Stöd, R., Verkasalo, E. and Heinonen, J. 2016. Quality and Bending Properties of Sawn Timber from Commercial Thinnings of Scots Pine (Pinus sylvestris L.). Baltic Forestry 22(1): 148-162.

   In this study, the visual characteristics and static bending properties of Scots pine (Pinus sylvestris L.) sawn timber were determined using the material collected from thinning and final-felling stands in eastern Finland. The quality of boards was assessed based on the Nordic visual strength grading rules for timber, and the bending strength, and modulus of elasticity were determined according to the European standard test EN 408. Based on the visual strength grading, the majority of boards met the requirements of the visual grade T1, whereas the highest grade T3 was achieved by less than 10% of the boards. The bending strength and modulus of elasticity of sawn timber from the first thinnings were 42.0MPa and 10.2GPa, and those from the second thinnings 52.6MPa and 12.8.GPa, respectively. The distribution of theoretic strength classes indicated a strong focus on C30 or higher for the material from the second thinnings, whereas the strength classes of C24 or lower were most common for the material from the first thinnings. Regarding the bending properties, the sawn timber from the butt logs of the first-thinning trees was comparable with that of the middle or top logs from later cuttings. The strength and modulus of elasticity of the first-thinning material were relatively low, whereas the Scots pine sawn timber from the second commercial thinnings may be comparable with that from the current final fellings.

Keywords: bending strength, modulus of elasticity, visual strength grading, Pinus sylvestris L., sawn timber, structural products, thinning.