67 



Equivalent Factors. 



The following table contains a series of converting factors 

 which are often useful. The first shows the number of board 

 feet that one can expect to obtain from a log per cubic foot 

 of solid wood. If one has a log which he wishes to scale and 

 is not equipped with a log rule, he can find the solid contents 

 by cubing the log as the frustum of a cone, and then, remem- 

 bering that the average log will yield 7 board feet per cubic 

 foot, he can convert his cubic contents into board feet. These 

 are the factors for round-edge lumber. In the case of square- 

 edge lumber an average factor is about 6.5 board feet. 



One will note that the equivalent factor is only 5 feet for 

 small logs, and 7.5 for the larger. The increase is due to the 

 fact that in the sawing of smaller logs there is a larger per- 

 centage of wood which must be wasted in the form of slab 

 and saw kerf. 



In the chapter on log rules we called attention to the caliper 

 cord. In commercial practice it is usual to state that it takes 

 a cord and a half to equal a thousand feet, or, to reverse the 

 statement, a cord is equal to 670 board feet of inch lumber. 

 Reference to the table will show that this is a very satisfactory 

 converting factor for a run of logs. The increase in yield 

 from the smaller to the larger logs is due to the same reason 

 as that advanced for the yield per cubic foot, namely, the 

 higher percentage of waste in smaller logs. In southeastern 

 Massachusetts, where the practice is to saw f-inch lumber, 

 it is common to call 1,000 feet of this sort of lumber equivalent 

 to a cord, although an average run of logs will slightly exceed 

 this yield. 



