Abstract: A method of manufacturing hollow pieces comprising the steps of forming a blank of single sheets each having a layer of gluing substance applied thereto; placing the blank onto an appropriate mandrel and subjecting it to a preliminary compression so as to impart to the blank a stiffness and to shape it into an unclosed profile as required for subsequent steps. Then the blank ends are brought together so as to define a cavity accommodating an elastic bag. The resulting blank is placed into a mould, and pressure is fed into the elastic bag to perform a final pressing.The above-described method is preferably used to manufacture helicopter rotor blades of glass plastic, which have variable cross-sectional shape over their length and exhibit higher strength and longer service life as compared with metal blades.

Abstract: A fiber-reinforced plastic article of manufacture having a multi-chambered, cellular structure with an outer shell having a fluid foil shape with a leading edge having a smooth radius of curvature and a trailing edge [noncircular]cross section over a substantial portion of its length and containing therein an inner shell which extends between at least two opposite interior walls of said outer shell thereby defining at least two chambers within said article, the walls of said shells being composed of a plastic having embedded therein at least on layer of a continuous roving of a fibrous reinforcement material, said at least one layer comprising two adjacent thicknesses of said roving with the rovings being in parallel alignment in each thickness and the rovings being in parallel alignment in each thickness and in diagonal orientation between thicknesses and with the rovings in the outer shell being continuous and unbroken over the leading edge of said foil shape.

Abstract: A method and apparatus are disclosed for making a molded pulp product such as a plate or the like which has an upper liquid impervious layer integrally secured thereon. The pulp product is formed on a foraminous mold and, together with the mold, is heated to the softening temperature of a liquid impervious thermoplastic sheet material which is caused to be cut to size by engagement with a cutting edge on the mold whereafter the severed portion is drawn by suction and bonded to a selected surface area of the pulp product.

Abstract: A method of laminating a plastic sheet onto a surface of a hollow body is disclosed.The method of laminating a plastic sheet onto a surface of a hollow body includes the steps of loading the hollow body into the female die, securing the plastic sheet in a clamping means, heating the clamped sheet to its softening temperature, moving the clamped heated sheet into registry with a male die and the female die, sealing one die of the male die and the female die to one member of the clamping means and the clamped heated plastic sheet to define therewith a sealed chamber, moving the male die toward the clamped heated sheet to form the clamped heated sheet about the male die, moving the male die and the clamped formed heated sheet against the surface of the hollow body in the female die, and applying fluid pressure to the clamped formed heated hollow body to transfer the clamped formed heated sheet to the surface of the hollow body.