Reprinted {ran FOREST INDUSTRIES, vol~ 103, nunber 6pages 42-44. June 1976.

-- JI~By laminating V4-in. rotary-cutveneer into structural lumber,manufacturers can expandlumber output by at least 30%without increasing volume log-ged. The idea merits intensivestudy. Manufacturing plus rawmaterial costs should totalabout$142/Mbf; sales price fordesirable widths and lengthsof the strong laminated prod-uct should approach or exceed$200/Mbf

. ...

By PETER KOCH

select structural and No I KD lumber(SPIB 1970) would have a modulus ofelasticity (2.000.000 psi). slightly higherthan that of the laminated log-run wood;allowable fiber stresses in bending for2 x 4s of these grades (2.650 and 2.250psi) would be slightly lower than thatof the laminated wood.

PINEVILLE, LA-Reconstituted wood,in one form or another, will increasinglyenter the marketplace in competitionwith solid wood and plywood. One ofthe promising reconstituted products isstructural lumber laminated from rotary-cut veneer. Although several labora-tories have published enthusiastic de-scriptions of such a product only onecompany in the United States is manu-facturing it. Since 1970, TrusJoist Corp.,Boise, ill, has produced lumber lami-nated from 1/8 and 1/100in. rotary-peeledDouglas fir veneer. The lumber is 1.5

Theeuthor is Chief Wood Scientist. Southern For-est Experiment Station, Forest Service-4JSDA,Pinevi//e. LA. This analysis was presented in Mem-phis, TN,attheOctober.1915. annual meeting ofthe Mid-South Section, For.t Products ResearchSociety.

Reasons for considerationIn addition to its superior strength.

lumber laminated from veneer can bemanufactured in desired lengths. widths.and thicknesses from short logs (8 ft)of small diameter (8 to 14 in.). This p0-tential for utilizing small logs seems par-ticularly useful in the southern pineregion. where log size is likely to dimin-ish with passing years.

to 2.0 in. thick in widths to 24 in. and.lengths to 80 ft. When loaded as ajoist,its 12-in.-depth laminated material israted by TrusJoist to have a modulus ofelasticity of 2,200,00> psi and an allow-able stress in bending of 2,800 psi.

Experimental data on southern pinealso show that laminated lumber is sur-prisingly strong. When 17-ft southernpine stems were bucked into 8~-ftpaired logs and one of each pair wassawn and the other peeled and laminatedinto 2 x 4s, the laminated 2 x 4sproved stronger than the sawn ones andalso stronger than the Southern Pine In-spection Bureau values for kiln-dry se-lect structural southern pine (SPIB1970). See Table I.

Only dense grades of southern pine

FOREST INDUSTRIES/JUne 197642

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~-:;;..C~::..~,- ~'" '-. ~ -~." cRafters 24 In. on centers, 3 in. thick, 12 in. deep and 32 ft. 10 in. in length weremanufactured from Va-in. rotary-peeled Douglas-fir veneer. They were designedto take roof load of 39 Ibs/ft2 (live plus dead load) without exceeding 1.5 in.deflection over a 30-ft span.

One method of predicting future logsize is to analyze diameters of logs ex-tractable from existing stands. T .R.Dell, biometrician for the Southern For-est Experiment Station, mlkie such ananalysis for Alabama's entire pine re-source. His study indicates that if allpines 6 in. dbh and larger were cut in6 to 16-ft lengths to a minimum small-end diameter inside bark of 5 in., logdiameter mix would be as shown in TableII.

the problem may not develop if futureharvests can be controlled to yield sub-stantially higher proportions of largelogs; however. the very real possibilityof such a large-log shortage gives impe-tus to studies of lumber laminated fromveneer.

Moreover, the laminating processpromises greater recovery of saleableproduct from each cu ft of log than ispossible with sawing.

data from a 1971 study, when adjustedto count lumber yield from cores and toeliminate spur trim from veneer (spurtrimming is not necessary on veneerfor laminated lumber), show only 23 to36% greater lumber yield with the lami-nating process than with sawing. In prac-tice, the yield advantage from peelingsouthern pine would probably be inter-mediate; at least a 30% gain seemsreasonable.

By the end of the century, log scan-ning equipment coupled with computer-ized log positioning and sawing equip-ment may boost sawmill yields of lum-ber to 0.40 to 0.45 too. However, dur-ing the same time span, improved ve-neer-bolt centering and peeling tech-niques will probably increase veneeryields slightly and hence potential yieldsof lumber laminated from veneer. Thus,

Although these data are for Alabama.the proportions would probably be simi-lar throughout the South. The high pro-portion of log volumes in diameterclasses of 10.9 in. and smaller (72.4%)signals a potential problem: 14-ft andlonger 2 x 10s and 2 x 12s of solid southernpine may be in short supply during thelate decades of the century. Admittedly.

Material flow an81yslsA ton (oven-dry basis) of barky logs

can yield as much as 5Wc mOl"e lumberif rotary-peeled and laminated than ifsawn. Material balances for the twoprocesses are approximated in Table Ill.

Studies at western plywood millsshow a smaller difference in yields fromlaminating and sawing. For example.

