Sit-ski designed to achieve the paralympian dream

With the global buzz just dying down after the Winter Olympics, it is now the turn of the Paralympians to take centre stage in Beijing. From 4-13 March athletes from around the globe will compete for their sport’s greatest prizes – and the competition will be tough.

At the recent World Championships in Lillehammer, Norway, the strength of athletes from Russia and Norway in the Nordic skiing disciplines was particularly strong. Trying to gain every possible advantage is therefore crucial if British athletes are to be competitive, and a team has been assembled behind these skiers to give them a technology boost.

The sub-divisions of Nordic skiing are cross-country skiing and biathlon. Gruelling events range from the 2.5km sprint to the 20km long distance in the cross-country, while the 7.5km biathlon (three laps of 2.5km) has the twist of the target shooting. “After every lap you shoot five targets and for every target you miss you have to do another 100m – adding distance and time onto your race,” explains athlete Scott Meenagh. “So, in biathlon you have to be a lot more tactical, preserve your energy, control your heartrate – but sometimes you need to gamble.”

Meenagh became the first GB representative in these events since the 1998 Paralympic Games in Nagano, Japan, and competes in the sitting category, the other categories being standing and visually impaired. Sitting competitors use a sit-ski, and it was the design of this that has been the subject of a project that combined the expertise of academia, industry and the athletes themselves.

“The bonding technology between athlete and equipment is not easy – there’s 50 per cent science and 50 per cent magic,” claims Meenagh. “You don’t want to sit in a sit-ski, you want to feel part of it, for it to be an extension of your body. It takes quite a long time to find that personal touch for each athlete.”

To achieve this, GB Snowsport – the national body for skiing and snowboarding – called on the expertise of the Williams Formula 1 team, who used the same process for creating a perfectly fitted seat as they use for Williams F1 drivers.

The carbon-fibre unit was made by project partner BAE Systems, with new materials and specialist tooling from Formaplex.

However, it was back in April 2019 when the first steps were made. There are four athletes involved in the Nordic ski squad – Meenagh is joined by Steve Thomas, Steve Arnold and Callum Deboys – and each athlete is a different shape. No one size will fit all. Paul Herriotts, professor of transport design at Coventry University, explains the role his institution played: “We had to get scan data to understand their bodies in some detail, because the interface between the lower body and the sit-ski is absolutely important to be optimised.”

The idea was to add scan data to portable pressure mapping to understand where the high- and low-pressure spots were for each athlete when using their original sit-skis. “Each of those is kind of a bad thing. We’re trying to even out the pressure to make this case more comfortable to start with, but then we’re trying to design the sit-ski to give our athletes the greatest chance of success.”

To do this requires additional biomechanical analysis, facilitated by using the sort of ball-laden suits used by the film industry to create animations. Pulling together all this information can reveal how the sit-ski design can allow the athletes to exert maximum force for a sustained period of time.

“By investigating quite visible changes in angles, the seat and the design of the seat, we get a result in different posture in the athletes,” says Herriotts. “We’ve come up with the finalised design that’s really going to suit them well.”

Aerodynamics also plays a role in the design. Although cross-country skiers will not reach the high speeds of the downhill skiers, there are downhill sections during which the competitors can reach speeds up to 45km/h for periods of several tens of seconds, so getting the marginal gains from being in an aerodynamic position really matters. Meenagh comments: “Our sport is about work/rest ratios, so during those long downhill periods you must get as much rest as you can, because as soon as it is over you are back to hard work. You want to get up to speed as quickly as possible and want that speed to carry on for as long as possible to optimise your efficiency and recovery.”

Central to the project was Williams Advanced Engineering (WAE), whose overall design of the sit-ski included the fin system that connects the seat to the skis. This is universal across all four rigs, with the seat being the customised part.

Ollie Guild, senior designer at WAE, believes that the real advances have been in identifying the optimal angle of sitting and the position on the skis, something that varies from person to person. However, the fin that provides that interface to the skis and a platform to position the seat on, was not originally designed with aerodynamics in mind. Guild says: “Their actual design came about through lightweighting and transfer of energy. We didn’t actually think that they would be going fast enough to have to factor in aerodynamics but when we did the CFD we found that this was a factor. Fortunately, our fin design was very aerodynamic.”

Meenagh, a former member of the armed forces in Afghanistan, adds: “The massive difference for me with this sit-ski is that it picks up speed quicker than my old rig, and it holds onto the speed that I’ve gained for a lot longer than a previous sit-ski would have done. I’m no engineer but I’m pretty sure aerodynamics has got something to do with that!”

The athletes have only had a few months to get used to their new equipment, and if they perform well in Beijing it will be a credit to their own efforts, but also to the contribution of the engineers back home.