WO1991011359A1 - High stability displacement hull device - Google Patents

High stability displacement hull device Download PDF

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Publication number
WO1991011359A1
WO1991011359A1 PCT/US1991/000485 US9100485W WO9111359A1 WO 1991011359 A1 WO1991011359 A1 WO 1991011359A1 US 9100485 W US9100485 W US 9100485W WO 9111359 A1 WO9111359 A1 WO 9111359A1
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WO
WIPO (PCT)
Prior art keywords
rail
rails
water
superstructure
bow
Prior art date
Application number
PCT/US1991/000485
Other languages
French (fr)
Inventor
Robert T. Price
Original Assignee
Hydro Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hydro Corporation filed Critical Hydro Corporation
Publication of WO1991011359A1 publication Critical patent/WO1991011359A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
    • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
    • B63B1/00—Hydrodynamic or hydrostatic features of hulls or of hydrofoils
    • B63B1/02—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement
    • B63B1/10—Hydrodynamic or hydrostatic features of hulls or of hydrofoils deriving lift mainly from water displacement with multiple hulls
    • B63B1/107—Semi-submersibles; Small waterline area multiple hull vessels and the like, e.g. SWATH

Definitions

  • Conventional displacement hull ships are slow, combat the waves, have undesirable pitch, roll, and yaw, have deep draft, must reduce speed in rough seas, are difficult to maneuver at slow speeds, drag appendages such as rudders for steering, require ballast for stability, carry cargo in the concentrated vapor zone near the water surface, must be strengthened to resist wave induced hull flexing, and compromise the shape of cargo areas to conform with the hydrodynamic imperative of moving mass through water.
  • the Tulleners watercraft depends upon an elevated pontoon parallel and above the displacement pontoon to create a vertical displacement force moment whenever the elevated pontoon noses into a wave.
  • the Tulleners watercraft's pitch stability is highly dependent upon the wave heights encountered being compatible with the pontoon spacing selected.
  • the present invention operating on different physical principles from Lang and Tulleners' inventions, differs in operating characteristics as well. Unlike Lang and Tulleners, the present invention increases in stability with speed, is highly insensitive to sea states up to its rated state, has a high tons per inch load rating, is highly stable in breaking beam seas, and being inherently stable, does not depend on auxiliary devices, like fins and pontoons to compensate for the watercraft's pitching.
  • the present invention provides a displacement hull ship with a new configuration that distributes the displacement over a greater area of the sea thereby experiencing a greater number and phases of wave activity.
  • This configuration coupled with limited reserve buoyancy distributed on rails with over fifty
  • • to one length to diameter ratios causes the ship to generally travel from wave trough to wave trough.
  • Optimal length to diameter ratios run from 60:1 to 75:1.
  • This ship is designed with wetted surface drag reduction through providing a laminar air flow between the hull surface and the surrounding water by utilizing pressure gradient control surfaces. Controlled differential fluid pressure creates lateral forces on the rail extremities generating turning moments for high speed ship direction control without the use of rudders or other appendages.
  • the advantages of the present invention over conventional devices are myriad. It provides a high speed displacement hull ship whose proportions are such that it can achieve exceptionally high speeds and maintain a constant level attitude in both calm and rough water. Multiple hulls with high length-to-width ratios minimize the amount of water disturbed during travel, and by minimizing the bow pressure wave, thus conserve horsepower and fuel and permit high speed travel.
  • the hull's travel, from wave trough to wave trough, provides a stable horizontal ride achieving superior stability by dynamically averaging wave forces.
  • the ship's weight is carried entirely by the displacement of its multiple hulls, without the use of lifting bodies or surfaces.
  • the ship's upper structure is supported by the multiple hulls, elevating working and load carrying spaces above the water surface, providing greater clear spaces and reducing humidity and water condensation on interior surfaces. Aerodynamic and not hydrodynamic forces set design constraints.
  • the ship's upper structure also permits bottom venting of heavy explosive gases.
  • the ship is not load sensitive and can adjust its reserve buoyancy and frontal area while underway or standing still in a minuscule period of time. It has a shallow draft which lends itself to beaching and off loading cargo or people in undeveloped areas without the need for harbors and docks. Inherent dynamic pitch and roll stability are achieved without the use of actively controlled fins or other powered balancing devices.
  • the device has at least two substantially parallel elongated displacement rails for supporting the device in the water.
