Effect of Air Permeability of Ski Jumpsuit Fabric on Flight Distance

Abstract

Ski jumping is a sport which competes for the flight distance and flight form. Thereby jumpers attempt to fly as far as possible. In the regulations for ski jumping competition, the outstretched fabric must show the air permeability of a minimum of 40 L/m²/sec with the differential pressure of the pressure head 10 mm. However, the effect of the air permeability of ski jumping suits on aerodynamic characteristics has not been completely clarified yet. The purpose of this study is to investigate the effect of air permeability of jumpsuit fabrics on aerodynamic characteristics, and four types of fabric with different air permeability are examined from aerodynamic point of view. The wind tunnel experiments were carried out using the fabric clothed elliptical cylinder. The flight distance for each test cylinder was calculated with the aerodynamic force data assuming that the elliptic cylinder flies. The drag coefficient decreases with increasing the air permeability. The maximum lift coefficient indicates the highest value for no air permeability case among the all cases. However, the stall delay occurs for high air permeability cases, and the lift to drag ratio at the high angle of attack can be improved. It was presumed that the flight distance can be extended by adjusting the air permeability of ski jumping suits.