FIFTY YEARS OF FLYING PROGRESS — LOENENG 215 



unsatisfactory as they were subject to tension variations under differ- 

 ent weather conditions, so doped linen or cotton was tried. Then ply- 

 wood entered the field, the beautiful Antoinette monoplane, built in 

 France, being an outstanding example of fine workmanship in the use 

 of this material. Whereas plywood was used for the covering of fuse- 

 lages, as introduced in the monocoque by Deperdussin in 1912, it was 

 not until toward the end of the First World War that Fokker pro- 

 duced cantilever wings of thick section with wooden beams and ply- 

 wood covering that took the torsional strains. This was a good deal 

 of an innovation in aircraft structure and pointed unerringly toward 

 the future, but at the time was not adopted very widely. 



These wooden cantilever plywood wings w^ere also subject to 

 weathering effects — drying out in the sun, and inability to stand too 

 much moisture — and the strength of the glued joints when subjected 

 to extensive weathering or vibration was questionable. The fore- 

 runner of things to come in aircraft structures was the Junkers all- 

 metal cantilever-wnng monoplane made in Germany around 1921 and 

 later adopted throughout the world. This was the death knell of the 

 wood-frame, wire-braced box kite of the Wrights and their contem- 

 poraries like Farman in Europe. But for a period of almost 20 years 

 the aircraft industry, at the insistence of their customers, continued to 

 build this unsatisfactory type of aircraft, thus delaying the process of 

 developing the Strato-Clipper of 1951 from the Junkers of 1921. 



The prejudice against aluminum in structural parts of aircraft was 

 very great in the early 1920's. The aluminum alloy Dural was rela- 

 tively new, and faith in its characteristic of having the strength of 

 steel for one-third of the weight was slow in taking hold. But grad- 

 ually it crept into more and more extended use until finally in the vast 

 production era of World War II, all-metal Dural riveted and welded 

 aircraft construction proved itself in the tool room, in the production 

 line, and in combat, so that it eventually became universal. This type 

 of construction is threatened today by the advent of magnesium, still 

 lighter than aluminum and with many other qualities in its favor ; by 

 several different kinds of glass and plastic resin materials that have 

 much to recommend them for aircraft structures; and finally by the 

 advent of that great new metal, titanium, which lias all the qualities 

 needed, but is too scarce for general use. There is no doubt that alloy 

 metals for aircraft will, from now on, be subjected to great improve- 

 ments and modifications, which might even include some mutation of 

 crystalline structures by virtue of atomic radiation or isotope appli- 

 cation. 



It is hoped that in the next two or three decades we may see as great 

 advancement in the development of light metals for aircraft con- 

 struction as has been achieved in the past 30 years. 



326511—55 15 



