Skis are sold in pairs but serious competitors have fleets of skis at their disposal, carefully paired with just the right springiness or “camber” to suit specific snow conditions. Snow is a more complicated and variable material than ice, but for sliding purposes the basic principle is still the same: Skis work because when they compress the snow, they also melt it just enough to create a liquid layer that the ski glides over – more like a boat slipping over water than a piece of plastic scraping over something dry.
The key issue for a competitive skier is just how much water is being generated. If the snow is near the melting point to begin with, excess water can hold onto the ski, causing a kind of suction, which slows the skier down. To combat this, competitive skis are stone ground with a fine pattern of scratches on the bottom. The scratches, know as “structure,” help channel excess water away when the snow is wet. When the snow is colder and drier, the structure tends to be finer and shallower so that the ski is better optimized for generating and preserving the thin water film.
Ski wax is used to enhance the desired effect. Wax that is rich in fluorine is especially water repellant because of the electrochemical characteristics of fluorine atoms.
What to watch for in Sochi
Weather and snow conditions will have a significant impact on Nordic events in Sochi. As in Vancouver, the concern going in will be what happens if the weather is relatively warm and the snow very wet. Rapid changes in snow conditions are also possible given Sochi’s climate, so the best strategy for Nordic teams is to be ready for anything.
Skiers will have many pairs of skis ready to go and dozens may be tested before a race to see which works best. Canada is among the countries that has been sending skiers and coaches to Sochi ahead of time to scout the snow and get a better feel for how it changes with the weather.
Steel runners on sloped ice
How it works
If going head first down an ice-covered concrete chute seems like a challenge to self-preservation, it’s also a study in how a race can be won with the smallest of adjustments in pressure and timing. All three sledding sports — bobsled, luge and skeleton — depend on gravity to pull a sled down an ice track. Gravity provides the power, and the key to winning is to minimize energy loss through friction on the way down.
But not all the possible ways of reducing friction are allowed. Runners can’t be heated to to make them slide more easily by speeding up their ability to melt the ice beneath them and form a water. And because mass can help overcome friction on a slope, there is a weight limit — without it, the heaviest sledder might waddle away with the gold.
In the case of skeleton sleds, the rod-shaped runners are all made from the same officially approved brand of steel that is marked for identification. This ensures that the race does not become one of differently engineered materials with slightly different heat capacities and behaviour on ice. One place where sled designers have some latitude is in the shaping of a skeleton runner’s “spine”. This is formed at the back of each runner by machining out two grooves. The precise profile of the spine affects friction, particularly on the turns when g-forces are pressing the runners into the ice. A sledder can then make slight body movements to vary the pressure on the runners and steer the sled. Competitors choose which set of runners offer the best balance of speed and control based on ice conditions on the day of an event.
What to watch for in Sochi
Unlike Whistler’s notoriously fast track, where a Georgian luger was killed at the 2010 Games, the sledding track at Sochi has uphill sections built in. These are the places where it’s predicted that races will be lost, as sledders make split-second decisions to try to conserve momentum on those upward sloping areas. The track is refrigerated so sledding sports will not be as affected by weather as skiing could be but air temperature and sunlight will still have an impact on the sliding surface and, for skeleton sleds, influence the choice of runners.
Granite on pebbled ice
How it works
Unlike a hockey or skate rink, a curling “sheet” has a bumpy texture, rather like the skin of an orange. The texture is created by first scraping the ice flat and then sprinkling it with water. The sprinkler head determines the shape and distribution of the water drops, which form tiny hills as they land and freeze on contact with the ice.