Abstract
In this study, the bending strength properties of finger-jointed (FJ) sugi (Cryptomeria japonica), hinoki (Chamaecyparis obtusa), and ezomatsu (Picea jezoensis) lumber having finger lengths of 17, 6.3, and 3.7 mm were investigated. Additionally, the bending strength properties of the hinoki FJ lumber with finger lengths of 6.5 and 6.7 mm were investigated. The following results are obtained. (1) There was no difference in the bending strength of the sugi FJ lumber with finger lengths of 17 and 6.3 mm. (2) No difference was observed in the bending strength of 17- and 6.3-mm hinoki FJ lumber composed of sawn lumbers with a bending Young's modulus of less than 14 kN/mm2. For FJ lumbers composed of sawn lumber with a bending Young's modulus of 14 kN/mm2 or more, the bending strength of FJ lumber with finger length of 6.3 mm was slightly lower than that of FJ lumber with finger length of 17 mm; however, the bending strength of FJ lumber with finger lengths 6.5 and 6.7 mm was equivalent to that of FJ lumber with finger lengths of 17 mm. If finger pitch is the same, the longer the finger length is, the larger the adhesive area; thus, it is considered that the bending strength of 6.5- and 6.7-mm FJ lumber is higher than that of 6.3-mm FJ lumber for larger adhesive area. Additionally, by setting the feed per knife during cutting to 0.50 mm, the bending strength of FJ lumber with finger lengths of 6.5 and 6.7 mm was significantly improved. (3) The bending strength for both sugi and hinoki FJ lumber with the finger length of 3.7 mm was low. (4) For ezomatsu, the bending strength of 17-, 6.3-, and 3.7-mm-length FJ lumber was the same.
