14 



STATE BOARD OF FORESTRY. 



Therefore, the sawdust allowance for the Doyle Log Rule = 4.5% 

 of the total volume left after 4" has been deducted from the diameter 

 as an allowance for slabs. This sawdust allowance is correct in prin- 

 ciple, since it is a definite per cent of the total volume after slabs have 

 been accounted for. It is, however, entirely too small. The thinnest 

 modern band saws take away at least 10% of the volume of the lumber 

 sawed unless the product be large timbers, and the allowance of 4.5% 

 is not one-half as large as it should be for even one of these saws. The 



AREA INSIDE BARK SMALL END-SO. FT 



FIG. 5. A graphic analysis of the Doyle Log Rule, based upon area in square 

 feet inside bark at small end of logs. This diagram shows the following: (a) Top 

 curve, total contents in board feet of logs of different diameters 16' long with no 

 allowance made for taper. (&) Next lower curve, volume in board feet remaining 

 after an allowance of 4.5% has been made for sawdust. (4.5% of the total volume of 

 logs, after slab allowance has been made, is the only portion of the waste allowance 

 of the Doyle Log Rule that varies directly as the volume. Therefore, it is the only 

 part of the formula that varies directly as the amount of sawdust.) (c) Curve "k," 

 values for volume in board feet after an allowance of 18% for sawdust has been 

 made. This curve intersects the log rule at about 56", showing, that, at this point 

 and above, the waste allowance which should cover slabs and sawdust is not sufficient 

 to even cover the sawdust. The Doyle Log Rule, however, is correct in principle, but 

 its values are ver" poorly chosen. 



principle upon which the Doyle Log Rule is based is correct, however, 

 since the slab allowance is proportional to the barked area and the 

 sawdust allowance is proportional to the total volume left after the 

 allowance for slabs has been made. But the allowance for slabs is 

 absurdly large and that for sawdust is absurdly low. In short, the 

 principle of the rule is correct, but the values are very poorly chosen. 

 Fig. 5 shows a graphic analysis of the rule. 



A log rule was used long before the Doyle rule came into existence, 

 which gave the same results, and was stated as follows : Deduct 4" from 

 the diameter for slabs, then, squaring the remainder, subtract one-fourth 



