Alternative Methods for Sawing and Drying Structural Lumber from Second-Growth Loblolly Pine ('Pinus taeda').

摘要

The processing of second-growth pine is a major problem. The combination of juvenile wood, compression wood and growth stresses makes the manufacture of straight lumber difficult. Several studies at the U.S. Forest Products Laboratory have shown that it is possible to minimize the warping of second-growth loblolly pine (Pinus taeda) lumber by manufacturing techniques. Two of the most promising methods, Saw-Dry-Rip (SDR) and press drying, are reported here. The SDR method employs live sawing (all cuts parallel), drying the wide boards (flitches), and then ripping the dried material to the desired widths for final use. This method, devised for hardwoods, has proven successful with pines. Results of studies are shown for 2.4-m stud (scantling) lengths. Yield of U.S. STUD and Select Structural grades were increased up to 20% compared to conventional processing. These grades require the lowest level of warp (crook, bow, and twist). The press drying method uses conventional sawing combined with drying under pressure between steam-heated platens. This method dries studs to 15% moisture content in as little as 90 minutes with gains in yield of STUD grade lumber up to 25% compared to kiln drying.