Fpj Technical Note

A SUBSTANTIAL PERCENTAGE of 2 by 4 studs cut from southern pine veneer cores or small logs warp excessively when kiln-dried to 9 or 10 percent moisture content (MC). Warp can be significantly reduced by mechanical restraint during the drying process (Koch 1971). One practical way of applying restraint calls for a top load on each kiln stack to impress sharply toothed kiln sticks into each board (Koch 1974a). Another approach is to restrain studs individually between continuously turning pairs of rolls. An earlier report (Koch 1974b) described trials of a prototype continuous kiln with nine pairs of 4-inch-diameter, 34inch-long, power-driven, smooth rolls spaced 12 inches Abstract Studs cut from veneer cores and dried by four con. figurations of roll.feeding mechaniams (for a oontinuous kiln like a roll-feed veneer dryer) were compared to conventionally stickered studs. Roll-dried studs averaged leas crook (0.14 in.), bow (0.17), and twist (0.16) than those conventionally sUckered (0.22, 0.26, and 0.34 inch, respectively). The data seemed to favor the dryer configuration in which studs were roll.fed on edge and guided by double low-shouldered rings, in that crook averaged leaat with this arrangement. The major disadvantage of all four of the roll.fed configurationa testOO is the necessity for accurately sizing each green stud in width and thickness before admitting it to the kiln.