Caracterização de alguns defeitos de toros e de madeira serrada de algumas espécies nativas

Abstract

This work aims to evaluate the defects of logs and sawn wood of the main commercial species of the forest industry in Mozambique. To achieve this objective, three species were characterized: the chanfuta (Afzelia quanzensis Welwf, the panga-panga (Millettia stuhlmannii Taub.) and the umbila (Pterocarpus angolensis DC..) In each species, 20 logs were characterized and these were grouped into two classes. 10 logs from the base and 10 logs from the top, and pieces of sawn wood from previously sawn logs were also characterized. Additional data were also obtained from interviews with those responsible for carpentry in the city and province of Maputo, selected according to the experience in the field of activity. The parameters studied were percentage of the presence of cracks, conicity, curvature and the number of defects per surface unit (m2) for logs and lumber. The mean values ​​and ranges of variation of the dimensions of the defects present in the logs and wood were also determined. sawn. In general, the results of the data collection revealed that cracks, scars, holes, living and dead knots are more present defects in the species under study. The results of the T-student test at a 5% significance level showed that, in general, there is not enough evidence to state that there are significant differences between defects present in round and sawn wood from the base and top of the three species. In turn, the analysis of variance showed that, in general, there are significant differences between the defects present in round and sawn wood from the base and top of the species under study. From the results of the Person correlation at 5% significance between the defects present in logs and sawn wood (holes, live knots and dead knots) it was found that there is a positive correlation. The questionnaire made to the carpentry shop revealed that cracks, knots, insect holes are more frequent defects in the species under study and in turn this same questionnaire revealed that these defects do not influence to a great extent the work of framing. Of the 60 logs classified based on the standard presented by AT,IBT(1982), 78.3% of the logs (47 logs) were classified in the first class, 16.7% in the second grade (10 logs) and 5% in the third grade (3 logs) which reveals the low intensity of the defects in the logs.