|The Curling Manual|
Table of Contents
Section 6 - Sweeping
This section will cover a wide variety of sweeping topics. Specifically, the areas covered are:
In the early days of curling, when games were played outdoors on the lochs, snow and other debris was cleared from the path of the moving rocks. Bunches of sticks were used as debris clearing devices. However, as the sport evolved, it became clear that, in addition to clearing debris, vigorous sweeping affected the moving rocks.
The purpose of sweeping is twofold:
Why Rocks Curl
Before discussing the mechanics of sweeping, it is important to understand what is happening underneath the rock as it travels down the ice. Curling rocks are approximately 12 inches in diameter; however, there is a smaller, ringed portion that the rock rides on. This narrow ring is about 5 inches in diameter and is called the running surface.
Rocks are intentionally rotated either clockwise or counter-clockwise when thrown. Intentional rotation provides the necessary degree of predictability as the rock travels down the ice. Most rocks, if thrown without a rotation, will assume a rotation at some unpredictable point. As the rock is rotating, one side of the running surface will always be moving faster than the other as it travels over the ice surface.
Example: If a rock traveling down the ice has a clockwise rotation, the left side of the rock is traveling faster over the ice than the right side.
Differences in pressure create frictional melting that cause a rock to pivot (or drag) over the slower side. A more detailed explanation of this is provided in the Field of Play section.
How Sweeping Works
First of all, let's discuss what is happening under the rock as it travels over the ice. The rock travels over the pebble. The pebble provides a low contact area with the running surface (the rock rides up on the pebble). The limited contact area created by the pebble allows a low friction environment to exist. Simply put, the heavy rock creates friction and causes frictional melting. The melted ice is more slippery. This naturally occurring frictional melting helps explain why rocks seem to "glide" down the ice.
Now add sweeping. The sweeping motion briefly polishes the ice (pebble) just before the rock travels over it. The sweeping action melts a molecular layer of ice for a very brief moment, resulting in a molecular layer of water. This creates an even lower friction environment that helps the naturally occurring frictional melting. This combination allows the rock to decelerate slower. This results in the rock traveling farther.
The technical definition of sweeping is that it decreases the rate of deceleration. The overall reduction in friction has another effect: Since the rock is dragging less on both sides, the rock will travel straighter.
Sweeping cannot make a rock move faster, only farther!
The Weight Window
The amount of force necessary to propel a rock forward is known as "weight". Good sweepers can add an additional 8 - 12 feet to a rock's distance. This is important to know because, as you are throwing the rock, your throwing weight needs only to fall inside this 8-12 foot "weight window". This provides a fairly comfortable margin of error for a thrower with good sweepers.
Example: A rock thrown 8 feet short of the house without sweeping can easily be swept into the house by good sweepers. As a thrower, your responsibility was to hit the "window" and not the actual finished shot. This is what makes sweeping such a critical part of the game.
There are a variety of sweeping devices being used today. Synthetic-type as well as the traditional horsehair or hog's hair. The more popular synthetic brooms have a fabric, such as Cordura, stretched over a padded surface. Although introduced many years ago, these synthetic brooms became popular in the mid 1990's and are the standard sweeping device today. They are very effective and keep the ice clean. Some people argue that the synthetic brooms are so effective in polishing the ice that they erode the valuable pebble that the rocks ride on. This creates an undesirable "flat" surface with more area of contact on the running surface.
Carbon fiber handles were introduced around the year 2000. They are much lighter than the standard fiberglass handles. They do not offer much in additional sweeping performance other than perhaps some increased head speed due to the lighter weight. These handle are much more expensive. If money is not an issue, choose the carbon fiber.
CurlTech Choice for individual (league type) sweeping:
The above brooms have the flexibility to sweep on both sides.
Mechanics of Sweeping
Let's talk about what makes a good sweeper. The best sweepers today are effective and efficient. Sweeping effectiveness has been the focus of much debate over the last thirty years or so. While many people argue that the most effective sweeping comes from rapid movement of the brush, others argue that effective sweeping is caused by increased pressure of the brush on the ice. CurlTech believes that a strong balance of both will achieve optimum results. Rapid movement with as much pressure as possible is what great sweepers strive for.
Sweeping efficiency refers to a sweeper's ability to be the most effective while using the least amount of energy. The sweeping style discussed in this section is the preferred method of most top teams. CurlTech teaches a sweeping style with the following main components:
The method, also known as "sweeping high" is the best combination of effectiveness and efficiency.
