Radially sawn timber : Knots - number, type and size in star-sawn triangular profiles of pine (Pinus silvestris L) and spruce (Picea abies Karst)

This paper describes the appearance and number of knots in star-sawn triangular profiles of pine (Pinus silvestris L) and spruce (Picea abies Karst). The emphasis is placed on obtaining the volume yield of boards with a given knot appearance, together with the sizes of the fibre disturbances around the knots and how they affect the yield. The test material has been taken from three regions in Sweden and is made up of butt logs of pine and of normal and fast-growing spruce. The results show that a large proportion of the knots found in the triangular profiles from butt logs are unacceptable in further refinement of the timber and must be removed. Very few healthy knots can be found. To produce knot free boards, a volume reduction of on average 8 and 21 percent is obtained for pine and spruce respectively, calculated with respect to the original profile volume. If the fibre disturbance around the knots is also removed, a further volume loss of 5 percentage for pine and 6 percentage for spruce is obtained. The boards produced have a broad spectrum of lengths between 2 and 500 centimetres for pine and between 2 and 400 centimetres for spruce