Structural Lumber Laminated from 1/4-Inch Rotary-Peeled Southern Pine Veneer

This study is one of a series, begun in 1963, that has evaluated the properties of beams and lumber laminated from thick southern pine veneers. This series of experiments has indicated that there are substantial advantages from making southern pine dimension lumber by parallel lamination of wide sheets of rotary-cut veneer into slabs 1-1/2 inches thick, and then ripping the slabs to net widths required for 2 by 4’s, 2 by 6’s, etc. In 1965 Koch manufactured a number of very strong, stiff, 8-ply southern pine 2 by 12’s in this manner. In the current experiment, nine 17-foot-long southern pine (mostly Pinus taeda L.) logs were randomly selected from a log pile in central Louisiana and bucked into pairs of 8-foot (nominal) logs. One log of each pair was sawn by band headrig and linebar resaw into 2 by 4’s and the other rotary-peeled into 1/4-inch-thick veneer. The air-dried veneers (10 percent MC) were cold pressed with resorcinol, glue into 6-ply slabs 102 inches long, butt joints in each ply were spaced 17 inches from joints in adjacent plys. A pair of 2 by 4’s was also sawn from each of the nine 5-1/4-inch veneer cores to yield 18 studs from cores. By the lamination process evaluated, 60 percent of total log volume ended as kiln-dry, end-trimmed, sized, saleable 2 by 4’s–approximately 50 percent more than that achieved by conventional bandsawing of matched logs Moreover, modulus of elasticity of the laminated 2 by 4’s (adjusted to 12 percent moisture content) averaged 1,950,000 psi compared to 1,790,000 for the sawn 2 by 4’s. Allowable fiber stress in edgewise bending was 2,660 psi for the laminated 2 by 4’s, more than twice the value obtained (1,270 psi) for the sawn 2 by 4’s. A manufacturing procedure for 6-ply lumber is described that calls for no major innovation in equipment. When the price per MBF of structural lumber is 50 percent greater than the price per M sq. ft. of 1/2-inch sheathing plywood, it should be more profitable to manufacture laminated lumber than plywood.

You must be logged in to download any documents. Please login (login accounts are free) or learn how to Become a Member