FOREST RESKARCII AND THE WAR 2G5 



anything in safety. On this latter recommendation alone work which 

 involved for its aircraft application the work of one man for not more 

 than two or three months would when measured in terms of a woods 

 force have run into thousands of men, without enumerating railroads 

 and other transportation and manufacturing facilities. 



Ordinary inspection of lumber and wood were found to be entirely 

 inadequate to meet the recjuirements of inspection of airplane woods. 

 The training of a new and special force was necessary. In this the 

 Service assisted through the preparation of a "Handbook for Inspect- 

 ors" and short training courses in wood inspection. To emphasize the 

 need for careful work, inspectors were finally required by the Bureau 

 of Aircraft Production to make initial flights in the planes for which 

 they were responsible, so that careful work or the absence of it brought 

 its own reward. Plans for the inspection and certification of glues 

 were also developed by the Forest Service and the Avork directed for 

 the Army. 



Very early the question arose as to the possibilities of built-up wing 

 beams to permit the utilization of an increased proportion of the ma- 

 terial cut, and the importance of this construction grew as the size of 

 airplanes increased. The solid wing beam in the plane, with a 30 or 40 

 foot wing spread, is easily possible ; but something else must be looked 

 for when the wing spread exceeds 100 or 150 feet as the other extreme. 

 The design and construction of laminated, spliced, and built-up beams 

 and struts is one of practically unlimited possibilities. Present specifi- 

 cations of the Army and Navy for laminated and spliced beams and 

 laminated struts are based on the results so far obtained in the Forest 

 Service. To supplement ordinary methods of inspection, two simple 

 non-injurious methods by actual test have been developed which reduce 

 by half the number of rejections under the standard method. 



Frequent trouble with propellers explains the large number of pro- 

 pellers prepared for each plane, a number which reached seven at one 

 time, at least in foreign practice, and which at the conclusion of the war 

 required three or four for American planes. Rejection of propellers 

 through all stages of inspection is large, but beyond this it is stated by 

 a French authority that 80 per cent of the French propellers produced 

 and shipped to the front are rejected by pilots mainly because they are 

 out of balance. This trouble is largely due to unequal absorption and 

 distribution of moisture and requires for its elimination a waterproof 

 coating. Such a coating was developed at Madison for airplane pro- 

 pellers which incorporates a thin aluminum leaf in the finish. This 

 coating was being placed in production by the War Department. 