The Sweeping Stroke
To start sweeping properly, take a standing position that is 45 degrees to the rock's path, trying to face the rock and the skip at the same time. With the brush head on the ice, place the inside hand (the hand closest to the rock) on the brush handle half way down using downward pressure. This is the bottom hand and it will be supporting much of your body weight during the sweeping stroke. The outside hand (top hand) should be placed underneath the handle (an underhand grip) about one foot from the top. The end of the handle will be tucked under the arm.
Using an outside hand down position is another popular method. Since most people have a stronger side, this position allows some people to switch sides without switching strokes. The advantage of an outside arm down position is a more perpendicular sweeping stroke. This helps two sweepers stay close. The disadvantage is the body position. The head travels in a more backward style. This results in poorer visual communication with the skip and poorer weight judgment (the field of play is moving sideways across the body instead of into it).
The rules state that you must move the brush from side to side. It is not clearly stated as to what side-to-side really means only that it should "roughly perpendicular" to the rock's path. The most effective sweeping motion is approximately 90 degrees to the rock's path and covers an area just wider than the running surface, (remember, it's only five inches). A sweeping motion that is shorter than this is subject to scrutiny by the officials and a motion greater than this is waste of energy. The stroke should be away from your body, and then back toward your body. Keep your top arm tight to your body. By staying tight, you will begin to put more and more pressure on the head as you begin to move your weight over the top of the brush.
With experience, you will gradually place more of your body's weight over the head of the broom.
The power of the sweeping stroke comes from the top shoulder (shoulder driven). The shoulder "drives" the brush head out and pulls it back. Because of this, most right-handed curlers (strong right side) will feel more comfortable sweeping on the right side of the rock.
For best results, place the strongest sweeper about 4 to 5 inches in front of the traveling rock. This is called "taking the rock". With the brush head perpendicular to the path, move the head back and forth with a clear and visible motion. Most adjustable brush heads are at least five inches long so the running surface is automatically covered by simply placing the broom head in front of the rock. Any clear and visible movement at this point is acceptable. The second sweeper should be as close as possible to the inside sweeper without risking contact with the brushes. As a beginner, you may want to stay well clear of the rock to avoid hitting it with the brush. The most effective team sweeping is with the sweepers on opposite sides because the brushes can easily stay close together. Eighty percent of team sweeping effectiveness comes from the inside sweeper. The outside sweeper representing the other twenty percent. However, the only way the inside sweeper can achieve this eighty percent is with the second sweeper present. The lead sweeper (farthest away) prepares the ice for the inside sweeper. They work together to create great sweeping. Sweeping with only one person will reduce the effectiveness by forty percent.
Note: Adding a third sweeper accomplishes almost nothing. As a skip or a thrower, avoid "jumping in" to help. This is a waste of time and only increases the chances of you or a teammate burning a rock.
The Adjustable or "Angle" Brush
The angle brush is a standard brush with the head turned at a 45-degree angle. It was created to cover the entire running surface while using a shorter stroke. This was done to keep the path as clean as possible without the need to move the brush quickly (Figure 6-2). Another strong benefit of the angle brush is the decreased distance between the inside and outside sweepers since the angle brush head is perpendicular to the path instead of parallel.
The Foot Motion
In the Delivery Section, the use of a slider was discussed. Proper sweeping must be done without a slider. If you throw with a slider, remove it for sweeping. If your slider is built into your shoe, cover it with a gripper. Sweeping effectiveness requires a solid platform to sweep from. The proper sweeping motion, when moving with the rock, looks like a skating motion. Walking fast or jogging next to the rock is not very effective or efficient. As you move with the rock, your inside foot should be skating forward. Your outside foot should also be skating forward but it will lead the body. The outside foot will extend much farther than the inside. The inside foot should also never cross the outside foot during the motion. The most pressure is created when the body weight is over the top of the brush. This can only happen using the tripod method (Figure 6-2) with two feet and a brush head. In the beginning, you will have to support your weight on your feet. When you become more comfortable, begin to shift more and more weight onto the brush head.
To have the greatest degree of flexibility with your teammates, learn to sweep effectively on both sides of the rock. This will allow you to sweep with anyone at any time.
Preparing to Sweep
As the shooter prepares to throw the rock, the sweepers must take a position near the tee line and the side lines. This allows the shooter to view the skip. As the shooter begins to come out of the hack, the sweepers slowly meet the delivery at or near the hog line. One sweeper will always "take the rock" which means sweep closest to the rock. As a general rule, the person taking the rock will "clean" the surface in front of the rock to avoid the rock picking up small debris. Clean by slowly moving the brush head across the surface. The pressure should be light as not to create too much friction. This cleaning should be done in a position ready for sweeping if the skip calls.
