Hardwood Record — Ve 



& 1^ 



Section 



25 



Making Airplane Propellers 



A Brief Discription 



)t the Materials and Methods 

 Laminations 



Used in These Specializec 



IK CASUAL OBSERVF.R of an jurplane is im- 

 pressed by the wide spread of the wings, the 

 machine guns and the bombs, the big motor and 

 the various devices for control, but is inclined to 

 take the propeller for granted. There is nothing spec- 

 tacular about it. In fact, thf coiislriict'on appears so 

 simple that al- 

 most any me- 

 chanic ought to 

 be able to make 

 a machine to 

 grind them out 

 as fast as you 

 could feed m 

 the timber. 

 .And better yet, 

 one thinks why 

 not make a 

 mold and cast 

 them out of 

 some light 

 metal, alumi- 

 num, for in- 

 stance. 



.And yet, 

 simple as a pro- 

 peller looks, it 

 is safe to say 

 that no part of 

 the whole ma- 

 chine receives 

 more care in its 

 manufacture. It 

 is only when 

 •che various 

 stages in its 

 evolution are 

 watched from 

 the rough lum- 

 ber to the fine- 

 ly finished 

 product that 

 one appreciates 

 t h e difficulties 

 involved, the 

 niceties of con- 

 struction, the high degree of skill and patience required, 

 the extreme care which makes for perfection. 



First, there is the choice of woods. For the combat 

 machines, mahogany from Mexico and Central America, 

 its near relative from the west coast of Africa, the best 



grades of our native white oak quarter-sawed, and black 

 walnut in such demand for gunstocks, comprise the pres- 

 ent list of acceptable material. For the training planes 

 where the demands are not so exacting the list is ex- 

 tended to include certain Philippine woods which ap- 

 propriated the name mahogany without being entitled 



to it, and also 

 certain native 

 woods, such as 

 birch and yel- 

 low poplar. 

 The last-men- 

 tioned is most 

 ly for the ma- 

 chines- which 

 navigate on the 

 ground, the 

 "penguins." 



Propel lers 

 are not cut out 

 of solid blocks 

 of wood, but 

 are built up or 

 laminated, the 

 number of lam- 

 inations vary- 

 ing from five to 

 ten, according 

 to the thickness 

 of the hub. It 

 was formerly 

 customary t o 

 use two or more 

 woods in the 

 same propeller, 

 but this practice 

 is no longer fol- 

 lowed in this 

 country. The 

 boards for the 

 laminations are 

 mostly one inch 

 thick, when 

 sawed, dressing 

 down to about 

 seven-eighths. 



The lumber must be carefully kiln-dried before it is 

 fit for use. The mahogany is usually received fairly well 

 air-dried because of the time required to get it from the 

 tree to the factory, but the speeding up of the operations is 

 reducing the time for seasoning. The writer recently saw 



