TIEMANN LOG RULE 1910 67 



63. Tiemann Log Rule, H. D. Tiemann, 1910. All of the com- 

 mercial log rules in use are open to the criticism that the taper is dis- 

 regarded, thus causing the over-run to vary according to the length 

 and amount of total taper of the log. The International rule, in which 

 taper is included, is not in commercial use to any extent. But one 

 attempt has been made to take proper cognizance of taper by the method 

 of applying a log rule for board feet to the middle diameter instead of the 

 small end. Most rules employing this method are cubic-foot rules or 

 based on cubic contents. The Tiemann log rule on the other hand is 

 a true board-foot rule based on a j^-inch saw kerf. The rule was made 

 from actual mill tallies accurately adjusted for saw kerf and for exact 

 thicknesses and the results worked out graphically by curves. Quite 

 remarkably the curves were found to correspond very closely to the 

 exceedingly simple formula 



B.M. = (.751)2 _2Z))^, 

 lb 



which equals ( -716—7 1.5Z) j— . 



The application of the rule is limited by its author to lengths not 

 exceeding 24 feet. 



This log rule applies to logs scaled in the middle. When this is 

 possible, the rule is more accurate than any other board foot log rule, 

 since neither the variation in taper nor length of log affects it. It can 

 be adjusted to apply to the small end just as well as any other rule can, 

 but it is intended primarily for middle diameter as this largely elimi- 

 nates errors in estimates of taper. For scientific records it is of distinct 

 value. It is superior to the International rule as it eliminates taper 

 as a variable instead of averaging it. The obstacles to converting this 

 rule or any other rule into equivalent values at small end are discussed 

 in § 31. The rule is given in Appendix C, Table LXXXIV. 



64. Formula Rules Inaccurately Constructed. Baxter Rule. If 

 the allowance for slabbing in a formula rule is excessive, and that for 

 sawdust too small, the resultant volumes will be too small for logs of 

 small diameters and too large for large logs, thus giving not only an 

 inaccurate but an inconsistent rule. If these errors in deducting waste 

 are reversed, slabbing allowance being too small, and that for sawdust 

 too large, the reverse is true, and the large logs will be under-scaled. 



Baxter Log Rule. In adopting a rule of thumb for the construction of a log rule, 

 the author may have in mind a certain result, but the rule when expressed in a formula 

 may give quite a different result. 



The Baxter Log Rule was constructed by the rule "Subtract 1 from the diameter 

 inside bark at the small end, square the remainder, and multiply by .52. The result 



