Process for Rapid Conversion of Red Oak Logs to Dry Lumber

Lumber is usually air- and kiln-dried in batch processes that take several weeks or months to complete. Processing costs are therefore high because of the expense of holding large lumber inventories during this long drying period. This paper describes a promising process for converting red oak logs or bolts to dry, 1-inch-thick lumber in several hours instead of the usual several weeks. The key to the process is a combination of sawing pattern and press drying that allows rapid drying with a minimum of drying defects. The most common drying defect that develops in press drying is honeycomb cracks caused by internal tension forces that develop as wood dries and shrinks. When quartersawn boards are press dried, the critical internal tension that causes honeycomb is directly opposed and suppressed by the compression of the platens. In this study red oak logs were quartered with the pith as the center of symmetry. These quarters were sawed into boards in a pattern that could be duplicated on a gang saw where all boards from a quarter are produced in one pass. Boards from the center of the quarters had perfectly quartersawn growth ring orientation. Boards from the edges of the quarters had growth ring angles that deviated somewhat from perfectly quartersawn. Results showed that honeycomb suppression during press drying was most effective in boards from the center of the quarters, and less effective in boards from the edges. Thickness loss ranged from 18 to 25 percent and width loss from 1.2 to 2.3 percent, depending on position in the quarter.

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