SCALING LOGS 39 



Pitch Rings 



DD=(''-^Y = 0.2iDXA) T = DDXL. 



\ 12 / 5 



D = diameter of ring, inches; 

 7r = 3.14. 



Remaining factors same as for pitch seams. 



Rot 



4 W^ 

 DD= { — ]- = —, T = DDXL. 



\12/- 



TT^=side of a square which can be circumscribed around the defect, 

 inches; 



Shingle Bolts 



144 



^ = area of end of bolt, square inches; 



L = length of bolt, inches ; 

 144 = dividing factor to reduce to B.M.; 

 .70 = per cent of utilization; 



y = total number feet B.M. in bolt. 



Explanation of Scaling Formulae 



There are various systems of m.aking allowance for the defects which 

 occur in logs but the simplest and most logical is to consider the amount of 

 the defect as equivalent to the piece of lumber which would be lost in sawing 

 it out in the saw mill. As tl^ Scribner rule makes an allowance for sawkerf 

 of J inch for each 1-inch board or a deduction of 20 per cent of the volume 

 of the log this deduction should also be taken into account in making the 

 defect allowance. 



In the formulae the defect deduction is first found per lineal foot and 

 then multiplied by the length of the defect as this is the easiest procedure 

 for the scaler to follow in practice as will be e.xplained below for each type of 

 defect. 



Pitch Seam. — To determine the amount of defect in a log with a pitch 

 seam or seams the scaler should determine if they show on both ends of the 

 log and whether they are straight or twisted, for the greater the twist the 



