Does Anyone Have the Time?
February 3, 2006 Revised Feb. 2013
First off, this is a hugely revised version of the original article. Truthfully that’s in part because the views on how stopwatches are used has changed in the last 6 years and in part because I think I’m a smarter coach than I was 6 years ago… In any case, this is my view in 2013.
Stopwatches have become a pretty regular piece of equipment for curlers. These days you find players at all levels using them in a variety of ways to help judge ice conditions with respect to weight. In the old days players relied on vague descriptions from their teammates to fine tune their weight. That generally sounded like the second asking the lead how fast the ice was, then the vice asking the second and so on. The problem with this is that there is no standard to explain “how fast” the ice is. “Oh the ice is quick tonight!” doesn’t really mean anything. Typically teams would call upon experience and relate weight back to what they were used to in their home clubs but still, weight descriptions were limited to fuzzy descriptions and more trial and error than any real reference. Even saying, “the ice is quick compared to home…” doesn’t help. How quick is quick? Using a stopwatch provides a very precise reference for judging the weight of the ice. Many of us are not able to control our weight with as much precision as is provided by timing measurements but that’s better than having precise control and no idea on how the ice is running. There are many misconceptions about how to use this tool and its effectiveness during play however. I’m going to go through the various ways a stopwatch can help you judge the ice and then help you with what to watch (no pun intended) out for.
First of all, lets be clear on what we’re trying to figure out with our handy stopwatch. The idea is to determine what force needs to be applied to a rock so it stops on the far tee line (or at any point past the far hog line). The force required is different on pretty much every sheet of ice you play on and can even change during a game so knowing how hard to throw your rocks BEFORE you throw them is a pretty handy thing! In curling of course, we call the “force” on the rock the “weight”.
“More weight” means higher applied force and “less weight” means less applied force. “But,” you say skeptically, “how does timing rocks tell me the force I need to put on the rock?” At this point, I have to apologize in advance for getting technical. I’m going to call upon my engineering background to explain the physics behind why a stopwatch works for this. Those of you willing to trust that the time measures the force on the rock can skip this next bit. Please jump back further down to read about how to time rocks and more… I personally find this part interesting but then…well, that’s the engineer in me.
Isaac Newton, who may or may not have ever seen a curling stone, tells us that the force on a curling stone is equal to its mass multiplied by its acceleration. Mathematically that looks like:
Force = Acceleration x Mass (F=M x A)
Mass is pretty much constant. All curling stones have slightly different weights but we’re talking about one curling stone at a time and it’s mass does not change while it’s traveling down the sheet. So what about acceleration?
Acceleration = Change in speed / Time
The change is speed of the stone is the speed at release minus the speed at the end of the shot.
Change in speed = Speed at release – Speed at end
For a shot that stops somewhere over the hog line, the speed at the end is zero so:
Change in speed = Speed at release – 0
So, the change in speed is equal to speed at release for a shot that stops in play.
Speed = distance / time
We knew this because speed units are km / hour for example (distance / time). Still with me? Hang in there, we’re almost through it…Now the fun part. If we put all of these equations together what you get is:
Force = Mass x distance / time(squared)
Hmm, now I know what you’re thinking… why am I putting you through this mathematical torture and what can this possibly have to do with timing curling stones?? First, engineers have a tendency of doing that to people. Second, if you look at the equation you’ll see the force can be affected by the mass of the stone, the distance it travels and the time it take to travel the distance. We know that the mass of the curling stone doesn’t change no matter how much force we put on it (I hope we know that…). We also know that the distance down the length of the curling sheet doesn’t change no matter how much force you put on the rock (I hope we know that too!). Now the big discovery…the only thing that changes with the force you put on a stone is the time it takes to get down the sheet! We already knew this too though didn’t we? After all, if you really heave a stone down the ice it doesn’t take as long to get to the far end as the one that your vice just hogged. (All right… as the one MY vice just hogged…) We can now say that timing shots gives us a direct measurement of the force required! Remember, in curling, we call the force on the stone the “weight”. For the mathematicians out there, the force (or weight) is inversely proportional to the square of time. (Impressed?) All you need to get out of that is that if the time is high (a slow rock…) then the force (weight) is low and vice versa. Take outs will have a short times and high weights, draws will have long times and low weights. Yes, I know, you already knew that but now you know that there is a hard scientific basis for it! Exciting stuff huh? Okay, enough of that.
