The present paper contains results of experimental study on a semi-planing catamaran. The aim of this study is to find the effect of hydrofoil usage on resistance of semi-planing catamaran and achiving optimal attack angle,arrangement of hydrofoils and displacement center of gravity.Tests have been done without and with hydrofoils in certain arrangement with different angles of attack then the results are compared.Results show that considerable resistance reduction obtained in semi-planing vessels which equiped with hydrofoil in optimized angle of attack in service speed range. Meanwhile the hydrofoils arrangement and the angle of attack are important so unsuitable design causes the instability in the motion and may be increases hydrodynamic resistance.

كلمات كليدي:

Catamaran – Hydrofoil - Model Test – attack angle - Hydrodynamic Resistance