WVFA Mountain State Forestry Fall 2021

F E A T U R E D N E W S 10 West Virginia Forestry Association Mountain State Forestry | Fall 2021 www.wvfa.org Results of the Study Visual Assessment of Yellow-Poplar The analysis of grades included initial grading of the yellow-poplar boards in the rough form (kiln-dried, 4/4,) by both NHLA and NELMA grading rules and regrading following processing (surface and rip) into uniform dimensions of 6 inches wide by 7/8 inches thick by 10 feet long. For the purposes of this article, the key comparison is how the NHLA grades of the rough lumber graded out as NELMA structural grades following processing. Based on the American Panel Association (APA) standards provided in APA PRG 320 (2018), a softwood board should achieve at least a structural visual grade comparable to a No. 3 NELMA grade for use in the production of CLT panels. From the researched population of NHLA low- grade yellow-poplar, 54.6% received a structural visual grade above the standard requirements for CLT and GLULAM manufacturing. The percentages of boards that achieved a structural grade (at least No. 3) within their NHLA grades were: 2A (64.4%); 2B (66.3%); 3A (52.3%); and 3B (30.7%). The grade 3B, with over 69% of boards being Below Grade, presented the least amount of yield when used as structural grade material, based on NELMA rules; therefore this grade is considered least likely to result in a significant amount of suitable materials for structural lumber and might not be worth the cost of remanufacturing. Table 1 summarizes the grading results by NHLA grade and NELMA structural grade. Of particular interest is the percentage of No. 2 and better structural grades, by NHLA grade. This is a very important consideration, given that a board must be at least a No. 2 structural grade in order to qualify for the parallel layers of a CLT panel. Both NHLA 2A and 2B grades had No. 2 and better structural proportions above 40%. During the grading process, the structural grader identified the limiting defect on each board and those results are displayed in Table 2 and Figure 2. The most common limiting defects, overall, were knots and splits. The most common defects in grades No. 1, No. 2, and No. 3 were knots, while in Below Grade the most common defect was splits. Most of the observed defects, such as knots, shake, wane and slope of grain, are inherent in boards following manufacture at the sawmill, while splits and cracks are more commonly associated with handling and processing of the boards. In fact, Lamb (1992) 2 indicates that splits and cracks are associated with four factors: wood characteristics, processing, drying, and handling. There was no conclusive way to fully understand how many of these splits and cracks were caused by handling and processing the boards during the research. We were not able to track every board and determine the effects produced from each step of processing surface and rip the board. In this study, the primary objective was to estimate a final NELMA grade after processing surface and rip NHLA graded low-grade lumber. Defect Type Percent Defects per NELMA Grade (%) No. 1 (n = 80) No. 2 (n = 222) No. 3 (n = 211) BG (n = 541) Total (1054) Knot 84 76 62 24 47 Splits 4 14 21 43 29 Slope of grain 1 2 5 4 4 Decay 3 0 0 5 3 Shake 3 3 4 11 7 Wane 3 2 6 10 7 Bow 1 0 0 0 0 Other defects 1 3 2 3 3 Where: BG = Below Grade; N = number of boards. Table 2. Percentages of limiting defects, by NELMA grade and defect type. 2 Lamb, Fred. 1992. Splits and cracks in wood. In the Proceedings of the 43rd Annual Meeting of Western Dry Kiln Association Reno, NV, USA (1992), pp. 16–24. NHLA Grade Number of Boards (before processing) NELMA Grade 1 (number of boards after processing (%) No. 2 & Better SS No. 1 No. 2 No. 3 BG Percent 2A 441 75 (17.0) 31 (7.0) 88 (20.0) 90 (20.4) 157 (35.6) 44.0 2B 169 15 (8.9) 18 (10.7) 44 (26.0) 35 (20.7) 57 (33.7) 45.6 3A 354 41 (11.6) 24 (6.8) 62 (17.5) 58 (16.4) 169 (47.7) 35.9 3B 228 7 (3.1) 7 (3.1) 28 (12.3) 28 (12.3) 158 (69.2) 18.4 Table 1. Final NELMA grade distribution, by NHLA grade, based on pre-processing (rough lumber) NHLA grade and post-processing NELMA grade. 1 Where: SS = Select Structural and BG = Below Grade