Abstract.Complete description of all forces acting on a flying Beach Volleyball was made based on measurements in the wind tunnel. Forces (drag, lift and side force) were measured for different angle of attack  which varies from 0° to 47°. Velocity region was from 10 to 25 m/s and revolution region was from 0 to 12.5 rps. Moments (Roll, Yaw, Pitch) were detected. Results are described by means of non-dimensional numbers, such as Reynolds number Re, spin s, drag CD, lift CL and side force CS coefficients. Differences in results of CD, CL and CS were detected for various angle  and are further described in the article. Conclusions of the investigation can be utilized 1 st by ball producers for practical use in development, 2 nd for sport Methodist to build more exact methodology for Beach Volleyball, 3 rd in basic and applied aerodynamic research.

The paper deals with results of measurements of forces acting on volleyball. Drag coefficients evaluated from measurements in two aerodynamic tunnels are compared. The other force components i.e. lift and side force obtained by experimental investigation with angle of attack related to the axis of rotation are studied.

Main investigations are focused to measurements of all forces and moments acting on the rotating volleyball, such as drag FD, lift FL, side force FS, moment of roll MX, pitch MY and yaw MZ. Based on previous first results roughness of surface is an important quantity to study. Description of measurement of surface roughness of volleyball is presented in the article. Devices used in the measurement are noted. Results of the measurement are discussed and meaning of the results for aerodynamic forces acting on volleyball is taken in consideration.

Measurements of forces acting on a flying volleyball were done. One conclusion, which was made is, that rotation n = 8.75 rps is the breaking point in the course of the lift coefficient C L vs. revolutions n. In the measurements were used just 4 dynamometers, 2 for lift force F L and 2 for drag F D . In first part of measuring it is not considered, that any influence of torque is acting on the volleyball. Non dimensional numbers -Reynolds number Re, spin s, drag C D and lift C L coefficient are described in the article. A proposal of a new experimental set-up has been prepared. All three forces and three torque components will be observed, resulting in a whole description of force effects acting on volleyball.