T He Pqssmlllty of Lamlna11nc Lumber from Sliced or Forest Products Journal

By the lamination process evaluated, 60 percent of total 108 volume ended as kiln-dry, end-trimmed, sized, salable 2 by 4's-approximately 50 percent more than that achieved by conventional bandsawing of matched lop. 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 4'8. 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. Ed1ols and Currier (1973) tested 4/4 Douglas-fir boards parallel-laminated from 1/6-indt and 1/10-indt rotary-Olt veneer. In flatwise bending (i.e., loeded as planks and not as joists), the 20 fabricated bO8rds CX)IDpared favorably in MOE and MOl. with Yertial-grain sawed bO8rds. The laminates had less resistance to dea~ than solid wood, chiefly because of lathe checks in the veneer. MOl. of the laminated bO8rds ranged from 9,270 to 11,400 psi; and MOE ranged from 2,112,000 to 2,248,000 psi. In tests of small d5r beams made from vertically laminated 1/2-indt rotary-Olt southern pine veneers, Moody and Peters (1972) found that average bending strength was 82 ~ of that for matched solid-sawn specimens; MOE was 95 ~t of that for solid wood. Shear strength in the tangential plane was 67 percent of the value for sawn wood; in the radial plane lathe dtecks reduced it to 59 percent. SdJaffer et at. (1972) laminated 1/4and 1/2-indt rotary-Olt ~ern pine veneers into beams 1.5 indies thick, 4.5 indtes deep, and 8 feet long. Two of the laminae in eadt beam were dear. Joists of 1/4-indt veneer averaged 5'btantially higher in MOl. and MOE than thole from 1/2-indt laminae and were less variable in strength. MOE and MOl. in the joists made from 1/4-indt veneers averaged 1,710,000 and 6,470 psi when tested at 12.6 percent moisture content in edgewise bend. ing; corresponding standard deviations for the 15 beams were 96,000 psi and 671 psi. Yield of product was ~t 60 percent of log volume. Jokerst (1972) described a system of utilizing residual heat from press drying to fabricate joists vertically laminated from thick veneer. T HE PQSSmlLlTY OF LAMlNA11NC LUMBER from sliced or rotary-cut veneer has interested researdters and industrialists for many YNrS because of the potential for increased yidd and uniformity of strength. Quantitative evaluatioos of laminated lumber have been sparingly reported, however. Lutz et al. (1962) found that knife chedcs in thick-sliced chestnut oak veneer (slicewood) caused a reduction in tensile strength me85Ured perpendicular to the grain; modulus of rupture (MaR) in bending also ap~ to be slightly lower than in sawn wood. Modulus of elasticity (MaE), however, did not differ between slicewood and sawed controls. Murphey et al (1967) made small vertically )AmiMted beams from sliced yellow-poplar veneer. They foond that MaE was substantially lower, and that maximwn f"tber stress in bending was higher, than in sawed controls. Bohlen (1972) described a process for converting Douglas-fir into 1/4-ind1 rotary-cut veneer and subsequently panlle1-IAminating it into lwnber; by comparison with conventional sawing methods, gains in yield ranged up to 47 percent. Bohlen tested two of his fabricated planks as joists; they had an average MaR of 6,790 psi. The author is Chief Wood Scientist, Southern Forest Expt. Sta., USDA Forest Service, Pineville, La. This ~per was presented December 6, 1972, In Pensacola, Fla., at the Forest Products Research Society's Fall Meeting of its Southeastern Section. The Tremont Lumber Company, Joyce, La., made substantial contributions of material, manpower, and mill time during the study reported here. This paper was received for pubUcation In becember 1972. FOREST PRODUCTS JOURNAL Vol. 23. No.7 17 . Crop trees in southern pine plantations tend to develop dear boles through natural pruning. Peeling permits recovery of dear veneers from the knct-free periphery of sudt boles. These veneers can be used to face the planks and joists. . The process of randomly laying up parallel-bonded, 8foot lengths of veneer into wide endless slabs with staggered butt joints placed in a controlled pattern, and then gang ripping to obtain planks of the desired width, will yield joists having fairly uniform MOE approximately equa1 to the average for outer wood of the species. Thus the extreme variation in MOE between corewood and outer wood will be avoided. Moreover, in planks loaded as joists, distribution of defects within the several plies will be random; MOR therefore will vary less from piece to piece than in similar-size joists sawn from solid wood. . With this system, product yield per cubic foot of log will be substantially increased, as peeling wastes less wood than sawing. . Finally, rafters and joists of any width and length can be made from short logs of fairly small diameter. The present study was executed to help establish data on yields and working stresses of strocturaI lumber laminated by the proposed method.