An improved kayak has a hull of thermoformed ABS plastic having a bow and a seat having a void between the bow and the seat, a top of the hull being a deck with a foam PVC block glued to a bottom face of the deck. A rotomolded polyethylene plastic insert is located in the void and joined to the hull by fasteners that pass through the insert and the deck of the hull and engage the foam PVC block within the hull, with caulking between the hull and the insert. A propulsion device is removably mounted in the rotomolded plastic insert that allows a user of the kayak to propel the kayak.

In one example, a method includes positioning, within a mold, a device with a movable element that defines a portion of a volume, and the volume is contained within the mold, as part of a molding process, at least partly defining a molded watercraft by introducing plastic into the mold, disposing the plastic about the movable element, and with the movable element, excluding the plastic from the portion of the volume that is defined by the movable element so as to define a recess and an undercut that are integral with the watercraft and extend lengthwise with respect to a centerline of the watercraft, and the recess and undercut are integral, and communicate, with each other.

Provided is an apparatus for molding a shell hull made of composite material for a boat having a first mold part and a second mold part, each having a molding surface and adapted to be coupled to jointly define a concave molding cavity that extends longitudinally between a stern end and a bow end. The apparatus has a humidity sensor for detecting humidity at the first and/or second mold parts. A plurality of sensors, arranged in a respective plurality of detection positions on a detection surface extending over at least one of the first mold part and the second mold part, and arranged directly in contact therewith, produce signals representative of respective strains of the detection surface in directions substantially perpendicular to the detection surface.

Provided is an apparatus for molding a shell hull made of composite material for a boat having a first mold part and a second mold part, each having a molding surface and adapted to be coupled to jointly define a concave molding cavity that extends longitudinally between a stern end and a bow end. The apparatus has a humidity sensor for detecting humidity at the first and/or second mold parts. A plurality of sensors, arranged in a respective plurality of detection positions on a detection surface extending over at least one of the first mold part and the second mold part, and arranged directly in contact therewith, produce signals representative of respective strains of the detection surface in directions substantially perpendicular to the detection surface.

In one example, a watercraft includes a hull in the form of a unitary, single-piece structure that is substantially hollow, and made of plastic. A grip is provided that is integral with the hull and includes a recess that is formed in a skin of the hull and is integral with the hull, and the grip also includes an undercut that is formed in the skin of the hull proximate an edge of the recess. The undercut is integral with the hull and communicates with the recess.

A deep-drawn, marine hull having a sandwich structure and watercraft utilizing same are provided. The hull includes an outer skin having a waterproof outer surface, an inner skin having a compartment-defining outer surface and a shock absorbing, cellular core positioned between the skins. The skins are bonded to the core by press molding. The cellular core has a 2-D array of cells, each of the cells having an axis substantially perpendicular to the outer surfaces. Thickness of side walls of the hull is substantially uniform to maximize stiffness of the hull. The cells absorb energy of an impact at the outer surface of the outer skin by deformably crushing. Air trapped within cells which are not completely crushed or punctured by the impact provide the hull with buoyancy to allow the hull to float at the surface of a body of water.

Personal watercraft and personal watercraft fabrication using a thermoforming process are described. The personal watercraft manufacturing process includes a set of molds, thermoforming equipment, and thermal formable materials. The process greatly reduces manufacturing costs, decreases manufacturing time, increases part consistency and tolerances, offers better performance characteristics and durability and results in less environmentally harmful deposits and waste.

In one example, a method includes positioning, within a mold, a device with a movable element that defines a portion of a volume, and the volume is contained within the mold, as part of a molding process, at least partly defining a molded watercraft by introducing plastic into the mold, disposing the plastic about the movable element, and with the movable element, excluding the plastic from the portion of the volume that is defined by the movable element so as to define a recess and an undercut that are integral with the watercraft and extend lengthwise with respect to a centerline of the watercraft, and the recess and undercut are integral, and communicate, with each other.

A deep-drawn, marine hull having a sandwich structure with a cellulose-based core and watercraft utilizing same are provided. The hull includes an outer skin of a fiber-based thermoplastic and having a waterproof outer surface, a first sheet of thermoplastic adhesive, an inner skin of a fiber-reinforced thermoplastic material and having a compartment-defining outer surface, a second sheet of thermoplastic adhesive and a shock absorbing, cellular core of a cellulose-based material and positioned between the skins The skins are bonded to the core by the first and second sheets and by press molding. Cells of the cellular core absorb energy of an impact at the outer surface of the outer skin by deformably crushing. Air trapped within cells which are not completely crushed or punctured by the impact provide the hull with buoyancy to allow the hull to float at the surface of a body of water.