Advanced textbooks of strength of materials dealing with the shear centre give examples of the simplest sections only (e.g., Ref. 1, Art. 8). Numerous articles in the technical press are devoted to the subject, and the method to find the shear centre of any open section is now well established (Ref. 2). However, the number of readily usable solutions for sections common in practice, is small. Consideration in this paper is given to a more complicated section, fairly common in practice, and a formulae is derived for the location of its shear centre. The section is a lipped channel, symmetrical about one axis, and the paper is followed by a diagram that enables the shear centre position for various ratios of lip to leg and leg to web to be read off.

Airscrew blade stresses caused by periodic displacement of the airscrew shaft and the possibility of their elimination by elastic connection of motor and airscrew. are investigated.

The theory of the flow past cascades or infinite series of aerofoils, regularly spaced, is of importance in connection with the design of turbo-blower blades, interference between propeller blade root sections, wind tunnel circuit design and kindred problems. The usual development of the theory involves some rather advanced applications of conformal representation which it is rather difficult to translate into numerical terms, and no general solution for an arbitrary form of aerofoil section is available.