Bare hull resistance

Bare-hull resistance is the calm-water resistance of the hull alone, with no appendages fitted: no rudder, shafts, brackets, bilge keels, or fins. It is the baseline a resistance test or a systematic series such as Series 60 or the Delft series reports, before appendage and air drag are added. In the ITTC-1978 breakdown the bare-hull total coefficient is C_T = (1+k) C_F + C_W, with C_F from the ITTC-1957 line, (1+k) the form factor, and C_W the wave coefficient. Appendage and air resistance are then layered on to reach the full-scale total used for powering.