Quick Tip: When a right-handed player throws the rock, their broom is extend out to the left. This interferes with the left side sweeper at the beginning of the shot. If possible have the right side sweeper take the rock, since there is no extended delivery broom. This allows the sweeper to clean or sweep at a much earlier point.
When finished, move immediately to the sides and walk back in a non-distracting manner. It is not necessary to stop completely.
The remainder of this section will cover some advance sweeping concepts and techniques that can be used by teams. The topics are:
Once the rock has been delivered, the sweepers are responsible for judging the weight. Is it moving too fast, too slow or just right? It is not realistic to expect the skip to judge the weight from 120 feet away. After the rock has been thrown, the sweepers communicate the weight of the rock to the skip. The skip then makes a line sweeping decision based on whether or not the rocks curl needs to be straightened out.
Judging the weight of the rock is very difficult and takes lots of practice. You can increase your ability to judge rocks with a few sweeping techniques.
1. Sweep as upright as possible, this allows you to visualize the entire field of play and judging motion and speed becomes easier. The fluids in the inner ear must remain as stable as possible for accurate motion judgment. By dipping the head down (leaning over too much) you change the orientation of the fluids. This not only decreases motion judgment, it causes a slight bit of vertigo (spatial disorientation) when the head is returned to the upright position.
2. Take a sweeping position that faces the skip. This also helps view the entire field of play and allows you to view the skip at all times. Curling clubs can be very loud at times and visual contact with the skip may be the only means of communication. This can be done by placing the inside hand in the lower position. This will naturally put you in a "forward facing" position.
Team sweeping refers to teams striving for similar sweeping styles. This continuity will make all sweeping calls more consistent. For example, the most effective sweeping is two sweepers sweeping from opposite sides of the rock. This allows the brushes to be as close as possible to each other, limiting the amount of cool down that happens after the brush passes over the surface.
For the most part, sweepers judge weight and skips judge line. It is very important for both parties to understand each other. For example, a skip judges line based on how he or she thinks the rocks will curl. Since rocks curl less with more weight, the skip must know any weight deviations as soon as possible.
Try the following:
Before the rock is thrown, make sure the sweepers know the exact shot and weight called. If throwing a draw for example, the sweepers should communicate the weight to the skip at the halfway point. Commit to an area of the house such "top four" or "back twelve". This can be verbal or visual depending on the circumstances. As the rock travels down the ice, the sweepers must continuously report the weight to the skip. To simplify matters, only communicate weight if it's different than what the skip expects. Over-communicating such as screaming-out "the weight is good" is not necessary. Effective communication is not necessarily constant communication.
Weight and Position Systems
Teams can use any communication and weight system they desire. Many teams use a numbered system to communicate draw weight and rock position. The 1-11 system works well.
Sweepers should communicate these numbers to the skip as soon as possible. It is not necessary to communicate detailed weight positions at the release point. At the half way point, the sweepers must commit to something. At the hog line the sweepers must be certain. Keep in mind, these are swept weights. The system will get very confusing if teams don't understand the "swept verses unswept" numbers. A better system that incorporates this numbering system is the "quiet system". Using this system, the sweepers say nothing if the weight is correct. This has three benefits:
This "by exception" system works well because it keeps the noise to a minimum especially in loud arenas and clubs.
Example of the Quiet System
The skip calls a draw to the top four- foot (6), the sweepers say nothing until they know (or think) it's not in the four foot. If they can get it to the four-foot with sweeping, they still say nothing. If the weight is heavy, they immediately communicate the heavy weight resting position, such as 8 or 9. The skip can then decide if an alternate is necessary. If the weight is light, the sweepers communicate the swept weight such as 3 or 4.
It is always necessary to confirm the shot with the sweepers and thrower before the shot is thrown.
When learning this system, teams can start by using a less complex numbering system. The following can be used when just starting out.
In the early 90's, a new sweeping concept became popular called corner sweeping. This refers to sweeping across one side of the running surface instead of sweeping across the entire running surface. This was done to gain even greater control over the rocks curl. For example, by sweeping the inside edge of a takeout (the slow side), friction is reduced on the slow side only, reducing the pivot action discussed earlier in this section. Because of this the rock runs straighter. Sweeping the outside edge of a draw could make it curl more. This results in more manipulative sweeping. There is a down side to corner sweeping however, it is very difficult to be control the consistency of the rock's curl. This could result in less predictable shots. Even though corner sweeping may be more effective, most good teams prefer to concentrate on good overall sweeping skills.
