• Journal of the Korean Wood Science and Technology
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• v.18 no.3
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• pp.53-68
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• 1990

This research has been executed for maximization of lumber yield and more efficient use of small diameter logs. Sample logs from thinnings carne from densed artificial stands at the Kwangnung Experimental Forests situated in the central region of Korean peninsula. Species of sample logs were obtained to execute sawing and strength test for larch, and lumber strength test in full size for pitch pine and Korean pine. A survey on sawmills consuming domestic logs was carried out to know sawmill production, costs and utilization structure of lumber as a guide to business analysis. Results showed that sawing pattern from small logs less than 15cm in diameter was necessary to cut 9cm by 9cm square per one log in order to obtain high lumber recovery and provide for wide market needs. The total lumber yield of squares plus side boards was 56 percent to 58 percent from small logs and the yield for log sweep in 30 percent decreased by 24.5 percent in sawing production, compared to yield for straight logs. In sawing efficiency, production of lumber by twin band saw could be improved 238 percent higher than lumber of the same species produced by conventional sawmilling methods, and sawing accuracy with twin band saw was much higher at the lumber production than band saw. Lumber from the small larch logs has shown 70 knots per $m^2$ on its faces and also lumber showed lots of face checkings by air drying on the yard, compared to other species. MOR in bending of lumber in full size from small logs of larch was found ranging from 380kg/$cm^2$ to 460kg/$cm^2$, resulting in 40 percent less than the strength from clear small specimens. In lumber containing knots, cross grain, etc, longitudinal stress wave speed was delayed about 48 percent by defects in lumber from both larch and pitch pine logs. The surveyed sample sawmills consumed the domestic logs at the rate of 54 percent to 84 percent in the total timber consumption, showing high consumption at mills located in the mountains.

• Journal of the Korean Wood Science and Technology
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• v.24 no.1
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• pp.11-16
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• 1996

The purpose of this paper is to present a summary of assignment design values according to domestic softwood structural lumber grading rules. Allowable stresses for visually graded lumber were determined from basic data on small. clear specimens. The data corrected for variability such as natural defects and other factors. The procedure adopted by Japan was used for assigning allowable design values. Strength ratios in relation to each defect were taken from ASTM D 245-81. Korean pine(Pinus koraiensis S. et Z.), Korean red pine(Pinus densiflora S. et Z.), Japanese larch(Larix leptolepis Gordon) and Needle fir(Abies holophylla Max) were applied to this study. The calculated allowable stresses were same in Korean pine and Korean red pine. These values were highest in Japanese larch lowest in Needle fir. So, it is desirable for these species to be classified into different catagories Species Group. However, accurate comparison in design values on lumber grading rules among U.S., Japan and Korea was somewhat difficult. And full scale testing will be necessary for accurate determination of the correction factors to setting up design values.

• Journal of the Korea Furniture Society
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• v.23 no.4
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• pp.407-414
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• 2012

In order to develop the end use of cylindrical laminated veneer lumber (LVL) such as wooden crafts, the light resistance properties of natural dye-colored and finished cylindrical LVL was investigated. The study results were as follows; The cross section of LVL showed the higher light resistance than its tangential section, and the light resistance also increased with surface coated. On the other hand, LVL specimen were colored by 9 natural dyes of amur cork-tree etc., and the natural and apparent hue harmonized with wood was found after coating and light resistance test. Particularly, The dyes extracted from amur cork-tree, persimon and sappan wood showed orange color, reddish brown and red color respectively, giving an accenting effect to original wood color.

• Journal of Korea Foresty Energy
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• v.22 no.1
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• pp.44-48
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• 2003

Flexural properties were investigated on clear specimens made from small diameter thinned trees of pitch pine (Pinus rigida Mill.), Japanese red pine (Pinus densiflora Sieb. et Zucc), Japanese larch (Larix kaempferi Carr.), and sawtooth oak (Quercus acutissima Carr.). MOR and MOE values of small clear specimen were depended on the species. The highest density of sawtooth oak shows the highest values of MOR and MOE. However, the lowest density of Japanese larch shows the lowest values of MOR. It was also shown that flexural properties could be predicted by stress wave MOE, since the correlations between stress wave MOE and flexural properties were relatively good.

• Journal of the Korean Wood Science and Technology
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• v.31 no.6
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• pp.22-30
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• 2003

This study was performed to obtain the basic data for high quality timber production and efficient utilization by investigating the effect of pruning on timber quality of domestic plantation-grown Korean pine (Pinus koraiensis Sieb. et Zucc.). The results were summarized as follows:Dead knots (unsound knots) in the pruned logs occurred more at upper parts when compared with in non-pruned ones. The numbers of knots on surface in heavily pruned trees were less than those in non-pruned trees, but there was no significant difference in moderately pruned trees. The required period to reveal clear timber surface without defects after pruning increased proportionally with the increase of knot diameter. The yield of clear lumber production increased by about 10% after 14 years from moderate pruning. The quality grade of log improved with more pruning practices. Knots appeared the most important factor in lowering the log grades.

• Journal of the Korean Wood Science and Technology
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• v.31 no.2
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• pp.16-23
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• 2003

The study was performed to obtain basic data for high quality timber production and efficient utilization of woods by investigating the effects of thinning on timber quality of domestic Korean pine(Pinus koraiensis Sieb. et Zucc.) planted. The results of this study were summarized as follows ; Comparing the appearance of knot per one meter on log surface, the heavy thinned trees contained less knots than non-thinned ones. And the ratio of dead knots was decreased in heavy thinned trees compared with the non-thinned ones, but the knot size was increased. The inclination angle of dead knot is larger than that of live knot. The crooked logs in heavy thinning plot appeared less than those in non-thinning plot. In heavy thinning plot, the log circle percentage of cross section and the ratio of clear lumber were increased, compared with in non-thinning one. The grade of log was the highest in heavy thinning plot.

