An apparatus including a carriage adapted to be mounted on and movable along the elongate composite stringer, and a compaction roller mounted on the carriage for compacting film material against the flange surface as the carriage moves along the stringer. The apparatus also includes a film feed roll assembly on the carriage adapted to hold a quantity of film material and to dispense the film material to the compaction roller. The apparatus also includes a take-up reel on the carriage adapted for taking up a backing on the film material as the film material is being dispensed to the compaction roller, a heater on the carriage for heating the flange surface as the carriage moves along the composite stringer, and a film trimmer for trimming edges of the film material to match a contour of the composite stringer after the film material has been compacted against the flange surface.