Measures and yields of products and residues 3259 



Row and Guttenberg (1966) expressed the International lA-inch log scale as a 

 regression expression containing both scaling diameter and length, as follows: 



V = 0.0498D2L - 0.185DL + 0.0422L + 0.00622DL2 + (27-8) 



0.000259L3 - 0.01 16L2 



To compute the contents of 16-foot logs by scaling diameter in tenths of an inch 

 (table 27-19), the following equation for the International !/4-inch log scale is 

 useful: 



V = 0.796D2 - 1.375D - 1.230 (27-9) 



For 8-foot logs (table 27-19): 



V = 0.905 (.44D2 - 1.20D - 0.3) (27-10) 



In these equations: 



V = volume, board feet 



D = scaling diameter, inches 



L = scaling length, feet 



Gross log scale may be reduced by deductions (board feet) computed by 

 selecting the diameter-related factor tabulated below (Forbes 1961 , p. 1 .62), and 

 multiplying it by the appropriate value from table 27-17. 



Scaling diameter Factor 



Inches 



8 to 14 1.2 



15 to 19 1.1 



20 to 36 1.05 



Gross volume in trees. — At least one-third — and in less than IVi-Xog trees 

 more than half — the board-foot volume in hardwood trees is in the butt log. For 

 hardwoods of average form class, the percentage of total tree volume in each 16- 

 foot log is as follows (U.S. Department of Agriculture, Forest Service 1965a): 



Merchantable Position of log in tree 



height. 

 Number of logs 1 Wi 2 IVi 3 Vh 4 



Percentage of total tree volume 



1 100 — — — — — — 



l»/2 70 30 — — — — — 



2 55 — 45 — — — — 

 21/2 45—40 15 — — — 



3 40 — 35 — 25 — — 

 3'/2 40 — 30 — 20 10 — 



4 35—30 — 20 — 15 



Volume per log in board feet (International !/4-inch rule) is given in table 27-20 

 for hardwoods in form class 78. 



The amount of taper typical of 16-foot logs taken above the butt log is 

 described in table 27-21. 



