Lumber Quality Research Articles

Stress wave sorting of red maple logs for structural quality

Existing log grading procedures in the United States make only visual assessments of log quality. These procedures do not incorporate estimates of the modulus of elasticity (MOE) of logs. It is questionable whether the visual grading procedures currently used for logs adequately assess the potential quality of structural products manufactured from them, especially those for which MOE is of primary concern. The purpose of this study was to investigate the use of stress wave nondestructive evaluation techniques to sort red maple logs for the potential quality of lumber obtained from them. Ninety-five red maple logs were nondestructively evaluated using longitudinal stress wave techniques and sorted into four stress wave grades. The logs were then sawn into cants and lumber. The same procedure was used to obtain stress wave times in the cants and lumber. The lumber specimens were then dried and graded using a transverse vibration technique. The results of this study showed that good relationships existed between stress wave times measured in logs, cants, and the lumber produced from the logs. It was found that log stress wave grades have positive relationships with the lumber grades. Logs with high stress wave grades produced high-grade lumber. These findings indicate that the longitudinal stress wave technique has potential in sorting logs and cants for the production of high MOE products.

Linear programming and optimizing lumber quality composition in secondary hardwood dimension mills

Linear programming has been widely applied in the secondary hardwood dimension manufacturing industries to solve the least-cost lumber grade mix problem, which refers to the search for minimal raw material costs. Most existing models are based on the assumption of a simple linear relationship between lumber grade mix and yield. However, this crucial assumption has never been verified. In this study, the results from a five-factor mixture design statistically proved that none of the cutting bills tested has a simple linear relationship between yield and different lumber grade mixes. It was observed that cutting bill characteristics and lumber quality affect the relationship between yield and lumber grades. Cutting bills that require wider and/or longer parts tend to behave non-linearly. In addition, the more dissimilar lumber grade qualities that are processed, the more likely is the occurrence of a non-linear response. The inability to predict the relationship between yield and lumber grades, coupled with the high percentage of non-simple linear relationships observed in this study, brings into question the validity of the linearity assumption applied in previous linear programming models. Further efforts are needed to construct a new least-cost lumber grade mix model that does not rely on the assumption of a simple linear relationship between lumber grade mix and yield.

The effect of two bucking methods on Scots pine lumber quality

Modern harvesters are equipped with measurement and bucking optimization systems able not only to continuously measure the length and diameter of the stem but also to predict the profile of the unknown part of a stem and to calculate the optimal cross-cutting points for the whole stem. So far, tree-bucking optimization in the Nordic countries has been efficiently applied only with spruce because the quality of pine and birch varies much more both within a stem and between stems. Since limitations in the measuring equipment mean that the presence and position of grade limits as well as additional defects in the stem will normally have to be detected and estimated manually. Consequently, optimization works inefficiently because the harvester operator is continuously forced to disregard the cutting suggestions supplied by the harvester’s automatic system. This paper presents the outcome of research intended to define how change from the current quality bucking principle to automatic bucking affects lumber quality. The study is based on field experiments and test sawing data on 100 Scots pine (Pinus sylvestris) stems from southwestern Finland in 2001. Automatic bucking does not markedly lower the amount of good-quality lumber compared to quality bucking. Since automatic bucking inevitably leads to log distribution that matches the length requirements of customers better, it may be regarded as appropriate for these harvesting conditions.

Log and Lumber Grades and Value from a Douglas-Fir Stand 20 Years after Thinning and Biosolids Fertilization

Abstract Three replications of four treatments: biosolids fertilization, thinning, thinning plus biosolids fertilization, and untreated control were established in 1977 in a dense, low site, 55-yr-old Douglas-fir (Pseudotsuga menziesii) stand in western Washington. In 1998, 12 trees from each treatment were harvested, bucked into logs, and sawn into visually graded lumber. Taking into account effects of treatments on stand yield and log grades, biosolid fertilization only, thinning only, and thinning combined with biosolids increased log value/ac by $1,142 (19%), $3,642 (62%), and $9,069 (155%), respectively, over the untreated control. When treatment effects were viewed in terms of changes in lumber yield and quality, per acre gains over the control were $2,107 (26%), $5,683 (70%), and $10,708 (132%), respectively. Willingness to pay analysis indicates that if the landowner intends to manage the stand to a rotation of about 75 yr, each of the treatments, and especially the combination of thinning and applying biosolids, appears to be financially attractive at both 5 and 9% interest rates. However, if the rotation had been set at 55 yr, only the thinning/biosolids combination at 5% interest rate would entice management to delay immediate harvest. West. J. Appl. For. 19(1):34–41.

Is a national park the way to save Taiwan's endangered cypress forest?

