eng Science and Education Publishing American Journal of Mechanical Engineering 2328-4110 2020-11-12 8 4 163 171 10.12691/ajme-8-4-3 AJME2020843 article Matin Mohebbi matinmoheby@yahoo.com 1 Mohammad A. Ghassemi 1 Hassan Ghassemi 1 Department of Maritime Engineering, Amirkabir University of Technology, Tehran, Iran Trim-tab is a device for controlling and stabilizing planing boats in different sea conditions. This paper presents to find dimensions of the trim-tab at various speeds of the boat to reach the minimum drag. The speed of the boat is from15 m/s to 30m/s. Drag of the boat is calculated by Stavisky¡¯s method. The minimum drag is found based on the optimum the trim angle. A Matlab program code is prepared for these calculations and all the all results such as drag, dimensions of the trim-tab, longitudinal center of pressure and time angle at different speeds of the boat are presented and discussed. http://pubs.sciepub.com/ajme/8/4/3/ajme-8-4-3.pdf trim-tab drag planing boat Stavisky¡¯s method