STONES OPEN FORUM Aberdeen

© World Curling Federation2 | STONES 4A= 64+2stones WCF 24001? to WCF 24066? 4B= 64+2 stones WCF 24101? to WCF 24166? 5A= 80+2 stones WCF 25001A to WCF 25082A 5B= 80+2 stones WCF 25101? to WCF 25182? 6A= 96+2 stones WCF 26001? to WCF 26098? New WCF stone consignments (384 stones + 10 spares) All these stones have been printed and measured and the differences in measurements demand adjustments to the running bands

© World Curling Federation3 | STONES running band inside diameter running band width running band area weight 80+2 stones New stone consignment 5A 4.5mm (120.6 to 125.1) 1.96mm (5.36 to 7.32) 8.46cm2 (21.54 to 30.00) 0.44kg (18.35 to 18.79) 1.4mm (122.4 to 123.8) 0.15mm (5.53 to 5.68) 0.62cm2 (22.35 to 23.00) 0.22kg (18.20 to 18.42) Important measurements for good stone quality Old stone numbers were WCF 30xx, 32xx and 35xx (Blue Hone inserts) New stone numbers are WCF to Old consignment New consignment Differences in: The “real” running band and the roughness are not yet possible to measure in a safe way

© World Curling Federation4 | R&D STONES Today

© World Curling Federation5 | R&D STONES

© World Curling Federation6 | R&D STONES Leif Öhman Tomorrow (today)

© World Curling Federation7 | Ny curlingsten Uppsala R&D STONES Leif Öhman

© World Curling Federation8 | R&D STONES Leif Öhman Running band roughness

© World Curling Federation9 | R&D STONES Testing roughness meter

© World Curling Federation10 | R&D STONES Stone standing on hard surface (maybe hard ice) Leif Öhman

© World Curling Federation11 | R&D STONES Stone standing on softer surface (maybe soft ice) Leif Öhman

© World Curling Federation12 | R&D STONE Stone standing on even softer surface Leif Öhman

© World Curling Federation13 | Leif Öhman R&D STONES Stone standing on very soft surface Similar result as using rolling pin, but is this the stone surface towards the ice?

© World Curling Federation14 | R&D STONES We need to develop a method to compare running bands and how they stands on ice We also need to find a method to measure the surface structure (scratches) When we know that we don’t need to match stones on ice any more The knowledge about the different parts involved is not sufficient yet Leif Öhman

© World Curling Federation15 | STONES Matching stones

© World Curling Federation16 | STONES Stone thrower 8 stones (example) To throw stones on ice is still the best matching method

© World Curling Federation17 | R&D STONES Other matching methods possible, but not developed –Camera to see the stone movement (X;Y) –Using total station to see the movement in x;y direction –Measure the speed in two positions and calculate the friction coefficient to match the speed

© World Curling Federation18 | Using cameras for matching the curling stones R&D a camera method

© World Curling Federation19 | Camera R&D a camera method

© World Curling Federation20 | R&D a camera method Automatic stone tracking Records the position of the stones in the image Translates to real world coordinates (X;Y) Camera

© World Curling Federation21 | (x,y) R&D a camera method

© World Curling Federation22 | Fitted according to eq(7)+eq(13) Good precision Far away, precision 3 cm Estimated lambda = 2.49

© World Curling Federation23 | R&D automatic total station Automatically measuring the stone movement with total station

© World Curling Federation24 | R&D Automatic total station Result of the measuring

© World Curling Federation25 | STONES Rubbing the running band? Greenacres Curling Rink has played more than 3000 games with their stones and the movement is still 4 feet and 24 seconds without rubbing “Crystal Ice” for high level competitions demands special running band rubbing Should normal club stones be rubbed?

© World Curling Federation26 | R&D STONES What happens in the long term when rubbing the stones? A scratch in Granite A scratch in Calcite

© World Curling Federation27 | Hair A hair is approx. 50 um thick = ggr thicker than the water film On the top of all ice crystals there is an extreme thin water-like film As colder as thinner Ice Crystal Thin watery film app. 0,002-0,1 um R&D ICE This gives wet friction

© World Curling Federation28 | R&D ICE Wet friction is a prerequisite to have a curling stone to curl. But why will a curling stone curl?

© World Curling Federation29 | R&D ICE On wet friction surfaces the friction coefficient changes with the speed and the temperature

© World Curling Federation30 | Stone speed Curl Stone curl Stone speed R&D STONE CURL

© World Curling Federation31 | Resulting Stone Speed Curl Stone curl R&D STONE CURL Resulting Stone Speed Stone curl