Discussion in 'Tennis Tips/Instruction' started by Ballinbob, Jul 17, 2009.
Title says all
I don't get how it differs than side spin?
Can someone help me out here?
That which we call side spin in tennis is spin about a vertical axis. Spiral spin is spin about a horizontal axis in the direction of the flight of the ball. Contrast this with topspin/underspin. These are spins about a horizontal axis that is perpendicular to the flight of the ball.
Think about the type of spin you would see on a football (American football, that is). This is spiral spin. Badminton shuttles also have spiral spin. Rifle and gun barrels are usually designed to induce spiral spin on the bullet. This spin tends to stabilize the flight of the projectile. Some, but not all, arrows are designed to produce spiral spin.
Note that side spin in tennis causes the ball to curve left or right while traveling thru the air (due to a Magnus force). However, this type of spin has no effect on the bounce of the ball. Spiral spin, on the other hand, does not produce a Magnus force and does not cause a left/right deviation in the flight of the ball. In fact, it tends to minimize a left/right deflection. Spiral spin will cause the ball to bounce off to the left or the right (depending on whether you have clockwise spin of CCW spin).
To keep things simple I'm going to talk about pure spins: topspin with no side or spiral, spiral with no topspin or side, etc.
Imagine hitting a tennis ball, taking a particular moment and drawing a dot on the point that is closest to you at that moment. If the dot moves upwards after this moment you have topspin, if downwards you have backspin and left or right indicates sidespin. If the dot doesn't move the shot may be flat, but another scenario in which the dot doesn't move is when the ball is rotating about the axis that goes through the dot. (If you can't understand what I'm saying, I'll try and get a picture.)
The fundamental difference is that at any given moment with topspin, backspin and sidespin, half of the ball is rotating into the direction it's travelling and half away from it, yet with spiral spin the rotation is all perpendicular to the path. This means that no part of the ball is special with spiral and hence it flies as if there was no spin. The spiral spin will only act when the ball hits the ground.
Since sidespin's axis of rotation is perpendicular to the ground, sidespin has no effect on the bounce. It can however give the appearance of making the ball jump to the side since when combined with backspin the forwards component of the velocity of the ball will decrease greater proportionally than the sideways component (and there is often some spiral spin too).
I don't know about that, but you shouldn't twist your spine considering you can be paralyzed.
In case you found some of the jargon I used earlier a bit scary, I'll throw out some more jargon (but with a picture). Altho' an airplane doesn't quite spin like a tennis ball, we can use some flight dynamics terms to illustrate the various spins in tennis.
Roll would correspond to spiral spin.
Yaw (yellow) would correspond to the vertical axis spin we call side spin.
Pitch corresponds to topspin & underspin.
with the racquet face perp to the ground it's a 20 degree angle for flat and a hard 45 for topspin. Or else you can hood the face a bit and wrist the sucker bolleterri style.
This picture explained it all, thank you! I'm a visual learner so it just clicked when i saw that haha
In case you missed it, I posted a video link that shows Andy Roddick hitting a drop shot with extreme spiral spin against Roger Federer in another spiral spin thread:
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