Tuesday, November 19, 2013

The Science Behind Doubles and In/Offs

Yesterday (11/17/13) in Medicine Hat, AB in the final game of the Grand Slam event, the 2013 Canadian Open, a shot known commonly as an "in/off" was pretty much the only shot left for skip Kevin Koe to win the game (and the $$$ that went with it, don't forget that). I did not see the game as at the time I was enjoying the hospitality of Team Canada (Sr. Women) in Truro, NS at the home of skip Colleen Pinkney. On the drive from Chez Pinkney back to the hotel, listening to a sports talk show on the radio, the on-air commentator was quite animated about skip Koe's "fantastic in/off" for the victory.

Naturally I couldn't wait to fire up my tablet to see the shot, as I was reasonably certain it would be front and centre on the SPORTSNET web site, the event's media carrier. If you've not seen it, go to the aforementioned web site to witness one of curling's most spectacular type of shot. This post will make a lot more sense if you do!

For those readers not familiar with an in/off, it's a shot whereby the running stone purposefully strikes a stationary stone for the sole purpose of redirecting the running stone for some intended purpose, in this case to remove an opposition stone. Koe's running stone had to be redirected and strike the opposition stone and not roll away. In curling parlance, Koe had to "stick it"! And stick it he did!

For those seeing the shot and muttering, "Well, that was certainly a 'lucky' shot!", you'd be in a group I would describe as "incorrect". Not only did 'luck' have very little to do with it, the purpose of this post will illustrate that Team Koe had some solid sports science supporting one particular element of the shot, which along with a good measure of talent, great line calling on the part of third Pat Simmons and "practice" (yes, the teams that entertain us week-after-week on television actually practise those shots) helped with the successful execution of the shot.

Let's begin with the sports science. This so-called "in/off" was essentially a "double takeout" whereby the back half of the shot was the only portion that mattered. Elite teams like Team Koe play those shots on a regular basis.

The first order of business is to determine the 'contact point' on the stationary stone to be struck first. For many decades in curling, that was more or less guess work and experience than exact science. That's no longer the case thanks to the work of Ron Mills (SK) who postulated that if one draws a straight line tangent to the circumference of the leading edge of the 'front stone' to the circumference of the back edge of the second or 'back stone', the point at which that straight line contacts the edge of the circumference (i.e. striking band) of the front stone is the contact point.

You can easily test this by placing the two stones to be removed in a makeable double takeout configuration. Now get any object that's straight (brush handle, curtain rod etc.) and place the straight object as described in the paragraph above. Note the contact point. Now, place a third stone to touch the 'front stone' of the double at that exact spot. That simulates the running stone, only it's frozen in time. To animate the entire situation, get a fourth stone and have someone crouch down close to that stone you placed on the 'contact point' and drive it with some force onto the nose of that stone. It will instantly remove the stone it's touching and redirect itself onto the nose of the second, target stone. It works every time!!! I've added some photos below to illustrate.

In a game setting, you'd be more than unpopular when lining up a double, or as in the case with Kevin Koe, an in/off, if you started placing your brush handle on the ice but, there's no rule against holding your brush in the air at about waist height so that the edge of the handle of your brush acts as that straight line then standing so that it visually touches "the front edge of the front stone and the back edge of the back stone" OR you can stand so that you can "visualize" a straight line. The point is this, now you've removed a troublesome part of making doubles and in/offs (knowing where to strike the first stone)!

The next decision involves rotation. The first consideration is that contact point. Choose the rotation that affords the better chance of striking that point. If that really doesn't matter, then ice might be a factor as I believe it might have been with Team Koe (more about that later). The severity of the angle between the two stones also may come into play.

Generally, when the stones are sitting at a relatively "steep" angle to one another, coming "into the first stone" will cause the redirected running stone to come off that first stationary stone at a "slightly" steeper angle, thus facilitating the successful double takeout. Conversely, if the two stones to be removed are at a relatively "flat" angle one to the other, then coming across the face of the first stone will see the redirected stone come off the first stone at an angle that's slightly reduced and it will redirect at a reduced velocity, which may or may not be relevant.

You need to be aware that coming across the face, as with that Koe stone, causes the rotation to be "reversed" (very likely accounting for its reduced velocity). Skip Koe delivered this stone with a clockwise rotation but after contact with the first stone (his as it turned out, but that didn't matter) it came across to tap the Gushue shot stone with just enough force to move it out of its shot position (with his stone taking its place for the win).

My sense is that he chose that "across the face" rotation because it was easier to strike the contact point going "outside in" rather than "inside out" which would have been the case with the counterclockwise rotation.* He would have had greater "jump" with the counterclockwise rotation but with the greater amount of curl, it might have been more difficult to hit that contact point and that's the key element. If you don't hit the contact point, all the rest of the elements are quite meaningless!

In/offs become even more challenging when it's for a hit-&-roll, where there's no second stone to "catch" the redirected running stone. In that case, coming across the face just might be the better rotation selection due to that reduced velocity after contact. Much of this type of shot is experiential in nature but not the contact point. That's sport science thanks to Ron Mills!

* In speaking with someone who did see the entire game, apparently Team Koe had played a shot or two in the exact spot with the clockwise rotation so perhaps that was the deciding factor. I'll invite someone from Team Koe to contact me with the real reason.

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