52 THE MEASUREMENT OF LOGS— BOARD-FOOT CONTENTS 



very short material such as box boards is used, crook does not cause 

 abnormal waste in logs. Care in laying off log lengths in the woods 

 to secure the maximum length of straight sections by dividing the 

 tree at the points of greatest crook reduces this source of waste to small 

 proportions. 



Waste from crook is deducted in scaling on the assumption that 

 the merchantable portion of the log must cut boards extending its 

 whole length. The influence of length of log upon the waste due to 

 crook is very pronounced, and where long logs are divided into shorter 

 lengths in the mill they should never be discounted for crook except 

 to the extent that this crook will affect the sawed contents of the shorter 

 pieces. For lumber longer than 12 feet the influence of crook rapidly 

 increases. 



The relation of normal crook to taper is shown in Fig. 7 in which the 

 line DE is the axis of the cylinder corresponding to a straight log. The 

 line AB is parallel to this axis and tangent to the margin at the small 



Fig. 7. — Method of measuring amount of crook in a log, in inches. The line JM 

 represents the proper measurement, coinciding with the shaded portion J A or 

 waste in the circle representing small end of log. 



end. The line AC is a straight line connecting the margins of both ends 

 of the log. Were the log cylindrical, the line HJ under these circum- 

 stances would represent the amount of crook. But the taper gives a 

 larger cross-section at JL than at AK . Unless crook exceeds the taper 

 for half the log, the cross-section JL when projected upon AK would 

 completely cover it, permitting as much lumber to be sawed as if the log 

 were straight. In the diagram the crook exceeds this taper and the 

 upper shaded portion of the cross section which represents the small 

 end must be wasted in slabs, in addition to the normal slabbing of a 

 round log. 



But this waste is incorrectly measured by any other method than 

 that shown by the line JM, which is the distance to the surface of the 

 log from a line parallel to the axis, and tangent to the margin of the small 

 end. This distance gives the crook in inches. 



• For a 16-foot log tapering 2 inches, a crook of 1 to 1| inches at the 

 middle point has no appreciable effect on the output. 



