Abstract: The present invention relates to a watercraft having a wave suppressing “M-shaped” hull design. The hull comprises a central displacement body flanked by two downwardly extending outer skirts. The outer skirts are attached to the displacement body by planing wings having wing channels. The bow wave is directed into the wing channels, thereby increasing planing efficiency and reducing the effect of such waves on other boats and the shoreline. One embodiment takes the form of a twin-hull catamaran with two M-shaped hulls and four arcuate channels for containing the spiraling bow waves from the two central displacement bodies, thus to increase lateral stability and to suppress boat waves to protect nearby boats and structures at the water/land interface.

Abstract: A bottom structure of a personal watercraft enhances the running performance of a personal watercraft. A concavo-convex face (21) having very small concave or convex portions for drawing air from an outside of a watercraft is formed on a water contact face (S) in a bottom surface (20) of the personal watercraft during planing. The air is drawn by the concavo-convex face (21), thereby separating a water flow from the bottom surface (20). Consequently, frictional resistance to the water in the bottom surface (20) can be reduced.

Abstract: An air propelled boat. It is provided with a pair of catamaran hulls, each having a unique catamaran hull design particularly adaptable for travel over land, water, ice or snow. Each catamaran hull has a pair of centered concave flutes extending from the aft end of the body to the forward end of the nose. At the nose end, the flutes are reduced in concavity and inclined longitudinally and laterally. Both inclinations are reduced in slope forward. The flutes guide water outward and under the hull and move the water hull contact aft. This decreases hull drag and increases lift. The hull bottoms are formed into a central longitudinal support flat which is flanked by parallel outboard support flats. The undersurface of a catamaran hull is covered by an ultra-high molecular weight plastic profile to reduce friction when traveling over a solid supporting surface. The catamaran hulls are foam filled for rigidity.

Abstract: A hull configuration for the planar surface region in the tunnel area between hulls(pontoons) in a fishing type catamaran. In the tunnel bottom surface is a raised frontwardly located center section adjacent the bow forms a venturi where low pressure is formed by incoming waves passing about the squared off rear portion of the center section. Behind the center section is a raised longitudinal stabilizer running to the rear(stern) of the boat which diverts and splits incoming air coming from the bow section to each side of the tunnel. Adjacent to the center section are two raised side stabilizers which straighten out incoming air and reduce the turbulence effects therefrom. On the rear ends of the two side stabilizers and the center section are through-holes that allow for venting excessive pressure from inside the tunnel to the interior of the bilge of the boat.

Abstract: A planing vessel has a hull and a propulsion and control system. The hull has a plane bottom formed of an equicrural triangle in the front and a rectangle at the back, two boards and one or more swell guideways. Each swell guideway has an inclined top line with a lower front and a higher back denting upwardly into and extending lengthwise throughout the bottom and paralleling its centerline. The hull also has a pair of wave-splash guards inlaid or dented one into the boards as an integrated body, a deck, a cabin and an upper construction. The planing vessel so formed can generate sufficient hydrodynamic buoyancy with reasonable distribution to quickly lift itself out of the water and enter a planing state. The planing vessel can have various fine performances, desirable speed and stability to move on rough waters.

Abstract: A tri-hull using air and water collectively channeled and controlled through its design to enhance speed and stability of the tri-hull as it moves forward through the water. Structural wings connecting the two outer hulls to the middle hull comprise operational flaps which direct air in a desired direction along with the flow of air into air intake channels, the air exiting into hydrochannels beneath each outer hull where the interaction of the exiting air on the water moving through each hydrochannel provides an equalization or an upward force to the rear of the tri-hull and a resulting equalization or a downward force to the bow of the tri-hull which enhances the stability of the tri-hull at high speeds. The tri-hull also has adjustable air flow relief valves for controlling the flow of air into hydrochannels and sub fins beneath each outer hull to provide traction during turns.