• Journal of the Korea Furniture Society
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• v.24 no.4
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• pp.408-415
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• 2013

In order to evaluate a feasibility of industrial art use of veneer such as cylindrical laminated veneer lumber, the veneers of 4 species of Korean pine, radiata pine, yellow poplar and Japanese cypress were natural dye-colored and clear finished. Natural dyes were red color originated from sappanwood, blue color from polygonum indigo, and yellow color from Amur cork tree and gardenia. the clear coats of crack seal clear and UV protection oil were applied on the dyed veneer. The dyeing and finishing characteristics through fading test were summarized as follows; In non-dyed and non-finished Korean pine veneer, lightness was decreased and yellow and red hues increased after fading test. In natural dyed- and finished-veneer, color difference of gardenia-mixed Amur cork tree was generally highest, and that of polygonum indigo was lowest. Compared to non-treatment of veneers of Korean pine and yellow poplar, color difference decreasing effect by finishing was shown in crack seal clear and UV protection oil. In addition, UV protection oil was more favorable than crack seal clear with more decreased color difference. In result, maximum values of color difference after fading for 8 days were recorded about 16 to 20, which are remarked 'very much' of 12.1 or more when reviewing with 'National bureau of standards unit in USA'.

• Journal of the Korean Wood Science and Technology
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• v.39 no.1
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• pp.1-7
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• 2011

Recently, the visual grading rule of Korea Forest Research Institute (KFRI) was revised and it is necessary to investigate the distribution characteristics of visual graded lumber in accordance with the revised rule. Therefore, in this study, the distribution characteristics of bending strength was investigated with revised visual grading rule and changed prior rule, respectively. The size of specimens was $38{\times}140{\times}3,000$ (mm) and the species were $Larix$ $kaempferi$ and $Pinus$ $koraiensis$. The moisture content was under 18% and the specimens were tested in accordance with ASTM D-198. The number of No. 1 and 2 grades, suitable for structural lumber, was increased when the revised visual grading rule was applied. Moreover, the revised rule was more effective to distinguish sharply between No. 1 and 2 grades and below No. 3 grade. Meanwhile, the lower 5% exclusion limit and allowable stresses were generally decreased when revised visual grading rule had been applied. However, the announcement of Korea Forest Service, tested with small clear specimen, was much lower than the allowable stresses of this test, tested with structural lumber. Therefore, the revision of allowable design values should be considered for more exact use and effective structural design.

• Mycobiology
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• v.30 no.1
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• pp.37-40
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• 2002

The susceptibility of radiata pine sapwood to fungal attack and the ability of selected fungicides to control colonization of sapstain and mold fungi on green radiata pine sapwood were evaluated. Radiata pine sapwood was highly susceptible to fungal staining, suggesting that prompt application of fungicides after sawing is essential for preventing fungal colonization. The ability of commercial fungicides to prevent fungal discoloration on radiata pine sapwood was assessed using an accelerated 6-week test on small samples in the laboratory, and in field tests using bulk-piled boards exposed outdoors for 6 weeks during summer rainy season. In laboratory tests, Hylite extra provided excellent protection against fungal discoloration even at the lowest concentrations. Hylite clear, Britewood S, and NP-1 Plus provided good short-term protection(2 to 4 weeks), but higher chemical loadings were, required for long-term protection(6 weeks). Woodguard produced little or no protection over the test periods. In field tests, Kathon 893 provided markedly superior protection at the concentration of 0.5 percent or higher. NP-1 Plus provided relatively good protection at all concentrations evaluated. Hylite extra was effective only for short-term protection(2 to 4 weeks) at all concentrations tested, but higher solution strengths were needed for longterm protection.

• Journal of the Korean Wood Science and Technology
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• v.25 no.1
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• pp.8-14
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• 1997

Stress wave velocity, wave impedance, and stress wave elasticity of small, clear bending specimens of five domestic softwoods (Pinus densiflora, Pinus koraiensis, Chamaecyparis obtusa, Cryptomeria japonica, and Larix leptolepis) and four tropical hardwoods(Kempas, Malas, Taun, and Terminalia) were correlated with static bending modulus of elasticity(MOE) and modulus of rupture(MOR). The degree of correlation between stress wave parameters and static bending properties was dependent on wood species tested. Stress wave elasticity and wave impedance were better predictors for static bending properties than stress wave velocity for each species individually and for softwood or hardwood species taken as a group, even though elasticity and impedance were nearly equally correlated with static bending properties apparently. Based upon the correlation coefficient between stress wave parameters and static properties, stress wave elasticity and wave impedance were found as stress wave parameters which can be used for the purpose of the reliable and successful prediction of bending properties. The degree of correlation between static MOE and MOR was also different according to wood species tested. Static MOE was nearly as well correlated with MOR as was stress wave elasticity. The results of this research are encouraging and can be considered as a basis for further work using full-size lumber. From the results of this study, it was concluded that stress wave measurements could provide useful predictions of static bending properties and was a feasible method for machine stress grading of domestic softwoods and tropical hardwoods tested in this study.