Internal Stiffeners Research Articles

The Stress Analysis of Simplified Structures

THE first practical application of a simplified form of aircraft structure was made by the Republic Aircraft Corp. in their production of the Seabee. This machine dispensed with conventional ribs and used external chordwise corrugations instead. These were found to be perfectly satisfactory; they resisted the air loading and were stiff enough to prevent undue distortion of the cross‐section of the structure. For machines of higher speed, however, these corrugations, or ‘beads’ as they were called, would be objectionable and would have to be replaced by internal stiffeners fixed to the skin. This is the type of structure it is now proposed to analyse—a general view is shown in FIG. 1.

Month in the Patent Office

A hollow air screw built up from sheet metal bent along a leading edge and joined along a trailing edge and having no internal stiffeners has a root end piece which is pivotally connected to the boss, whilst the blade is formed widest at the root tapering more or less uniformly to the tip. The sheet metal blade 2 is of aerofoil section and riveted or otherwise secured along the trailing edge. A channel‐sectioned end piece 9 is secured and riveted to the base of the root and bolted thereto is a hinge piece 13, drilled to take a bolt 14 for connection with lugs 15 on the boss 8. The single pin joint may be replaced by a double pin forming universal joint.