ONR Hydrofoil Boat XCH-6 209 
HYDROFOIL SYSTEM 
Two surface-piercing hydrofoils (one on each side of the boat) are located forward of 
the vehicle center of gravity and one fully submerged foil is located aft of the transom. 
Approximately 77.0 percent of the vehicle weight is supported on the forward hydrofoils. 
As seen in Fig. 3, each of the forward hydrofoil assemblies incorporates a vertical 
strut supported to the hull in its upper region. A cruise foil element is attached to the 
lower end of each strut. A portion of this element is cantilevered so as to extend inboard 
of the strut bottom. In addition, it extends outboard and up from the lower end of the strut 
with positive dihedral. The upper end of each cruise foil is joined to the upper region of 
the strut by a diagonal foil element with negative dihedral. 
Fig. 3. A forward hydrofoil assembly 
Cross sections of the foil and strut elements of the forward foil assembly are shown in 
Fig. 4. The cruise foil elements embody a basic supercavitating section which has a 
circular-arc bottom shape, a flat upper contour, a sharp leading edge, and a blunt trailing 
