Recruitment of curling pebbles during repeated passes of a curling stone

Engineering of Sport 15 - Proceedings from the 15th International Conference on the Engineering of Sport (ISEA 2024)

In the winter sport of curling, curling stones glide over carefully prepared ice. Water droplets are sprayed over the ice and most freeze into circular cones which are colloquially known as “pebbles”. Pebbles come in various sizes and heights and oftentimes before a competition they will be “nipped”. This means that a sharp edge will be dragged over the ice surface to truncate the conic pebbles. Once this is done, the ice is ready for curling. As curling stones repeatedly pass over the nipped pebbles, the pebbles slowly change. Ice is gradually shaved off the tops of the pebbles. This results in two distinct effects: the tops of the nipped pebbles increase in area, and as the tops get shaved, new (shorter) pebbles are “recruited” and become truncated cones themselves. This is important in curling because this gradually increasing surface area over which the stones glide is the primary source of increasing dynamic friction forces that the curling stones experience. As the pebbles change, so do the playing conditions. Characterizing these changes can help competitors as well as ice technicians. It may also help further the understanding of the physics driving the “curl” in curling. Prior to this study, the temporal changes in the nature of the pebbles had not been characterized in any detail.