A low wind, lightweight horizontal axis wind generator with two adjustable rotor assemblies that include at least one set of lightweight blades that can be manually or automatically unfurled or furled in low, moderate and high winds. In one embodiment, each blade has an airfoil shape in cross-sectional with a rounded leading edge and a thin tailing edge. In a second embodiment, each blade is sail shaped made of one thin cover or panel that assumes a concave cup-like configuration in the wind. In both embodiments, the blade are made of lightweight flexible material supported by an inner frame. In one embodiment, the cover moves longitudinally over the inner frame. In the second embodiment, the cover moves laterally over the inner frame. The unfurling and furl of the blades are controlled by a voltage sensor that constantly measures the voltage output of the generator and/or by wind sensors.