Abstract
Material characteristics of large diameter sugi logs grown in Miyazaki and flat squares sawn from them were investigated and their bending performances were examined. Modulus of elasticity from longitudinal vibration (Et) of first logs was about 19% lower than that of second logs. However, modulus of rupture in bending (MOR) was only 2% different between lumber without pith sawn from first logs by taper rule sawing and lumber with pith sawn from second logs by center rule sawing, and the difference was not significant. In relationships between Et of logs and Et of flat squares, Et increased only 2% for lumber with pith obtained from second logs, while Et increased 25% for lumber without pith obtained from first logs. It shows that taper rule sawing is an effective method to improve the bending performances. Also, it shows that its effect easily appeared in logs with lower Et and larger taper rate (Tr).
