Tests were performed to determine the comparative stiffness and rigidity of nor-reversible, double-face, flush, four-way, notched, three-stringer, stapled 48" by 40", warehouse and exchange pallets made of 17 hardwoods occur on southern pine sites. The hardwoods included white ash, American and Winged elm, hackberry, red maple, nine oaks, (blackjack, cherrybark, laurel, northern elm past, scarlet, southern red, water, and white), sweetbay (magnolia), black tupelo, and yellow poplar. Each pallet was made of shook and single species. Of the 35 pallets tested, 29 had a 1 7/8"- wide stringers and six (four sweetbay and two yellow poplar) pallets had 2 1/4"-long, 15-guage, 7/16" crown, plastic-coated, pallet staples, 144 (204 for white ash pallets) per pallet.

The findings are directly comparable to those for matched nailed pallets, assembled with 111, hammer-driven, pointless, umbrella-head, helically threaded, hardened-steel, 3" x 0.120", pallet nails (see VPI & SU Wood Research and Wood Construction Laboratory Bulletins Nos. 158 and 165).

The following major observations were made:

1) The static bending stiffness of the pallets assembled with staples and nails was similar when, on the average, 77% of hte deflection was stringer-dependent. The northern red oak pallets were the stiffest and the post oak ones were the least stiff pallets among the stapled as well as the nailed pallets.

2) The impact rigidity of the stapled pallets was, on the average, one-fifth of that of the matched nailed pallets, suggesting the use of a considerably larger number of staples than nails if similar pallet rigidity is expected from stapled and nailed pallets.

3) The impact of rigidity of the stapled pallets as well as nailed pallets is inversely related to the specific gravity of the wood species used for the pallet shook, hence, to the test weights of the pallets of same type and design assembled with the same fasteners in a like manner. Among the stapled as well as the nailed pallets, those made of yellow poplar and sweetbay (having the lowest specific gravities among the hardwoods tested) and provided with 2 1/4"- wide stringers, were found to be the most rigid pallets. Among the stapled pallets provided with 1 7/8"- wide stringers, the southern red oak pallets were the most rigid ones and the winged elm pallets were the least rigid ones.