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    • "Climbing" loop / Loop dynamics

    Walter & Group........

    From Carl McNeil:-

    'day Gordy

    I've attached a paper by Gatti and Perkins (Noel) titled "Effect of

    Loop Shape on the

    Drag-Induced Lift of Fly Line" - I'm presuming it's out in the public

    domain and OK to do this.

    Bruce was good enough to track it down for me.

    They outline that the loop face does indeed create lift, and that a

    loop with a positive angle of attack - the 'Climbing loop' - creates

    substantially more lift than other loop shapes.

    I have to read around the math, however here's a couple pertinent

    excerpts for the group:

    "Fig. 1 The fly line ‘‘loop’’ is formed after the ‘‘stop’’ in a cast-

    ing stroke and propagates as a nonlinear wave. This loop is

    asymmetrical and possesses a positive angle of attack. Such

    loops are a hallmark of expert fly casters."

    "The results of Table 1 show that the lift generated by a climbing

    loop is approximately four times greater than that of a semi-

    circular loop with the same characteristic dimensions. The source

    of this additional lift is the contribution of form drag on the

    ‘‘belly’’ of the fly line that has a positive angle of attack.

    "The negative angle of attack for the falling loop shape results in

    a net

    negative ‘‘lift,’’ again due to the form drag on the belly. The

    symmetrical loops circular and pointed generate approximately

    the same lift. These results may be readily generalized to other

    loops shapes. "

    Noels paper leaves the reader to surmise how these varying loop

    shapes are created.

    For while I believed that a climbing loop was created by sufficient

    (very high) line speed (all other things being equal) However I've

    since had this beaten out of me by Bruce.

    Carl

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    Carl:   I've added the attachment.                  Gordy

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    From Tony Loader:-

    Hi Gordy,
     
    Thanks Guy, for the link to Grunde and Jason's paper.
     
    This one - http://castanalysis.com/links/jam2004.pdf  - looks like the definitive statement on climbing loops.
     
    Regards,
    Tony.
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     
    Comment :-  This paper was written in partial answer to the question on, "climbing loops" posed to Noel Perkins by Bruce Richards in 1994.
     
    I can't follow the math all the way........ perhaps some of you can.  My interpretation of the study is as follows:
     
    1.) The authors (Caroline Gotti-Bono & Noel Perkins) were computing the likely physical factors behind the observation that loops shaped with a, "positive angle of attack" (pointed at the top) stayed aloft longer than symmetrical loops such as semicircular ones or ones where a symmtrical point existed.
     
    2.)  As far as I can see by studying this paper, they did NOT study loops which were seen to actually climb above the horizontal when aimed parallel to the ground or water.
     
    3.)  Their math calculations supported the hypothesis that these loops shaped with a, "positive angle of attack" did stay aloft longer than symmetrical loops.  They used the term, "positive angle of attack" to describe a loop shape pointed at the top.
     
    4.)  The calculations resulted in conclusion that this was due to a combination of factors including line skin drag and form drag which, theoretically, produced four times the, "lift" calculated to exist with symmetrical loops.
     
    5.)  Take note of the fact that they placed the term, "climbing loop" as I did, in quotes.  In their introduction, they used it as a synonym for loops which stay aloft longer.... (NOT THOSE WHICH TRULY CLIMB.)
     
    I remain in doubt as to any loop which truly, "climbs" when its launch angle of trajectory is parallel to the ground and there is no added vertical curve and/or outside lifting forces such as atmospheric updrafts and static electricity.
     
    Gordy
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    From Al Crise:
     
    Howdy Ally and Gordy
     What does the term: Vibration Line   mean. I have not heard that term before
    ol Al

    Allen R. Crise
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    ol Al.....
    See, below, for the fact that this was really a description of the, VIBRATION model of Grant's rod......Not a line.  noted by Guy Manning.
    Gordy
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    I had the unique experience of casting a 3 piece, 15 foot Grant vibration made in the first decade of the 20th century. It belongs to a member of The Golden Gate Casting Club. The owner brought it to the Spey-O-Rama last year and let me play with it for a bit.  It was kind of an emotional few minutes because I really felt I had history in my hands.

     Taken from Guy Manning's prior message.                               Gordy

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    Guy Manning has sent us a copy of Noel Perkins' article on loop dynamics.  Lots more math for those of you who can digest it.  Good information even for non-math folks, however.  (See our second attachment)

    Gordy

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    Attachment: Gatti&PerkinsJAM.pdf
    Description: Adobe PDF document

    Attachment: loop dynamics perkins.pdf
    Description: Adobe PDF document