心持ち角材の乾燥性

抄録

Box-hearted square timbers are very liable to ckeck containing heartshake on the end where splits develop on the surfaces by growth stress and drying stress. In order to prevent check and split, veneers were bonded on the surfaces of square timber perpendicularly intersecting each fiber direction to reduce the shrinkage during drying.
The summary of the results obtained is as follows:
(1) Checking and splitting can be minimized or eliminated by decreasing the surface shrinkage of square timber.
(2) Internal check partially occurred in wood at high temperature conditions during vacuum drying of timber with high frequency heating. The drying condition of eliminating check and split in wood was below 50°C wood temperature.
(3) Tensile stress was distributed in the shell of timber while compressional stress was distributed in the core. Though these stresses increased or decreased during drying, there was no reversal in drying stress.
(4) Impregnating the cross section with polyethylene glycol prevented checking and heartshaking of cross section.
(5) The most suitable adhesive for bonding surface square timber and veneer was a resorsinol resin because of its heat resistance and its ability to bond with wet wood.