Solid Wood Products 2629 



inch to equal or exceed performance of y4-inch-thick northern red oak spaced 

 deckboards. This conclusion was based on evaluation of damage from handling 

 impacts, bending stiffness, and diagonal rigidity. Pallets with fiberboard decks 

 on wood stringers do not rack nearly so much, but crush at the corners more 

 easily, than all-lumber counterparts. Stern also concluded that fiberboards for 

 decking on stringer-type pallets should have a density of at least 39 pounds per 

 cubic foot. 



To evaluate pallets with 1 -inch-thick fiberboard top decks, R. K. Stern (1980) 

 glue-laminated (with phenol-formaldehyde adhesive) two /z-inch hardboards 

 comprised of about 85 percent oak fibers and 15 percent sweetgum and elm, and 

 nail-fastened them in place of lumber top decks. These pallets, and red oak 

 lumber, notched-stringer, partial 4-way-entry pallets of warehouse design were 

 tested in the laboratory and in service. The hardboard-lumber pallets withstood 

 impact better, racked much less during cornerwise drop testing (but failed 

 sooner), and performed similarly to the all lumber pallets during indoor and 

 outdoor handling and storage conditions. The study indicated that standard 

 helically threaded pallet nails can be used satisfactorily for both exterior and 

 interior exposure. 



PALLET DESIGN 



Block versus stringer design. — The literature contains conflicting opinions 

 of the relative merits of block versus stringer designs. Stern and Dunmire 

 (1972), after testing of yellow-poplar, hickory, and oak pallets before and after 4 

 years of service, concluded that the descending order of rough-handling resis- 

 tance of reusable pallets was picture frame (a block design with mitered lower 

 deckboard comers; see fig. 22-30), three-stringer design without notches in 

 stringers, and notched-stringer pallets. Kurtenacker et al. (1967) reached a 

 similar conclusion. 



Reeves (1975) found that stringer pallets required less lumber to construct, 

 and were stiffer, stronger, and more durable in use than block pallets without 

 "picture frame" design (fig. 22-35). 



E. G. Stem (1973a) found that both block and stringer designs can be service- 

 able. In a 1980 review of this chapter he noted that block pallets, given prefer- 

 ence to stringer pallets in Europe, have to be well built if they are to be used as 

 permanent warehouse and exchange pallets; he concluded that in this country, if 

 there is no compelling reason to use block pallets, they should be confined to 

 one-way expendable use. 



Deckboards of stringer type pallets. — There is general agreement, based on 

 laboratory tests, that impact resistance and rigidity of stringer-type pallets is 

 increased by leaving no space between the end deckboard and the deckboard 

 adjacent to it (fig. 22-31). This improvement has been noted in top deckboards 

 by E. G. Stem (1973b), R. K. Stem (1975), and Franco (1978). E. G. Stern 

 (1973b, 1977d) concluded that bottom as well as top end deckboards should be 

 snug against adjacent deckboards for improved performance. Six-inch-wide end 



