A method for manufacturing frame-type composite panels to a desired length comprises forming an elongate core-frame composite in which frame members have been received in slots on a slab of core material. The composite is cut to the desired length and the frame is finished by application of end members. The method described herein allows composite frame panels to be formed without restriction on the length typically due to the length of the mold in which the core is formed. A drum for use in a system for creating composite panels is disclosed having protruding rings concentric to the drum. A slab of core material is passed between two such drums which form slots in the slab for receiving frame members when they contact the slabs.