Study of Overlength on Red Oak Lumber Drying Quality and Rough Mill Yield‪.‬

Abstract Lumber stacking practices can directly affect drying defects, drying rate, and moisture content uniformity. The effect of overlength on drying is generally thought to be detrimental, yet large volumes of overlength lumber are used by secondary manufacturers. Managers of secondary manufacturing facilities need quantitative information to assist them in determining if overlength is beneficial or detrimental to their operation. The goal of this research was to compare the drying degrade, kiln capacities, and rough mill yields of red oak lumber with overlength to lumber that was precision-end trimmed. Degrade and rough mill yield studies where conducted at four manufacturing facilities located within Tennessee, Kentucky, and Virginia. Each facility used predriers prior to kiln-drying red oak. Differences in kiln capacities for precision end-trimmed vs. non-precision end-trimmed lumber were determined from company records for previous kiln charges that were composed of one or the other type of lumber. The results of the four mill studies demonstrated that: 1) drying degrade was not significantly different between the two trimming and stacking practices; 2) kiln capacity can be increased by an average of 4 to 12 percent for precision-end trimmed lumber; and 3) using lumber with overlength leads to an increase in rough mill yield. A modified version of the ROMI-RIP rough mill simulation software was used to determine theoretical yield differences for different lumber grades and cutting bills. Simulation results indicated that there was a definite increase in rough mill yield for 1 Common lumber regardless of the difficulty of the cutting bill. For 2 Common lumber, yields were either not significantly different or higher for lumber with overlength, depending on the cutting bill.