To those of you who skipped the theory, welcome back!
Now that we believe timing shots can tell us the force needed to get the stone down the sheet, how do you actually use a watch to give you useful information? Watches are used in a few different ways. A common method of timing rocks is to measure how long it takes a rock to go from the near hog line to the far hog line. There are many variations of this method such as timing rocks from the near tee to far hog or from the near hog to the far tee line. Measuring times over the length of the sheet like this is not intended to provide information you can act on for the shot you’re measuring. Rather, it gives you an idea on how fast the ice is for subsequent shots. I said my preference was to measure times from hog to hog and I’ll explain why. If you start measuring the time from a point before the thrower has released the rock then the time you get is going to be strongly affected by their delivery and their release in particular. If, on the other hand, you start the watch from a fixed point after the thrower releases (the hog line…) then the time you get will be totally dependant on the ice conditions. Okay not TOTALLY dependant but at least you won’t have the release effect to worry about. Hog to hog times are also unaffected by the dreaded “push” or “pull” at release.
Be aware that there are many other factors that will affect the time you get from stones. For example, the rotation on a stone can have a large impact on its time. A rock with a lot of rotation (aka a “spinner”) will give an artificially high time for draw weight. These stones have a lot of rotational momentum that takes longer to dissipate than a stone with less rotation. Watch the rotation closely on rocks that you are timing and discard any times you get from stones that don’t have rotations similar to yours. After all, this is about figuring out how much weight YOU need to throw so it’s important to gather information on shots that are thrown they way you throw them. Hopefully everyone on your team will be putting a positive rotation (two and a half to three and a half rotations down the length of the sheet) on the stones. That way any stone you time for your team will be useful to you personally. Be careful though, when someone doesn’t throw a positive rotation, you have to be wary of the times you measure. This is also something to keep in mind when you’re timing rocks thrown by your opposition.
Another reason as a skip that I prefer timing from hog to hog is that I can usually see when the rock crosses the hog lines from the far house. As a short skip it’s difficult to see when the rock crosses the first tee line during the delivery. I have to stand on my tippy toes…
Another way to time rocks is by measuring the split or interval times. Now, back when this article was originally written, split times were all the rage. They were a touted as a great tool for giving sweepers an idea of rock speed. This thinking has shifted however in recent times. After I explain what split times are, I’ll explain why I try to move teams away from them.
Split times are taken from the near tee (or back line for the pros) to the near hog line. The information from these times can be stored for reference but also can be used by the sweepers on the immediate shot! It is commonly believed that taking these times can provide sweepers an early clue as to whether a stone is too light or too heavy. For example, if a draw shot should take 2.80 seconds from tee to hog and your third (it wouldn’t be your skip, heaven forbid…) throws 2.50 seconds then your sweepers will know at the near hog line that it’s going to sail right on through the house. On the other hand if your third throws 3.1 seconds then the sweepers better start sweeping right away. The relationship between time and weight are always the same no matter the timing method used so if the time is high then the force (weight) on the stone is low. Split times need to be very precise because they are so short (this is one major issue with split times). Differences of tenths of a second are significant when using split times and if you’re sloppy about how you take these times they aren’t going to be helpful. Split times are also more sensitive to release effects. The player delivering has their hand on the rock pretty much all the way through the split time (unless they release it before the near tee line…). If a player comes out of the hack very slowly then pushes the rock right at the end, the split time will be meaningless.
Okay so what’s the problem with split times. Well, first off I said before that timing was a very precise way to measure rock speed but precision doesn’t mean accuracy. More engineering, I know. Precision is NOT accuracy. I can measure time to the hundredth of a second simply by having a cheap stopwatch but making sure the watch starts and stops at the correct hundredth of a second is accuracy and THAT’s the part that you can’t count on. Split times are incredibly sensitive with a tenth of a second meaning approximately 6 to 10 feet of distance. Can you confidently start and stop your watch within less than a tenth of a second every time? If not, well… you can see the issue. The next problem with split times is that players tend to lean on them like a crutch. They tend to believe their watch over their own observations and lose their ability to judge weight. These days top teams might use a watch but rely on their own experience and judgement over the times they take. Teams I coach now can use watches but only one sweeper uses it. Also, I teach them to use their times as a guide ONLY.
