Because of the complicated analysis of the blade, the problem is discretized. The blade is divided into 15 discrete panels (I am not sure if the term ``element'' is appropriate for this). Values such as geometry, resultant force, and ply layup can vary from panel to panel, but are assumed constant within the panels.
The panels are of constant length; each is 1/16 the rotor's radius. (The rotor hub occupies the inner sixteenth of the radius.) The inner three panels have a thickness of 28% of the chord; the next four panels are 18% thick; the next four are 12% thick; and the outer four are 9% thick. All panels have a chord of 20.5 inches.