ITTC-57 line

The ITTC-1957 model-ship correlation line gives the frictional resistance coefficient as C_F = 0.075 / (log10 Re - 2)^2, where Re is the Reynolds number based on waterline length and ship speed. Adopted at the 8th ITTC in 1957, it is not a pure flat-plate friction line: it sits above the Hughes two-dimensional line by a deliberate margin so that it acts as a correlation line absorbing part of the three-dimensional form effect when no separate form factor is used. It is the friction basis of the ITTC-1978 powering procedure and the reference every modern resistance extrapolation is built on.