FIELD OF PLAY
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FIELD OF PLAY |
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The term "Field of Play" refers to two essential parts of the game, the ice and the rocks.In this section, the field of play is discussed in depth. Topics included in this section are:
FIELD OF PLAY: ICE | MODERN | TIMING | MAINTENANCE | PERFORMANCE
IceA discussion of modern day curling and the success of your club, events, team, programs, etc.would not be complete without talking about the ice.Today's curlers expect the ice conditions to be fast and true.However, the ice is constantly changing and will change from club to club, event to event and even during the game.Local ice technicians study the control factors, listen to playability feedback and make adjustments to always improve the ice conditions. In addition to your good delivery, sweeping mechanics and strategy, the ability to assess and monitor the ice (and rocks), will determine you team's success. Ice playability has evolved rapidly in the last twenty years to thirty years.The invention of the curling ice scraper and the use purified water has changed the game.The ice of the past; slow, straight and dirty, is no longer acceptable.
FIELD OF PLAY: ICE | MODERN | TIMING | MAINTENANCE | PERFORMANCE
Modern Ice Performance StandardsWhat do we expect when it comes to the ice?In some countries rigid field of play standards have been developed for championship play.To date, the World Curling Federation has not developed a set of printed standards.In the United States, for example, club and championship field of play conditions must meet the following standards:
The above standards were developed through a partnership between athletes and US governing body.They represent a good balance between ice that plays well for the athletes and ice that is suitable for an aggressive game, where lots of rocks are in play.Television audiences prefer the action of a house cluttered with rocks.
FIELD OF PLAY: ICE | MODERN | TIMING | MAINTENANCE | PERFORMANCE
Timing RocksSee the section dedicated to Timing Rocks for a full explanation of how and why we time rocks.
FIELD OF PLAY: ICE | MODERN | TIMING | MAINTENANCE | PERFORMANCE
Ice MaintenanceTo achieve the above standard, the ice must be maintained using some basic maintenance techniques.Ice should be scraped daily to remove the pebble from earlier games.A proper scrape completely removes the old pebble so new pebble can be applied.In many clubs, the ice is either not scraped daily or under-scraped.It may also be over-pebbled.This means the pebble will build up over time, creating a course surface which be slower and straighter and keep dirt from being scraped away.The ice will also slowly increase in thickness as the pebble builds-up. In championships conditions, the ice is leveled during the pre-event preparation and is scraped after each game.This completely removes the old pebble before the new pebble can be applied. The information below is a guideline for ice making.Every facility is different and ice standards may be different.Work with your facility to make the best ice possible. Club Ice Maintenance Recommendation
To re-pebble the ice during back-to-back games, adjust you're your time and coverage.A 30 second, 80 swing pebble could work.Be sure to nip again.
FIELD OF PLAY: ICE | MODERN | TIMING | MAINTENANCE | PERFORMANCE
Ice PerformanceSeveral factors come into play when trying to achieve the ice playability standard.We break them down into three categories:
Facility Related
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| Standard | Acceptable Deviation | |
| Rock Type | Blue hone inserts | Well-matched rocks |
| Rock Pairings | Closely matched by pair | None |
Rock Performance & Maintenance
Even though the rocks are solid granite, they do wear down in certain areas.The width of the running surface starts at about 5mm from the factory.Over time, the running surface wears and gets wider.As they wear, they begin to lose their "aggressiveness" or sharpness and start to straighten-out and sometimes get faster.Running surfaces in the 7-8 mm range need to be reconditioned to regain their sharpness.The striking bands also wear over time.Factory striking bands may be in the 2 cm range and wear to the 4 cm range.As they wear, they lose their "activeness" meaning they don't bounce as well.This is due to the increased contact area.
Treat your rocks with care.Limit their use by NOT using them to drag the ice before games.Rotate the rocks by sheet occasionally since most practice rocks are thrown on center sheets.
˙Cleaning˙Scratching˙Frequency˙Type˙
The rock's running surfaces get dirty by picking up small dirt on the ice.Small pieces of rubber from deteriorating grippers can attach themselves to the running edges. Solvent clean rocks running surface once per week.
˙Cleaning˙Scratching˙Frequency˙Type˙
There is a method to gain aggressiveness in your rocks.Scratching or texturing the rocks will roughen the running surface and gain aggressiveness.This method is very popular in the competitive world as the world class curlers demand more and more rock performance. It is not uncommon to scratch the rock mid-way through a world or provincial championship.This method does not actually sharpen the running surface.It roughens it.