The sweeping of one corner only is a violation of the rules. To conform to WCF rules, the corner must be swept by using differential pressure. The entire brush head will cover the running surface but only the desired edge will receive pressure. This is done by "twisting" the handle on a fixed head broom. We suggest you use good, solid sweeping most of the time and twist in the extreme cases. Working the edge is nearly impossible with a swivel type broom.
"Split" Timing (Interval Timing)
Interval timing is a scientific method that helps sweepers judge weight. A designated sweeper can time a shot between two points, usually the back line and nearer hog line. This "split" is the time it takes the rock to travel from back line to hog line and will indicate its ability to make it the rest of the way. This is a relative measurement. The time that is measured cannot be easily calculated into a long time due to the deceleration of the rock. The times can be used as a reference.
Example: On 24-second ice, one of your players normally throws a 3.65 second draw split (time from back to hog). If the same player throws a 3.90 second split, it is likely to need sweeping.
The following is rough example of converted split times on 24 second (hog to tee) ice.
Splits by position will only be same with players that have consistent, fluid deliveries such as the one described by CurlTech in the Delivery section. Different delivery types may yield different split times on the same shots.
A word of caution. Don't rely on the clock as your sole judge of sweeping. As you develop, you will be able to judge rocks without the use of clocks. Great teams use a combination of judgment and clock speeds.
"Finishing" the Draw
Most curlers associate sweeping with rocks traveling farther and straighter. This is true for most shots. There is a case though when sweeping will cause a rock to appear to curl more. As a draw is coming to rest, many newer curlers continue to sweep the rock in an attempt to keep it straight. Sweeping will keep the rock moving, which means it continues on its path. Imagine the arc of a rock that is curling. It begins straight then starts to curl (see The Curl Profile in Section 3). If the rock could move forever, it would eventually leave the sheet of ice across the sideline. Sweeping rocks after the curl begins does two things:
Finishing the rock refers to keeping it moving on its arc. This pulls the rock even deeper behind a guard because the rock is still moving on its curl path. This is important to know since many come-around shots can be "finished", meaning the rocks can be swept under the guard. The mistake many new skips and vices make is to stop sweeping. This only makes the rock stop short and not continue to curl under. On the other hand, if a rock is curling too much at the end, stop sweeping. Additional sweeping here will only continue the rock's path.
A sweeping system is an interrelated group of sweeping activities. Teams should design their own system by compiling known and proven components. In any sweeping system, you will have the following components:
The best team brooms are the ones that create the most friction with the least effort and allow the two sweepers to sweep in close proximity. Lighter, carbon fiber handles dramatically reduce the weight of any broom reducing fatigue, particularly over longer competitions. The carbon fiber handle brooms are slightly harder to control due to the lack of weight. Head "float", meaning the head of the broom drifts off the line, may result during the transition to these brooms. As the head grabs the ice, the friction pulls the head toward the rock causing an oval pattern to the sweeping stroke. Many teams, however, will agree that the advantages outweigh the disadvantages of these brooms. For team sweeping, where the players are in fixed positions for each shot, swivel-head brooms provide the best coverage. Fixed angle brooms allow for differential pressure if desired.
If using fixed angles, it will be necessary to switch brooms for different players. A team switching system is simple if the players are in proper position after each shot. A team can own four broom types for efficiency. A straight broom for sliding and skipping and angles for sweeping.
CurlTech Choice for team sweeping equipment:
The same sweeping style described earlier in this section should be used by the advanced players. The sweeping stroke must be short, vigorous and with as much pressure as possible.
Positioning refers to where and when each team members place themselves during the game. Competitive games are timed and effective positioning helps play quickly without rushing. Select a position for each player that can be replicated each end.
The "Ready Position"
Those of you that coach or play baseball or softball understand the "Ready Position" concept. This refers to the position of the players as the ball is put into play. In curling, the sweepers take a ready position just before they need to sweep (or are called on to sweep). The person taking the rock (closest to the rock), must be in the ready position AND cleaning the path at all times. Cleaning the path helps prevent "picks" and allows the sweeper to sweep immediately when the skip calls. The outside sweeper (not on the rock) needs a ready position that is upright and facing the skip. This sweeper communicates weight information to the skip.
Clean in front of the rock at all times unless you want a pick. Create a skip's signal to stop cleaning. There are times when a pick may help.
Who Takes the Rock?
The "throwing arm" side sweeper should always take the rock. When a right-handed player throws the rock, their broom is extend out to the left. This interferes with the left side sweeper at the beginning of the shot. Since there is no extending delivery broom, the right-side sweeper can clean or sweep at a much earlier point.