THE INFLUENCE OF GROWTH-CHARACTERISTICS ON WARP IN 2 STRUCTURAL GRADES OF SOUTHERN PINE LUMBER

The impact of growth characteristics on warp was evaluated for 438 pie ces of grades No. 2 and No. 3 Structural Joists and Planks (22) (nomin al 2 by 6 by 16 southern pine lumber (dry-dressed size 1.5 in. by 5.5 in. by 16.0 feet (3.8 cm by 14.0 cm by 4.88 m)). Compression wood cube d had significant influence on variation in bow. Compression wood cube d and wane had significant influence on variation in crook. Juvenile w ood, distorted grain, slope of grain, specific gravity, fast-growth wo od, knot area, knot quantity, and largest knot had no significant impa ct on variation in bow, crook, or twist in the graded lumber. Although certain growth characteristics did significantly influence the variat ion in either bow or crook. the total impact of these growth character istics was slight. Regression analyses showed that the variation in bo w, crook, and twist explained by growth characteristics ranged from 0 to 9 percent. Therefore, most warp in the study pieces was caused by f actors other than the growth characteristics tested.