43F~EST INOUSTRIESI.kIne 1976

veneer yields will continue to substan.tially exceed sawn lumber "yields.

Economics of manufactureBecause industry operating data are

not available, a precise statement ofmanufacturing costs is impossible. How-ever, estimates of economic viability ofa plant manufacturing lumber laminatedfrom southern pine veneer can be madeby: (I) comparing lumber and plywoodprices; (2) estimating requirements ofman-hours, energy, and capital; and (3)equating costs specific to the plywoodindustry to those for manufacturinglaminated lumber.

The points which follow assumemanufacture of laminated lumber wouldnot differ greatly in manpower, energyand capital costs from manufacture ofconventional sheathing plywood. Thisassumption should be conservative be-cause southern pine veneer for lumberwould measure V4-in. thick whereas ve-neer for plywood averages about l"B-in.In comparison with ~-in. veneer, useof ¥4-in. veneer increases lathe, dryerand layup productivity and decreasesadhesive consumption. For example, acu ft of %-in. sheathing plywood requiresabout 0.74 lb of resin solids if mixedadhesive is spread at 90 Ib/M sq ft of

double glue line; a cu ft of 1.5-in.-thicklumber laminated from V4-in. rotary-cutveneer requires only about 0.56 lb ofresin solids at the same glue spread.

equal the price pet cu ft of plywooo(i.e., $126/42 = $177/59 = $3.00/cu ft).

In fact, the market price per Mbf offavored sizes and grades of southernpine structural lumber is usually morethan 40% higher than the price perM sq ft of plywood. Moreover, becauseof the extraordinary stiffness andstrength of laminated lumber, it shouldcommand a premium over the same sizesof No. 2 KDlumber. For example, 2-byl2~in., 16-ft-long, No.2 KD and bettersouthern pine lumber was quoted at$190 net FOB mill per Mbfin the October17, 1975, issue of RANDOM LENGTHS.No. I KD in the same width and lengthshould sell at a $10 premium and selectstructural at a $25 premium. A net salesprice FOB mill of $200/Mbf of 16-ft 2 x12 lumber laminated from veneer wouldtherefore appear likely; longer lengths,for example 24-ft, could be expected tosell at over $260/Mbf. These pricesamount to $3.39 and $4.41. per cu ft. Be-cause of these high prices, a plant mak-ing laminated structural lumber wouldnaturally concentrate sales efforts onwide, long products-probably 16ft andlonger-and on specialty products re-quiring high stiffness and strength suchas truss chords.

Another approach is to compare re-quirements needed to manufacture a ton(oven-dry basis) of sawn lumber and oflaminated lumber, as shown in TableIV.

Such a tabulation is not the entirestory, however, because the greaterstiffness and strength of laminated lum-ber permit its use in sizes smaller thanthose for sawn lumber. For example, infloor systems calling for joists on 16-in.centers covered with %-in. plywoodunderlayment and carpet, lumber joistsmight have a net dimension of 1.5 by9.25 in., whereas joists laminated fromveneer might measure only 1.5 by 7.5

Lumber-plywood pricesAs of October 1975, l-7.-in. sheathing

plywood sold for $126/M sq ft FOBthe mill. since 1,000 sq ft of l-7.-in. ply-wood contains only 42 cu ft of woodand 1,000 bd ft of dimension lumbercontains about 59 cu ft, laminated lum-ber would have to sell for at least$177/Mbf (or 4Wo more than the pricefor 1,000 sq ft of l-7.-in. plywood) to

in. for the same spacing and span.A comparison of requirements for

the joists required per 100 sq ft of suchfloors (including logging, manufacture,and transport to house site) would beas shown in Table V.

Thus during logging, manufactureand transport, the joists laminated fromveneer require less raw material andfewer man-hours than sawn joists butare more capital and energy intensive.

A less complex analysis can beachieved by equating manufacturingcosts of laminated lumber with those ofsheathing plywood. In October 1975,Peter Vajda, president of Columbia En-gineering, Vancouver, B.C., estimatedthe cost of producing %-in. plywood.See Table VI. Vajda's costs aSSl'me a$15,000,000 investment in a plant cap-able of manufacturing 160 million sq ft(%-in. basis) of sheathing grade ply-wood annually.

By this computation, costs per 1 ,(xx)sq ft of :}8-in. sheathing ranged from$69.50 to $86; Vajda believes that 25%of all sheathing plywood produced in1975 was manufactured at a cost of $75(or less) per thousand sq ft (%-in. basis).This amount corresponds to $2.40 percu ft of sheathing plywood.

Assuming that it is technically pos-sible to build a plant to make laminatedlumber on the same scale and be oper-able at the same efficiency as the ply-wood plants described by Vajda, thenthe costs per thousand bd ft of lumberproduced (i.e. , for 59 cu ft) would beonly $142. Since the October 1975 salesprice of 16-ft, 2 x 12, No.2 KD andbetter, southern pine lumber was $I~Mbf, there would appear to be ampleprofit in such an operation.

Long lengths of wide structurallum-ber laminated from ¥4-in. rotary-cutsouthern pine veneer should bring a bet.ter price per cu ft than plywood. .

FOREST INDUSTRIES/June 197644