Sailwing windmill characteristics and related topics. Quarterly progress report (4th), 1 Oct-31 Dec 74

The method of experimentally determining the performance of large scale windmill models mounted on a moving vehicle is discussed. As a result of the wind tunnel experiments, analysis, and the large scale vehicle work, an optimization of a particular rotor is described, as are the results of blade twist experiments as a method of RPM control. Because the wind tunnel models were necessarily small scale, rigid rotor blades were used; however, the large scale rotors tested and reported upon were of the Princeton Sailwing type. By means of dimensional analysis and by experiments, the significant tension coefficient for the trailing edge cable of the Sailwing rotor was determined and evaluated. This tension coefficient enables the design of such a rotor to be such that the luffing threshold can be avoided for any given set of conditions.