3312 



TIGHT COOPERAGE 



Chapter 27 



Specifications for tight cooperage generally require clear heartwood (see sect. 

 22-8). Therefore, to permit close inspection of the interior, logs are cut into short 

 lengths of 23 to 39 inches for head and stave material, respectively, and then 

 split into quarter sections called bolts. 



Bolt volume is expressed in bolt feet, also called chord feet (Smith 1952). 

 This measurement is taken from a point on one edge of the cross-section surface 

 where heartwood and sapwood meet to the same point on the other edge. (In 

 some localities, sapwood may be included.) When this linear distance is exactly 

 12 inches, the volume contained in the bolt is 1 bolt foot; for a distance of 15 

 inches, the volume would be 1.25 bolt feet. 



The expected bolt foot yield from white oak trees 12 to 36 inches dbh is given 

 in table 27-123. 



The ratio of bolt foot volume to board foot volume (Doyle scale) was deter- 

 mined by Goebel (1956) using the following regression equations: 



Head Ratio = [0.03354(D) + 0.00014(D2)] L (27-43) 



Stave Ratio = [0.059(D) + 0.00002(D2)] L (27-44) 



where: 



D = log diameter, inches 

 L =log length, feet 



The ratios for white oak logs 14 to 26 inches in diameter and 6 to 12 feet long are 

 shown in figure 27-20 and in table 27-124. 



16 18 20 22 24 26 14 16 18 20 22 24 26 



DIAMETER INSIDE BARK (INCHES) 



Figure 27-20.— Board foot/bolt foot ratio for white oak logs cut for head stock (left) and 

 for stave stock (right). (Drawing after Goebel 1956.) 



