Izvleček: Raziskali smo fizikalne lastnos1 hrastovega lesa (Quercus sp.), pri katerem je od poseka minilo od 4 do 512 let in smo ga razdelili v stoletne starostne skupine 100-600. Mlajši les smo pridobili ob poseku dreves, starejši les pa iz zgodovinskih konstrukcij v Sloveniji. Izbrani les smo najprej dendrokronološko da1rali, izdelali normirane vzorce za analize ter določili gostoto, barvo, dimenzijsko stabilnost in sorpcijske lastnos1. Vizualno in v CIELab barvnem prostoru smo ugotovili, da je barva jedrovine s starostjo postala temnejša. Pri starem hrastovem lesu smo ugotovili tudi manjšo higroskopnost in izboljšano dimenzijsko stabilnost, zlas1 v tangencialni smeri, ter manjšo prečno krčitveno anizotropijo. Gostota hrastovega lesa se s staranjem ni spremenila, odvisna pa je bila od širine branik (naraščala je z večanjem deleža kasnega lesa). Rezulta1 nakazujejo, da na dimenzijsko stabilnost in higroskopnost poleg procesov staranja verjetno vpliva tudi mesto vgradnje in klimatska nihanja tekom uporabe lesa.

The quality potential and possibilities of using beech logs and sawn wood was investigated. Twenty-seven beech logs, with a mean diameter of 48 cm, were cut from 10 trees from a Hacquetio epipactidis-Fagetum site in SE Slovenia. The trees were pre-selected according to the national 5-level quality scale for forest stand evaluation, using two trees per class. Beech logs were classified according to the EN 1316-1 and sawn afterwards into unedged boards of 35 mm nominal thickness. Altogether, 250 boards were visually graded according to the rules of the European Organisation of the Sawmill Industry (EOS). Longitudinal vibration of logs and boards with the determination of stress wave velocity by MTG timber grader was additionally included into the quality assessment. In the case of logs, we confirmed significance of the relationship between visually assessed log quality and stress wave velocity. The stress wave velocity in logs was also related to the stress wave velocity in boards, where it varied considerably, especially for low-graded material. In the case of sawn wood, the relationship between sawn wood grade and stress wave velocity was insignificant. The research confirmed the possibility of presorting of logs, visually or non-destructively, for better classification and utilization of sawn timber.

Izvleček / AbstractIzvleček: Raziskali smo akus7čne lastnos7 bukovine (Fagus sylva7ca L.)

For the purpose of making of a solid body of an electric guitar the acoustic-and mechanical properties of walnut-(Juglans regia L.) and ash wood (Fraxinus excelsior L.) were researched. The acoustic properties were determined in a flexural vibration response of laboratory conditioned wood elements of 430 × 186 × 42.8 mm used for making of a solid body of an electric guitar. The velocity of shearand compression ultrasonic waves was additionally determined in parallel small oriented samples of 80 × 40 × 40 mm. The research confirmed better mechanical properties of ash wood, that is, the larger modulus of elasticity and shear modules in all anatomical directions and planes. The acoustic quality of ash wood was better only in the basic vibration mode. Walnut was, on the other hand, lighter and more homogenous and had lower acoustic-and mechanical anisotropy. Additionally, reduced damping of walnut at higher vibration modes is assumed to have a positive impact on the vibration response of future modelled and built solid bodies of electric guitars. When choosing walnut wood, better energy transfer is expected at a similar string playing frequency and a structure resonance of the electric guitar.