The feasibility of replacing currently widely used sandwich construction with helically stiffened construction for a Formula racing car structural shell is studied. The torsional deformation behavior of circular and square cross-section shells is analyzed as an approximation to the real car structure. Shells with different sandwich and helically stiffened configurations are analyzed with finite elements. For closed square and circular cross-section shells, the highest torsional stiffness is obtained with helical stiffening. For circular cross-section shells with the cockpit cutout and reinforcements usually present in real racing car structural shells, ±4S' helically stiffened shells are 200% stiffer in torsion than sandwich shells. For square cross-section shells, the torsional stiffness improvement obtained with the helical stiffening is only 27%. The cross-sectional shape of the shell, cockpit opening, and different type of reinforcements (present in a real car structure) affects the selection of the best stiffening for torsional stiffness. The role of the terms of the stiffness matrix of the helically stiffened configuration in the torsional behavior of the shells is studied. The 0/90 waffle stiffening is more efficient than the helical stiffening for the square cross-section shells with the cutout and reinforcements. In the case of circular cross-section shells, the 0/90 waffle stiffening yields approximately the same results than the helical stiffening. The skin-stiffener configuration for maximum torsional stiffness depends on the crosssectional shape of the shell. The advantages of the ±45° helical stiffening over the sandwich construction depend on the cross-sectional shape of the shell and on the way the cutout region is reinforced. / Master of Science