|This article does not cite any references or sources. (November 2009)|
Curl, in association football, is spin on the ball which will make it change direction, called a 'screw shot' in the 19th century. When kicking the ball, the inside of the foot is often used to curl the ball, but can also be done by using the outside of the foot. Similar to curl, the ball can also swerve in the air, without the spin on the ball which makes the ball curl. Curl is especially evident from free kicks, shots from outside the penalty area and crosses. Differences between balls can also affect the amount of swerve and curl: traditional leather footballs are too heavy to curl without great skill, whereas the lighter modern footballs curl with a much lower effort threshold. As a general rule, the lighter and smoother the ball the more deviation there is. Making the ball curl in the air was first developed in Sheffield during the late 1870s. At the time it was referred to as a screw shot.
There is a degree of confusion surrounding the correct naming of different aspects of curl. The technique of putting curl on a ball is known as chanfle to some, from Spanish, and also as the Trivela. The deviation from the straight path in the air is the actual curl, or swerve; however, the spin on the ball that causes this is also known as the curl. Shots that curl or swerve are known as curlers, swingers, or ones that bend, also in extreme cases, banana shots. However, it is extremely rare, these days, to hear any shot described as a "banana shot".
Free kick takers often curl and put spin on the ball, to curl it over or around the wall of defending players, out of the reach of the goalkeeper. Goalkeepers usually organise walls to cover one side of the goal, and then stand themselves on the other side. Thus, the free kick taker has several choices, including; either to curl the ball around the wall with finesse, to bend the ball around the wall using power, or to go over the wall.
Curling can be an effective technique when taking corners. The ball gradually moves in the air towards the goal. This is referred to as an in-swinging corner. Occasionally, a corner-taker will bend the ball towards the edge of the penalty area, for an attacker to volley, or take a touch and then shoot.
The reason that spin on a football makes it curl is known as the Magnus effect. This causes a rotating ball to form a whirlpool about itself, with one side's air moving with the ball and the other side's air moving against the ball. This creates a difference in air pressure, and the ball deviates from its path to compensate for this.
|This section does not cite any references or sources. (April 2012)|
Many players curl the ball in their game. Notably Franz Beckenbauer relied routinely and expertly on this skill. Other players who uses this skill noticeably are Nelinho, Maradona and the Portuguese player Ricardo Quaresma. David Beckham, who became known as a free-kick specialist, regularly curls the ball when taking free-kicks and crossing. A 2002 film, Bend It Like Beckham, was named after his curling ability.