  • Each rail has a length greater than 50 times its average width taken across a plane perpendicular to the rails' axis of elongation.
  • a superstructure is supported above the water level and connects the rails.
  • the device preferably has a propulsion system for driving the device in a direction parallel to the rails' axis of elongation.
  • the propulsion system can drive either one or more of the rails, or it can propel the superstructure.
  • FIG. 3 is a front elevation view of the fish freighter of FIG. 1;
  • FIG. 4 is a front elevation view of a recreational cabin cruiser according to the present invention having a narrow main body and triangular rails;
  • FIG. 5A is a schematic representation of a rail according to the present invention traveling through idealized surface waves
  • FIG. 5B is a schematic illustration of the rail of FIG. 5A in which the idealized surface waves are shifted 180°;
  • FIG. 6 is a front cross-sectional view of a rail according to the present invention
  • FIG. 7 is a broken side elevation view showing the rail of FIG. 6;
  • FIG. 8 is a side elevation view showing the front portion of an alternative rail according to the present invention
  • FIG. 9A is a side elevation view of portions of a rail according to the present invention showing wetted surface drag reduction and navigational features
  • FIG. 11 is a top elevation view of the rail of FIG. 9A;
  • FIG. 12 is a detail of the ribbing on the rail of FIG. 11;
  • FIG. 13 is a side elevation view of a rail according to the present invention showing the pivoting action of the bow and stern tips;
  • FIG. 14 is a top elevation view of the rail of FIG. 13 showing the pivoting action of the bow and stern tips.
  • the leg heights elevate the superstructure above the mean water height at a ratio of 30 to 60 percent of beam width depending on the device's sea state rating.
  • the superstructure in the preferred embodiment, has substantially rectilinear surfaces providing clear conventionally shaped working spaces.
  • the preferred embodiment utilizes modular components for ease of mass production.
  • FIGS. 1, 2 and 3 show an example of an embodiment of the present invention outfitted as a refrigerated fish carrier.
  • the device has a starboard rail 2 and a parallel port rail 4 which support a superstructure 6.
  • the superstructure includes a set of six legs 8, three on each side. Three of the legs connect to the top surface of each rail and support a substantially flat platform 10 upon which the rest of the superstructure is built.
  • the superstructure includes a cabin and bridge 12 near the front of the piatf ⁇ rm, a processing area and a hold 14 and a pair of engines 16.
  • the rails operate as conventional displacement hulls to support the superstructure above the surface of the water whether the device is moving forward or standing still.
  • the legs hold the superstructure above the water high enough to prevent any significant water contact with the platform.
  • the freighter can be used as a short term dock for fishing boats.
  • the device anchors in a location where boats are fishing and the fishing boats 20 tie up alongside a central portion of the rail.
  • a crane 22 then moves fish caught by the fishing boats from the fishing boats into the freighter's processing and hold area 14.
  • the fishing boats then move a short distance back to their preferred fishing site and the freighter moves to an area where other fishing boats are waiting or brings the fish to port.
  • the hallmarks of the device of the present invention are stability and high speed efficiency in both calm and rough water.
  • Using the present invention as a pickup and delivery station allows the devices to concentrate on what they do best.
  • the fishing boats because of their reduced travel time, can spend more time fishing and the freighter, capitalizing on its stability and high speed, travels the long distance from the fishing areas to port.
  • FIG. 2 is an elevational top view of the freighter.
  • the rails 2, 4 are parallel to each other and very thin and long. It is preferred that the length be at least 50 times greater than the diameter or average cross section of the rail, the longer the rail, the greater the stability in rough seas. However, longer rails are more expensive to produce because of the difficulty in maintaining structural integrity in very long and thin structures. It is presently preferred that the rails be approximately 65 times as long as their diameters to minimize cost while still obtaining good device stability.
  • the superstructure 6 is substantially shorter than the rails. It is presently preferred that the superstructure be approximately one third the length of the rails.
  • FIG. 3 shows an elevational front view of the freighter. This view emphasizes that the rails 2, 4 are very thin in comparison with the other parts of the boat. The rails are spaced far enough apart to hold the entire device stable considering its substantial height.
  • the bottom of the platform 10 which supports the structures on the superstructure is raised high enough above the water level to prevent the superstructure from interfering with waves.
  • the superstructure may span the entire distance between the rails or just a part of it. For stability, it is preferred that the superstructure be no wider than the rails and that its weight be centered between the rails.
