en سازه کشتی Ship Structure مقاله پژوهشي Research Paper <span style="font-size:8pt"><span new="" roman="" style="font-family:" times=""><span style="font-size:10.0pt">This study presents a comprehensive experimental investigation into the hydrodynamic performance of high-speed planning vessels equipped with adjustable trim tabs. Two scaled 40-foot beam-type models were tested under controlled towing tank conditions to assess the effects of trim angle variations on resistance, dynamic stability, and transition into the planning regime. The tests evaluated both untrimmed and trimmed configurations using multiple trim tab heights, measuring resistance forces, trim behavior, and planning onset velocities. Results demonstrate that optimal trim tab deployment significantly reduces hydrodynamic resistance, lowers the Hump Resistance Region, and enhances vessel stability at critical speeds. Trim tab configuration &ldquo;B&rdquo; showed superior performance, enabling earlier planning transition with lower power demand and reduced bow impact. Additionally, this study addresses model scaling effects, construction tolerances, and control system calibration to ensure fidelity with full-scale vessel behavior. The findings underscore the importance of trim tab integration in the design of modern high-speed vessels, offering practical insights for resistance minimization, propulsion efficiency, and structural safety in dynamic marine environments.</span><span style="font-size:10.0pt"></span></span></span><br> &nbsp; High-speed vessels,Trim tab optimization,Hydrodynamic resistance,Planing performance,Experimental model testing,Towing tank analysis,Beam-type hulls,Resistance reduction,Trim angle effects,Marine propulsion efficiency 1 13 http://ijmt.ir/browse.php?a_code=A-10-8180-7&slc_lang=en&sid=1 Seyed Reza Samaei samaei@srbiau.ac.ir 10031947532846004422 10031947532846004422 No Assistant professor, Department of Civil Engineering, SR.C., Islamic Azad University, Tehran, Iran Mohammad Asadian Ghahfarokhi m.asadian@srbiau.ac.ir 10031947532846004423 10031947532846004423 Yes Assistant professor, Department of Civil Engineering, SR.C., Islamic Azad University, Tehran, Iran;