Hambini Roasts Zipp Dimples
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  1. #1
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    Hambini Roasts Zipp Dimples

    He's at it again, and the results are not in Zipp's favor. Oddly enough, he highlighted an innovation by Mavic of all companies where they invented a rim strip that improved the aero profile where the rim and tire meet. A rim strip which the UCI subsequently banned.

    Ghurarmu shirkush’ agh azgushu. Zant ya apakurizak. Gűl-n’ anakhizak.

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    So dimpled side tire tread it is. Plus the lip next to the tire bead for smoother transition to the rim.

    BTW, aren't you supposed to include (language) in the title?

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    Quote Originally Posted by bvber View Post
    BTW, aren't you supposed to include (language) in the title?
    English
    Ghurarmu shirkush’ agh azgushu. Zant ya apakurizak. Gűl-n’ anakhizak.

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    Thought it was a very poor video. Doesn't explain why dimples don't work in any quantitative or theoretical way and ignores any counter arguments.

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    Quote Originally Posted by SauronHimself View Post
    English
    What I meant was like the title of this thread.

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    Quote Originally Posted by flanman View Post
    Thought it was a very poor video. Doesn't explain why dimples don't work in any quantitative or theoretical way and ignores any counter arguments.
    I saw the part that he explains why the location of Zipp's dimples are useless.

  7. #7
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    Quote Originally Posted by flanman View Post
    Thought it was a very poor video. Doesn't explain why dimples don't work in any quantitative or theoretical way and ignores any counter arguments.
    Yes it does. Perhaps you just didn't understand it.
    Custom Di2 & Garmin/GoPro mounts 2013 SuperSix EVO Hi-MOD Team * 2004 Klein Aura V

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    I'm thinking of marketing dimple tape. And include a tube of silicone for the bead/rim interface. I think that's got it!

    His interrpetation of english is pretty good for a second language?
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    Quote Originally Posted by duriel View Post
    And include a tube of silicone for the bead/rim interface.
    That's not a bad idea. Market it as anti-burp tubeless tire sealant!
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    Quote Originally Posted by duriel View Post
    I'm thinking of marketing dimple tape. And include a tube of silicone for the bead/rim interface. I think that's got it!
    Mavic already has such tape but without dimples. One of the comments from consumers was, lets hope that it never loosens up during ride and becomes a bigger wind drag or entangle with the rest of wheel.



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    Quote Originally Posted by tlg View Post
    Yes it does. Perhaps you just didn't understand it.
    I have reviewed hundreds of scientific papers and reports as part of my job, and have edited an engineering journal. What he claims as an explanation is laughable. Big fat F.

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    Quote Originally Posted by flanman View Post
    I have reviewed hundreds of scientific papers and reports as part of my job, and have edited an engineering journal. What he claims as an explanation is laughable. Big fat F.
    I'm open to learning. What would you say about Zipp's dimple location?

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    Quote Originally Posted by bvber View Post
    I'm open to learning. What would you say about Zipp's dimple location?
    I'm sure that Hambini is right, however I don't consider his explanation to have any merit without some backup. I'd expect him to do some basic calculations based on known theory, and/or reference some data or other papers that show the flow regime or Reynolds numbers are not relevant to the size, placement and distribution of the dimples.

    Standard way of presenting and supporting an argument. He's lacking in this.

    An aerodynamics PhD should be able to destroy Zipp's reasoning in a couple of minutes. Instead he's more interested in handwaving tomfoolery with no physical insight and his priority is getting onto his scale of ****ishness for the entertainment of his acolytes.

    He also ignores the arguments for dimples on the trailing edge and that lots of air meets the deep rim section only and not the spokes. This should be addressed

    Good entertainment for those aged 5 but lousy way to make a case for or against something.

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    Quote Originally Posted by carlosflanders View Post
    I'd expect him to do some basic calculations based on known theory, and/or reference some data or other papers that show the flow regime or Reynolds numbers are not relevant to the size, placement and distribution of the dimples.

    An aerodynamics PhD should be able to destroy Zipp's reasoning in a couple of minutes.
    Not really, This is a complex surface in a dynamic environment. It would take a fairly heavy duty computational fluid dynamics model to study this, and even then you would want to back it up with experimental measurements.

    My favorite two quotes in my research career are "The literature said that it would work, but it didn't." and "The literature said it wouldn't work, but it did."

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    I have an advanced degree in... well, I studied... Okay, I'm a creative. My ability to assist my kids with math petered out around 6th grade. So, maybe I missed something in this and other discussions of aerodynamics and wheels...

