Structural Lumber Grade and Yield Estimates for Yellow-Poplar Sawlogs

Yellow-poplar is an accepted species for structural light framing in the National Grading Rule as adopted by the Northern Hardwood and Pine Manufacturers Association (NHPMA). If utilization of yellow-poplar as a framing lumber species is to be realized, lumber yield and residue information is needed to allow sawmill operators to evaluate the economic feasibility of producing structural lumber from yellow-poplar logs. A total of 53 yellow-poplar trees (337 8-ft. logs) were processed into 8-foot 2 by 4 structural lumber using the Saw-Dry-Rip system. The 2 by 4’s were then graded using the NHPMA structural light framing grading rules. Prior to sawing, the 8-foot logs were graded using the U.S. Forest Service hardwood and southern pine log grading rules. Also, log defects such as knot size, knot type, sweep percent, and crook percent were measured and recorded. Using stepwise regression techniques, the effects of various log characteristics on saleable structural lumber yield manufactured by the Saw-Dry-Rip system were examined. This examination, along with the comparison of the current traditional log grading system, led to a suggested yellow-poplar structural grading system. This log grading system incorporates the clear face concept of the southern pine log grading system with limiting defects established from the study of the influences of various log characteristics on structural lumber yield. Using the yellow-poplar structural lumber log grades to stratify the logs, regression models were developed that predict the amount of structural lumber by grade from 8-foot yellow-poplar logs processed by the Saw-Dry-Rip system as a function of scaling diameter. The equations for No. 2 and Better structural lumber yield are presented in this paper.

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