I aim to answer the question "How does the spill angle of an overshot waterwheel affect its efficiency?" in an essay. I plan on conducting experiments to help show the relation between the spill angle and the efficiency. I am still trying to figure out some experiments for that, but I believe that once I have a firm grasp of the derivation it may help me. Can anyone help explain the derivation of an overshot waterwheel? or can anyone help me with the experiments?