After cooking and steaming the bamboo blades, each rotor was loaded with buckets of water to simulate the thrust force generated by the airfoils during operation of the turbine. For a blade of one meter length (approximately 18 mm thick with a chord of 58 mm), the bamboo bent 2.5, 7, 9.5, 18.5, and 29 centimeters under a weight of 5, 10, 15, 20, and 25 kilograms respectively. Each blade is lovingly hand crafted by myself, so it is difficult to compare the cooked, steamed, and untreated bamboo since the thickness and chord of each blade can vary significantly.
The bamboo also doesn’t fully spring back (this is known as hysteresis or plastic deformation or some other term like that) once the weights are removed from the rotor. For the example listed above, after the 25 kg weight was removed, the blade was deformed 19.5 cm from its original position. On a positive note, the bamboo is able to hold a significant amount of weight, and the bamboo is also very flexible, which would allow it to furl during high wind speeds. However, one of the concerns is that if the blades were to furl, the turbine may never be as efficient as it was with brand new blades due to the permanent deformation.