The study aimed to determine the effect of joint forms on the Ulin (Eusideroxylon zwageri Tet B) wood spread on its strength. The type of wood used in this study is the Ulin type (Eusideroxylon zwageri T et B), which is a beam with a standard market size that is traded 8 cm x 8 cm x 400 cm. The Ulin beam is wrinkled to four sides so that it gets a uniform size (wide and thick). Beams are made various forms of connection, namely straight edge joints, sloping edges and tilted edges related to each other.. Testing includes the mechanical properties of MoE and MoR using Panter MPK-5 test equipment in the laboratory of the physical and wood mechanics properties of Samarinda State Agricultural Polytechnic. The data analysis used was a Complete RandomIzed Design with 10 repeats, and further tests using LSD (Least Significant Difference). Based on the results of the research obtained it was found that; The defect-free Ulin wood used in the study had an average MoE value of 318,846.52 kg/cm2, MoR 1,049.66 kg/cm2 classified as wood with strong grade I, with an average test water content of 19.57% and a wood density of 1.00 g/cm3. The connection in wood results in a decrease in stiffness (MoE) between 23 - 57.04% of the rigidity (MoE) of wood without a connection, when the rigidity of wood without a connection is considered 100%. The form of the connection, greatly affects the rigidity (MoE) of the wood connection. From each treatment the shape of the sloping edge connection and the sloping edge joint produces the highest rigidity value (MoE).

Keywords : Ulin Wood, Connection form, MoE and MoR.