Rock manufacturers will agree that texturing the rocks should be the last step in the overall ice/rock performance plan.There are several ice maintenance tricks that will give you more curl without touching the rock's running surface.
Every time a rock is played, practiced with, and/or used for dragging it is slightly polished by the ice friction.The more the rock is used, the more polished it gets.This gradually changes the rock ice interface.
If you decide to texture your rocks, use a texturing jig to roughen the running surface.The jig allows you to consistently sandpaper the running surface.Several methods can be used based on how aggressive you need them.
Considerations:
Adjust your texturing schedule after considering the following:
On the other hand, warmer, freshly scraped ice has less friction.Nipping instead of running rocks will lengthen the interval.
*Note: Contact rock manufacturer for more information and any possible warranty issues.
Determine how many rocks throws occur at your club.
˙Cleaning˙Scratching˙Frequency˙Type˙
Use the following as a guide to rock texturing frequency.Determine if your rocks are high, medium or low use by counting the number of times each rock is thrown per week.Count your regularly scheduled draws, practice sessions and the number of times the rocks are used to drag.Multiply that number by the number of weeks in your season.
| High Use Club | 3000 annual or more throws each |
| Medium | 1500 - 3000 annual throws |
| Low | Below 1500 annual throws |
If you keep your ice warm (23-25 degrees) which is recommended texture your rocks every 2000 throws.
If your ice is cold and/or frosty (20-22 degrees) texture every 1500 - 1800 throws.
˙Cleaning˙Scratching˙Frequency˙Type˙
Using the texture jig and aluminum oxide paper.One piece per rock.
| Type | Grit | Process |
| Full | 80 | Push, pull, 90 degrees turn, push, pull again |
| Maintain | 100 | Push, pull, 90 degrees turn, push, pull again |
| Light | 150 | Push, pull, 90 degrees turn, push, pull again |
| Using a flat surface (2X4) wrapped with sandpaper | ||
| Cleaning | 150 | Light circular motion |
FIELD OF PLAY: ICE | MODERN | TIMING | MAINTENANCE | PERFORMANCE
CONTROLS | STANDARDS | SUMMARY | ASSESSMENT | ARENA | MEASURING
Running surfaces (running edges) don't last forever.The manufacturer shapes the edge on the lathe with a cutting tool.When the rock is placed into service at the cub, it begins a slow polishing and deterioration process.The edge can either wear away or "pit".Pitting occurs slowly as the rocks expand and contract.A pitted edge is very inconsistent in how it plays.
Aggressive edges smooth-out as they age and must be retouched occasionally.Some ice techs believe rocks should be "worked" before every large event."Working" the rocks or "scratching" the rocks is achieved by sanding the running edges with sandpaper or emery. Different techniques exist but they all involve turning or dragging the rock on a piece of sandpaper.This roughens the edge and makes the rock more aggressive.It also helps gain consistency in the rock sets.
FIELD OF PLAY: ICE | MODERN | TIMING | MAINTENANCE | PERFORMANCE
CONTROLS | STANDARDS | SUMMARY | ASSESSMENT | ARENA | MEASURING
Good teams have a plan to assess the field of play before each game.Below is a sample plan for assessing the conditions.
Assessing the Ice
Assessing the field of play conditions is not the same as reading the ice.Good teams understand ice and the variables that affect performance.There are four key ice variables a player should know.
˙Method˙Temperature˙Pebble˙Heat & Humidity˙Rocks˙Sheet˙
The type and frequency of the ice scraping will have huge impact on the ice speed and curl.Understand how often the ice is scraped and if the pebble is completely scraped off before it is pebbled and nipped again.
˙Method˙Temperature˙Pebble˙Heat & Humidity˙Rocks˙Sheet˙
Teams should know the ice surface temperature at the beginning of the game.They should also know when the compressor "pulls".Surface temperatures in the 21-22 degree range will produce a slower, straighter condition.Temperatures in the 23-24 range will produce faster and swingier ice.Know the factors that affect the surface temperature during a game.There is no such thing as a constant surface temperature.At night, when the lights are off and the ice is not in use, the refrigeration system will maintain a surface temperature in the set range with very little margin of error.Large heat loads (lights, players. heaters, etc.) are difficult to remove quickly resulting in a spike of surface temperature.For example, a surface that will remain at or near 23 degrees when the ice is not in use may increase or spike to 25 or 26 degrees when the players start the game.The capacity of the plant and the set points dictate how high the spike will be.
