The initial buckling stresses of rectangular panels under applied axial loads are in general increased both by circumferential tensile stresses and by the curvature of the panel. The present Note gives theory to estimate these stresses for panels forming part of an unstiffened cylindrical shell. All edges are free to rotate. This condition is often closer to the actual rotational edge restraint of curved panels in conventional stressed-skin construction than the clamped condition, especially in the case of lightly-reinforced shells. The axial generators in the mid-plane of the panels are held straight at the longitudinal edges. All other axial generators are also assumed to remain straight before buckling (no “mattress effect”). The middle surface is restrained at the curved edges of the panel against radial deformation during and after buckling.

Design curves are presented for several values of the parameter (ab/Rt), followed by a typical example.