9.1 Introduction

Planing vessels are used as patrol boats, sportfishing vessels, service craft, ambulance craft, recreational craft, and for sport competitions. The Italian vessel Distriero, designed by Donald L. Blount and Associates, won in 1992 the Blue Riband Award for the fastest transatlantic passage without refueling. The average speed was 53.1 knots. The vessel is a 67 m long planing monohull equipped with gas turbines and three waterjets with a combined horsepower of 60,000. Use of hydrodynamic test facilities was an important part of the design. However, the amount of research on planing vessels is relatively small, considering the large amount of different recreational craft that exist. Our focus is on monohull vessels, but catamaran types also exist. Most of the planing vessels have lengths smaller than 30 m. Recreational craft are typically smaller than that.

A vessel is planing when the length Froude number Fn > 1 .2 (Savitsky 1992). However, Fn = 1 .0 is also used as a lower limit for planing; that is, we cannot set a clear line of demarcation between planing and nonplaning conditions just by referring to the Froude number. During planing, the weight of the vessel is mainly supported by hydrodynamic pressure loads, with buoyancy having less importance. The hydrodynamic pressure both lifts the vessel and affects the trim angle.

Figure 9.1 shows a typical high-speed planing hull. In order to avoid negative pressures relative to atmospheric pressure on the hull at high speed, it is essential to have flow...