The present invention provides a hull-conversion device and method for modifying the underside of a watercraft, more specifically a multihull watercraft. The hull-conversion device comprising a water diverting surface, a kinematic assemblage, and a frame. The hull-conversion device may be operable to adjust the watercraft's characteristics in displacement mode and planing mode. The hull-conversion device may function to provide a more stable, controllable, and efficient platform for operating a multihull watercraft, and provide a suitable wake for towable water sports.

A marine vessel or watercraft may be provided with an aft extension that, in one configuration of the watercraft, alters the wake of the watercraft, for example by reducing the height of the wake, and which may include a sealable opening to provide crew or payload access into or out of the watercraft at a location (e.g., aft of the transom) that may be difficult for an observer to perceive. The aft extension may be positioned above the watercraft's waterline when the watercraft is in another configuration such that it does not contact with the water to reduce adverse impact on performance characteristics, such as drag, of the hull when the watercraft is in that configuration. The watercraft may transition between the two configuration by selectively varying the displacement of the watercraft or by articulating of the aft extension.

A boat includes at least three trim devices positioned aft of the boat's transom. To improve the boat's ability to get on place, each trim device is initially positioned to a deployed position. The speed of the boat is then determined as the boat gains speed. When the speed of the boat exceeds a first predetermined threshold, the first trim device is moved from the deployed position to a non-deployed position. When the speed of the boat exceeds a second predetermined threshold, the second trim device is moved from the deployed position to a non-deployed position. When the speed of the boat exceeds a third predetermined threshold, the third trim device is moved from the deployed position to a non-deployed position. At least one of the first, second, and third predetermined thresholds is different from the other two of the first, second, and third predetermined thresholds.

A boat includes at least three trim devices positioned aft of the boat's transom. To improve the boat's ability to get on place, each trim device is initially positioned to a deployed position. The speed of the boat is then determined as the boat gains speed. When the speed of the boat exceeds a first predetermined threshold, the first trim device is moved from the deployed position to a non-deployed position. When the speed of the boat exceeds a second predetermined threshold, the second trim device is moved from the deployed position to a non-deployed position. When the speed of the boat exceeds a third predetermined threshold, the third trim device is moved from the deployed position to a non-deployed position. At least one of the first, second, and third predetermined thresholds is different from the other two of the first, second, and third predetermined thresholds.

A recreational sport boat includes a hull, having starboard and port sides and a transom, and a wake-modifying devices positioned aft of the transom. The wake-modifying device includes a plate-like member and at least one downturned surface. The wake-modifying device is pivotable between a non-deployed position and a deployed position about a pivot axis. When a wake-modifying device is in the deployed position, the downturned surface is lower than it is in the non-deployed position so as to be able to modify the boat's wake.

A recreational sport boat includes a hull, having starboard and port sides and a transom, and a wake-modifying devices positioned aft of the transom. The wake-modifying device includes a plate-like member and at least one downturned surface. The wake-modifying device is pivotable between a non-deployed position and a deployed position about a pivot axis. When a wake-modifying device is in the deployed position, the downturned surface is lower than it is in the non-deployed position so as to be able to modify the boat's wake.

A recreational sport boat includes a hull, having starboard and port sides and a transom, and a pair of wake-modifying devices positioned aft of the transom. One of the wake-modifying devices is positioned on a port side of the boat's centerline and another of the wake-modifying devices is positioned on a starboard side of the boat's centerline. Each wake-modifying device includes a plate-like member and at least one downturned surface at a trailing portion of the plate-like member. Each wake-modifying device is pivotable between a non-deployed position and a deployed position about a pivot axis that is horizontal or inclined no more than about 35° from horizontal. When a wake-modifying device is in the deployed position, the downturned surface is lower than it is in the non-deployed position so as to be able to modify the boat's wake.

A recreational sport boat includes a hull, having starboard and port sides and a transom, and a pair of wake-modifying devices positioned aft of the transom. One of the wake-modifying devices is positioned on a port side of the boat's centerline and another of the wake-modifying devices is positioned on a starboard side of the boat's centerline. Each wake-modifying device includes a plate-like member and at least one downturned surface at a trailing portion of the plate-like member. Each wake-modifying device is pivotable between a non-deployed position and a deployed position about a pivot axis that is horizontal or inclined no more than about 35° from horizontal. When a wake-modifying device is in the deployed position, the downturned surface is lower than it is in the non-deployed position so as to be able to modify the boat's wake.

A transom mounted fluid hinge bracket having one mounting plate that is connected at a lower distal end to a horizontal bracket portion which extends forward and aft of the transom of a watercraft in a bow to stern axial displacement, the horizontal bracket abutting the underside of the hull of a watercraft sitting flush with the underside of the watercraft, at least one fluid hinge receiver secured to the back side of the horizontal bracket portion on which the back of the substantially planar surface of the trim tab may rest, the at least one fluid hinge receiver containing the substantially planar surface in a position of the planar surface resting about parallel to the hull of the watercraft, and the at least one fluid hinge receiver without any load from the planar surface except at rest keeping the planar surface from descending below a horizon parallel to that of a horizon of the hull.

A transom mounted fluid hinge bracket having one mounting plate that is connected at a lower distal end to a horizontal bracket portion which extends forward and aft of the transom of a watercraft in a bow to stern axial displacement, the horizontal bracket abutting the underside of the hull of a watercraft sitting flush with the underside of the watercraft, at least one fluid hinge receiver secured to the back side of the horizontal bracket portion on which the back of the substantially planar surface of the trim tab may rest, the at least one fluid hinge receiver containing the substantially planar surface in a position of the planar surface resting about parallel to the hull of the watercraft, and the at least one fluid hinge receiver without any load from the planar surface except at rest keeping the planar surface from descending below a horizon parallel to that of a horizon of the hull.