This paper outlines the scope of the problems encountered in the design of thin wings and presents a simple method of determining the optimum proportions for minimum weight multispar box beams in pure bending. In the development, it is assumed that simultaneous failure of the skin in compression and the web in crushing of a concentric pin-connected multispar constitutes the basis for optimum structure in pure bending. Test results using formed channels with small bend radii indicate that these assumptions closely approximate the behavior and proportions of the optimum structure for straight thin wings.
The general nature of this paper excludes the effects of large bend radii formed channels, attachment size, spacing, and location, and combined loads. These effects are important and must be considered in final analysis.
The results are presented in the form of a design chart for 75S-T6 non-clad material. Similar charts may be constructed for other materials from the general equations and their stress-strain curves.