Abstract: A surface effect hull particularly suitable for use with a catamaran vessel. The twin hulls each comprise a V-shaped portion and a recess portion that receives pressurized gas therein. The V-shaped bow portion create dynamic lift and the pressurized air portion creates an air cushion for reduction of drag.

Abstract: A power boat hull has an inner running surface with a central running surface and an outer running surface that flanks the inner running surface. The outer running surface forms a channel with concave curvature which extends from the bow to the stern. An improved channel is shaped so that pressure builds in the channel during turning of the boat to lock the hull to water throughout the turn. A transom is provided with a deflector plate having a curved surface that is lifted out of the water during high speed running of the boat and operatively deflects water downward to force the bow of the boat into the water during low speed running of the boat. The transom dimensions are altered to accommodate varying length boats.

Abstract: A pontoon-type boat comprising a deck having opposite sides, and a modified tunnel hull supporting the deck and including a first outer sponson located adjacent one of the sides of the deck, a second outer sponson located adjacent the other of the sides of the deck, and a center sponson which is located and spaced between the outer sponsons, which extends substantially the entire length of the boat, and which includes a rearward portion having a maximum depth and a maximum width, and a forward portion having a maximum width greater than the maximum width of the rearward portion and having a maximum depth greater than the maximum depth of the rearward portion, the forward and rearward portions defining therebetween a step.

Abstract: A single-body transom type of hull includes reaction flaps extending along side platings of the hull in a direction from bow to stern over at least 10% or more of the length of the ship. Inner surfaces of the flaps, along with outer surfaces of the side platings, form structures having inversely U-shaped cross sections defining recesses of parabolic cross sections so that water may flow smoothly along the hull. The reaction flaps thus suppress the outward flow of spray from the hull and impart lateral stability to the hull even at high speeds.

Abstract: An improved performance marine surface vessel that includes pressurized supporting gas cushions in multiple hulls, normally catamaran-like sidehulls, where such pressurized supporting gas cushions support a majority of boat weight in operation. The preferred embodiment of the invention utilizes long fine pointed bow catamaran-like sidehulls that are in mechanical communication with a connecting hull structure. The long fine sidehulls offer performance advantages over a single large supporting gas cushion. Sidehull gas cushion outer sidewalls are preferably wider and deeper than inner sidewalls which insures minimum resistance coupled with maximum transverse stability in roll. Further, sidehull gas cushion sidewalls optionally have angled to horizontal flatter surfaces forward and then transition to more rounded shapes aft which provides for good pitch stability and minimum hydrodynamic resistance.

Abstract: There is disclosed an inverted bottom structure having generally convex, longitudinal buttock and waterlines lines which creates a venturi structure and a variable pressure/suction situation along the boat hull bottom. The under sides of the boat hull are highly concave resulting in the varying speed of flow which limits the throw-out of water wake while the inverted bottom of the boat hull eliminates turbulent, drag flow. The depth of the longitudinal bottom channels progressively deepens, thereby encompassing a growing volume of smooth water flowing aft in the channels which creates inertia lateral resistance while causing minimal increase in resistance to forward movement. The finely contoured, longitudinal, horizontal and cross sectional lines create a controlled flow situation whereby uncontrolled turbulent flow is replaced with controlled laminar flow, introducing an unprecedented reduction in resistance, to forward movement per displacement, and a profound increase in lateral resistance.

Abstract: A number of embodiments of hull arrangements for watercraft that permit forward positioning of the propulsion device but also permit the hull to be constructed as a planing hull. In some embodiments, jet propulsion devices are disclosed and in another embodiment an outboard motor propulsion device is shown.

Abstract: A hull configuration for a small personal watercraft having a hull configuration that permits the watercraft to be ridden and leaned like a motorcycle and which will preclude excess spray from passing upward beyond the gunnel. A ventilating cover assembly is provided for accessing the engine compartment and a forwardly positioned fuel tank is incorporated having a filler neck that is accessible at one side of the deck.

