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  1. pingpongpaddy is offline
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    Advanced TTD Member 155 218
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    Jul 2019
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    #19
    Quote Originally Posted by brokenball
    I haven't posted on this thread so I will now.
    I have a definition of sorts.
    A looped ball will dive due to the Magnus effect.
    Since all balls with top spin will dive a little bit, it is necessary to qualify my statement
    The Magnus effect, this is the force that makes the ball dive or arc, is proportional to the spin times the speed or v*ω
    where:
    v is the velocity of the ball
    ω is the spin in radians per second.
    So spin and speed are required.
    However, good loops are low over the net and
    ω*r > v r is the radius of the ball.
    This means the bottom surface speed of the ball is moving faster backwards than the ball is moving forwards. On contact the ball will push off the table resulting in more speed but losing some spin. The ball will jump out low at the opponent.

    Too many people call anything with top spin a loop.
    I recently posted a link to a Timo Boll video showing how he loops balls by waiting for them to drop between net and table height. He must hit the ball up a bit to get it over the net but that is good because the highest point in the trajectory should be at the net. Boll relies on the top spin to make the ball drop once the ball goes over the net. Yes, it takes some paddle speed and good timing to manage this.

    Since the Magnus effect is proportional to v*ω it is easy to see that hitting through the ball will result in no spin and thinly brushing the ball will result in no or low speed. The ball should be hit in such a way to maximize v*ω. This can be calculated and optimized. That is what hard headed old fuddy-duddy engineers do. I forgot a few other adjectives.

    Think Goldilocks, not to hard, not too soft, not to thin, not to thick, just right works best.

    I just want to point out that while some low loops can be effective as explained by Timo Boll in a recent video, many that are low are weak and vulnerable to being punished for bad length. The basic good topspin lands deep near the end line which means a higher arc over the net . The depth of the shot is key in pushing the opponent back from a controlling position close to the table. I am sure that there are many occcasions when Boll is driving a ball that is not dropping, as it does not make sense to give his opponent time. However his excellent and unusual facility with spin allows him to play an effective shot, even when hindered by a dropping ball

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    UpSideDownCarl

    Last edited by pingpongpaddy; 10-13-2021 at 11:39 AM.
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