Two species of cypress (Formosa cypress and Taiwan cypress), endemic to the highlands of Taiwan, have been reduced to forest stands that represent barely one third of their original extent. These trees are similar in longevity, lumber quality, stature and majesty to the redwood trees of North America. Although logging halted in 1989, removal of dead standing trees and downed logs, as well as recreational pressures remain a threat to these cypresses. Environmental groups favor absolute protection via the establishment of a national park. However, indigenous peoples are distrustful of the national park solution, because they feel that they have been adversely affected by the establishment of parks elsewhere in Taiwan. The Government's Forestry Institute favors continued removal of dead trees and artificial reforestation, and cautions that national park status might only exacerbate recreational pressures and hence risk.

Predicting branch diameters on second-growth Douglas-fir from tree-level descriptors

The quality of lumber and veneer recovered from logs of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) is directly influenced by the maximum limb size attained on the crop tree. Because limb sizes are influenced by stand-density regimes, a need has arisen for quantitative tools that link a wide array of silvicultural regimes to wood-product quality by accounting for silvicultural effects on crown development. An equation for estimating maximum branch size at a given level within the live crown was developed from data collected on 96 felled sample trees in the Coast Ranges and Cascade foothills of Oregon and Washington. Height and basal diameter of the largest branch within each live whorl were measured on each felled tree, and a predictive equation was developed by various regression techniques. The final mixed-effects nonlinear model estimates maximum branch size as a function of depth into crown and tree diameter at breast height, height, and live crown length.

木質材料 カラマツ同一等級ラミナ構成集成材の強度性能 （第１報） カラマツ同一等級構成集成材の実大材曲げ強度性能

With a continuous mechanical grading-machine (MG) which can be used to measure Young's modulus (MOE) of lengthwise portion of a lumber, the average of MOE (MGEAVG) and the minimum of MOE were obtained on 6400 lumbers of Japanese larch. The average of the difference (=MGEAVG-MGEMIN) was 0.92GPa and MGEMIN was extremely lower than MGEAVG in some cases.Next, horizontally (H-type) and vertically (V-type) laminated glulams of homogeneous-grade composition were made to examine the bending strength of glulams. They were composed of lumbers classified according to MGEMIN, because it was supposed that MGEMIN should be useful for estimating the bending strength (MOR) of glulams.In V-type glulams, the laminating effect which lowers the variation of MOR distribution was evidently observed. On the contrary, MOR of H-type glulams was almost independent of the number of laminae, because it depends on the quality of lumber in the outermost layer. Particularly, this result suggests that lumbers for the outermost layer of H-type glulams should be classified according to MGEMIN instead of MGEAVG.

Stem Characteristics on the Lower Log of 35-Year-Old Western Redcedar Grown at Several Spacings

Abstract Information on stem characteristics of western redcedar (Thuja plicata) grown in managed stands is quite limited. Stem characteristics are important because they influence the quality of logs and lumber produced. We measured branch diameter, number of branches, taper, and fluting severity on the first 5m log of stems grown at spacings of 1.8 to 4.6 m in a 35-yr-old spacing trial on the University of British Columbia Research Forest. Average branch diameter increased from 15 mm to 25 mm as tree spacing increased from 1.8 m to 4.6 m. Number of branches per unit of stem length was unaffected by spacing. Trees at wider spacings tended to be more tapered and have more butt swell than those at narrower spacings. At wider spacings, more trees showed fluting, and that fluting was more severe than at narrower spacings. However, most trees had no fluting or only mild fluting even at the 4.6 m spacing. Branch diameter, taper, and fluting were all related to stem diameter. Smaller diameter stems tended to have smaller branches, less taper, and were less likely to have severe fluting than large diameter stems. Branch diameter was larger at wider spacings even for trees of the same stem diameter. West. J. Appl. For. 12(1):9-14.

An Empirical Assessment of the Dimensions of Softwood Lumber Quality

Abstract On the basis of previous research (Garvin 1984, Parasuraman et al. 1988), an 80-item, 12-dimension model for measuring total product quality in softwood dimension lumber was developed. This model was tested using confirmatory factor analysis and buyer perception data from three segments of the softwood dimension lumber market. Test results did not support the 12-dimension model. Consequently, exploratory factor analysis was used to develop a model consisting of five dimensions: Supplier/Salesperson Characteristics, Supplier Services, Supplier Facilities, Lumber Performance, and Lumber Characteristics. This model was tested by asking softwood lumber buyers (the same ones used for original model development) to rate their suppliers on the five dimensions. On each dimension, buyers rated most-preferred suppliers higher than least-preferred suppliers, providing evidence of the model's appropriateness. For. Sci. 42(4):407-414.

