PLEASE NOTE: In order to post on the Board you need to have registered. To register please email paul@sexyloops.com including your real name and username. Registration takes less than 24hrs, unless Paul is fishing deep in the jungle!

Upward Force from Form Drag

Moderator: Torsten

Post Reply
User avatar
Graeme H
Posts: 2887
Joined: Fri Jan 25, 2013 2:54 pm
Answers: 0
Location: Perth, Western Australia

Upward Force from Form Drag

#61

Post by Graeme H »

Merlin wrote:If you shoot a video, you will see a marker on the inclined section going down nearly vertically (the red arrow).
Hi Merlin,

I tried to shoot the video but I was standing too far from the camera and could not make out the marks on the line.

In the same session I also shot another series of casts to show fly leg momentum, these much closer to the camera. Some of these were "sexy loop" shapes before they crashed into the net/board, so I think we can see that your conclusion of the mark moving down and very slightly forward is supported. Forward velocity in the inclined section of the sexy loop is very close to 0m/s relative to the ground.



Cheers,
Graeme
FFi CCI
User avatar
VGB
Posts: 6128
Joined: Thu Jan 10, 2013 12:04 pm
Answers: 0

Upward Force from Form Drag

#62

Post by VGB »

Some great video there Graeme, thank you
Casting instruction - making simple things complicated since 1765

https://www.sexyloops.com/index.php/ps/ ... f-coaching
Geenomad
Posts: 436
Joined: Tue Aug 06, 2013 10:11 pm
Answers: 0
Location: Melbourne

Upward Force from Form Drag

#63

Post by Geenomad »

Nice Graeme. Thanks.

Cheers
Mark
"The line of beauty is the result of perfect economy." R. W. Emerson.
https://thecuriousflycaster.com
User avatar
Merlin
Posts: 2101
Joined: Wed Jan 09, 2013 8:12 pm
Answers: 0
Location: France

Upward Force from Form Drag

#64

Post by Merlin »

This is the magic of sorcerers Graeme. :sorcerer:
Nice video. Amazing dolphin nose generation for tiny loops which reminds bed chains in similar conditions. My guess is that it is related to line stiffness.

:pirate:

Merlin
Fly rods are like women, they won't play if they're maltreated
Charles Ritz, A Flyfisher's Life
User avatar
Graeme H
Posts: 2887
Joined: Fri Jan 25, 2013 2:54 pm
Answers: 0
Location: Perth, Western Australia

Upward Force from Form Drag

#65

Post by Graeme H »

Merlin wrote:This is the magic of sorcerers Graeme. :sorcerer:
Nice video. Amazing dolphin nose generation for tiny loops which reminds bed chains in similar conditions. My guess is that it is related to line stiffness.

:pirate:

Merlin
I suspect so too but I have three competing models in mind at the moment so I need to device some experiments to remove at least one, preferably two or more of those models. :)

The problem with the stiffness model is that it happens in slow casts with wider loops than what we've seen here. Wider loops should not approach the radius where line stiffness comes into play.

The other two things I have in mind are a standing compression wave and the inertia of the line mass resisting the acceleration due to "rapid" change of direction.

Devising experiments that disprove any or all of these hypotheses should keep my mind occupied for a while. :pirate: The inverted loops with dolphins noses absolutely removes the possibility of them being caused by gravity interacting with tension forces.

Cheers,
Graeme
FFi CCI
anjill
Posts: 23
Joined: Thu Jan 10, 2013 7:37 am
Answers: 0
Location: Sydney, Australia

Upward Force from Form Drag

#66

Post by anjill »

Hi Graeme,

Great video. :worthy: Standing compression wave would be my guess.

Regards,
Tony.
User avatar
gordonjudd
Posts: 1858
Joined: Sat Jan 19, 2013 11:36 pm
Answers: 0
Location: Southern California

Upward Force from Form Drag

#67

Post by gordonjudd »

Amazing dolphin nose generation for tiny loops which reminds bed chains in similar conditions. My guess is that it is related to line stiffness.
Merlin,
Until you get to a ball on ball situation what is the stiffness of bead chain?

The image that Alejandro captured of the dolphin nose shape when he pulled a length of bead chain is blurred, but it appears there are still spaces between the balls.
Image

Dr. McMillen says the DN shape is related to the viscoelastic properties of the line, but I don't know if bead chain can be classified as a viscoelastic material either.
Standing compression wave would be my guess.
Tony, I don't know what a standing compression wave might be, but how can you get compression in a flexible string?
Gordy
User avatar
Graeme H
Posts: 2887
Joined: Fri Jan 25, 2013 2:54 pm
Answers: 0
Location: Perth, Western Australia

Upward Force from Form Drag

#68

Post by Graeme H »

2C42DDCC-FCCA-49F7-9D9A-FE1675891C8E.jpeg
Fly line has stiffness. This is a 6wt MED. The 8 in the video is stiffer again.

Cheers,
Graeme
FFi CCI
TrevH
Posts: 288
Joined: Wed Jan 09, 2013 7:13 pm
Answers: 0

Upward Force from Form Drag

#69

Post by TrevH »

Where can I find a copy of Dr McMillen’s work? I would be interested to read it (hope there’s not too
much complicated maths in it :D )

Isn’t viscoelasticity a kind of stiffness? We know bead chain has stiffness and the effect that has in forming the loops we see in siphoning bead chain.

Cheers
Trev
anjill
Posts: 23
Joined: Thu Jan 10, 2013 7:37 am
Answers: 0
Location: Sydney, Australia

Upward Force from Form Drag

#70

Post by anjill »

Hi Gordy,
Tony, I don't know what a standing compression wave might be, but how can you get compression in a flexible string?
Gordy
I'd align it, accelerate it (as in the fly leg of a loop) and then restrict it's forward motion (as in causing it to form a narrow loop).I reckon the rearwards elements would be pushing on the forward elements. I've actually never heard the term but I like the sound of it. Maybe Graeme made it up.

Regards,
Tony.
Post Reply

Return to “Flycasting Physics”