Solid Wood Products 2627 



shock absorbency. Stem (1969a) concluded that stiff-stock (non-hardened) nails 

 should be used, instead of hardened (medium-carbon) steel nails for the assem- 

 bly of plywood pallets, thus providing joints better able to absorb shocks; some 

 experts disagree with this conclusion, however. Use of two-piece decks, instead 

 of one-piece, also improves shock absorbency of plywood pallets slightly. 



Major advantages of plywood for pallet decks include resistance to splitting, 

 high impact and puncture resistance, continuity and smoothness, rigidity, and 

 light weight. Of increasing importance in automated pallet handling systems is 

 the surface smoothness of the decks and the accurate sizing possible when 

 plywood decks are used. 



Softwood plywood top decks yg-inch thick perform comparably to 13/16-inch 

 hardwood butted-end-board construction. For bottom deckboards softwood ply- 

 wood y4-inch thick may be needed to perform comparably with 13/16-inch 

 hardwood boards. 



E. G. Stem (1979b) found that stringer-type, double-face, four-way, flush, 

 non-reversible pallets with solid decks can be made very impact resistant if Va- 

 by 6-inch oak end boards are combined with y4-inch-thick plywood central 

 panels; performance was best when face grain of the plywood portion of the deck 

 was oriented perpendicular to the stringers. 



Hardwood plywood, in 1980, was little used for pallets, but new technology 

 for rounding up, and peeling short, small hardwood logs (fig. 18-252) should 

 improve the competitiveness of hardwood plywood for structural uses. Hard- 

 wood plywood pallet decks could be a large and important market for pine-site 

 hardwoods. 



Readers interested in design of plywood pallets are referred to the manual on 

 the subject published by the American Plywood Association (1975). 



COMPOSITE BOARD 



A hardwood flakeboard core overlaid on top and bottom with dense hardwood 

 veneer (fig. 24-53) has much promise for pallet decks. Mechanical properties of 

 such a composite are given in section 24-19, and an economic feasibility study of 

 an operation to manufacture the board is summarized in section 28-26. 



The hardwood composite has most of the advantages previously cited for 

 softwood plywood, and should be considerably cheaper to manufacture. More- 

 over, the hardwood raw material is closely adjacent to manufacturing regions 

 and population centers where pallet markets are concentrated. Because most 

 pallet deckboards are less than 4 feet long, short hardwood veneer logs — 

 available in plentiful supply — can be used for their manufacture. 



Perceiving that pallet decks need the impact resistance provided by solid 

 hardwood end boards, and the rigidity provided by a panel deck, Netercote et al. 

 (1974) combined hardwood lumber end boards with a central panel of hardwood 

 randomly oriented flakeboard, all overlayed on both surfaces with rotary-peeled 

 hardwood veneer to make a composite full-deck panel yg-inch thick. The veneer 

 was oriented with grain perpendicular to the end boards and parallel to the 

 stringers of the 48- by 40-inch warehouse-type pallets. The stiffness and resis- 