  • FIG. 4 is a front elevational view of a second example embodiment of the present invention.
  • This embodiment shows the device as a recreational cabin cruiser.
  • the cabin 24 is typically approximately 8 meters long in a conventional recreational application and is suspended by legs 26 over a starboard rail 28 and a port rail 30.
  • the rails have enough displacement to maintain the superstructure out of the water even when the craft is at rest;
  • the superstructure is narrower than the rails for enhanced stability. It is also preferred that each rail have enough displacement to support the entire weight of the ship, or in other words, that each rail have 100 percent excess buoyancy displacement. More than 100 percent excess buoyancy unnecessarily increases wave influences on the devices.
  • the superstructure contains watertight compartments providing flotation when rails are optionally flooded to lower the superstructure nearer to or to rest on the water surface. The operator may choose to lower the superstructure for a variety of operating purposes.
  • the rails should be approximately 24 meters long and should, accordingly, have a diameter of a little over 36 centimeters (the preferred length-to-diameter ratio being 65:1).
  • the cross section of the rails shown in FIG. 4 is an equilateral triangle, the equivalent to a 36-centimeter diameter for a triangle corresponds to each side measuring a little over 36 centimeters.
  • the legs 26 should suspend the cabin 24 about 2.4 meters from the water line, that is, 20 percent higher than the device's highest expected wave encounter.
  • the triangular rails have an equilateral triangle cross section. Each side of the equilateral triangle is 40 centimeters long. Each rail has 100 percent excess buoyancy. This means that when the device is at rest, one half the volume of each rail will be submerged. In an upright equilateral triangle, this occurs when one third of the height of the triangle is submerged.
  • the triangle is approximately 36 centimeters high, which means the draft of this recreational cabin cruiser is about 12 centimeters.
  • a 12-centimeter draft is more common among canoes than seaworthy devices. The device can be docked and navigated in the shallowest of waters and beached directly on the shore.
  • FIGS. 5A and 5B show an example rail 34 floating in an idealized water surface wave 36.
  • the wave has two crests 38 and 40 and two troughs 42 and 44. At the crests 38 and 40, the buoyancy of the rail pushes the rail up.
  • Each rail is preferably at least 1-1/2 times the wavelength for the highest sea for which the device is rated. This minimum is the length illustrated in FIGS. 5A and 5B.
  • each wave 36 before each crest 38 water moves upward. This pushes the rail surface upward.
  • the buoyancy of the bow causes the boat to move upward.
  • oceangoing devices have reserve buoyancy of seven times the operating buoyancy, making them very reactive to the influence of wave forces.
  • a leading edge of an incoming wave also pushes the bow of the rail upward, however, the buoyancy of the rail is small in its bow as compared to the rest of its length.
  • the upward push of the leading edge of the oncoming wave is counterbalanced by the downward push of the falling water in the passing wave in other points along the length of the rail.
  • Each wave creates equal amounts of heave and fall, or upward and downward force.
  • the rail By making the rail at least 1-1/2 times the length of the longest expected wave, the heave and fall balance each other out . across the length of the rail. The longer the rail, the less it is affected by heave and fall. As a result, the rail naturally travels flat through surface waves rather than over them as conventional hulls do. If the rail were maintained at the same length, but its diameter, and therefore its buoyant volume, were substantially increased, the rail would still be able to balance the effects of waves across its length. However, the leading edge of each wave would have a much greater effect on the pitch of the rail because the rail's buoyant bow would create more lift.
  • the rails are able to pierce through waves little affected by the waves' leading and trailing edges. It is not necessary to provide auxiliary pontoons to add buoyancy when a rail becomes significantly submerged. Because the aft ends of the rail hold the rail level, it is not necessary for the bow of the rail to have a downward pointing tip because the rail does not have to overcome its own inherent buoyancy, the buoyancy of the rail being spread out along its entire length. The rail simply rests on the water largely unaffected by weather conditions. The stability is enhanced by the speed at which the rail travels through the water. Accordingly, unlike a conventional ship, when rough seas are encountered, a device according to the present invention is not required to slow down.
  • FIG. 6 shows a cross-sectional view of a single rail in an embodiment preferred for speeds over 50 knots and where a shallow draft is not the overriding concern.
  • the cross section in FIG. 6 is rectangular, the height of the rectangle being approximately double it width. Because the rails have a 100 percent excess buoyancy, the cross section of the submerged portion of the rail is normally substantially square. It is preferred not only that the rail be kept small in diameter to distribute its buoyant effects over a very long length, but also that the rail be kept narrow. As the rail is pushed through the water, it must open the water to make space for the rail. This normally causes a large amount of drag.
