Measures and yields of products and residues 3257 



Doyle log scale. — The Doyle log scale is defined as follows: 



V - UP - 4f <2^-3) 



16 



To faciliate linear programming studies, Grosenbaugh (1952, p. 12) expressed 

 the Doyle log scale as a regression equation: 



V = 0.0625D2L - 0.500DL + l.OOOL (27-4) 



where: 



V = volume, board feet 



D = scaling diameter, inches 



L = scaling length, feet 



Gross board foot volumes in logs as computed by the Doyle scale (equation 27- 

 3) are shown in tables 27- 1 3 and 27-14. For a given scaling diameter, volumes of 

 8-foot logs are half those shown in table 27-14. 



Gross log scale may be reduced because of defects in logs. The reductions 

 (table 27-17) calculated for the Scribner rule, are adjusted to Doyle scale by 

 multiplying by the diameter-related factor tabulated below (Forbes 1961, p. 

 1.62). 



Scaling diameter Factor 



Inches 



8 to 1 1 0.6 



12 to 13 .8 



14 to 20 .9 



21 to 31 1.0 



32 to 40 1.1 



Actual scaling practices differ widely from textbook scales. Some deviations 

 occurring in the application of log rules are: giving logs 8 inches or less in 

 diameter their length in feet as the board foot value; rounding scaling diameters 

 to the nearest inch; and including various bark thicknesses in the diameter 

 measurement. A modification of the Doyle rule, to include one bark thickness in 

 the diameter, gives upward bias of: 



Scaling diameter Upward bias 



Inches Percent 



6 20.0 



9 10.7 



12 9.2 



15 8.4 



18 1.8 