Example
A curling club maintains a 23-degree surface when not in use and the lights and heaters on.When all of the players enter the ice area and begin to play, an enormous heat load is added to the static condition.Each player represents a certain BTU (British Thermal Units) heat load.This heat will be transferred to the ice surface and the compressor will have to pull it out.There is a lag between the addition of the heat load and the compressor sensor.In some cases, the compressor is unable to pull the heat out fast enough and the surface temperature rises.When players leave the ice (removing a heat load) the surface will either remain constant or drop (if the compressor is pulling).
Begin your ice assessment by having a discussion with the ice technician.Prior to the competition, ask to see the refrigeration plant and ask what the compressor cycles on;
| Sensing Area | Short Result | Long Result |
| Brine temp | Long lag time | Large temp range |
| Bed temp | Medium lag time | Med Temp range |
| Surface temp | Short/No lag time | Small temp range |
Ask the ice tech what the ice surface temperature will be at the beginning, middle and end of the game.Ice with surface temperatures in the low 20's may be straighter and slower.As the temperatures rise, the rocks curl more and it becomes faster.This is the case until about 27 degrees.Temperatures higher than that create soft, unplayable ice and there's probably something wrong with refrigeration system.The pebble will last longer in lower temperatures and will break down faster in higher temperatures.
The key to managing the surface temperature is knowing when it changes.Everyone has experienced a change in speed and curl after the all the other sheets have left the ice.With four to six sheets of people on the ice, the refrigeration system is working to remove the heat load (BTU's).If the heat load leaves quickly, the compressor lags behind and continues to operate.The surface temperature can drop a full degree by the time the system shuts off on temperature.In addition, the heat source offered by the players is no longer available, resulting in the air losing its moisture-suspension qualities.
˙Method˙Temperature˙Pebble˙Heat & Humidity˙Rocks˙Sheet˙
Ask the ice technician what size pebble he or she plans to use.A medium pebble will last longer while a fine pebble will break down earlier.
˙Method˙Temperature˙Pebble˙Heat & Humidity˙Rocks˙Sheet˙
Ask the ice tech if the club or arena has heat and/or dehumidification.Dry air has less moisture than humid air.With no moisture in the air (dehumidification) there will be no condensation on the surface.This means no visible moisture (frost).Early condensation looks like a dull film across the ice.You will notice that the sweeper's shoes will displace the moisture and cause a smooth spot.The moisture taken up by the shoes may even leave a spot on the ice where the shoe stops.Dry ice conditions promote speed and curl.Moist conditions lubricate the running surface and prevent curl.
˙Method˙Temperature˙Pebble˙Heat & Humidity˙Rocks˙Sheet˙
At the higher levels, your ability to assess rocks is critical.Games have been decided on a team's inability to spot a bad rock and deal with it.The following is a guide to rocks and how to assess them.
There are many different types of rocks in play across the world.Wear and tear on these rocks differ with the type of granite used and the amount of playing time they get.As mentioned earlier, some granite is susceptible to wear and pitting causing them to behave differently.Mismatched rocks are a growing concern.With the good ice conditions we have today, particularly the speed, mismatched rocks can play an important role in the outcome of the game.As rocks age, the running surfaces change shape.They either wear (get flatter) or they "pit" which means small pieces of granite break lose due to constant freezing and thawing (expansion and contraction).This aging process is important to advanced curlers because it rarely happens evenly across a given set of rocks, causing the speed and curl of some rocks in the same set to differ.Most players use the rock numbers to throw rocks in sequence but there is no guarantee that these rocks travel over the ice at the same speed or in the same manner.
Know the Granite
Your first step in rock assessment is knowing what granite you're playing with. Most rocks today are Trefor granite with blue hone inserts.This is the best rock type.The running surface is made of blue hone which is a durable running surface.Visually inspect the running surface and determine if the rock is aggressive or conservative.An aggressive running surface will feel rough to the touch.The aggressive running surface will curl more with less speed.
Matching Rocks
Mismatched rocks (one slower or faster than the other) can greatly affect your ability to calibrate draw weight.A rock that is ten feet slower than the other will cause you to over compensate on each throw.
The best way to determine if two rocks are running at the same speed is to throw many, many draw shots on a good quality ice surface.The larger the sample size, the more accurate the data.Record the results and use the information in the future.
Steps for assessing rocks during a competition:
Throw the Rocks
In practice throw the rocks that you will be throwing in a game.Start by playing the rocks straight up the numbers.If you suspect a mismatch move to step 2.
