174 SYMPOSIUM ON AERONAUTICS. 



1. Improvement in the elements of design and in the materials 

 of construction. 



2. The selection of such a size of wing as shall insure for the 

 type of design and for such wing as an element in the structure as a 

 whole, the maximum net carrying capacity. 



3. Increase in speed to the upper limit practically ffttainable. 



4. Increase in number of planes. 



Recent experimental work with three, four and five planes seems 

 to point to the multiple plane as perhaps the most immediate means 

 of increasing carrying capacity. Or in other words, given the limita- 

 tions imposed by structural materials and the upper limit of speed 

 considered practicable and expedient, multiple planes seem to be 

 the immediately remaining recourse for further advance in net car- 

 rying capacity. 



Passing now briefly to the actual materials available, we may 

 make a classification as follows. 

 Surface material (cotton or linen duck fabric). 

 Wing skeleton or structure — wood (spruce and mahogany), steel. 

 Struts and braces connecting wings in multiple — wood (spruce and 



mahogany), steel or special alloys. 

 Body or boat material : Framing : wood or steel. Covering : wood 



veneer or sheet m.etal. 

 Ties for serving as tension members in connecting wings to body or 



in multiple : steel wire, single or laid up in cable. 

 Fastenings-: drop forgings, sheet steel, bronze. 

 The two fundamental problems are : 



1. The development of materials furnishing more strength for 

 the same weight. 



2. The better disposition of the materials which we now have. 

 Passing the above classes of materials briefly in review, we may 



note as follows. There does not seem to be anything immediately in 

 sight better than the materials now used for surfaces. With suit- 

 able treatment (usually coatings of celluloid dissolved in acetone 

 with varnish finish) the material stretches tight, takes a smooth 

 surface and has sufficient strength to support itself between the 

 supporting ribs. 



