To improve production efficiency and quality of fiber-glass boatyards many research have been done both through technological as well as management aspects. One of these developments is Vacuum Assisted Resin Transfer Molding (VARTM) which is claimed to have high strength and material efficiency. This method has not much been applied in Indonesian boatyards, most of them are still using conventional hand lay-up. The research is aimed to investigate the strength of the composite and the optimum amount of materials to obtain the required strength for its application on boat buildings. Experimental approach was conducted in the research using 800 biaxial and 900 unidirectional E-glass for reinforcement, and vinylester (RIPOXY R-802-EX-1) resin for the matrix. The ultimate tensile strength and Young's modulus of the composites are obtained through tensile and flexural test based on ASTM D 3039 and ASTM D 790 standards. The data obtained are used to determine the optimum number of layers and fiber content on certain locations of the boat hull structure in order to comply with the requirements of classification rules.