Run the Rocks
If you suspect a bad rock, run the two rocks one in front of another for about fifteen to twenty feet.If the rocks are matched, they will run together in both directions.If one is faster, it will pull away from the other.This is not an exact science.Use this process only to determine really bad rocks.
Look for Patterns
Since most players do not have the luxury of running rocks (particularly at other clubs), the next best thing is to watch each rock closely for signs of unusual behavior.Designate a player to watch the rocks and the tracks on the ice.Bad rocks usually create a pattern (always light but with a good split, for example).Always confirm split times with the team timer if you suspect a bad rock.
If time is not a concern (rocks at your own club) a good way to match rocks is to time them.If you have an opportunity to throw practice rocks, or you want to match rocks at your club, throw as many rocks to tee line as you can.Time them from hog to tee.This will give you the rock's speed in seconds.When complete, match the similar times.Teams using "split" or "interval" timing can match rock speed quickly by monitoring the splits.Consistent rocks will have consistent times in either case.
˙Method˙Temperature˙Pebble˙Heat & Humidity˙Rocks˙Sheet˙
At first glance, the sheet of ice, excluding the houses, has many parallel lines and other lines that intersect at 90-degree angles.In particular, the center line and the four-foot lines, if in use, represent reference lines for throwers and sweepers.However, only a few shots in a game will run parallel to these lines.Since all shots are thrown from the hacks that are fixed a few inches away from the center line, most shots will initially travel at an angle to the center line.Compounding the issue is the draw back point of the individual player.Some will draw back on the center line while others will draw back to the hack toe.This represents four inches or so at the front end of the line of delivery (imaginary line between the skip's broom and the starting point).
The Outturn Issue
Outturn shots, particularly the ones farther outside, are visually complex since the LOD in most cases, crosses the centerline first, then the four-foot line.These shots will, for most of the path, be travelling away from these lines.Since they are actually moving away from the parallel lines, the rock "appears" to be "falling" to the outside.If the center line and four-foot lines were not there, there would be no apparent fall.In addition to the visual, sideways delivery and release energy may straighten the rocks' curl profile contributing to the wide and/or fall problem.See the Wide Trifecta.
FIELD OF PLAY: ICE | MODERN | TIMING | MAINTENANCE | PERFORMANCE
CONTROLS | STANDARDS | SUMMARY | ASSESSMENT | ARENA | MEASURING
With the popularity of curling growing every year, new clubs are forming without dedicated curling facilities.By acquiring rocks and basic equipment, new clubs can form using ice at the local skating rink.This is a great way to enjoy curling at a low cost.Curling on arena ice does present some challenges.Most arenas share ice with hockey and figure skating.Preparing the ice temperature and surface for each group looks different.Hockey players want a cold, flat surface at about 20 degrees.Figure skaters want a warmer, flat surface at about 25 degrees.Both hockey and figure skating don't necessarily need a level surface.Curlers want a level, pebbled surface at about 23 - 25 degrees.
All preparations for daily use involve the Zamboni.The Zamboni is an efficient machine for prepping hockey and skating ice.For curling however, it can be a problem.The machine scrapes the surface and lays water down to fill holes and create a seemingly flat surface.It does not create a level surface.Even the curling scraper can't level the surface properly.
A surface that's not level may produce a "negative ice" situation.Negative ice happens when the surface is not level.The physics under the rock that make it curl no longer exist (see Why Rocks Curl).In this case gravity may make the rock curl, even against the turn.Our staff has arena experience and they report situations where rock curl twelve feet with the turn and back up eight feet against the turn.
Your game strategy and shot calling may have to be adjusted to make shots on the non-level surface.
Tips for Playing on Arena Ice
Throw shots down the middle of the sheet.Typically, the center of the sheet is the most level.Because of this, shots down the center can be more predictable and very effective.Playing the outside sheet is dangerous and is where the fall (negative ice) exist.
Throw more draws than takeouts.Even on a non-level surface, draw weights can be normal.A team that can fill the house with draw shots has an advantage since the takeout is less predictable.We've seen teams throws eight takeouts in a row and miss everyone.
Is the ice is running negative, gravity is making the ice curl and not differential frictional melting.If gravity is making the rock curl, sweeping makes it curl more.Of course this is the opposite result from normal curling.
FIELD OF PLAY: ICE | MODERN | TIMING | MAINTENANCE | PERFORMANCE
CONTROLS | STANDARDS | SUMMARY | ASSESSMENT | ARENA | MEASURING
Occasionally, two or more rocks are too close to measure by eye, whether it is to the tee or around the perimeter.Measurements come in two categories:
Measuring the rocks by device will help.There are four types of measuring devices available at most clubs.
