January 14, 2010

The ABCs of Curling - S

illum_s is for sweeping. The most iconic thing in curling, the thing that makes people unacquainted with the game ask, "what the heck is that all about?" is the sweeping: two guys with brooms sweeping the ice in front of a piece of granite, and everybody else screaming their heads off at them.

What the heck is that all about?

Although nobody knows for sure, it isn't hard to deduce how sweeping the running rocks in curling began. Curling was originally played outdoors, on frozen ponds and rivers. Early participants would certainly have brought brooms along, in order to brush accumulated snow off the playing surface. If it was snowing, or windy, it isn't difficult to imagine regular breaks necessary during the game to reclean the surface...and have a wee nip o' whiskey. In fact, letting imagination run, one can naturally arrive at an image of a player cursing because his rock was impeded by a little tendril of snow that had crept across the rink unnoticed. From there it's a short step to the idea of appointing a team member the duty of escorting a running rock down the sheet, and sweeping away any snow or debris that might interfere with its natural (and perfect - naturally) path. After that innovation, it was only a matter of time until a thrower shifted the blame for a missed shot off of the ice, and onto the sweepers - and thus, the modern game was born.

So, what, exactly, does sweeping do? The answer to that question was touched upon in the entry L is for line, where we talked about why a curling rock curls. If you clicked through to the "sciency stuff," you learned that the downward pressure on the ice of the weight of a running rock momentarily melts the surface a bit, reducing friction, and allowing the rock to travel smoothly along the ice. Vigorous sweeping in the path of a running rock slightly warms the ice surface, adding to the effect, and reducing the friction even more. So a rock that is swept will travel farther than an identically thrown rock that is not swept. Conventional wisdom has it that a rock swept end to end, by two strong sweepers, will travel as much as twelve feet farther than it otherwise would have. The sweepers will decide to sweep a rock if they believe it is not going to travel far enough to make the shot as called.

Another aspect of the game is that the rocks curl more dramatically as they slow down. Because sweeping a rock helps it maintain its momentum, a swept rock will curl less than an unswept rock. This leads to the classic sweepers' conundrum. In order to reach the desired spot in the rings, a rock must both have the right amount of weight and the right amount of curl. If a rock is going to curl too much, it needs to be swept...unless it also has too much weight, in which case it should not be swept...except then it will curl too much...you get the picture. I am reminded of one of the guys I played with in high school, who called sweeping on every shot like this: "Yeah!...No!...Yeah!...No!...Yeah!...No!..."

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