props
"Reinforcing the Wood
All wooden propellers, with rare exceptions, are laminated. This has more to do with the efficiencies of cutting, drying, and milling of the materials than anything else. Additional strength could be obtained by using additional materials, like fabric and metal.
Many wooden propellers have fabric wrapped around the tips, or sometimes extending the length of much of the blade. Some early propellers even used animal hide, such as pigskin for this purpose. The wrapping improved the strength of the ends of the propeller, particularly to splitting. As testimony to the strength of oak mentioned above, it should be noted that many oak propellers do not have fabric tips, whereas almost all mahogany and walnut propellers do (at least as originally manufactured.) Most propellers that appear to have painted tips, on closer inspection will be found to have fabric beneath the paint.
Metal sheathing was added to some early propellers, but by 1913 there were so many fatal accidents in Europe from throwing off sheet metal that the whole practice of sheathing was nearly abandoned for some time. The need for sheathing, however, became apparent with propellers used by flying boats, so after carefully calculating and testing the methods for attaching the sheathing, the practice was re-instituted several years later. Copper, tin, and monel were all used along the tips and leading edges of many propellers. Typically, the sheathing was applied to the tips and held in place with either screws or through rivets, the exposed heads of which were then soldered and smoothed down. Sheathing has continued to be used in manufacturing of propellers to this day, although plastic and epoxy have replaced the traditional metal in most of them. "
Cool search. Interesting stuff.
James