Performance evaluation of a designed and fabricated vertical axis wind turbine (VAWT) are revealed in this work. Six different geometries of the VAWT rotors were designed and manufactured. These geometries are: two straight bladed (2HB) VAWT, three straight bladed (3HB) VAWT, Savonius rotor (SI), Savonius rotor (SII), Savonius rotor (SIII) and Savonius rotor (SIIII). The Blades are manufactured from beech wood using CNC machines then they subjected to different processes to improve its aerodynamic performance. Savonius blades are merged with the straight blades rotor to improve the self-starting ability of the VAWT. A fan of (0.8 m and 2000 rpm) is installed to blow air with the required speed ranged from (0-12 m/s) A conducting duct is designed and constructed to conduct the flow with reasonable uniformity. All geometries are tested under different operating condition to predict the performance of the designed VAWT. Number of blades (N), chord length (c), radius (R), and blade pitch angle (β), are studied to evaluate the performance of the VAWT. Double multiple stream tube methodology is used to study these parameters. To do so, a computer code written in Matlab is built. Results show that the performance is highly affected by the design parameters. Theoretical results are compared with the experimental data. A good agreement is obtained.