Stern flap application on planing hulls to improve resistance

Drag is one of the main factors in improving fuel efficiency. Various study in regards to improve drag performance of a planing hull amongst them is a stern flap. The main parameters to design a stern flap are span length and angle of stern flap. The stern flap works by changing pressure distribution over the ship's bottom and creating a lift force on the stern transom part. This study aims to analyze the behavior of stern flap in variations of span length and angle of stern flap towards drag performance of Fridsma hull form. Finite Volume Method (FVM) and Reynolds-Averaged Navier-Stokes (RANS) are used to predict the hull resistance during simulations. Results show that shear drag is very sensitive towards the total drag value, proving that shear drag valued at least 60% of the total drag in each planing hull multi-phase characteristics phase. Stern flap with 58% of hull breadth span length installed at 0° is considered the most optimal, reducing 10.2% of total drag, followed by 18% displacement reduction. In conclusion, the stern flap effectively improves the Fridsma hull’s total drag and its components on 0.89 < Fr < 1.89.