Blue Hone Granite , Puffins, and Ice Pebbles, The Strange and Fascinating Science of CurlingMore than you ever wanted to know about Curling
I wanted to put together a science post about the Winter Olympics that are coming up in Sochi next month and came across an interesting article in this month's Scientific American on From Scottish Magma to Sochi Ice: The Geologic History of Curling Stones
, Why granite from a Scottish island makes the best curling stoneshttp://www.scientificamerican.com/article/from-scottish-magma-to-sochi-ice/
I got a lost in research and had a dozen of tabs open, so here it is.
Curling, that newish member of the Winter Olympics (since 1998) is actually one of the oldest winter sports. Curling is a sport in which players slide stones across a sheet of ice towards a target area, which is segmented into four concentric rings. It is related to bowls, boule and shuffleboard. Two teams, each of four players, take turns sliding heavy, polished granite stones, also called "rocks", across the ice curling sheet towards the house, a circular target marked on the ice. Each team has eight stones. The purpose is to accumulate the highest score for a game; points are scored for the stones resting closest to the centre of the house at the conclusion of each end, which is completed when both teams have thrown all of their stones. A game may consist of ten or eight ends.
WIKI CurlingCurling is thought to have been invented in medieval Scotland, with the first written reference to a contest using stones on ice coming from the records of Paisley Abbey, Renfrewshire, in February 1541
The best stones for Curling, and the official olympic stones, all come from a island off the coast of Scotland, called Ailsa Craig. The 220-acre island, about 10 miles from mainland Scotland, is the source of two varieties of granite used in elite curling stones. Blue hone granite makes up the layer that glides down the ice, and common green granite makes up the middle layer, or striking band. “The layer of rock that runs along the ice doesn't chip or absorb water, but most important, it's very predictable on ice—you know what your shots are going to do,” Brown says. “And the middle layer doesn't break when the stones collide.”
(SciAm above.)The stones' performance traces back to the island's formation about 60 million years ago. Ailsa Craig is a volcanic intrusion—a mass of magma that forced its way up between existing formations—explains John Faithfull, a geologist at the University of Glasgow. The magma then cooled relatively quickly to form granite, and the surrounding rock eroded away, “leaving just the very resistant hard mass of Ailsa Craig poking up out of the water,” Faithfull says.
SCIAMAs the volcanic rock crystallized, it developed a strong, uniform surface. “When magma cools quickly, it creates very small crystals. These ones interlocked, and chemical bonds developed between them,” says Martin Gillespie, a geologist at the British Geological Survey. “It also doesn't seem to have any microcracks,” he says of the granite.
These rocks are quarried, and then formed into the round squashed globe that you see below. The rock is actually made of two type of the famous granite of Ailsa Craig (AC); the largest portion is the AC green granite, the bottom piece that slides on the ice is the AC Blue Hone granite. The How It's Made Video on the sciencekids.co
website below shows the entire process of making curling stones; from cutting the big boulders with a huge diamond cable saw to polishing the stone on a lathe. http://www.sciencekids.co.nz/videos/sports/curlingstones.htmlThe Island of Ailsa Craig
The island of Ailsa Craig has its own interesting history, at one time it was going to be the headquarters of the fleet of the Spanish armada as they took Scotland for Spain. Pirates also operated off of Ailsa Craig for a time, and it was home to a prison in the 19th and 19th century. There is an automated lighthouse on the island; the original lighthouse was featured extensively in Peter Hill's book Stargazing: Memoirs of a Young Lighthouse KeeperThough quarry blasting is no longer allowed, loose granite rock from the island has been recently used for manufacture into curling stones by the Kays of Scotland company. The island is now a bird sanctuary, leased by the Royal Society for the Protection of Birds (RSPB) until 2050. Huge numbers of gannets nest here and, following a pioneering technique to eradicate the island's imported population of rats, a growing number of puffins are choosing to return to the Craig from nearby Glunimore and Sheep Islands.
WIKI (Ailsa Craig)
The island of Ailsa Craig has, strangely, been for sale for a number of years and has just now been sold. This article from the Guardian discusses the sale and more of the history of the island. A nature conservation trust will this week buy a famous Scottish island, in a move that would secure the future of one of Europe's most important bird colonies.Ailsa Craig, a volcanic island immortalised in the memory of a million childhood holidays, climbs out of the Firth of Clyde 10 miles off the Ayrshire coast. For the last two years, its future has been uncertain since it was put up for sale for £2.5m by the Marquess of Ailsa.The island is home to Europe's biggest gannet colony and an increasingly significant number of puffins. Its blue hone granite is considered ideal for the manufacture of curling stones, two-thirds of which are made from it.http://www.theguardian.com/uk-news/2013/dec/07/ailsa-craig-gannets-puffins-clydePhysics of the Curl
Scientist have been studying the possible reasons that the stones curl as they travel down the ice, and only last year have definitive results been announced by researchers at Uppsala University in Sweden; Harald Nyberg, Sara Alfredsson, Sture Hogmark and Staffan Jacobson.If the player gives the stone a clockwise rotation as it is released, it curls to the right, while an anti clockwise rotating stone will curl to the left. The stone is heavy, almost 20 kg, and the rotation is very slow, typically 2-3 rotations during the roughly 25 seconds it takes to slide to the target. This is much too slow to cause the curved path taken by the ball in sports such as table tennis, tennis or soccer.
