Results of an extensive series of model tests that define the longitudinal surface wake profiles aft of prismatic hulls having deadrise angles of 10º, 20º and 30º are presented. Empirical equations are developed that quantitatively define these profiles and are in a form that can be easily applied by designers of stepped planing hulls. These equations are applicable for an expected range of variations in trim angle, speed coefficient, and loading coefficient typical for these hulls. A brief introduction to the concept and to the hydrodynamic advantages of stepped planing hulls is presented to orient the reader as to the importance of wake data in their design. Examples are presented that illustrate the application of these wake data for stepped planing hulls with wetted forebody chine to achieve maximum hydrodynamic lift/drag ratios. Finally experimental results are presented that illustrate the potential resistance penalty associated with the operation of chines dry forebodies where the stagnation line crosses the step.

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Recently there has been increasing interest in the fluid-structure interaction problem of planing hull bottom structure during slamming events. Significant work has been done in estimating the bottom pressures that occur during a slam and incorporating this into structural models of planing craft. In this article, empirical equations for the pressure distribution on prismatic planing hulls are developed, including both hydrostatic and hydrodynamic effects, deadrise variation, trim, and wetted length. The empirical method is based on relevant experimental measurements of planing hull bottom pressures that have been made over an 80-year period. This analysis may readily be extended to the impact problem by substitution of an equivalent planing velocity, which is discussed in the article. The end result is a closed form solution for bottom pressures on prismatic planing craft that can be rapidly calculated using a simple spreadsheet. The method is applicable for deadrise angles from 0 to 40 , trim angles up to 30 , and wetted lengths up to five beams. This wide range of parameters is significantly larger than most current models. The empirical method is modular, allowing for substitution of more accurate formulae as more data become available in the future.

This article summarizes experiments to determine the effect of shallow water on flatbottomed prismatic hulls towed fixed in heave and trim over a wide range of speed regimes. The experimental design allowed for the separate measurement of pressure forces normal to the bottom and viscous forces tangential to the bottom. The experiments showed that below a depth Froude number of unity (subcritical speeds), shallow water resulted in a reduction in pressure forces on the bottom of the hull. Around a depth Froude number of unity (critical speed), a solitary wave formed at the model, increasing the wetted length and also increasing the bottom pressure forces, which became unsteady. Above a depth Froude number of unity (supercritical speeds), the pressure forces on the bottom of the hull were greater in shallow water than in deep water. Observations of the inception of transom ventilation showed that full ventilation occurred at lower Froude numbers in shallow water and that trim has a strong effect on transom ventilation at all water depths. To assist in explaining these effects, each of the forces acting on a flat-bottomed hull are discussed and it is shown how they vary with speed and water depth. The observed trends from these fixed model tests are in qualitative agreement with experiments with free to trim and heave models as well as two-dimensional theories of planing in shallow water.Early work on shallow water effects such as Schlichting (1934), Landweber (1939, and Lackenby (1963) focused on estimating the speed loss of seagoing displacement ships during sea trials in shallow or restricted waters or estimating towing tank blockage corrections. It has been found that as the depth Froude number approaches unity (critical speed), there is an increase in resistance, which often results in speed loss for ships.Supercritical behavior of displacement and semidisplacement hulls has been studied more recently. Kirsch (1966) computed the theoretical wave resistance for a simplified ship form in shallow and restricted channels using Sretenskii's (1937) method. Calculations were at subcritical and supercritical speeds, showing that resistance decreased in shallow water at supercritical speeds. Millward (1983) and Millward and Bevan (1986) extended Kirsch's calculations and found that the method correlated well with resistance measurements from towing tests of semidisplacement Manuscript received as SNAME headquarters

The design of successful water-based aircraft requires a close collaboration between the aeronautical engineers and naval architects, who perform high-speed towing tests, stability calculations, or computational fluid dynamics in support of the design. This article presents the fundamental design considerations of waterborne aircraft, which are outside of the typical educational scope of most naval architects, but which they are sometimes asked to address. These include 1) the hydrostatic and hydrodynamic problems associated with seaplane design, 2) early-stage methods for sizing the hull, 3) prediction techniques using archival data, and 4) hydrodynamic model testing procedures. Although a new design will often require substantial iteration to achieve the desired outcome, the information in this article will assist in developing a reasonable starting point for the design spiral and provides sufficient details for a hydrodynamic model testing facility to perform a successful series of model tests on the design. Although much of the work in this field dates from the 1940s, it is important to review this material in light of the current practices being used at hydrodynamic research facilities today. A detailed description of the model testing apparatus and procedure, used in a recent study at the U.S. Naval Academy, is presented to demonstrate the current applicability of these methods and some pitfalls that can be expected in testing.