˙Mechanical˙Laser˙6 Foot˙T-Square˙Procedures˙LSD˙
The first and most often used device is simply called the "measure".It is used to determine the counting rock or rocks in the house.There two types of mechanical measures, the spring gauge and the manual touch no touch device.Since the spring gauge is a mechanical device with moving parts (springs, levers, etc.), there may be some inaccuracy on very close measures.The TNT device eliminates the mechanism and the determination is made based on where the device touches or not.This is far more accurate.The spring gauge device can also be used as a TNT.
A note on both devices:
Any downward pressure on the device may cause a bad reading.In addition, many of these devices have significant "play" when trying to move the device from a point near the center.On very close measures, have a teammate moving the device from the end, near the twelve-foot.This will eliminate the play.
˙Mechanical˙Laser˙6 Foot˙T-Square˙Procedures˙LSD˙
The Laser is an electronic device that reads distance via laser and provides a reading in 100's.
˙Mechanical˙Laser˙6 Foot˙T-Square˙Procedures˙LSD˙
The six-foot is used to determine whether or not a rock is in the house.It is also used as a perimeter measure at the back of the house at the intersection of the center and backlines.Unlike the above device, it may be used during the end before all eight rocks have come to rest.There are only two reasons to use the six-foot measure during an end:
˙Mechanical˙Laser˙6 Foot˙T-Square˙Procedures˙LSD˙
The third measuring device is called the "90 degree" measure.It is an L shaped piece of metal use to determine if a rock is in play around the perimeter of the playing area.
˙Mechanical˙Laser˙6 Foot˙T-Square˙Procedures˙LSD˙
Measurements are needed when the teams can't agree by eye.A quick note about measuring rocks.The object of the game, of course, is to get closest to the tee, which is an exact spot where the center line intersects the tee line.Measurement by device actually measure s closest to the center of the hole that is drilled over the tee.In some cases, where the hole is drilled improperly, erroneous results could occur.In addition, the standard measure has a cone shaped tip that fits into any size hole.The Laser measure may have a smaller tip and may not fit slush into the hole.Always push the laser toward the rocks being measured.
If officials are not present, the vice skips are responsible for measuring rocks if necessary.The following is the correct procedure for measuring.Rocks are measured clockwise from the back of the house.This is the standard.
Too Close to Call?
If it cannot be determined by device or by eye, the end is considered blanked.Mechanical devices do not give an exact measure.Some interpretation of the dial value is necessary.It is also difficult to determine tie using mechanical device because it is not exact.Since the Laser measure, more ties are recorded since the numeric readout could be the exact same.
Measuring Two Rocks (standard championship procedure)
Measuring Three Rocks
In both situations it is acceptable to swing the device back to the first rock for a closer look.If rocks cannot be determined by device, a blank end will result.This is very rare.If the measure is very close, consider moving the mechanical sensor "away" from the rocks.This reduces friction between the sensor arm and the rough rock running surface.If the sensor arm cannot provide a reading, visually determine.
If two or more rocks are so close to the button that the device cannot be used, a decision must be made visually.Find an impartial person to do this for you.
Using the Laser Measure
Using the Six-Foot Measure
If, during a free guard zone measure, another rock is in the six-foot path, a decision must be made visually.
Using the T-Square
The T-Square helps determine perimeter rocks and can determine rocks in play.Since the rocks have an "overhang", the 90-degree angle helps sight the perimeter line by extending the sight downward.
Procedure:
Visually check the bottom of the device compared to the line.
˙Mechanical˙Laser˙6 Foot˙T-Square˙Procedures˙LSD˙
In championship play, where the Last Stone Draw (LSD) is used to determine hammer in most games, rocks are measured from the center of the rock.A tape measure or laser is used for the initial reading from the closest edge of the rock.Then, the radius of the rock is added to complete the distance measure.It may be necessary to measure two rocks that both cover the tee.At the highest level, it is common to cover the tee on more than one shot.The official in charge would take measurements from two spots, one on the tee line at the intersection of the four foot circle and the other on the center line at the intersection of the four foot.With these two numbers a mathematical formula can determine which rock's distance from the tee.
FIELD OF PLAY: ICE | MODERN | TIMING | MAINTENANCE | PERFORMANCE
CONTROLS | STANDARDS | SUMMARY | ASSESSMENT | ARENA | MEASURING
