﻿BULLETIN 1128, U. S. DEPARTMENT OF AGRICULTURE. 



rock elm 4 are sometimes used instead of white ash. Hickor}', 5 so 

 far, has been principally used for tail skids. The two finest woods 

 for propellers are black walnut (Juglans nigra Linn.) and true 

 mahogany {Swietenia mahagoni Jacq.), also known as Central 

 American mahogany. Other species commonly used are yellow 

 birch (Betala lutea Michx. f.), sweet birch (B. lenta Linn.), Afri- 

 can mahogany {Khaya senegalensis A. Juss.), black cherry (P'runus 

 serotina. Ehrh.), hard maple, white oak, and yellow poplar. How- 

 ever, a number of other woods are occasionally utilized, and in the 

 future a wide variety of species will probably be admitted. Euro- 

 pean designers even now are less exacting in this respect, sometimes 

 using two species of wood in the same propeller, which on the 

 whole is considered poor practice in this country. 



Table 1. — Distribution of wood in airplanes, showing the service requirements 

 and the adaptation thereto of the different grades of the several species. 





Species of wood and quality designation (grade). 



Designation of assembly and name of part. 



o 



2 



o 



T3 



l-l 

 o . 



0.3 



u 







to 





 



PQ 



8- 



| 

 2 



a 

 Is 



a 



o> 

 *j ° 



is* 



a 



i 



a 



<D 



& 



a 



■a 



a 



^< 

 

 



>> 



M 



O 



M 

 



3 



Main and center planes, ailerons, stabilizer, 

 elevator, rudder, and fins: 



A 

 A 

 C 

 B 



h 



i 



A 



A 



B 



A 

 A 

 C 

 B 



C 



B 



A 

 A 

 A 



B 



A 

 A 

 C 

 B 



C 



B 



A 

 A 

 A 



B 



"c" 



B 



C 



B 



A 



"a 



A 

 A 

 C 

 B 



C 



B 



A 

 A 

 A 



B 



A 

 A 

 C 

 B 



C 



B 



A 

 A 

 A 



B 



A 

 A 

 C 

 B 



C 



B 

 A 

 A 



A 

 A 

 C 

 B 



C 













































Panel blocks- 



c 



c 



c 



C 

































































Trailing edge- 



Ti 



B 

















A 



A 



A 



A 



A 



Entering edge — 



B 



B 



B 





B 



B 



B 



B 





Bent 



A 



A 



A 



A 



A 





.... 

 B 

 A 

 B 



i 



A 



B 



A 

 B 

 A 

 A 



A 



B 



A 

 B 

 A 

 A 



A 





B 

 A 

 B 



B 

 A 

 B 

























Interplane struts 



B 



B 













A 

 A 



A 



A 



B 



A 



A 



A 

 A 



B 



A 

 A 



A 

 A 



B 



A 

 A 



B 















Fuselage: 



Longerons — 



Bent 

























Struts, vertical, and horizontal- 

 High stress 



A 

 B 

 B 

 A 

 B 

 B 

 B 



A- 

 B 

 B 

 A 

 B 

 B 

 B 



A 

 B 

 B 

 A 

 B 

 B 

 B 



b" 



B 

 B 



A 

 B 

 B 

 A 

 B 

 B 

 B 



A 

 B 

 B 

 A 

 B 

 B 

 B 



A 

 B 

 B 



A 



1 



B 



A 

 B 

 B 

 A 

 B 

 B 

 B 

















Supports, heavy 



A 

 B 

 B 



A 



A 







B 



B 



B 







C 



C 



C 



C 





Furring strips 



B 

 C 



c 



A 



A 



B 

 C 

 C 



A 

 A 



B 

 C 

 C 

 A 



A 



B 

 C 



c 



A 



B 

 C 



C 

 A 



B 

 C 



C 



A 



B 



C 

 C 



A 



B 

 C 

 C 



A 







































Tail skid 



A 

 A 



A 



A 

 A 



A 



A 

 A 



A 

















A 

 A 



\ 



Landing chassis: 



A 

 C 



A 

 C 



A 

 C 















Stream lining 



C 



C 



c 



C 



C 















4 Hock elm includes rock elm (Ultnua racemosa Thomas) anfl the more dense stock of 

 both white elm (U. americana Linn.) and slippery elm (V. pube*cciw Walt.). 



'The true hickories include mockernut hickory (Hicoria alba (Linn.) Br.), shellbark 

 hickory (H. laciniosa (Michx. f.) Sarj;.), pignut hickory (H. glabra (MilL) Br.), and 6hagr- 

 bark hickory (H. ovata (Mill.) Br.). 