Timing stones seems like a fantastic way to judge weight but as we’ve seen, there can be problems. Always remember that the stopwatch, no matter how you use it only provides a reference. In that respect, it’s not that much different than hearing “it’s a bit sticky”, but now you know that it’s 1.5 seconds sticky. To be really useful, you have to have a feel for how much harder or lighter to push out over a range of times. It’s no good knowing the ice is running 24 seconds from hog to hog if you have no idea how hard to push out of the hack to make it go that fast! You’re going to need help from your team to build this experience and feel. You need them to time your shots then tell you what those times are so you can start to relate times with weights. The better you get at putting a time together with a weight, the more useful the watch will be for you. Not having an internal feel related to various times is like knowing where the target is but not knowing how to fire the gun.
It would appear from what we have discussed, that you really only need to time draw shots and guards. What about take outs? Take out shots require as much control with respect to weight as draws and guards. We have all seen shots that were “over thrown” and missed because they ran straighter than the skip expected. Those types of misses are a direct result of players not controlling their take out weight and simply throwing it “up”. If your skip knows what weight to expect on shots, even take outs, then she can place the broom precisely. Many players, especially new players, think that take out shots are easier because the weight doesn’t need to be as precise. This just isn’t true. If you want to be proficient at removing opponents’ stones then you need to control the weight thrown on those shots just as much as you do for lighter shots.
So how does a watch help you be more consistent with take outs during a game? Timing take outs won’t tell you much about how the ice is running. The reason is in the physics behind timing. On take out shots you’re measuring a much smaller decrease in speed over the length of the sheet. (see, you shouldn’t have skipped the theory!). You would have to do some more complex figuring from take out times to get an idea on how fast the ice is. It would be much more complicated than simply timing a draw shot. The best reason for timing take outs during a game is to see if you’re throwing the take out weight that your skip called. Let me explain. How often have you heard a skip call for “normal” take out weight? What is that anyway? Most people recognize that “normal” weight is more than hack weight but how much more? Timing a take out will give you some reference for “normal” and it’s up to your team to define what that should be. You could all agree for instance that “normal” take out weight should take 10 seconds from hog to hog. Your team should then work towards throwing this consistently in practice. Then in a game you can time your take outs and see if you’re close. At the risk of repeating myself (over and over again…) it’s all about consistency. Having this sort of control will help the skip to call ice because she’ll know precisely how much weight to expect when she calls for “normal”. Better yet, if all players are able to throw three distinct take out weights (say 10 seconds hog to hog, 9 seconds and 8 seconds) then your skip no longer has to call “hack weight” or “board weight” and she’ll be able to call more precise shots with confidence! Timing take outs is not something many players do because many players don’t fully appreciate the need for weight precision on take out shots. There are a great many types of stopwatches out there. You may have seen players with the stopwatch on a strap that wraps around the shaft of the broom. This design of stopwatch came directly from the popularity of split or interval timing. It puts the watch in a place where the sweeper can conveniently start and stop the watch while keeping their hands in a position to sweep quickly if required. I don’t personally find that this style works well for me in the house and I have a more conventional stopwatch tied to my belt. I did accessorize it by putting it on a retractable cord, which I find very handy. This retractable cord lets me pull the watch out in front of me where I can see it while timing but then keeps it tight to my belt when not in use. Some players use their wristwatch, which makes sense as long as you can easily start it and stop it and as long as you can read it fairly easily. Pretty much any stopwatch will work but be wary of watches that are hard to manipulate. If the buttons are small or the display is too small to conveniently read then you may want to keep looking. The best tools make your job easier and not more complicated.
Finally don’t let timing rocks consume you during a game. It’s only a tool and you shouldn’t be concerned if you miss timing a few rocks or if some of the times you get don’t make sense. If you simply can’t get times that make sense during a game then put the watch away. Also, don’t start thinking a watch is going to solve your draw weight problems. Your stopwatch won’t throw rocks for you, all it will do is give you an idea how hard YOU should throw them based on ice conditions. The watch only tells you where the target is. You still have to know how to aim and fire. Timing stones can be an incredibly helpful tool but if it’s not used properly it can cause a lot of confusion and frustration.