A SYSTEM OF EQUATIONS FOR PREDICTION OF PLYWOOD VENEER TOTAL YIELD AND YIELD BY GRADE FOR LOBLOLLY-PINE PLYWOOD BOLTS

A system of equations was developed that predicts square foot veneer t otal yield and yield by grade for loblolly pine (Pinus taeda L.) plywo od bolts. The system predicts square foot yields based on a 1/8-inch p eel for all veneer, grade B and better full sheets, grade C full sheet s, grade D full sheets, a miscellaneous category consisting of grade C and better strips as well as fishtail and centercut, and a category c onsisting of grade D strip and D sawcore (full sheets that cannot meet requirements for grade D). The equation for prediction of total squar e foot veneer yield is a linear function of bolt volume within the sma ll-end diameter inside bark (SEDib) excluding the core, and volume in the tapering portion of the bolt outside the cylinder defined by SEDib . Equations for grade yield are constructed by multiplying predicted t otal yield by a function that predicts the ratio of yield in a particu lar grade to total yield. Therefore, the system is constrained so that predicted total yield is equal to the sum of predicted yields by grad e category. The ratio function depends on independent variables such a s bolt grade, SEDib, and bolt position in the tree. Since total volume was a dependent variable in one of the system equations and a predict ive variable in other nonlinear system equations, nonlinear 3-stage le ast squares techniques were used to estimate parameters in the system.