LOG RULES FOR CUBIC CONTENTS OF SQUARED TIMBERS 33 



cylinder in board feet. This suggested ratio is therefore lower than those adopted 

 for the New Hampshire and most other converted cubic log rules. 



Note. Weight as a Basis for Measuring Cubic Contents. Actual weight of logs 

 is seldom used as a basis of measurement, as the variation in moisture contents 

 caused by seasoning prevents standardization even for a given species. A few 

 valuable timbers are imported by weight. The long ton of 2240 pounds is used. 



The ton as ordinarily used in measuring timber is a cubic measure equivalent to 

 either 40 or to 50 cubic feet and is usually applied to squared timbers. The unit of 

 50 cubic feet is also termed a "load" and is used in measuring teak. 



Red cedar logs are sometimes purchased by weight, on account of their extreme 

 irregularity and the difficulty of measuring them. 



35. Log Rules for Cubic Contents of Squared Timbers. A definite 

 departure from the use of total cubic contents is found in log rules 

 giving the cubic contents of the squared timbers which may be hewn 

 or sawed from round logs. The waste constitutes the portion hewn 

 or slabbed off. A square inscribed in a circle occupies 63.6 per cent 

 of its area. Rules based on this principle would give a waste factor 

 of 36.4 per cent of the cylinder scaled. 



Inscribed Square Rule. The width of a square inscribed in a 24-inch 

 circle is 17 inches. 1 The width of any other inscribed square is seven- 

 teen twenty-fourths of the diameter of the log. The cubic contents 

 of the log is that of the square so determined, measured at the small 

 end of log. 



The width of a square inscribed in a 17-inch circle is 12 inches, each 

 foot of log containing 1 cubic foot of squared timber. The cubic con- 



D 2 



tents of any log is y^L. By either of these rules of thumb, the so-called 



Inscribed Square Rule is obtained. The latter method is termed the 

 Seventeen-Inch Rule. The rule gives 63.4 per cent of the cubic contents 

 of the small cylinder, and proportionately less of the entire log depend- 

 ing on taper, length and diameter (§31). 



Big Sandy Cube Rule. Synonyms: Cube Rule, Goble Rule. This 

 Cube Rule, used on the Ohio River, assumes that it requires a log 18 

 inches in diameter at small end to give a timber 1 foot square. This 

 rule scales 56.6 per cent of the small cylinder. The volume of logs of 

 other sizes is found by the formula, 



D 2 

 V=—L 



This rule is sometimes expressed in board feet by multiplying the 

 cubic contents by 12. 



1 The side of the inscribed square is found by squaring the diameter of the log, 

 dividing by 2 and extracting the square root, 



