On the shape of the wake behind a planing boat

Recent developments in slender planing theory permit rather precise estimates of forces and moments to be made. So using a methodology first suggested by Epshtein for flat plate wakes, the modern theory is employed to find the longitudinal shape of a flat plate's wake. The result is in better agreement with experiment than previous formulations. The same approach is then applied (for the first time) to a prismatic wake, and the agreement with experiment is found to be excellent. Finally, the equations developed are used to deduce the wave energy developed by the passage of the hull, and from this, its wave drag. Although there are no experimental data available for comparison, the ratio (wave drag)/(total pressure drag) follows the same trend with Froude number as earlier two-dimensional solutions by Sedov and Squire, and tends to zero as Froude number tends to infinity.