INTRODUCTION: The height of the flying curve can be affected by a number of factors, including the ski jumpers' equipment. In recent years, permitted jump suit sizes changed frequently (from + 6cm in the 2012/2013 season, to + 2cm in the 2012/2013 season, and + 4cm in the 2014/2015 season). Ski jumpers raised the issue of smaller jump suits, claiming that as a result of poorer aerodynamic efficiency, these suits negatively affected their flying sensations and increased the risk of falls during landing, as particularly evident in the long jumps past the hill size point. The aim of this paper is to determine the correlation between the height of the flying curve and the length of the jump at World Cup Finals in the seasons of 2008/2009 and 2012/2013, and at the 2010 Planica Ski Flying World Championship. METHODS: The heights of the flying curves were determined by means of a kinematic analysis of flights made at the HS215m hill at the Planica Ski Flying Competition. Ski jumpers were recorded in flight with a camera placed perpendicular to the direction of flying (distance approx. 30m) at the expected average flight height above the profile of the out-run (4.5m) and at a distance of 112m from the take-off. For each ski jumper, the height of the flying curve was measured from the difference between the hip joint axis and the reference point for the expected average flight height. Reference data were used to calculate the aerodynamic index of the flight. Variable data, e.g. flight length, in-run speed, wind speed, and direction, were based on the official FIS records. RESULTS: In Planica, the average height of the flying curve rose considerably in the 2012/13 season, when the allowed jump suit size was lowered to + 2cm (Figure 1). The correlation coefficients between the flight variables and jump lengths in the season of 2012/13 were significant (r = .34 - 0.72) DISCUSSION & CONCLUSION: The results showed that the reduction in the size of jump suits (+ 2cm in 2012/2013) had a considerable effect on the increase of the average height of flights on the Planica hill. This led to an increase in the incidence angles in the second part of the flight and the angles at the point of landing and, as a result, intensified the pressure forces exerted on the jumper upon contact with the surface. There were very few extremely long flights past the 225m mark. In the longest-ever jump in Planica, Anders Bardal of Norway grazed the snow on landing at 231m, in favorable winter conditions. The height of the flying curve in the central part of the flight was constantly in statistically significant correlation with the jump length, although its relevance changed and was lowest at afternoon time. The reduction in the size of jump suits to + 2cm, introduced in the season of 2012/2013 led to a considerable increase in the height of the flying curve on the Planica hill, in particular in the afternoon time when the conditions for flying on the Planica hill are much worse. --- The hosting University of Jyväskylä is planning to publish conference proceedings "Science and Nordic Skiing III". In case you are interested in this publication please contact the editors (Anni Hakkarainen anni.s.j.hakkarainen@jyu.fi) to become registered for the book.
© Copyright 2015 3rd International Congress on Science and Nordic Skiing - ICSNS 2015. 5-8 June 2015, Vuokatti, Finland. Veröffentlicht von University of Jyväskylä; University of Salzburg. Alle Rechte vorbehalten.