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  1. #1

    Default physics of fly casting

    Hi all,

    my name is Tobias Hinzmann, I'm 45 years "young" and I live close to Potsdam (Germany). I started with fly fishing in the 1970ties.

    In 2013 I investigated what the deflection of a fly rod could do for the fly cast. Many of the conclusions I pointed out astonished me a lot !

    If someone is interested in having a "deep" - but not too difficult - look in the physics that take place during the fly cast could follow this link to experimental investigations on the fly rod deflection.

    Hope you enjoy ! Thanks !

  2. #2
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    Default Re: physics of fly casting

    Hi Tobias,

    I admire your efforts in producing that, clearly a lot of work has gone in to it. I'll send you your membership forms for the casting geeks club soon .

    I do have a couple of issues with the approach you've taken however. To keep the maths easy it seems that you've separated the lever from the spring. This, to me, propagates the myth that the rod is a spring which is loaded and then subsequently unloads after the caster has made the stop.

    Many researchers have shown that the fly rod is best modelled as a flexible lever. That is to say that the spring and leverage part work in unison and cannot be separated. Taking this approach in a dynamic situation makes the maths much more complicated, involving forced harmonic motion etc. However, as you state one of your aims was to keep it simple.

    Are you aware of the technical discussions that take place on the Sexyloops board?

    Rather than self publish, why didn't you go for a journal article thus getting your paper peer reviewed?

    All the best, James

  3. #3
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    Default Re: physics of fly casting

    I totally agree with James about the leverage part of the equation being the accepted thinking right now.

    Also people with big brains like you should also take a look at the sexyloops board....its right up your street.

    Well done on the paper though.
    Steve Parkes
    AtomSix Fly Rods
    Hidden Content

  4. #4

    Default Re: physics of fly casting

    Hi James,

    I tried to have a clear look on every physical effect that work on fly casting. Therefore I seperate.

    Where did you read in my investigations that fly casting is about loading and unloading the fly rod ? To me a good fly cast is about bending (not only "loading" in the meaning of a spring) the fly rod. An optimal bend can increase the efficiency clearly ! The reason for this is essentially the interaction of the angular momentum and the tension force (see section F) ! Both effects work together and causes a better transfer of the energy from the grip to the tip in relation to an absolutely stiff fly rod (in the casting sequence the efficiency of the flexible fly rod was more than twice) !

    Dr. Schmitt and I agree the bend of the flexible fly rod could increase the efficiency clearly !

    Best wishes, Tobias

  5. #5

    Default Re: physics of fly casting

    Quote Originally Posted by hshl View Post

    Dr. Schmitt and I agree the bend of the flexible fly rod could increase the efficiency clearly !
    I'm assuming you knew this before you started, interesting read, it leaves me thinking the lever versus spring equation needs another look, given the 100% lever is 50% less efficient,

    Does your research suggest the usual 'lever' v 'spring' could have been the wrong model in the first place?

  6. #6
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    Default Re: physics of fly casting

    Quote Originally Posted by hshl View Post
    Where did you read in my investigations that fly casting is about loading and unloading the fly rod ?
    Here: "e.g. the fact that the fly rod releases the potential tension force starting from the initiation of the stop"

    This 'fact' isn't one that is supported by other researchers work on the subject.

    Cheers, James

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    Default Re: physics of fly casting

    Quote Originally Posted by ohanzee View Post
    I'm assuming you knew this before you started, interesting read, it leaves me thinking the lever versus spring equation needs another look, given the 100% lever is 50% less efficient,

    Does your research suggest the usual 'lever' v 'spring' could have been the wrong model in the first place?
    Alan,

    At a recent casting (more like drinking) meeting, one of the outfits cast was a 'broomstick' i.e. a non-bending rod.

    The results showed that the average distance cast with it was 24.4m (15 casters). In comparison the average distance the same casters recorded with a standard #5wt was 29.7m.

    Ignoring the complicated maths, I think this supports the flexible lever model's prediction that ~80% of linespeed comes from the lever.

    Cheers, James

  8. #8

    Default Re: physics of fly casting

    Quote Originally Posted by James9118 View Post
    Alan,

    At a recent casting (more like drinking) meeting, one of the outfits cast was a 'broomstick' i.e. a non-bending rod.

    The results showed that the average distance cast with it was 24.4m (15 casters). In comparison the average distance the same casters recorded with a standard #5wt was 29.7m.

    Ignoring the complicated maths, I think this supports the flexible lever model's prediction that ~80% of linespeed comes from the lever.

    Cheers, James
    Sure, i wouldn't argue with that, but i have never been comfortable with the idea that comparing a broomstick with a fishing rod tells us something scientific, that can then be used to extrapolate complex theories,

    What the experiment shows is how much the 'spring' of the rod contributes to the forward momentum,

    My point is that 'forward momentum' is not what 'spring' directly contributes, this is a dead end, but it does add by helping leverage do its job.

  9. #9
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    Default Re: physics of fly casting

    Quote Originally Posted by ohanzee View Post
    but i have never been comfortable with the idea that comparing a broomstick with a fishing rod tells us something scientific, that can then be used to extrapolate complex theories,
    The idea behind casting the broomstick was to test the model. We all know the result that was predicted, in fact I posted it on here years ago. Getting the result we did surely suggests that there may be something in the complex model and it shouldn't be dismissed. That's the nature of science, a hypothesis is proposed and then tested, it either holds up or falls down.

    Don't get me wrong, I think we're agreeing here - the more 'useful' part of the spring is to flatten the tip path. But we can model that also .

  10. #10
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    Default Re: physics of fly casting

    I am very sorry gentlemen but the term 'flexible' lever is a contradiction in terms. A lever is a rigid implement usually moved about a pivot to move a heavy or firmly fixed load with one end when pressure is applied to the other. I would respectfully suggest avoiding calling a fishing rod a lever. A friend of mine talked himself into a world of hurt by calling a rod a lever during an assessment.

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