Abstract: Molds for the production of fiber reinforced plastics material boat hulls filled with hard foam plastics material are constructed of plastics material and reinforced against deformation by rigid cores and tension bands to accurately shape the hulls even when subjected to high stresses during molding and foam filling. The molds have separable top and bottom halves connected around their peripheries by interfitting flanges forming a seal and also provided with ventilating channels. The outer shell of the bottom mold half between the flanges has a free catenary curve configuration supporting the reinforcing cores for the molding surface or inner shell of the mold.

Abstract: The fore and aft sections of a folding boat frame each have a post located in the longitudinal median plane of the section, and two sets of elongated stringers extending away from the post on respective sides of the median plane. Each stringer has a first portion attached to the frame and a second portion hinged to the first for folding the two portions on each other. Each set includes a bottom stringer having a major longitudinal face. The first stringer portions are pivotally connected to a rib frame which may be folded about an axis in the median plane toward and away from the plane. The bottom stringers are fastened to the rib frame in such a manner that they move angularly relative to each other from a position in which their major faces converge toward the median plane at an obtuse angle to a position in which the angle is much smaller and acute when the rib frame is folded.