USE OF CUBIC FOOT IN LOG SCALING 



31 



In order to permit measurement of diameter at the small end of log instead of 

 the middle (§ 31), a further modification of the rule more radical in its character 

 was now made. The loss in cubic contents by measuring the small cylinder was 

 offset by arbitrarily increasing the ratio of board feet to each Blodgett foot. This 

 new ratio was set for logs of all sizes at 



106 Blodgett feet = 1000 board feet. 



When compared with the cubic contents of the small cylinder this makes the ratio 

 1 : 9.44. For the ratio of 1 : 9.44 the per cent of the small cylinder scaled as boards 

 is 56.2 per cent. But for the true cubic contents of the log the ratio would vary 

 with length and taper of log ( § 31) . 



9.44 

 12 



■ 78| 

 1.396 



: =.78f 



= 56.2 per cent. 



From Table I, § 31, the following comparisons can be made between the volume 

 thus expressed and the true volume. Taking 16-foot logs with 2-inch taper, 



The attempt to convert this rule to apply at small end gives values which agree 



with the current ratio of 115 Blodgett feet to 1000 board feet in 16-foot only when 



these logs are 24 inches in diameter and with 2-inch total taper, while for 6-inch logs, 



41.2 

 tapering 2 inches the scale is or 79 . 3 per cent, incurring a loss of 20 . 7 per cent 



oi . y 



of the true cubic scale measured at the middle point. 



Thus the change in point of measurement destroys the consistency of this log 



rule for cubic contents, while the conversion to board feet introduces still another 



error, discussed in § 42. The rule should either be used for Blodgett feet only, as a 



cubic measure, and applied only at middle diameter, or if the end diameter is used, 



the conversion factor should have been separately computed for logs of different 



diameters and lengths on basis of an average taper. 



34. Use of Cubic Foot in Log Scaling. The cubic foot has been 

 substituted for the Blodgett foot as the basis for measuring logs, by 

 the U. S. Forest Service on the National Forests in Maine and New 

 Hampshire. 



