Solid Wood Products 2697 



and center ply 3/16. Performance after accelerated aging tests, however, suggest 

 face-glued blockboard should not be used for exterior application even if hot- 

 press bonded with phenolic resin (Bowyer 1979b). 



Bowyer (1979a) concluded from a brief economic analysis that manufacture 

 of hardwood face-glued blockboard would likely be profitable if the product 

 were marketed as industrial shelving or as combination subfloor-underlayment. 

 See also Bowyer and Stokke (1982). 



Fraser (1975) illustrated and described a Finnish plant that produces endless 

 4-foot-wide sheets of three-ply face-glued blockboard with a single-opening 

 traveling hot press. The panel, which has scarf-jointed 2-mm-thick birch veneer 

 faces and backs glued to pine core strips, is cut to market size from the continu- 

 ous sheet. 



LAMINATED BEAMS AND LUMBER 



It is difficult to glue dense southern hardwood veneer into plywood that will 

 yield 85 percent wood failure when sheared after being subjected to the vacuum- 

 soak test described in footnote 14. This does not mean, however, that laminated 

 dense hardwoods such as white oak are precluded from severe service. On the 

 contrary, laminated white oak has served admirably in such diverse and demand- 

 ing applications as keels and frames of wooden ships of the U.S. Navy (Kuenzel 

 1950, 1952; McKean et al. 1952), and in laminated flooring for truck beds. 

 Hickory, another dense wood, is laminated to ash for extraordinarily tough and 

 serviceable baseball bats (McDonald 1951). 



The structural uses of laminated hardwoods are many. In addition to laminat- 

 ed truck trailer and railcar flooring described later, laminated oak is being used 

 for stairway railings, restraining structure around tanks in the holds of liquid 

 methane tankers, for foundations under large cryogenic tanks holding methane 

 and ammonia, and for decorative structural members in residences and commer- 

 cial buildings. 



General guidelines for laminating lumber can be found on pages 1158 through 

 1175 of Agriculture Handbook 420 (Koch 1972). Guidelines for laminating, 

 edge gluing, and end gluing southern hardwoods are being prepared by T. 

 Sellers of Mississippi State Forest Products Laboratory, Mississippi State, 

 Miss. , in a state-of-the-art report written as a companion volume to this text. For 

 fabrication procedures, the interested reader should find the comprehensive 

 work by Freas and Selbo (1954) useful. Steps in fabrication include organization 

 of laminae, spreading, layup, curing under pressure, and finishing. 



The introduction of nondestructive testing techniques to evaluate the strength 

 of individual laminae has led to several publications describing systems to 

 position laminae efficiently in beams (Koch 1964ab, 1967bc, 1971b; Koch and 

 Bohannan 1965; Koch and Woodson 1968; Bohannan and Moody 1969; Moody 

 and Bohannan 1970; Moody 1974, 1977). Industry has, to an increasing degree, 

 adopted the principle of placing laminae having the highest modulii of elasticity 

 in the outer, most highly stressed region of each beam. Because eastern hard- 

 woods vary significantly in modulus of elasticity (table 10-6) it is possible to 

 place laminae in beams according to species. For example, the hickories, cher- 