    I get the dimples - increases the "stickiness" of the surface to pull the air toward the middle, reducing the trailing pressure wave. But... all of these discussions make it seem as though the wheel is a straight(ish) plane similar to a wing or front of a car... just sliding - not rolling - along. 359.9999 degrees of that wheel is NOT attacking the wind head-on. So, that diagram applies to .0001 degree's worth of that wheel.
    - How do the dimples impact aero at the 12:00 and 6:00 positions? Seems at the top and bottom of the wheel, the dimples are just adding drag with no aero benefit - since the pressure wave at exactly 12:00 and 6:00 is nonexistent.
    - At the 9:00 position - assuming that 3:00 is the "pure front" - the wheel/tire is now leading with the dimples, slowing the air to then slip passed the dimple-less tire. Seems if it helps at the 3:00, it must hurt at the 9:00... right?

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    If it's so complex how is hambini so sure?

    Not a fan of CFD unless it's backed up by experiment. Worked with too many CFD engineers who were desk jockeys with no physical insight.

    Here's a research quote: "The evidence provided does not support the conclusions".

    He's probably right, but needs to show some studies that back up his claims.

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    Quote Originally Posted by flanman View Post
    If it's so complex how is hambini so sure?
    You made me laugh Possibly the Dunning-Kruger effect?

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    Quote Originally Posted by Kerry Irons View Post
    You made me laugh Possibly the Dunning-Kruger effect?
    I agree with most of hambini's opinions. Don't agree with how he expresses them.

    There are some things though where I feel he's not well- informed.

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    Quote Originally Posted by flanman View Post
    I agree with most of hambini's opinions. Don't agree with how he expresses them.

    There are some things though where I feel he's not well- informed.
    In technical fields, opinions should be based on facts. When you don't back up your opinions with facts, then you've got nothing but an opinion. Then you enter a world where there are no facts, just opinions.

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    But seriously - why do these aero discussions not address the fact that the wheel is:
    A. Round. It's not a plane's wing, car's bumper... it's not a vertical plane
    B. Rolling. That "pure front" that is always shown in cross-section is only in "front" 1/360th of the time. It spends the same amount of time at the back - now, with the dimples on the wrong side.
    C. The velocity of a wheel, relative to the environment in which it's moving, is not constant even when the bike is traveling at a constant speed. V would be at a constantly fluctuating range of the bike's speed - from 0 MPH to 2x MPH of the bike. At the 12:00 position, V would be 2x. At the 6:00 position, it would be 0 MPH. 3:00 and 9:00 would be equal to the speed of the bike... right?

    Come on... help a creative guy understand the sciencey aero stuff.
    Last edited by OldZaskar; 2 Weeks Ago at 07:30 AM.

  21. #21
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    Quote Originally Posted by Kerry Irons View Post

    My favorite two quotes in my research career are "The literature said that it would work, but it didn't." and "The literature said it wouldn't work, but it did."
    Mine is "This works, but we don't understand the mechanism by which it does so, but it's not the one we expected."

    See e.g., stretching and message benefits. . .
    Dr. Cox: Lady, people aren't chocolates. Do you know what they are mostly? Bastards. Bastard-coated bastards with bastard fillings. But I don't find them half as annoying as I find naive bubble-headed optimists who walk around vomiting sunshine.

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    Quote Originally Posted by OldZaskar View Post
    But seriously - why do these aero discussions not address the fact that the wheel is:
    A. Round. It's not a plane's wing, car's bumper... it's not a vertical plane
    B. Rolling. That "pure front" that is always shown in cross-section is only in "front" 1/360th of the time. It spends the same amount of time at the back - now, with the dimples on the wrong side.
    C. The velocity of a wheel, relative to the environment in which it's moving, is not constant even when the bike is traveling at a constant speed. V would be at a constantly fluctuating range of the bike's speed - from 0 MPH to 2x MPH of the bike. At the 12:00 position, V would be 2x. At the 6:00 position, it would be 0 MPH. 3:00 and 9:00 would be equal to the speed of the bike... right?

    Come on... help a creative guy understand the sciencey aero stuff.
    Your analysis of rim speed is correct, and that is why my earlier comment that "This is a complex surface in a dynamic environment. It would take a fairly heavy duty computational fluid dynamics model to study this, and even then you would want to back it up with experimental measurements. "

    carlosflanders' comment that this was a simple calculation was way off base. Computational fluid dynamics is a powerful tool but the reality is that modeling alone is rarely sufficient to optimize such a complex system. People like to argue from first principles like that was all that is needed, but the real world is a very dynamic and complex place.

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