to operate the turbine and further makes possible an unusually thin blade the blades of the preferred form of the invention are configured to have a uniform discharge velocity along the length of the blade this makes the blade length uncritical and makes possible the use of only a few basic blade patterns for all propeller sizes of from about ten inches in diameter to fifteen feet or more since the basic pattern need only be enlarged or trimmed to change its size changes in camber become unnecessary the achievement of a uniform discharge velocity involves both theoretical and empirical considerations the actual value of the discharge velocity depends on all the geometric proportions of the design and the rotational speed of the impeller at a constant rotational speed and a constant ratio of the propeller diameter to radius of blade curvature producing the camber the vertical discharge velocity u in any section along the radius of the blade is a function of the horizontal linear velocity v the angle of attack u03b1 and the angle of the trailing edge of the blade u03c6 however for a constant rotational speed the linear velocity v is directly proportional to the radial distance from the propeller centerline to the.