Patent ID: 7108821

Claim:
A method of fabricating a double-walled shell of fiber reinforced plastic material by centrifuging, wherein the double-walled shell has an outer wall having a thickness, an inside face, and an inside diameter, the method comprising: projecting glass fibers and resin in a liquid phase against an inside face of a cylindrical mold rotating about its horizontal axis, forming the outer wall, applying a curved metal section member against the inside face of the outer wall with a device for fabricating curved section members from a metal strip, wherein the metal strip is pressed against the inside face of the outer wall and the mold is rotated about its horizontal axis forming a plurality of turns having a diameter substantially equal to the inside diameter of the outer wall and separated from one another by a distance substantially equal to the thickness of the outer wall, said section member defining a channel section, wherein said channel section has a web and two flanges extending radially outward having free edges wherein said free edges penetrate said outer wall, defining a sealed helical duct extending from one end of said shell to the other end of said shell, and wherein the distance between the turns defines a space, filling in the space between the turns with resin by centrifuging, forming a helical spacer, and forming the inner wall by centrifuging, wherein said section member is applied continuously and substantially tangentially to said inside face and is formed as a function of the speed of rotation of the mold, and wherein said device and said mold are displaced axially relative to each other.