Bow variation in kiln-dried boxed-heart square timber of sugi (<Emphasis Type="Italic">Cryptomeria japonica</Emphasis>) cultivars |
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| Authors: | Kana Yamashita Yasuhiko Hirakawa Shuetsu Saito Hiroshi Nakatani Motoyoshi Ikeda |
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| Institution: | 1.Forestry and Forest Products Research Institute,Tsukuba,Japan;2.Prefectural Agricultural, Forestry & Fisheries Research Center,Forest Products Research Laboratory,Imizu, Toyama,Japan;3.Forestry Research and Instruction Station of Kumamoto Prefecture,Kumamoto,Japan |
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| Abstract: | To evaluate the bow variation in boxed-heart square timber of sugi (Cryptomeria japonica), bows from kiln-dried timber for five sugi cultivars with different longitudinal shrinkage trends were compared for two
stem heights. Two general trends were observed, depending on the cultivar: (1) either the bow was larger at the lower than
at the upper part of the stem, or (2) the bows at the lower and the upper parts of the stem were similar. In timber that had
larger bow values, the gradients of longitudinal shrinkage were large across the radius and along the length of the timber.
There was a positive relationship between the bow and longitudinal shrinkage. These results suggest that the bow variation
between the timbers was caused by a variation in longitudinal shrinkage, which was affected by the microfibril angle. Furthermore,
the bow was inversely proportional to the modulus of elasticity, which suggests that timber with a low modulus of elasticity
is susceptible to a large bow due to large longitudinal shrinkage. |
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