  • the rectangular cross section for the rail, shown in FIG. 6, reduces, compared to conventional devices, the distance the water must travel to pass by the rail and thereby the amount of power expended to open water for the rail.
  • the rail includes a pointed bow tip 50.
  • This tip opens the water more gradually, reducing water acceleration rates and therefore the volume of disturbed water through hull speed limiting bow pressure wave build up. Power consumption and drag are reduced commensurately.
  • the bow tip is ten times longer than the diameter of the rail. This ensures a gradual transition to ease the opening of the water.
  • the bow tip in FIG. 7 is shown shorter than the preferred length.
  • the rail also includes a stern tip 52. The stern tip reduces the drag of water closing around the rear of the rail as the rail leaves the water. The precise proportions of the bow and stern tips can be adjusted to accommodate the anticipated cruising speeds of the device. At higher speeds, a longer bow tip would be desired more than at lower speeds.
  • FIGS. 6 and 7 also show a tunnel 54 in the bottom surface of the rail 48.
  • the tunnel is entirely submerged beneath the water.
  • the water's entry into the tunnel is controlled by a set of flaps 56.
  • flaps 56A and 56B at the bow of the rail and a pair of flaps 56C and 56D at the stern of the rail.
  • the flaps can be arranged so that they pivot from the upper surface of the groove, allowing or preventing water from flowing into the tunnel, as shown in FIG. 7.
  • Air nozzles 58 are also supplied to the tunnel for pumping air into the tunnel. The position of the flaps controls the level of water within the tunnel. The air nozzles fill the part of the tunnel between the flaps with air, increasing the buoyancy of the rail.
  • the flaps together with the air nozzles, allow the attitude of the device to be controlled. Moving all four flaps downward increases the volume of the tunnel filled with air. This makes the rail more buoyant raising it along its entire length. Moving the rear flaps up while maintaining the front flaps down causes the more buoyant front of the rail to move up relative to the rear of the rail.
  • the flaps allow the device to be trimmed without using protruding rudders. The ride height of the device can also be adjusted.
  • the buoyancy of the rails be kept to a minimum.
  • the rails have no more than a 100 percent excess buoyancy. This is thought necessary to prevent the device from capsizing if subjected to extreme side loading. However, as mentioned above, too much excess buoyancy increases the effect of surface waves on the attitude of the rails.
  • the buoyancy of the rails can be adjusted to match its load. When the ship is lightly loaded, the flaps can be moved upwards, eliminating air from the tunnel 54. This reduces the frontal area of the rail and amount of water disturbed per. meter, optimizing device fuel efficiency when less than fully loaded.
  • the flaps When the craft is fully loaded the flaps can be moved downward and the tunnel filled with air to maintain the designed reserve buoyancy under the heavier load. With the appropriate electronic control mechanism, the flaps can also be adjusted to trim the device maintaining its attitude when entering seas with extended wave periods.
  • An electronic device coupled to level sensors can be used to. control the position of the flaps and the air supply volume in order to minimize short term variations in device attitude.
  • the flaps may be attached to the top of the tunnel and hinged as shown in FIG. 7, or they may be placed on tracks so that they slide up and down with respect to the tunnel or they may be mounted in any other fashion which allows them to be adjustable. Adding more flaps and air nozzles between the flaps allows the buoyancy of the rail to be controlled locally. This may offset the propulsion centerline of thrust variations discussed below. Because the rails move quickly through the water, and because the nozzle 58 supplies a steady stream of air, it is not necessary that the flaps seal against the inside edge of the tunnel to complement the hydrodynamic seal. However, if this is desired, it can be done using inflatable seals. The seals deflate when the flap is moved and inflate when the flap is located in position to seal the flap against the side walls. If a sliding flap is used, sealing might be easier.
  • the front flaps may be integrated into the front surface of the bow point 50 to reduce drag or, as shown in FIG. 7, they may be located further back along the tunnel.
  • FIG. 8 shows a side elevational view of a rail 56 suitable for compensating for the pivoting effect of the engines 16 of the embodiment of FIGS. 1-3.
  • the bow tip 58 of the rail of FIG. 8 is configured in a conventional vee shape well known in recreational boats for developing lift to bring boats up on a plane.
