Fig. 25.—T section fuselage strut.
In the general features of those struts associated with the construction of the fuselage and nacelle, there is very little diversity of practice, the majority of constructors favouring a square spruce strut, [Fig. 24], channelled out for lightness. A defect with this type of strut is the tendency, engendered by irregularities in the fittings and wiring, to buckle laterally, although this can be obviated by the provision of a strut of larger section at the centre and diminishing in width to the ends. A strut not nearly so popular but nevertheless in use is that indicated by [Fig. 25], consisting of spruce spindled to a T section the web being of considerable width at the centre. It would seem that the piece of wood necessary to obtain such a strut is out of proportion to its actual finished dimensions, and from the standpoint of economy in both labour and material is not justified. The circular turned and tapered strut noticeable on a number of machines disposes the material in probably the best manner for the conditions applicable to this component, although it necessitates the provision of tubular ferrules in the fuselage clip. On one modern machine the fuselage struts are circular, but of hollow section, built up of two pieces glued together. An obsolescent method is that in which the strut is shaped to something approaching a streamline section, as the fact that all aeroplane bodies are now fabric covered renders it unnecessary.
CHAPTER IV.
PLANE CONSTRUCTION.
Of the various components which comprise the complete machine, the wings, aerofoils, or planes, as these items are variously designated, may be said to contribute the greater part of the ultimate success of the complete machine. The aerodynamical properties of a wing are now fairly well determined, and have been the subject of a great number of experiments, resulting in the clearing away of many hazy ideas and notions, so that the actual design of the wing section for machines of given purpose is almost standardized. From this it might be deduced that the methods of construction were equally well determined, and although absolute uniformity of practice does not exist, the wing construction of most machines is similar, as far as the main assembly is concerned.
Effects of Standardization.
Incidentally, one may point out the detrimental effects of undue standardization as applied to an industry in its preliminary stages. These effects are well exemplified by certain machines, in which standardization has been studied to an almost meticulous extent, with the logical result that their performance is considerably inferior to that of other machines of contemporary design, but in which desirable improvements are incorporated as they occur. Although at present one cannot give actual figures, the average performance of modern British aircraft in range of speeds, rate and extent of climb is superior to the products of any other country, and one certainly cannot cite the construction of the average British machine as an example of standardization. Seeing that, as a typical instance, wing sections are frequently altered in minor detail, the impracticability of standardization is apparent, for this would entail, to a firm wishing to keep pace with developments, a considerable loss, through scrapping of jigs, etc., consequent upon the new design. When the principles of aeroplane design are as well defined as those pertaining to internal combustion engines, one may expect the various manufacturers to produce one type of machine per year, and the various improvements adduced from the year’s experience would be incorporated in the type of the succeeding year.
Fig. 26.—Plan view of wing assembly.
However, leaving the realms of vaticination for the more prosaic subject of wing construction, it will be realized that the process of producing the full-sized wing, accurately conforming to the measurements, etc., deduced from experiment, and so constructed that the chief characteristic of the section will permanently remain, is of importance. As one or two of the spar sections in use were dealt with in the first chapter, it will be unnecessary again to consider them in detail.
[Fig. 26] shows diagrammatically the plan view of a wing assembly typical of modern practice, so far as the disposition of the various components is concerned.