STUD: Improved Spruce Timber Utilizations : Prediction of Twist and Industrial Validation. Sub-task B9.1.

• It has been shown that the number of straight battens after drying can be easily increased by avoiding converting logs with a somewhat large left-hand spiral grain measured under bark and by avoiding converting the central cylinder of logs with a diameter about 50 mm around the pith. It is assumed that more than 10% of the trees (Norway spruce) exceed a spiral grain angle of 3° measured under bark. Between 80% and 90% of the studs from these trees displayed an unacceptable amount of twist (3°). It should be of great interest for the sawmill industry to be able to reject logs with respect to their overly large spiral growth in order to improve the straightness of sawn lumber in service (at low moisture content).Other conclusion drawn from this study is that the spiral grain angle and the annual ring curvature of the stud can predict twist. If it is possible to measure effectively spiral grain angle on the logs or on the sawn timber prior to drying the twist-prone material would be possible to sort out and thus increase the value of the timber products. Simple models expressed in diagram form can produce enough information about twist to be a useful tool for improving the number of straight studs after drying.Over 90% of the studs sawn closer than 50 mm from the pith from five trees displayed unacceptable twist when dried to 12% moisture content. All the studs sawn from a tree (five logs) with a left-hand spiral grain of about 15° displayed very large twist after drying and they were all classified as rejects, independent of the grading criterion. 

Ämnesord

LANTBRUKSVETENSKAPER  -- Lantbruksvetenskap, skogsbruk och fiske -- Skogsvetenskap (hsv//swe)

AGRICULTURAL SCIENCES  -- Agriculture, Forestry and Fisheries -- Forest Science (hsv//eng)

Nyckelord

Twist

spiral grain

shape stability

Norway spruce

picea abies

Forestry and Wood Technology

Skog och träteknik

Publikations- och innehållstyp

vet (ämneskategori)

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