Abstract: A hybrid double backer for the formation of a double face corrugated paperboard web combines an upstream driven holddown belt section and a downstream static porous mesh belt holddown section that provides optimum curing and drying of the paperboard web.

Abstract: A corrugator double backer includes a web holddown apparatus that provides both heat and a holddown force to the upper surface of the paperboard web to maintain the web in intimate drying contact with the lower heating units without the use of a conventional driven holddown belt. A heated holddown mat which is longitudinally and laterally flexible is provided by a series of generally parallel, somewhat flexible, closely spaced heating tubes which are suspended above the web in the heating section in catenary fashion in the direction of web travel. Lift devices on one or both ends of the mat of tubes can vary the amount of mat contact with the web and, therefore, the heat and load imposed on the web. The tubes are steam heated and have flat low friction, high wear resistant lower surfaces which lie directly atop the corrugated paperboard web running thereunder.