It is a very great honour indeed to find myself addressing the Royal Aeronautical Society. If, as I am often told, “a little learning is a dangerous thing” then you are in for a very dangerous address. For much as I would like to say that I know nothing about aviation it would not be altogether true. My knowledge is of the picked-up rather than the learned variety. During the war I was either at the receiving end of enemy aviation or under a friendly and comforting umbrella, which counts as passive experience. I started flying as a passenger in about 1935, and in common with many others 1 have put up with all the frustrations and delays of airline travel, particularly getting to and from the airfields—this I put down to semi–active experience! The active part of my experience began two short years ago when I started to learn to fly.

From this you will gather that any views I express this evening must be treated with caution if nothing else.

When men of the first Elizabethan era looked to the Arctic, they dreamed of a North–West Passage over the sea to enable them to reach by a short cut the fabulous riches of the Far East. Between 1576 and 1578, Martin Frobisher doggedly took three expeditions beyond Greenland to explore what he thought was an open channel but which in reality is the bay of Baffin Land and today bears his name—as tribute to a great pioneer. Others to take unsuccessful expeditions North were Davis, Baffin and Hudson, and their names too have been immortalised in the geography of the Arctic. These men had to contend not only with the severity of the elements and with inadequate equipment in their frail sailing craft; mutiny at sea was prevalent in those days. Thus in the huge bay which now bears his name, Hudson with eight of his companions was put ashore by a mutinous crew and abandoned to his fate. Not until 1847 came Sir John Franklin's triumph in which he and his expedition perished after the moment of discovery, his two ships Erebus and Terror being crushed in the ice.

In this paper a theory of wrinkling in Sandwich Construction is presented in two parts. In the first part, the thickness of the core is regarded as finite. The wrinkling stress is given by a simple square root formula consisting of the Young's moduli of the materials and the ratio of the thickness of the face and core. In the second part of the theory the same procedure is followed, with the main difference that shearing stresses in the core are also considered, and the analysis is extended to the case where the face is supported by a sufficiently thick or a semi-infinite medium. The result for the wrinkling stress is a cubic root formula which consists of the moduli of the materials but indirectly depends upon the geometry of the structure; this formula is valid only if the ratio of the thickness of the core and the face is greater than or at least equal to the ratio of the width of the marginal zone of distortions in the core, and the thickness of the face. The width of the zone is also useful as the criterion which discriminates between the two cases of buckling as envisaged in this paper. The theory is compared with the previous works, and also with the test results already available. The selection of the experimental data comprises steel, aluminium alloy and Papreg (laminated paper plastic) as the face; and onazote, cellular cellulose acetate, granulated cork, sponge rubber and expanded formvar as the core materials over a wide range of core-face thickness ratio. The agreement between the theory and the tests is satisfactory.

It would be possible to write a paper conforming, literally, to the above title in very few words by simply describing the behaviour of the crescent wing in various circumstances. Such treatment, however, would avoid what is really the prime question of all, namely, why is the crescent wing used? What is the attraction of this layout? The answer to that question is performance. One essential characteristic of the crescent wing is thus its performance characteristic.

Therefore, in this paper, the matter will be introduced from a performance angle and an attempt will be made to show, in general terms, why there should be a performance gain from the crescent layout. Having established the case, the aerodynamic and aeroelastic characteristics will be considered in some detail so that, with these properties explained, the way will be clear to consider a performance comparison in greater detail and thus gain a fuller appreciation of the situation.

Attention is confined to civil aviation and the present scope of investigating procedures is outlined on a world-wide basis. Deficiencies in these procedures are noted and some suggestions are made for possible future developments of technique. In particular it is suggested that there can be little progress in air safety without the assimilation of “ human engineering data” by investigators and the Industry alike. Opinions expressed are entirely personal to the author and are not associated in any way with the official views of The British Aviation Insurance Co. Ltd.

This note gives the stress distribution in an infinite wedge subject to a general polynomial law of loading along either edge. The method used is that of Complex Potentials, the results of which may be summarised as follows:—

The stress combinations and and the complex displacement are given in terms of two complex potentials Ω(z) and ω(z) by the relations

1

2

3

body forces being assumed absent and pq denoting the stress intensity across a face perpendicular to p and resolved in the direction q, for a body in a state of generalised plane stress, µ is Lamé's constant and k is related to the modified Poisson's ratio σ, by the equation:

.

Although this problem is one which has been investigated by many photoelasticians, there appears to be no record of any systematic exploration of the effect upon the stress distribution of the ratio of hole–diameter to width of bar.

In this investigation tests were made upon a standard sized bar with four different sizes of holes, and the stress distribution on the cross section of the bar through the hole centre was explored for the four cases.