Solid Wood Products 2693 



accommodate the small crooked logs typical of pine-site hardwoods, greater 

 utilization of 4-foot veneer logs is desirable and, in the eyes of some manufactur- 

 ers, practical (fig. 18-252). Such 4-foot veneers can be end-scarfed to obtain 

 needed 8-foot lengths. A thousand square feet of three-ply ys-inch-thick panel 

 with oak faces and sweetgum or yellow-poplar core would weigh about 1 1 5 

 pounds more than this amount of loblolly pine plywood, which weighs about 

 1,100 pounds at 8 percent moisture content. Five-ply, ys-inch-thick plywood 

 with '/s-inch oak faces and sweetgum or yellow poplar inner plys would weigh 

 about the same as an all southern pine panel of equal thickness. 



Lutz and Jokerst (1974) studied the problem of using hardwoods for structural 

 plywood and concluded that, in general, new plywood products have been 

 readily accepted if they conform to existing standards such as PS 1-74 for 

 Construction and Industrial Plywood (American Plywood Association 1974). 

 This standard provides quality control and aids in acceptance by code authori- 

 ties. The standard lists five groups of species in which group 1 has highest 

 strength, and group 5 is the weakest. Domestic hardwoods in each of these 

 groups, as listed in PS 1-74, are: 



Group 1 — American beech, sweet and yellow birch, sugar maple, and 

 tanoak. 



Group 2 — Black maple, sweetgum, and yellow-poplar. 



Group 3 — Red alder, paper birch, and bigleaf maple. 



Group A — Bigtooth and quaking aspen, eastern cotton wood, and black 

 Cottonwood (western poplar). 



Group 5 — Basswood and balsam poplar. 



Not appearing in the foregoing list are the eastern and southern oaks, 

 hickories, red maple, black tupelo, or sweetbay. Amendments are made to 

 Product Standard PS 1-74 by a standing committee; it is a voluntary standard 

 developed by manufacturesrs, distributors, and users in cooperation with the 

 Office of Engineering Standards of the National Bureau of Standards. 



The first step, therefore, would be to have these species added to the proper 

 group in the standard, by formal request to the standing committee. Oak- 

 sweetgum or oak-yellow-poplar plywood should qualify for C-D panels and for 

 structural II panels which permit groups 1, 2, or 3 species in face, back, and all 

 inner plys. Structural I panels, however, are at present limited to group I species 

 in all plys. 



Yield of structural veneer from trees of four southern hardwoods. — See 

 table 12-5 through 12-10 for average yield of dry 1/6-inch, rotary-peeled veneer 

 by grade and tree-diameter class for yellow-poplar, sweetgum, white oak, and 

 black tupelo. Veneer grades tabulated are those defined by Product Standard PS 

 1-74. 



Yield of veneer from grade 3 Appalachian oak logs. — Craft (1970, 1971) 

 processed through a southern pine sheathing plywood plant a mill-run sample of 

 factory grade 3 Appalachian oak logs cut to 8-y2-foot lengths and averaging 11.7 

 inches in diameter at the small end. The sample logs scaled 3,567 board feet 

 Doyle scale, or 4,933 board feet International y4-inch scale. The yield of usable 