Abstract: A catamaran for pastime, model construction or racing with induced hydrodynamic stability, having a hull with a board (1) and a pair of longitudinally extended semi-immersible appendages (2, 3; 8, 9; 13, 14; 24, 25) arranged parallel to each other symmetrically to the center-line of the hull, the respective bottoms of which, at the bow tips (4, 5; 12, 12a; 21, 22; 32, 33) of said appendages, have mutually opposite slopes, each slope being contrary to the slope of the respective aft rest of the bottom with respect to the median symmetry plane of the hull.

Abstract: A surface for use in connection with an object in relative motion through a luid medium includes a plurality of surface elements arranged in rows on the surface, with surface elements of each row being arranged generally orthogonal to the direction of relative motion of the object in a medium. Each surface element includes means defining a cavity, the means including a bottom surface layer, sidewalls, and an upper lip supported along an upstream edge in a cantilevered manner and extending in a downstream direction over the cavity to define a gap permitting fluid communication between the medium and the cavity. The lip is flexible so as to facilitate deflection in response to differentials between pressure inside the cavity and outside the cavity. The cavities of the surface elements in each row are interconnected by means of passageways thereby to facilitate fluid communication therebetween.

Abstract: A system of elongated rails installed on the exterior hull surfaces of boats and projecting externally from the exterior hull surfaces of the boats, and having the functional attributes of: deflecting spray, reducing the tendencies of the bows to go under in choppy or turbulent seas, reducing heel and side-slipping while turning, contributing lift, acting as fenders to protect the hulls, providing accessible hand holds and foot steps, reducing the rocking motions of the boats and adding flotation to the boats. The rails are formed of a polymeric foam interior and a skin formed of a polymeric sheet or a fabric material.

Abstract: A boat is disclosed having a hull with improved operating characteristics. The hull includes a central sponson and outer sponsons on each side of the keel. The sponsons include chines which extend from the transom to the peak of the bow. The chines have ski-like flat portions for providing lift. Between the chines and the keel are a pair of arched tunnels. The chines, the bottom edge of the keel and the gunwales all meet at the peak of the bow. The chines, the keel and the tunnels are all linear and parallel between a mid-section of the hull and the transom.

Abstract: A small watercraft adapted to seat one or more riders in motorcycle fashion and which has a hull configured so as to facilitate leaning without capsizing. The foot area for the riders is such that a rider may either sit on the seat in straddle fashion or stand behind the seat and may move between these positions easily and while the watercraft is in motion.

Abstract: A power boat hull that has central running surface and na outer running surface that flanks the central running surface. The outer surface forms a channel with concave curvature which extends from the bow to the stern. The channel is shaped so that pressure builds in the channel during turning of the boat to lock the hull to water throughout the turn. A transom may be provided with a deflector plate having a curved surface that is lifted out of the water during high speed running of the boat and operatively deflects water downward to force the bow of the boat into the water during low speed running of the boat.

Abstract: A catamaran design has a third hull positioned between the conventional hulls. The third hull has a length equal to about two-thirds of the length of the conventional hulls, and a recess is formed in the underside of the deck aft of the third hull. The recess has a depth sufficient to accommodate the rooster tail created by the third hull. The third hull enhances the buoyancy of the craft and prevents formation of waves under the leading end of the deck. The recess prevents the rooster tail from impinging against the underside of the deck. The third hull produces a concave wake and it is submerged to a similar extent as the twin hulls when the watercraft is at rest floating in a body of water. In combination, the third hull and recess provide a catamaran that can handle heavy seas, with control and safety, that is not subject to the pounding of waves on the underside of its deck, and which performs in all other respects like a conventional catamaran.