Grade yields and wood properties of Norway spruce [Picea abies (L.) Karst.] from the Maritimes

Norway spruce [Picea abies (L.) Karst.] is one of the major non-native softwood species in the Maritimes. A project was undertaken to evaluate the grade yields and mechanical properties of Norway spruce. The project also provided comparative information on the wood quality of two Norway spruce provenances from Germany and Poland. Four plantations were selected for the study with two of these plantations containing trees of known provenances. One plantation was mature and the other three were juvenile. In total, 530 pieces of lumber and the same number of matched small clear specimens were tested for bending properties. Prior to testing, the lumber was visually graded according to both British and Canadian specifications. Quality of lumber varied significantly between sites. Lumber from the Polish provenance had slightly better mechanical properties than that from trees of the German provenance. Compared with published information, the plantation-grown Norway spruce had lower clear wood bending properties and specific gravity than primary eastern Canadian spruce species and balsam fir, and natural Norway spruce grown in Europe. Key words: Norway spruce [Picea abies (L.) Karst.], wood quality, bending properties, grade yield

Adaptive control of stochastic batch lumber kilns

Lumber drying is a stochastic batch process. Thousands of dimension lumber are stacked and charged into a kiln where circulating air with controlled and varying temperature and relative humidity is used as the drying medium. The objective is to maximize overall lumber quality within reasonable drying time. Due to varying individual lumber properties and other product and process conditions, boards show a distribution of drying related degrade; and furthermore, consecutive batches do not necessarily behave the same way. The control problem is to continuously adapt a drying schedule for the remaining time to maximize the performance of each individual batch. Final product value can be inferred through a stochastic process model which in turn can be updated for accuracy by an observed process variable. Actual product value can only be assessed at the end by direct measurements.

Effect Of Span-Length On The Reliability Of Truss Bottom Chords

As input to the development of an LRFD specification for wood construction, seven truss patterns were studied to determine the impact of lower chord length on (conditional) probability of failure. The truss spans ranged from 5.59 m (18.33 ft) to 20.2 m (66.33 ft). The tensile properties of the lower chord were simulated using a lumber model that characterizes the serial correlation of tensile strength and modulus of elasticity (MOE) along 0.76 m (30 in.) segments of lumber. A companion value of bending strength for each piece of lower chord lumber was simulated based on the average MOE of the segments. Combined stress analysis was used to calculate the theoretical probability of failure of all the segments composing the lower chord. Based on the results and assumptions of the study, truss span length had no significant effect on the reliability of truss bottom chords. Also, truss pattern and lumber quality appear to have strong impacts on the reliability of bottom chords.

Long-Term Effects of Thinning and Pruning on the Quality, Quantity, and Value of Oak Lumber

Abstract After 32 years, experimental plots established to examine thinning levels and pruning effects were harvested. Randomly selected trees in each treatment were felled and sawn into 4/4 lumber, and the lumber from each tree was tallied by grade. For black oak, the species that became largely relegated to the understory, thinning caused a significant increase in the total volume outturn with the greatest increase occurring in the lowest lumber grade (3B). For scarlet oak, the species that became primarily dominant and codominant, thinning increased the total lumber yield per tree with most of the increase accumulating in the lumber grades #1C and #2C. Pruning did not affect the quantity or quality of lumber outturn in either species. North. J. Appl. For. 5:258-260, December 1988.

Economics of Thinning and Pruning – A Case Study

This case study, conducted 20 years after thinning and pruning in a 33-year-old mixed stand of 86% Douglas-fir and 14% western hemlock, showed that the effect of thinning was to reduce mortality when compared with a control. Thinning increased merchantable volume by 88% compared with 44% in the control, although there was no difference in tree growth rate between the two plots.Associated with pruning, however, were severe grain distortions and very brittle grain structure of wood around pruning stubs, which resulted in poor lumber and veneer quality compared with product quality from the control.Indications are that total stand revenue would have been higher had the treated plot remained untreated, but would have been highest had it been thinned only and not pruned.

Betriebsmessungen an Kanaltrocknern mit Querbelüftung

Measurements were carried out of air velocity, temperature and lumber moisture content on five cross circulation drying tunnels with heat recovery equipment at Swedish saw mills, and the power consumption of the blower motors was determined. The measurements were completed by the evaluation of works' records, giving data of water removal and energy consumption. The mean air velocity along height of stack showed variations between 0,35 and 1,69 m/s for different tunnels and piling properties and the velocity distribution was of different character. With regard to the quality of export lumber (discolouration, resin flow) a maximum dry bulb temperature of 50°C was not exceeded and the wet bulb temperature was not higher than 35°C at the initial stage of drying. At these temperatures there may arise stains caused by fungi, the kiln operation thus must be balanced between jungi and cracks. In one plant a drying schedule was worked out on this basis.—This final mean moisture content varied between 12.2 and 15.7% for sideboards and between 19.7 and 24% for planks, the initial moisture content was 112...122% and 62...87% respectively. The moisture content distribution is shown by statistial diagrams. The total energy consumption was approx. 830 kcal per kg of water removed or approx. 1280 Mcal per standard at one plant, and according to works' statistics at another plant was rated at an annual average of 880 to 1010 kcal per kg water removed or 1160 to 1290 Mcal per standard, the energy consumption increasing with time, probably caused by corrosion in the heat exchangers.