They describe in their article that the curved path is due to the microscopic roughness of the stone producing microscopic scratches in the ice sheet. As the stone slides over the ice the roughness on its leading half will produce small scratches in the ice. The rotation of the stone will give the scratches a slight deviation from the sliding direction. When the rough protrusions on the trailing half shortly pass the same area, they will cross the scratches from the front in a small angle. When crossing these scratches they will have a tendency to follow them. It is this scratch-guiding or track steering mechanism that generate the sideway force necessary to cause the curl.The importance of having a proper roughness of the sliding surface on the stone to give it he expected trajectory, is since long known among curlers. However, this has not previously been coupled to the steering mechanism.
Read more at: http://phys.org/news/2013-05-mechanism-stone-revealed.html#jCpThe asymmetrical friction mechanism that puts the curl in the curling stone
Scientists now know what curling experts had already known: it was that special Blue Hone granite stone from the island of Ailsa Craig that had the special roughness that caused the curl, and the green granite had the toughness to withstand the impacts, and not chip.
But what about the ice? Well, it has a special finish, too. First, the ice is scraped down with a battery powered scraper, like this one from Canada Curling stone company. You walk behind this scraper. Canada Curling Stone Co. is excited to become the newest distributor for “The BOSS” Ice Scraper.Designed with the ice technician in mind, “The BOSS” has a considerably longer run time than the competition enabling you to handle more sheets with ease. A state of the art 3 stage charging system which ensures long battery life The blade is lifted and swung with 24 volt linear actuators all controlled with a push of a button from the rear of the machine http://www.canadacurlingstone.on.ca/boss.php
After the ice is scraped, it is sprinkled with water, the drops of which form pebbles that are just the right size for the curling effect to work. You can see the pebbles in the image below. You usually do this with a tank that is worn on the back and a spray with very special pebble spray heads. Each spray head has exactly 65 holes and each hole is the same size. You can buy a set of these brass tournament nozzles for $260. They also come in 52 hole styles. Remember this is just the nozzle for the spray head to give the ice that exact pebbling that it needs for the rock to curl.
High dome style 65 hole competition pebble head set includes #70, 72, 74, 76, 77.http://www.canadacurlingstone.on.ca/catalogue.php?c=1
The other aspects of the physics have also been studied. CNN has an article on the science of Curling discussing the study of using the broomstick to help change the curl of the rock.http://edition.cnn.com/2013/10/28/sport/science-friction-curling-feature/John Bradley was brought in by the Scottish Institute of Sport in the wake of Britain's success at the Salt Lake City Olympics in 2002, when Scottish housewife Rhona Martin captained her team to gold.Bradley looked at two major aspects. One was the physical demands of the game bearing in mind teams can be competing on the ice for 25 to 35 hours in the Olympics en route to a podium position.But, from a scientific sense, the other area -- the area of sweeping -- is more interesting when it comes down to the pure workings of the sport.Using what is known as a Sweepergometer, which is effectively a normal curling broom with all manner of wires attached to it to measure movements of the sweeping strokes on the ice, Bradley sought to uncover what difference sweepers made to the direction of the stone.Explaining the basis to the research, he said: "Curling is the only sport where you can do something with the projectile to affect its trajectory once you get rid of it.
_"You can extend the path of the stone by half a meter in a straight line -- and that's quite a difference in a sport of fractions and centimeters in deciding matches despite it being a 30 meter rink."He added: "It's been a case of is it better to sweep faster or sweep harder? We found it's better to sweep harder at certain points and sweep faster at others. Also, if you brush an area of ice more then you'll obviously get a much greater transfer of heat."http://edition.cnn.com/2013/10/28/sport/science-friction-curling-feature/Curling Equipment
If you wish to buy a set of curling stones from the island of Ailsa Craig, Kays of Scotland is where the Olympics got all of theirs. Ailsa Craig Common Green Granite curling stones are the bespoke choice for your curling club or association.Manufactured to the highest possible quality to provide years of reliable and consistent performance.All stones feature 2 new Ailsa Craig Blue Hone Ailserts, one on each side of the stone including the Olympic Specification 8mm cups.http://www.kaysofscotland.co.uk/new-curling-stones.php
Why curling stones are made on Ailsa Craighttp://www.pjonline.com/blog_entry/why_curling_stones_are_made_on_ailsa_craig
World Curling Orghttp://www.worldcurling.org/from-island-to-ice-a-journey-of-curling-stonesNot just any rock: curling stones' special granite comes from Scotlandhttp://vorige.nrc.nl/international/Features/article2485285.ece
Lastly I will leave you with this quote from a book Essay on Curling, and Artificial Pond Making
by J. Cairni, written in 1833. Curling although very different in the mass of materiel bears more resemblance to the game of Billiards than any other of our out door sports and when we consider the impetus and execution done by a piece of polished granite weighing from 30 to 60 pounds at a distance of from 40 to 50 yards and that too almost with the precision of a well struck billiard ball is it to be wondered at that this amusement should be year after year increasing and that parish after parish is seen following up this the best and perhaps most manly of all games with which we are acquainted and vying with each other which shall carry off the palm of victory. http://books.google.com/books?hl=en&lr=&id=WgUN9a7bMpkC&oi=fnd&pg=PA1&dq=Ailsa+Craig+Blue+Hone+granite&ots=-V4IvM_qJe&sig=cHz6MpNsbE04Io3GtV0cyjanY2c#v=onepage&q&f=false
Image: Curling stones on rink with visible pebble. commons.wikimedia.org