Abstract: The main rotor (1) located at the bow (3) of the hull (4) is transverse to a vertical plane through the axis of the hull and consists of two or more units of cylindrical wheels (5), which are equipped with blades (17). Each unit of cylindrical wheels (5) is provided with its own independent braking device (13). Longitudinal channels (30 and 31) are made on the bottom (29). These channels have different cross-sections along the axis of the hull. To be more precise, their cross-sections decrease from bow (3) and stern (32) to the bottom center (29). Secondary propelling and maneuvering devices consist of secondary rotors (2), water-jets or similar components which are housed on the bottom (29) in pairs of two.

Abstract: A system of elongated rails installed on the exterior hull surfaces of boats and projecting externally from the exterior hull surfaces of the boats, and having the functional attributes of: deflecting spray, reducing the tendencies of the bows to go under in choppy or turbulent seas, reducing heel and side-slipping while turning, contributing lift, acting as fenders to protect the hulls, providing accessible hand holds and foot steps, reducing the rocking motions of the boats and adding floatation to the boats.

Abstract: A jet ski hull has a lower section formed with a pronounced and sharp leading keel portion defined by oppositely disposed curvilinear fluted side walls extending downwardly from the peripheral edge. The leading keel portion expands outwardly to define a central longitudinal flat bottom which divides each of the fluted side walls. A fluted longitudinal groove is formed along the outer edge of each of the fluted side walls, starting approximately at a point rearward of where the leading keel begins to flatten out.

Abstract: A multi-hulled boat has at least three hulls, with the outside hulls extending forward beyond the central or inside hull or hulls. The hulls are tapered with a cross-sectional configuration that increases in side front to rear, thus forming a channel or tunnel between adjacent hulls which decreases in cross-sectional size front to rear. Air entering the tunnels is compressed, thus imparting a lifting force to the hulls lifting the hulls partially out of the water to decrease the hydraulic drag on the hulls. The hulls have identical cross-sectional areas at identical transverse planar sections thereof. The bottom of each hull is flat and inclined at an angle with the horizontal. The hull bottoms join the hull sides at a chamfer which increases in size front to rear. Shutters or flaps may be used to partially or fully close off the tunnels between the hulls to control airflow or to trap water-borne material to be collected and recycled.

Abstract: An improved performance marine surface vessel that includes pressurized supporting gas cushions in multiple hulls, normally catamaran-like sidehulls, where such pressurized supporting gas cushions support a majority of boat weight in operation. The preferred embodiment of the invention utilizes long fine pointed bow catamaran-like sidehulls that are in mechanical communication with a connecting hull structure. The long fine sidehulls offer performance advantages over a single large supporting gas cushion. The invention may also include a center bow disposed between the sidehulls that adds to stability in rough seas and gives a racy yacht-like appearance. Recesses in the sidehulls may include, at least in part, fixed and/or movable seals. Fixed seals may include inset vented steps to reduce wetted surface area. The recess gas pressurization system may include a controller to control pressures in individual recesses which allows at least some control of boat motions in rough seas.

Abstract: An elongated vehicle body has a forward bow portion, a stern, and a lower portion with the floor and sides runners defining a longitudinal rearwardly opening air channel in the underside thereof. The bow portion has a duct with a driven impeller therein communicating with a plenum chamber in turn communicating with the air channel. Valves are provided at the outlet for directing air flow from the plenum chamber selectively downwardly, rearwardly and forwardly and also for developing a vacuum under a forward portion of the vehicle to pull down a bow wave that may develop under forward movement of the vehicle. The runners have lateral openings adjacent the rear portion of the vehicle and actuator controlled rudders are disposed at these openings for movement inwardly to steer the vehicle and outwardly beyond the outer side of the runners for establishing a reverse thrust of the vehicle.

Abstract: A planing hull of a water craft including side keels and a center keep. A downwardly open chamber is defined rearwardly of the center keel and is flanked on either side by the side keels. The chamber confines a cushion of air which supports the hull in the planing mode, air supply to the chamber being wholly via the underside of the hull by being channelled between the keels without the use of air vents which open into the chamber. The absence of air vents provides improved drag at medium and low speeds.

