Re: Smith's Crew in SA
Reply #295 –
Isn’t reverse swing achieved by loading one side of the ball with moisture? Sandpapering the ball would make the surface more absorbent.
I think it's easier to think about golf balls.
How do golf balls work, imagine if you created a golf ball with dimples on only one hemisphere?
The dimples on a golf ball work by trapping air in the pits which is dragged along with the ball acting like a low friction boundary layer between the ball and the air, an air lubricant. That is why a dimpled golf ball travels further and straighter, and why the golf authorities regulate the allowed patterns. At one stage manufacturers were proposing asymmetrical dimple patterns that allowed you to set up for fade or draw generated by the orientation of the dimples. They have been outlawed.
You can make any cricket ball swing as long as you create a physical asymmetry between the two hemispheres, you are effectively forming a wing with one side super-lubricated by the air boundary layer and the other exposed to friction. Then it becomes the bowlers skill to orientate the wing correctly relative to the direction of release.
There is no right or wrong way, if you know the basics you can create swing either towards or away from the polished side. Often when bowlers cannot get the ball to swing trying it backwards to the way they normally swing the ball will work.
The mechanism of conventional and reverse swing is exactly the same, it's just that the asymmetry is caused by different effects, as the ball gets older the effects of the seam orientation diminish and the asymmetry is caused by changes in the surface areas.
You are correct about the liquid, loading one side of the ball with lots of moisture also causes an asymmetry, but if you are looking for reverse swing this can act in opposition to the roughing effects. You do not want to increase the surface area of both sides at the same time. If you really want reverse swing you need to keep the polished side smooth and dry to minimise it's surface area, and the unpolished side to become as ragged as possible to maximise it's surface area. This effective difference in surface area of the two sides creates a wing. The 1/2 taped up tennis ball behavior, which is like a golf ball with dimples on only one hemisphere. Loading the polished side with too much moisture causes it to also expand, reducing the area difference between hemispheres.
As I posted earlier, any swing bowler who sees a fielder using saliva on the polished side should punch them in the face, if will effectively be reducing or delaying the amount of reverse swing you can get, it's a problem if the plan isn't well coordinated!
What the Aussies did has little benefit, the sort of trivial sanding they attempted would remove pits and peaks making the roughness similar without introducing a significant change in surface area.
I suppose if they did this enough in conjunction with saliva on the polished side they would eventually grind enough of the ball away get a asymmetry but it's a hell of a long way around a very simple problem! No wonder the bowlers were furious, what the trio had planned was probably counteracting what the bowlers had been taught to do, this would probably mean the reverse swing would start much later in the innings.
All this plays out when choosing a new ball. Batsmen / Captains will often search through a box of balls and find a ball that looks symmetrical about a proud seam, or a ball that appears slightly barbell shaped. That is a ball that is good for seaming or spin bowling but not for swing. The best ball for swing is the one that looks like it has one hemisphere larger than the other in addition to a proud seam, because that ball will most likely behave through all phases of the game with the desired characteristics.