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  1. #1
    Join Date
    Aug 2012
    Location
    Melbourne, Australia
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    Default Efficiency Trumps Effort - Physics FOR Fly Casting

    After becoming frustrated with textbook and online discussion of physics for fly casting I decided to write a series of articles discussing physics in the context of fly casting instead of fly casting in the context of physics. I am neither a physicist nor a casting guru. Instead, I'm a guy who can mostly get his head around the relevant physics well enough to write stories about it for fly casters who are interested in reading them because they are, like me, interested in casting better.

    If that sounds like you the results of my labour can be found here. Physics FOR Fly Casting – The Einstein Series | The Curious Fly Caster

    I recruited some very heavy hitters to my advisory group as insurance against producing another pile of BS but if any stuff ups got past my sentries then I take full responsibility for them.

    No money, no selfies and no hidden agendas are involved. What I came away with was a clear and scientific understanding of why efficiency (always) trumps effort. If you get even a sniff of that from reading the Series, yours and my time will have been well spent.

    Cheers
    Mark

  2. #2
    Join Date
    Sep 2012
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    Scotland
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    214

    Default Re: Efficiency Trumps Effort - Physics FOR Fly Casting

    Excellent article, I enjoyed that.

  3. #3
    Join Date
    May 2016
    Location
    Sheffield
    Posts
    6,980

    Default Re: Efficiency Trumps Effort - Physics FOR Fly Casting

    Really good, not sure I agree with the degree to which you attribute a rods spring contributing to a cast but I will read it several times (I've bookmarked it) to be certain I've understood it correctly.. IMO a rod, or spring, can only return to a state of rest at the rate any load allows it to, the line being the load.

  4. #4
    Join Date
    Dec 2018
    Location
    London
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    Default Re: Efficiency Trumps Effort - Physics FOR Fly Casting

    Well done for trying to get to grips with a complicated subject. I've often wondered about the dynamics of fly and beach casting. There was a website on the subject of fly casting physics some years ago but it's no longer there.

    The mathematics of working out the dynamics is pretty difficult and as far as I know hasn't been done. So I would like to know where you get the 80/20% figures from.

  5. #5

    Default Re: Efficiency Trumps Effort - Physics FOR Fly Casting

    Mark,

    Very well written, not got to the end yet, horrified to arrive early at the old 'about' 80/20, still reading and looking for recognition that it varies or is 80/20 proposed as optimum efficiency?

  6. #6

    Default Re: Efficiency Trumps Effort - Physics FOR Fly Casting

    Thanks Mark. Very well written.

    Pete

  7. #7
    Join Date
    May 2006
    Location
    In between the old and new Arsenal grounds
    Posts
    8,446

    Default Re: Efficiency Trumps Effort - Physics FOR Fly Casting

    ark
    just bookmarked your site for future delving .
    say Hi to Vince for me !
    Andy Wren
    Still fishing but slowly!

  8. #8
    Join Date
    Aug 2012
    Location
    Melbourne, Australia
    Posts
    502

    Default Re: Efficiency Trumps Effort - Physics FOR Fly Casting

    Thanks guys. Appreciate the positive comments. When you go to my site you won't find a comments section. This might seem a little old fashioned and grumpy but the truth is I have had my fill of pointless argument. In keeping with that I decided not to enter into debate about the contents of the Einstein Series when posting links to it on fora.

    It's interesting that the rod loading, lever v. spring debate continues. Because it is so perennially controversial and because I think it is important to understand where the evidence points I will make an exception to my "rule". And btw when writing the series I deliberately avoided an academic approach, complete with footnotes.

    My primary source was an article by Grunde Lovoll and Jason Borger. The Rod & The Cast
    Grunde is a physicist and was on my Advisory Committee. Several other members have advanced knowledge of physics and the mechanics of fly casting and none of them thought my account of What the Rod is and Does - Really was screwy.

    Bumble. Bro, check out the first picture in Grunde and Jason's piece. As the rod slows the butt stops sooner than the tip, the rod unbends, the line overtakes the tip forming the loop. During the first part of this process the stored elastic energy in the rod is released and does work on the line.

    Cheers
    Mark

  9. #9
    Join Date
    Feb 2009
    Location
    Scotland
    Posts
    2,248

    Default Re: Efficiency Trumps Effort - Physics FOR Fly Casting

    Interesting read Mark thanks for sharing it, personally I think the 80/20% makes sense, I have wondered why I can't really notice any significant difference regardless of the rod quality I'm using, I put it down to me being either really poor or fairly good at casting?

    Al
    Last edited by speytime; 04-02-2019 at 12:52 AM.

  10. #10
    Join Date
    Apr 2010
    Location
    Bradford, West Yorkshire
    Posts
    43

    Default Re: Efficiency Trumps Effort - Physics FOR Fly Casting

    Thanks Mark - very interesting reading! From a quick read with the benefit of half a bottle of wine to smooth out the thought processes I'd offer the following:

    The impulse-momentum equation is one that is possibly more applicable than the work equation. For non-scientists this just states that the change in momentum is proportional to the product of the force applied and the time it is applied for. Simply put the force times the time is proportional to the change in velocity. The deflection of the rod increases the time over which we exert a force on the fly line. Theoretically the most efficient casting mechanism is the brick and the broom handle but very few people would have the ability to manage this setup. Interestingly the brick and the broom handle doesn't require a back cast to work, which rather explains why the 40plus type lines are so popular with casters of average ability.

    I agree with the concept of the rod as a lever (the spear thrower model). When we compress a rod we reduce the effective length of the rod/lever making it easier (takes less skill) to generate line speed (impulse-momentum again). More skilled casters can use faster taper rods, create narrower loops and maintain higher line (loop) speed during the cast.

    Tension in the rod leg of the line loads the rod in the back cast. As the loop moves away from the rod tip the tension increases and tip deflection increases. This shortens the lever and makes it easier for us to apply force in the forward cast. During the forward cast the rod bends more, reducing the lever length and making it easier for us to generate line speed.

    In effect what the rod does is to increase the time period over which the average force of a cast is applied. The amount of deflection in the rod increases the force that we can exert by reducing the lever length.

    If you find that last comment difficult to believe try this: take a 3lb test curve fast taper carp rod and a through actioned 6wt fly rod. Walk out about 20 metres of line on each attach the end to a spring balance and, holding each rod with the butt vertical, exert as much force as you can. I'll pretty much guarantee that the fly rod will give the highest reading on the balance. It's all about lever length....
    Last edited by seanmeeghan; 06-02-2019 at 10:20 PM.
    Quot homines, tot sententiae.

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