EXERCISE 9 

 PHYSICAL CHARACTERISTICS OF OAK WOOD 



Materials. Sticks of seasoned white oak one inch square and two 

 feet long; other sticks of the same wood but only one-half inch 

 square ; several rectangular blocks of oak ; several small boards of 

 green oak, which may be sawed from a freshly cut log as directed 

 in Exercise 8. Some boards must be radial and others tangential. 



Directions for work. What is the weight of oak wood ? De- 

 termine this by measuring several of the rectangular blocks, 

 weighing them, and calculating the weight per cubic foot. 

 Average results from the several blocks. 



What is the strength of oak wood ? Support a stick of oak 

 at two points, as by laying it across two bricks. Measure the 

 distance between the places of support. Note the approximate 

 amount of bending under different strains, as when persons of 

 known weight stand on a stick at a point midway between the 

 supports. If the stick is broken, note the weight which breaks it. 



What is the difference, if any, between plain and quartered 

 oak as to amount of warping ? Select several of the green boards 

 for a drying test, making sure that in the lot there is at least 

 one radial (quartered) board and one tangential (plain) board. 

 Expose them to the air and heat, but see that all boards have as 

 nearly as possible the same exposure. Support in such manner 

 that the air has access to both sides of each board, and turn them 

 daily in order that both sides may be equally exposed to drying. 



Which boards warp the most ? Which the least ? Which side 

 of a plain-sawed board becomes concave ? 



In your notes sum up what you have learned about the weight, 

 strength, and seasoning of oak wood. 



References 



BERGEN and CALDWELL. Practical Botany, pp. 393-395. 



BERGEN and CALDWELL. Introduction to Botany, pp. 62-67, 107, 108. 



"Mechanical Properties of Woods grown in the United States," Cir- 

 cular No. 213, Forest Service, U. S. Dept. Agr. 



CLINE and HEIM. "Tests of Structural Timbers," Bulletin No. 108, 

 Forest Service, U. S. Dept. Agr. 



[12] 



