Abstract: A mandrel is fitted with a molded sleeve of low-temperature alloy for forming a rigid bulge along the surface of the mandrel. The sleeve is shaped to define the. internal surface of the shell at the bulge. After the mandrel has been so modified with the low-temperature alloy sleeve, it is wrapped with composite cloth containing any thermosetting resin. These resins heat to a known temperature, and permanently set when cured at the set temperature. The curing temperature of the prepreg cloth composite material is lower than the melting point of the low temperature alloy. After curing, the temperature in the curing oven is raised above the cure temperature until it reaches the melting point of the low-temperature alloy, and the alloy liquifies and drains out the drain passageways provided in the mandrel without melting the thermoset resin binder in the fiber cloth as well as leaving the bulge formed by the composite cloth in the shell without obstructing the removal of the mandrel.

Abstract: A mandrel is fitted with a molded sleeve of low-temperature alloy for forming a rigid bulge along the surface of the mandrel. The sleeve is shaped to define the internal surface of the shell at the bulge. After the mandrel has been so modified with the low-temperature alloy sleeve, it is wrapped with composite cloth containing any thermosetting resin. These resins heat to a known temperature, and permanently set when cured at the set temperature. The curing temperature of the prepreg cloth composite material is lower than the melting point of the low temperature alloy. After curing, the temperature in the curing oven is raised above the cure temperature until it reaches the melting point of the low-temperature alloy, and the alloy liquifies and drains out the drain passageways provided in the mandrel without melting the thermoset resin binder in the fiber cloth as well as leaving the bulge formed by the composite cloth in the shell without obstructing the removal of the mandrel.