Comparison of hydrodynamic performance of a monohull planing vessel equipped by combined transverse step and transom wedge with a no appendage model: An experimental study

One of the most well-known strategies to eliminate or reduce the longitudinal instabilities in planing hull, is to reduce the trim of the craft. In the current study, porpoising is controlled through creating a transverse step, and the combination of adding a wedge to the stern and transverse step in the vessel. Usually, performance of stepped boats is not suitable in pre-planing regime. However, through the proposed method, stepped model performance can be improved prior to the planing regime. The investigated craft is a 2.56 m long monohull high speed model with speed range of 1,3,5,7 and 9 m/s. The obtained results indicate that best performance is acquired by the step and wedge model at the beginning of the planing regime. From 3 to 7 m/s, drag of stepped and wedged models has the lowest value and above 7 m/s and at 9 m/s, the stepped model has the lowest resistance. Among the investigated methods, using combined step and wedge indicates largest reduction in trim angle (At speeds of 3 to 9 m/s). It can therefore be concluded that model equipped by combination of wedge and step improves the poor performance of the stepped models prior to the planing regime.