These materials replaced aluminum and steel metals in blade construction, which allowed the blades to be made thinner and stronger.[11] Computer-aided design was also useful in refining blade characteristics. Since the blades bend and deflect with higher power loading and centrifugal force, the initial designs needed to be based on the in-motion shape. With the help of computers, the blade designers would then work backward to find the optimal unloaded shape for manufacturing purposes.[12]