A method of forming a hollow composite construction member of the type suitable for use as building material includes providing an elongated inflatable mold assembly having a longitudinal axis. The mold assembly further has a flexible, substantially tubular bladder wall defining an elongated inflatable cavity, wherein the cavity is movable between a deflated condition, an inflated condition, and a plurality of partially inflated conditions. A reinforcing fabric is positioned concentrically around the flexible bladder wall. A flexible air-impervious outer layer is positioned concentrically around the fabric, with the bladder wall and the outer layer defining an elongated annular space. The fabric is positioned within the space. An intermediate member is inserted within the elongated annular space between the reinforcing fabric and the tubular bladder. A fluid is introduced into the cavity to at least partially inflate the mold and shape the fabric. The mold assembly is bent along the longitudinal axis to a curved shape. The elongated annular space is infused with a rigidification material such that the fabric is permeated with the rigidification material. The rigidification material is hardened to form a rigid hollow composite construction member.