Optimum Cross Sections of Green Square-sawn Japanese Larch Timber with Pith Allowing for Reshaping Warped Cross Sections after Kiln Drying

A practical method was proposed for determining optimum cross sections of green Japanese larch timber with pith to improve the yield of products taking account of twist, crook, and bow caused by the drying process. Green Japanese larch square-sawn timber was dried to target moisture contests of 10% and 20%. The required cross-sectional dimensions of this timber were 105 mm×105 mm after drying and reshaping. Resultant twist, crook, and bow were measured. The optimum cross-sectional size of green square-sawn timber was calculated based on the data above. The calculated optimum size of green timber was affected by twist clearly more than by crook and bow for both target moisture contents. The theoretical cross-sectional size of green timber that maximized volume yield was 123.9 mm for specimens with target moisture content of 10% and 118.8 mm for specimens with target moisture content of 20%. When the cross-sectional sizes of green timber were these values, 98% of the total products met the required sizes.