Abstract: The marine hull has a forebody, a transom, and a bottom extending therebetween having pairs of upwardly formed channels between the forebody and the transom. The channels of each pair diverge rearwardly. Fluid flow exit paths interrupt the channel walls so that fluid from some of the channels can flow laterally outwardly, and the rear ends of at least some of the channels open at a peripheral edge of the bottom whereby water in these channels is free to discharge in both a rearward and laterally outward direction.

Abstract: A boat hull having inner ribs and outer chines interconnected by an inverted V-shaped planer surface and with the ribs and outer chines being pronounced at both sides of the stern of the hull and gradually disappearing as they converge and form strakes extending towards the bow of the hull. With the keel of the hull as level, the outer chines extend downwardly from the hull to be below the outermost extremities of the ribs.

Abstract: A small boat comprising a helmseat positioned at the center of the forward half of the boat, and a control stick for steering the boat positioned at the front of this helmseat. Since the helmseat is positioned at the center of the forward half of the boat, the driver is located approximately equidistant from the left and right gunwales, which makes it easier to steer the boat. In addition, a control stick is positioned to the front of the helmseat, and, because this control stick can be used to steer the boat and also to change the direction of the boat, the amount of space required to steer the boat is less than that required in a design wherein steering is performed by turning a circular steering wheel, such as with the prior art already described. This is effective particularly for a small boat moving at a high speed.

Abstract: A propulsion system for high-speed powerboats whereby the water level in a tunnel containing a surface-piercing propeller is controlled by admitting external air into the tunnel through an air outlet in the tunnel forward of the propeller. The air is admitted through a duct which has an air intake on the exterior of the boat. The duct may contain a valve which may be opened or closed to control the air supply. Particular configurations of the tunnel and the air supply system are disclosed which maximize the ability to control the water level in the tunnel and the degree to which the propeller is submerged as well as best utilize the configuration of the vessel.

Abstract: A jet ski hull includes upper and lower sections joined along a peripheral edge which edge is arranged to extend above the nominal waterline. In accordance with the present intention the lower hull section comprises (1) a central section extending from the bow of the ski to the stern thereof, 2) a concave section disposed on each side of the central section, (3) a pair of side walls joined to the upper hull section of the peripheral edge and extending downwardly and inwardly from the peripheral edge and (4) a transition section joining the lower portion of each side wall to a respective concave section. Each concave section defines a channel extending substantially the length of the hull for channeling water therethrough to prevent the hull from skidding during turns.

Abstract: A motor-boat hull (10) includes a planing bottom (C) having a V-shaped forward portion, two float-like side portions (14) connected forwardly to the V-shaped portion (12), and a flat recessed aft portion (16) delimited by the side portions (14) and forwardly by a transverse step (18) connecting it with the V-shaped forward portion (12) of the bottom (C).

Abstract: A pleasure boat having a rectangular passenger area for operation at high speeds in moderate seas, planes on ski-like planing surfaces on the bottom of laterally spaced, knife edge hulls located on the starboard and port sides of the craft and the stern end of a wedge shaped bottom rounded to assist in turns; the rounded bottom also having flutes to improve tracking and strakes to assist in the lift and to divert spray from the craft; the two forward hulls terminating in tunnels located along either side of the rounded bottom to reduce greatly the surface area in the water and to provide lift to assist in planing.

Abstract: A tunnel hull boat with enhanced turning stability is provided. The boat hull hereof includes a pair of sponsons defining an air capturing tunnel. Each sponson includes front, middle, and rear sections delineated by distinct inclinations of the sponsons's inner sidewall. The forward sections of the sponson inner sidewalls are angled generally downwardly and outwardly to allow the sponson bow to slide towards a desired direction. The rear section of the sponson inner sidewalls are angled downwardly and inwardly to inhibit skidding of the stern in a direction opposite to a desired turn.

