Swing bowling

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Historical Styles
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Swing bowling is a technique used for bowling in the sport of cricket. Practitioners are known as swing bowlers.

Swing bowling is generally classed as a subtype of fast bowling.

Contents

1 Physics of swing bowling
2 Normal swing
3 Reverse swing
4 Swing Bowling Tips
5 See also
6 External links

Physics of swing bowling

The essence of swing bowling is to get the cricket ball to deviate sideways as it moves through the air towards the batsman. In order to do this, the bowler makes use of four factors:

The raised seam of the cricket ball.
Asymmetry in the ball caused by uneven wear of its surface.
The speed of the delivery
Their action

The asymmetry of the ball is encouraged by the constant polishing of one side of the ball by members of the fielding team, while allowing the opposite side to deteriorate through wear and tear. Over time, this produces a marked difference in the aerodynamic properties of the two sides.

At speeds around 80 mph, the airflow around the ball is in transition between smooth, or laminar flow, and turbulent flow. At speeds of 90 mph and above, all the flow is turbulent. A medium-pace bowler, working at 75 to 80 mph, takes advantage of this. In this critical region, the raised seam and other minor imperfections in the ball's surface can induce turbulence while air flowing over other parts of the ball remains laminar. Turbulent air separates from the surface of the ball later than laminar flow air, so that the separation point moves to the back of the ball on the turbulent side. On the laminar flow side it remains towards the front. The result is a net force in the direction of the turbulent side.

Thus by keeping the seam and roughness to one side, the bowler induces the ball to swing in that direction. Skilled bowlers can even make a ball swing one way, and then 'break' the other way upon bouncing, with an off cutter or leg cutter hand action.

Note that swing of a cricket ball is not caused by the Magnus effect, which gives rise to a force perpendicular to the axis of rotation (in this case up or down). The swing of a cricket ball is parallel to the axis of its rotation.

Normal swing

Typically, a swing bowler aligns the seam and the sides of the ball to reinforce the swing effect. This can be done in two ways:

Outswinger: By aligning the seam to the left and placing the roughened side of the ball on the left, the ball will swing to the left. To a right-handed batsman, this results in the ball moving away to the off side while in flight, usually outwards from his body.
Inswinger: By aligning the seam to the right and placing the roughened side of the ball on the right, the ball will swing to the right. To a right-handed batsman, this results in the ball moving in to the leg side while in flight, usually inwards towards his body.

The curvature of swing deliveries can make them difficult for a batsman to hit with his bat. Typically, bowlers more commonly bowl outswingers, as they tend to move away from the batsman, meaning he has to "chase" the ball in order to hit it. Hitting away from the batsman's body is dangerous, as it leaves a gap between the bat and body through which the ball may travel to hit the wicket. Also, if the batsman misjudges the amount of swing, he can hit the ball with an edge of the bat. An inside edge can ricochet on to the wicket, resulting in him being out bowled, while an outside edge can fly to the wicket-keeper or slip fielders for a catch.

An inswinger presents relatively fewer dangers to the batsman, but can result in bowled or leg before wicket dismissals if the batsman misjudges the swing on the ball.

An inswinger combined with a yorker can be especially difficult for the batsman to defend against, especially if used as a surprise delivery after a sequence of outswingers.

It is a common belief amongst both players and fans that balls swing more in humid weather conditions, although no objective research exists to bear this out.

Reverse swing

Normal swing occurs mostly when the ball is fairly new. As it wears more, the aerodynamics of the asymmetry change and it is more difficult to extract a large amount of swing.

When the ball becomes very old—around 40 or more overs old (although Wasim Akram, Waqar Younis, Irfan Pathan, Shoaib Akhtar, Andrew Flintoff and Simon Jones have produced reverse swing in balls as few as 15 overs old [link])—it can begin to swing towards the polished side rather than the rough side. This is known as reverse swing. In essence, both sides have turbulent flow, but here the seam causes the airflow to separate earlier on one side. The result is always a swing to the side with the later separation, so the swing is away from the seam. See External Links

Reverse swing is difficult to achieve consistently, as it relies on uneven wear of the ball, tends to occur mostly in hot, dry weather conditions, and requires bowling at high speed. Normal swing can be achieved at relatively moderate bowling speeds, but only the fastest bowlers can regularly produce reverse swing.

Reverse swing tends to be stronger than normal swing, and to occur late in the ball's trajectory. This gives it a very different character to normal swing, and because batsmen experience it less often they generally find it much more difficult to defend against. It is also possible for a ball to swing normally in its early flight, and then to reverse as it approaches the batsman, giving its trajectory an S-shape through the air.

Notable practitioners of reverse swing have mostly been Pakistani fast bowlers. Sarfraz Nawaz and Imran Khan are often credited as the first bowlers to produce reverse swing, and they have been followed by bowlers such as Wasim Akram, Waqar Younis, Irfan Pathan, Aaqib Javed, Shoaib Akhtar, Ajit Agarkar, Darren Gough, Andrew Flintoff and Simon Jones. In the early days of reverse swing, Pakistani bowlers were suspected of using unfair means to achieve it, but today they are considered to have been simply ahead of their time.

Swing Bowling Tips

A very slight change in your action (by tilting your body at release for instance) can completely negate swing. Try to stay upright and if you find yourself becoming tired and losing swing, take a break.
Polish one side of the ball vigorously on your flannels and ask the fielders to do likewise. Some say rubbing sweat into the ball can increase swing. Experiment, but remain strictly within the laws and spirit of the game!
A fuller delivery is more likely to swing but less likely to carry. A good length is often the best target for an away swinger and a fuller length for an inswinger.
A little bit of swing is usually more effective than a pronounced amount as most batsmen cannot connect with a prodigously swinging ball. The old adage is that you only have to swing the ball a couple of inches to find the edge of the bat. If you are getting too much, try bowling with the seam straighter.
Sometimes, "trying" to swing the ball is counter-productive. In swinging conditions the ball will swing on its own, so control it but don't "force" it.
If you are no longer getting swing from the ball, try bowl cutters or breaks or varying your pace.

External links

[The Science of Swing]
[Excerpt from DG Bradman's The Art of Cricket] describing swing bowling.