  • the vee shaped bow tip generates enough lift at the device's cruising speed to maintain the proper trim on the device.
  • a vee shaped rail can also be built with a tunnel 60 and flaps 62 as described with respect to FIG. 7.
  • the rail preferably has a bow and stern point which are tapered.
  • the surfaces of the points are flat and move straight from the centerline of the rail to the edges of the rail. This provides a neutral attitude for piercing surface waves.
  • FIG. 9A shows the front portion of a rail adapted for high speed operation with reduced drag and additional navigational features. It is generally preferred that between the bow and stern tips, each rail 64 have a constant uniform cross section. The uniform cross section reduces drag by eliminating the need to open the water past the bow tip 66 and by eliminating flow irregularities. It is also preferred that the rail be free of protruding rudders, fins and wings. At speeds above 50 knots, these items create much drag.
  • the bow tip preferably has a length ten times that of the rail's diameter; however, it is shown in FIG. 9 here with a steeper rake. At the tip of the bow tip there is long thin extendable boom 68.
  • the boom can be drawn into the bow tip 66 for slow speed cruising and docking and extended when the rail is moving at high speeds.
  • the features of the rail shown in FIG. 9A are specifically adapted for a cruising speed of approximately 52 knots. Since the present invention uses a much longer hull than a conventional boat and is capable 'of travelling at much higher speeds, the drag on the wetted surface of the hull becomes a significant factor.
  • the air nozzle 70 helps open the water as the extendable boom travels forward.
  • the air is ejected from the nozzle and it flows in the directions shown by the arrows.
  • the high pressure air emitted at the boom tip expands upon exiting the tip and, because its pressure is higher than the surrounding water, it accelerates the water at the tip a substantial distance ahead of the bow taper. This provides a more gradual taper angle as needed to reduce acceleration of the displaced water at elevated speeds.
  • the high pressure air acts as a bow taper extension. As the water and boom move with a relative speed, the air between the water and the boom is sheared. Shearing the air rather than the water significantly reduces the drag on the rail. It also provides a cushioning effect when rough seas are encountered.
  • a second nozzle 72 which extends around the entire circumference or perimeter of the rail.
  • This air nozzle ejects low pressure air which travels along the entire length of the rail with the water, reducing or eliminating the wetted surface drag along the entire length of the rail.
  • the nozzle surrounds the entire perimeter of the rail and ejects a substantially even stream of air around the entire rail. While the craft is in motion, portions of the rail can be entirely submerged under the water while other portions of the rail are substantially above the local water level. Therefore, it is important that the entire perimeter of the rail enjoy the benefits of the air nozzle.
  • the air ejected from the nozzle in addition to reducing wetted surface drag, extends the apparent length of the rail with respect to the water closing about the stern of the rail by back filling the low pressure area.
  • the wetted surface drag on the rail of FIG. 9A is further reduced with a corrugated surface.
  • the corrugated surface presents a series of elongated ribs substantially parallel to the rails' axis of elongation which is also substantially parallel to the flow of water.
  • the preferred shape of the corrugated surface is shown in detail in FIG. 9B and greatly enlarged in cross section in FIG. 10.
  • the corrugated surface presents a uniform series of vee shaped ribs 74 and valleys 76.
  • the distance between ribs is preferably approximately 3/16 of an inch.
  • the purpose of the corrugated surface is to trap air and reduce the amount of surface over which water flows.
  • the valley between each rib serves as an air reservoir.
  • the air is more likely to be held within the valleys 76 between the ribs. As the water travels along the rail, it contacts only the ridges of the rail, greatly reducing the amount of wetted surface drag.
  • Water moving horizontally along the rail has a slight vertical component. At 52 knots, the vertical and horizontal components together result in water travel at approximately 5° upward from the horizontal. To ensure that the ribs best retain the entrained air, the ribs are offset downward from the horizontal by the same 5°, creating an action pumping air downward to match the surrounding water pressure. This can be best seen in FIG. 9B. This optimizes the wetted surface drag reduction for the device's rated cruising speed. A greater or lesser angle is preferred for lower and higher speeds, respectively. A higher speed craft would have ribs even more parallel to the rails' elongation axis. A slowmoving craft would not significantly benefit by ribs at all.
  • FIG. 9A shows a portion of a leg 73 fastened to the rail 64, the rail has nearly horizontal ridges along its length and a long vertical nozzle 76 at its leading edge. It is preferred that the legs be kept as narrow as possible. As with the bow point, it is preferred that the legs flare at a rate no greater than 10:1.