Abstract: A hull configuration for a watercraft that improves stability in straight ahead running without significantly increasing the resistance to forward movement. The hull is comprised of a generally flat center section that is surrounded on each longitudinal side by a pair of arcuate sections, the outer peripheries of which are defined by respective chines.

Abstract: A deep vee entry hull having a central running surface extending fore and aft thereof, the cross-section thereof transitioning from a pronounced vee to a nearly planar configuration from fore to aft of the hull, the central running surface narrowing at its aft end portion and being flanked, in the after portion of the hull, by first and second inner running surfaces, intermediate running surfaces and outboard running surfaces, the first inner running surfaces being planar and exhibiting, with the central running surface, a vee configuration in cross-section; and the intermediate and outboard running surfaces exhibiting a cross-section of uninterrupted concave curvature commencing amidship to the extreme aft exit end thereof; the hull including sidewalls and the curvature of the concave intermediate and outboard running surfaces, at any given fore and aft positions, are constant, up to and including, an outer lip of said outboard running surfaces merging the same with the hull sidewalls; the intermediate and o

Abstract: A V-bottom planing hull has longitudinally elongate recesses formed in its bottom surface symmetrically of and parallel to the hull centerline. The recesses are open at the forward and aft ends and are concave downwardly of the hull. The recesses are semicircular in cross-section. The recesses provide lift to the hull as water moves through them during forward motion of the hull. The lift generated in the recesses augments conventional planing forces created by the hull, allowing the hull to move faster.

Abstract: A marine hull including a plurality of channels extending rearwardly and inclined, in plan, with respect to the central longitudinal vertical plane of the hull, the cross-sectional shape of each channel being curved so that its surface intercepts water when the hull is mobile and that water is caused to leave each channel in a downward direction thereby imparting lift over a major portion of the length of the hull.

Abstract: The invention comprises a stepped bottom structure of a boat, in which the steps (5) are mainly straight. The number of the steps is from 2 to 4, preferably 3, and the angle between the mainly straight edge (8) of the step and the keel (1) is from 20.degree. to 60.degree., preferably from 20.degree. to 45.degree.. In addition, the bottom structure includes rising laths (10), in which the side (19) facing the keel (1) is narrower than the side (20) facing the side of the boat.

Abstract: A low drag surface construction utilizes a plurality of longitudinally extending, parallel, spaced apart linear vortices extending transversely of the free stream to reduce drag between the free stream and the surface. The surface is provided with stabilizing means which retains the vortices in their relationship with one another but causes them to traverse the surface in the same direction as the free stream but at approximately half the speed. The stabilizing produces a regular variation in boundary flow across the surface and may comprise dynamic means such as sequenced jets of fluid escaping from apertures in the surface.

Abstract: An improved boat hull is provided that combines the handling characteristics of a V-bottom hull with the speed and acceleration characteristics of a tunnel hull boat. The boat hull hereof includes a V-shaped outer hull portion, and an opposed pair of narrow sponsons that depend downwardly from the gunwales to individual sponson base lines positioned between 5 degrees and two-thirds the V-hull dead rise angle, as measured relative to the horizontal from the apex of the V-hull portion.

Abstract: A hull for a boat having a forward section with two twin subhulls or sponsons joined by a bridging structure which forms, approximately midway along the sponsons, the fore-end of a third subhull. The twin forward subhulls each have a modified W cross-sectional shape which is continued to a spoiler located near the mid-section of the hull. Water flowing past the undersides of the sponsons gives rise to a lifting action as the boat starts to move. The bottom of the central subhull runs downward and rearward between the sponsons but remains separated from them past the spoilers. In the rear section, the extension of the central subhull is deeper than the remainder of the hull and has a substantially flat bottom joined to sides inclined outwardly and upwardly to form a generally V cross-sectional shape. As the boat picks up speed, it merely rises in the water with little change of attitude until the aft part of the hull skims on the surface of the water.

