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Paul Arden
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Re: Lift force acting on a fly line

#315

Post by Paul Arden » Sun Jul 21, 2019 3:40 pm

Did you accidentally delete some of Gordy’s posts, Torsten? I thought Graeme was replying to a different thread?

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

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Torsten
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Re: Lift force acting on a fly line

#316

Post by Torsten » Sun Jul 21, 2019 3:53 pm

Hi Paul, no only merged, I've checked the log - moved from modelling topic - well I hope there is no bug in the phpBB software.

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Paul Arden
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Re: Lift force acting on a fly line

#317

Post by Paul Arden » Sun Jul 21, 2019 4:17 pm

Ah ok. :D I’ve just lost my ability to follow it!
It's an exploration; bring a flyrod.

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Walter
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Re: Excellent FP on modeling

#318

Post by Walter » Sun Jul 21, 2019 6:06 pm

gordonjudd wrote:
Sun Jul 21, 2019 1:21 pm
It is not applicable to a fly line IMHO.
Merlin,
I see it the same way although there is certainly a drag force in the -x direction that is associated with the lift force in the +y direction. As the tilt angle of the line increases the +y lift to -x force ratio will decrease. There is no free lunch.

You cannot change the momentum of the air with a moving inclined section of line without producing forces in both the x and y directions.

The lift that results from a simple momentum change is different than the multitude of effects that produce lift due to the flow of air around a curved airfoil such as a wing in an airplane.
in fact the term lift-induced drag (LID ?) has yet to find any use whatsoever in looking at fly line 'flight'?
Magnus, I agree with that assessment. I don't think the lift-induced drag concept for an airfoil has any relevance to a moving piece of fly line.
NASA also has some great information.
Agreed. You just have to search for videos that apply to a fly line, not an airfoil.

This video from NASA is much more relevant to demonstrating the lift that comes from the air's momentum change that happens when in inclined section of fly line moves through the air.
Image

Gordy
Gordy

Glad I could help.

Walter
"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

#319

Post by Graeme H » Mon Jul 22, 2019 12:14 am

Torsten wrote:
Sun Jul 21, 2019 2:52 pm
I've moved lift related stuff from the modelling topic over here.

Graeme, great video, seems to me that the bow in the wool seems to indicate the drag force. The overall aerodynamic effect is difficult to isolate, because this loop has a complex compound shape - so we can't draw a conclusion.
Thanks Torsten, but please look carefully at the video again. The bow in the wool clearly results from the wave generated by the rod tip lifting as I finish the cast (as I pointed out to Gordy above).

You see the wave start at the 5 second point and progress to the right in the rod leg until the moment selected by Gordy.

From the 22 second point to the 33 second point, it falls faster than everything else.

Thus, at the fall speeds seen here drag is not significant.
FFi CCI

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Graeme H
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Re: Lift force acting on a fly line

#320

Post by Graeme H » Mon Jul 22, 2019 12:28 am

Torsten wrote:
Sun Jul 21, 2019 2:52 pm
The overall aerodynamic effect is difficult to isolate, because this loop has a complex compound shape - so we can't draw a conclusion.


Torsten,

This loop shape is the same one that has generated years of discussion on this forum. Now you want to claim it’s too difficult to draw conclusions based on the shape of it? This shape is what people are basing their arguments for lift on: an inclined lower leading edge.

If we were ever going to see form drag lift in a cast, this would have shown it.

Unbelievable
FFi CCI

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