Problem of fuel efficiency is one of the hot topic in vehicle designing process. There are many things that affect fuel efficiency, one of it is resistance. In the design process, engineer will consider the magnitude of the resistance that will occur, both when designing marine, air, or land vehicles because it involves the fluid media that is passed by the vehicle. Many ways have been done to add efficiency to the ship, such as optimizing the shape of the ship like the addition of bow, or also with the addition of tools that work specifically to reduce resistance such as stern foil. In this study, stern foil was used on patrol boats and examined at high speeds, namely Froude Number 0.6-1.3, and it was concluded that the load borne by the foil stern was too heavy in the full draft, so it was unable to work optimally and instead added more resistances to ship when the froude number reaches 0.9-1.3. But on FN 0.7, the resistance was decreased up to 16.279% and 13.194% with 3˚ and 0˚ stern foil respectively.