16 STATE BOARD OF FORESTRY. 



The following deduction will show the total waste allowance of the 

 Doyle Log Rule for logs of different sizes expressed in per cent of total 

 sawed out, as indicated by the rule : 



( J L = BJL = volume in board feet of log D inches in di- 



V 4 ) ameter at small end inside bark and L feet long. 



nocA j~\i 



L = total volume in board feet contained in log D inches in 



12 diameter and L feet long. (No allowance for taper.) 



/ D 4 \ 2 



L f - - ) L = total waste, allowance. 



12 



^- - X 100 = total waste allowance for log D 



(^J~_^A inches in diameter and L feet 



4 J long expressed in per cent of 



used volume 



_ J _ X 100. 



.0625 D 2 .51) + 1 



When D = 10", the waste allowance based on the total sawed out 

 as shown by the Doyle Log Rule = 191%. 



When D = 20", the waste allowance = 63.8%. 

 When Z> = 30", the waste allowance .= 39.5%. 

 WTien Z) = 40", the waste allowance = 29.4%. 

 When D = 50", the waste allowance = 23.8%. 



This waste allowance is obviously too high for small logs and too low 

 for large ones. This is due to the fact that the slab allowance is too 

 generous and the sawdust allowance too small. Small logs will invari- 

 ably over-run the scale ; intermediate logs will usually scale about right, 

 since the large slab allowance makes up the shortage for sawdust; large 

 logs will invariably under-run the scale, because the combined slab and 

 sawdust allowance is too small for waste, though the actual slab allow- 

 ance is too large for slabs alone. 



The McKenzie Log Rule. 



The McKenzie Log Rule is based on mathematical principles and is 

 designed to cover all conditions encountered in the manufacture of 

 lumber from logs of various diameters and lengths. All factors influ- 

 encing the total volume sawed out have been taken into consideration 

 and treated separately, thus making the rule flexible to the varying 

 conditions, both in milling operations and in the character of the timber. 