  • FIG. 9A also shows navigational features of a preferred embodiment of the present invention for maneuvering the craft both at low and high speeds.
  • the bow tip there is a set of pressurized air nozzles 78 which blow air laterally. It is preferred that both sides of the bow tip 78 include a set of nozzles.
  • the air expelled from the nozzles causes disruptions in the oncoming water increasing its acceleration rate and changing the bow pressure wave forces acting on the rail. This is analogous to moving the rails' bow point off center.
  • the device's propulsive force pushes the device through the effectively offset bow point generating a turning moment. Steering can be done without the use of rudders or fins, both of which create continued drag.
  • FIG. 9A also shows a side thruster 80 for use at slow speeds.
  • the side thruster 80 is a pair of propellers 82 and a shaft 84 which extends through the entire width of the rail.
  • Each rail would have a pair of propellers at both the bow and stern ends.
  • a propeller in the appropriate direction is simply engaged, drawing water through the shaft and expelling it out the other side.
  • the device can easily be pivoted within its own length.
  • the thrusters in the same direction the device can be moved sideways. This can be an advantage for maneuvering in small ports or when it is desired to beach the device.
  • the device can be beached by propelling it sideways until one rail rests on the shore. Passengers or cargo can be unloaded from the top surface of the beached rail, using an extendable ramp on the top of the rail. To move the device back to open sea, the beached rail is raised off the shore and the trusters 80 are driven to draw the device away from the beach.
  • the rails of the device can easily be raised and lowered, using the tunnel 54, flaps 56 and nozzle 58 described with respect to FIGS. 6 and 7.
  • the combination of side thrusters and an inflatable tunnel allows even very large devices to beach in undeveloped areas. Landing boats are unnecessary. This is impossible with a conventional hull.
  • FIG. 11 shows the rail of FIGS. 9 and 10 in an elevational view from above.
  • the top surface of the rail is also textured with a series of nonintersecting ribs 74 between valleys 76.
  • On the top surface there is no vertical movement upward of water flowing by the rail but, instead, general outward movement from the center of the rail towards the sides.
  • the ribs are, as in FIGS. 9 and 9A, substantially parallel to the rails' axis of elongation and the flow of water over the rail.
  • the ribs are preferably angled three degrees from the direction of elongation, extending toward the stern of the rail as they extend outward in a vee fashion. This is shown in greater detail in FIG.
  • the bow point 66 and the boom 68 are similarly textured.
  • the angle of 5 degrees has been chosen to optimize the drag reducing effect of the ribbing at 52 knots. However, a different angle can be used for optimizing different speeds.
  • the bottom surface of the rail is generally not ribbed, and, in the rail shown in FIGS. 6, 7 and 8, only a small portion of the bottom surface of the rail contacts the water. Most of the wetted surface drag on the bottom surface of the rail is eliminated by the tunnel 54, which would typically be filled with air, at least in part, when the device is operating at speed.
  • the tunnel may be ribbed.
  • the device be operated completely without the use of conventional fins, rudders and trim flaps. All of these devices increase surface drag on the rail. If they are built large enough to effectively control the boat at low speed, they become hypersensitive at high speed. Similarly, if they are built as small as possible to minimize drag at high speed, they are ineffective at low speed. For low speed maneuvering, it is preferred that a set of thrusters, as described with respect to FIG. 9, be used.
  • the tunnel flaps 56 described with respect to FIG. 7, together with the nozzles 78 in the bow point can be used. Alternatively or in addition, the bow and stern points can be made available.
  • FIGS. 13 and 14 show a rail 64 with a cone-shaped bow tip 78 and a cone-shdped stern tip 86.
  • the bow tips have a length 10 times the cross section of the rail in order to more gradually open the water for the rail, they are shown here shorter for convenience.
  • FIG. 13 is a side elevational view which shows the bow and stern tips directed straight out in a conventional operating mode. However, as shown in dotted lines, the bow tip as well as the stern tip can be pivoted up or down to trim the attitude of the device. If the bow appears to be submarining excessively, the bow tip can be turned upward to present the underside of the bow tip 88 as a lifting surface.
  • FIG. 14 shows the same rail 64 in an elevational top view.
  • the bow tip 78 and stern tip 86 may be pivoted from side to side. This allows the device to be steered.
  • the bow and stern tips are both moved towards the starboard side, or upwards as shown in FIG. 14.
