A Dkckxxiai, Kfa'oui) 1-.) 



and lightened as nmeli as p().ssil)le tln-ougli tlie nse of liglitening holes. 

 The proper selection of species and thicknesses of piles resnlted in an 

 appreciable increase of strength without increase in weight. Similar 

 parts were designed for several Xavy planes. 



^Nluch attention was devoted to the nse of thin plywood as a wing 

 covering and a nnniher of tests were made in the hope of de\eloping a 

 satisfactory linen substitute. Several types of construction were tried 

 out. and interesting preliminary results secured. Xo covering oi- ty])e 

 of construction was ])erfeete(l. however, which was superior to the 

 standard wood and linen type. 



Development of JVafer-resi.sfanf Glues 



Closely associated with most of the aircraft proldems upon which 

 the laboratory worked was the all-important one of glues and gluing. 

 A great deal of reliance is ])laced upon glue in the construction of the 

 ordinary plane, since many of the structural pai-ts are glued together, 

 and it is essential that only the best glues and best gluing techni(iue 

 be employed. The first request for help came from the Signal C()r})s 

 in the spring of 1917. asking for assistance in hide glue inspection. 

 Xo standard, usable system of grading and inspection was available, 

 but one was quickly developed at the laboratory by an inspector as- 

 signed to the work, and all hide glue used by the Army Air Service 

 as Avell as much of that used by the Xavy Air Service Mas inspected 

 and certified by him and his assistants. 



Attention was then directed to the great desirability of using 

 water-resistant glue in aircraft construction, not alone on account of 

 exposure to the weather when in service, but also because of the severe 

 conditions during shipment and storage. It had been known for many 

 years that so-called "'water-proof" glues could be made from blood 

 albumin and from casein, and various secret formulas had been devel- 

 oped and were in use to a certain extent. In fact, it is well established 

 that the enemy was using casein glue in his aircraft before our entrance 

 into the war. In this country there were se^'eral small manufactiu-ers 

 of "waterproof" plywood glued with blood albinnin. However, there 

 was not available for general use an appreciable amount of a suitable 

 water-resistant glue, for either plywood or joint Mork, Therefore, 

 the perfection of several ty])es of water-resistant glues was immedi- 