Abstract: There is disclosed a water-ski construction in which there is provided an elongated element having an upper and lower surface. The lower surface is divided, in the longitudinal direction, into a fore zone, a mid-zone, and an aft-zone, the lower surface of the element being adapted for contact with water. The fore-zone is designed by a single concave surface the nature of an arrow-like depression. The mid-zone is defined by first and second concave longitudinal channels separated by a sharp edge. The longitudinal channels extend throughout the mid-zone of the ski and into the aft-zone. The mid-zone further includes a flat surface which defines and frames the outer periphery of both the fore and mid-zones of the elongated ski element, thusly defining the outer transverse extent of the longitudinal channels. The depth of the concave longitudinal channels progressively deepens at the mid-zone and lessens at both the aft and fore zones.

Abstract: The specification discloses a modified V-hull for a boat in which an elongate pad forms the lowermost portion of the hull. At positions toward the front of the pad, it has a transverse cross-sectional rounded V-shape across its width, but at the back of the pad, the transverse cross-section is almost flat. The pad has a gradually increasingly acute V-shape in transverse cross-section from the back to the front of the pad, and the pad is linear along linear tracks extending from about the longitudinal center (the keel line) of the elongate pad rearwardly at a track angle with respect to the longitudinal center of the pad. The track angle remains approximately constant from about the back to the front of the pad. Also, the pad is linear at its rear end along an infinity of tracks extending from a point on the pad's longitudinal centerline about three feet from the back of the pad to any point on the back of the pad.

Abstract: A water jet propelled boat that includes a source of pressurized air that by a single action control may be delivered to bow and stern portion positioned resilient bags to inflate the same to vary the contour of the wetted portion of the boat to a desired configuration. The boat includes a number of laterally spaced sponsons that have forward bottom surfaces that taper downwardly to merge into substantially straight rearward bottom surfaces on which the boat rides when traveling at high speed. Pressurized air is discharged from the source to flow rearwardly under the boat and impart a lift to the latter. The desired configuration of the bags is one which in combination with the action of the sponsons and the rearwardly flowing bubbles results in the boat moving through the water in a fuel efficient manner.

Abstract: A boat which greatly reduces ventilation under a boat and cavitation in an outboard motor's propeller is disclosed. Preferably, a skeg and hulls are arranged to produce a zone behind the boat which is substantially free of froth and in which a propeller may operate efficiently. Preferably, the skeg is trapezoidal in cross-section with substantially planar surfaces. It runs forward from its broad end to its source, which preferably lies in a section about 60-75% of the boat's length forward from the stern. Channels running between the skeg and hulls uniformly decrease in area as they run aftward. Thus, lift of the stern is increased by the increase in the apparent water pressure and velocity in the channels. The skeg's shape acts as a shield for the propeller and helps to direct the water outwardly to develop a zone behind the skeg where the motor can operate more efficiently.

Abstract: There is disclosed a water-ski construction in which there is provided an elongated element having an upper and lower surface. The lower surface is divided, in the longitudinal direction, into a fore zone, a mid-zone, and an aft-zone, the lower surface of the element being adapted for contact with water. The fore-zone is designed by a single concave surface the nature of an arrow-like depression. The mid-zone is defined by first and second concave longitudinal channels separated by a sharp edge. The longitudinal channels extend throughout the mid-zone of the ski and into the aft-zone. The mid-zone further includes a flat surface which defines and frames the outer periphery of both the fore and mid-zones of the elongated ski element, thusly defining the outer transverse extent of the longitudinal channels. The depth of the concave longitudinal channels progressively deepens at the mid-zone and lessens at both the aft and fore zones.

Abstract: A small watercraft adapted to seat one or more riders in motorcycle fashion and which has a hull configured so as to facilitate leaning without capsizing. The foot area for the riders is such that a rider may either sit on the seat in straddle fashion or stand behind the seat and may move between these positions easily and while the watercraft is in motion.