Ahamada Zziwa¹, Kambugu Robert¹, Simon Kizito², and Agatha Syofuna³

1. Department of Agricultural and Biosystems Engineering, Makerere University, Uganda

2. China Agricultural University, Beijing, China

3. Department of Forestry, Biodiversity and Tourism, College of Agricultural and Environmental Sciences, Makerere University, Uganda

 

 

Abstract: This study investigated the effect of knot size on flexural strength of E. grandis. Sample trees were obtained from Uganda National Forestry Resources Research Institute’s Eucalyptus grandis plantations at Kifu, Mukono district. Specimen preparation and testing was in accordance with ASTM D198 (2003). The effect of knot size on MOE and MOR were analyzed using linear regression analysis and ANOVA using Minitab software (version 14.0). Results showed that the mean MOE was 10,845.98 N/mm2 and mean MOR was 73.14 N/mm2. There was a significant relationship between flexural strength and knot size; timbers with more knots had lower MOE and MOR. The findings point to the potential of using knot size and number in visual timber grading in timber yards of most developing countries. Although E. grandis is taken to be self pruning, there is need for early pruning as a silvicultural practice to minimize knotty wood.

 

Key words: Knots, MOE, MOR, flexural strength, timber, wood, defects