Our Company has been making wooden helicopter blades of different types since 1937 I want to tell you something of their materials and manufacture and would welcome questions in the course of my talk

Fig 1 shows a cross-section of the big Cierva blade as used on the W 11 This is monocoque construction Notice the centre of gravity of the blade and the incidence of the tip superimposed on that at its widest section

The main spar is built up at one-inch thick blocks of compressed wood laminated of 1/32 inch Canadian birch veneers bonded with resin film and pressed to about 2,000 lbs per square inch at 300°F The density is about 1 2

As a matter of interest, by laminated wood we mean that the grain in all the laminations runs parallel, whereas in plywood the grain of adjoining laminations is at right angles