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Title: Effect of drying temperature on warp and downgrade of 2 by 4's from small-diameter ponderosa pine

Source: Res. Pap. FPL-RP-624. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory: 8 pages

Author(s): Simpson, William T.

Publication Year: 2004  View PDF »

Category: Research Papers

Abstract: Kiln drying at high temperature may reduce warp in dimension lumber sawn from small-diameter trees. In this study, we examined the effect on warp of high drying temperatures in conjunction with top loading immediately after drying and after storage in typical conditions that result in further moisture loss. Eight-foot-long 2- by 4-in. (2 by 4) boards sawn from open-grown, 30- to 35-year-old, 9-in.-diameter at breast height ponderosa pine trees were kiln dried at three temperatures, 160F, 230F, and 280F. Crook, bow, and twist were measured and compared. Total grade loss from exceeding Structural Light Framing grade warp limits was also measured. Crook, bow, and twist measured after boards had equilibrated to 14% moisture content decreased by 12%, 29%, and 20%, respectively, with increase in kiln drying temperature from 160F to 280F. Total grade loss caused by all forms of warp was 24% lower in boards dried at 230F than at 160F and 39% lower in boards dried at 280F than at 160F. When boards were equilibrated to 4% to 5% moisture content, warp and grade loss from warp increased significantly.

Keywords: kiln drying, ponderosa pine, small-diameter timber, drying degrade

File size: 2 kb(s)

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RITS Product ID: 12500

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