  • the bow and stern tips are moved to port.
  • the rail of FIG. 14 includes a propeller 92 which is connected to the end of the stern tip, moving the propeller, starboard or port, increases the steering effect. While pivoting the bow and stern tips provide adequate maneuverability at moderate speeds, it is preferred that the thrusters 80 be retained for slow maneuvers.
  • both the bow and stern tips pivot.
  • the device can be controlled merely by pivoting either the bow tip or the stern tip.
  • Conventional mechanical and hydraulic drivers can be used for controlling the position of the tips.
  • the effect of each tip can be equalized by providing strain gauges in the legs. If the leg nearest a tip is, for example, experiencing more strain than other legs, then the amount of pivot on that tip can be altered.
  • the device of the present invention can be propelled in a variety of ways. Turbojet or propeller aircraft type engines may be mounted to the rear of the superstructure, as shown in FIGS. 1 through 3. However, this high centerline of thrust will tend to rotate the device downward. This can be overcome using any of the trimming techniques discussed above.
  • the device may also be propelled by propellers at the ends of the rails as shown in FIGS. 13 and 14.
  • the aerodynamic drag on the superstructure will tend to rotate the bow of the device out of the water. Again, this can be countered using the trimming techniques discussed above.
  • the thrust centerline should be somewhere between the superstructure and the rail. However, the exact location of this optimum centerline will vary depending on the speed of the craft and the water conditions. The hydrodynamic drag on the rails will increase faster than the aerodynamic drag on the superstructure.
  • the device can also be propelled by some type of propeller located at the front or bow end of the tunnel 54 and the rail. This propeller draws water into the rail and thrusts it towards the stern of the rail through the tunnel. Drawing water into the rail reduces the amount of water which must be opened to accommodate the rail as it moves through the water, further reducing bow pressure wave drag. In addition, the influence of the flaps 56 within the groove 54 would be greatly increased. Additionally, the device
  • FIGS. 1 to 3 show the device adapted for use as a fish freighter.
  • the device is equally well suited for hauling other kinds of freight. It is especially valuable for freight which is sensitive to large pitching and rolling motions and which must be transported quickly.
  • FIG. 4 shows the device adapted for use as a recreational cabin cruiser. As a cabin cruiser it offers greater speed, a shallower draft, and lower fuel consumption than a conventional boat.
  • any of the devices described above may be fitted with anchors attached to the superstructure.
  • the invention may be utilized in both powered and nonpowered forms.
  • a nonpowered form the invention provides a rough water stable platform that shares the low load sensitivity and other beneficial features of the invention in powered form.
  • Examples of nonpowered forms are floating airplane runways, piers, and open ocean platforms. These may be constructed in modular units for on-site assembly.
  • any of the nozzles described as air nozzles could provide some other fluid, whether in liquid or gas form, to achieve the same beneficial wetted surface drag reduction effects.

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  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
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  • Ocean & Marine Engineering (AREA)
  • Other Liquid Machine Or Engine Such As Wave Power Use (AREA)

Abstract

An ultra stable high speed water vessel rests upon long slender rails (24). The rails function as displacement hulls to support the ship's superstructure (14) above the water level. The rails' long length and narrow cross section allow them to pierce through waves rather than riding over them averaging the forces of heave and fall. Air nozzles (70, 72) and surface texturing (74, 76) allow higher speeds by reducing wetted surface drag. A tunnel (54) through the bottom of the rails controlled by flaps (56) and air injection (58) controls the trim of the vessel, and navigational control is obtained with air nozzles (78) and low speed side thrusters (80). The vessel may be outfitted as a fixed platform, a freighter, a pleasure craft, or in many other ways.

Description

HIGH STABILITY DISPLACEMENT HULL DEVICE
Field of the Invention
The present invention relates to a displacement hull device with high stability and reduced water surface drag, in particular, a device that rides upon long slender displacement hull rails which raise the device's superstructure above the water level.
Background of the Invention Traditional displacement hull ships with their high freeboard plow a furrow through the water. They are water surface followers, changing attitude as the surface undulates. With their high freeboard they create a standing bow wave that they push upon, consuming excessive energy. The bow wave grows at an exponential rate to ship speed. The bow wave and its companion stern wave create a hill in the water that the ship is always trying to climb over. Conventional displacement hull ships, compared to the invention, are slow, combat the waves, have undesirable pitch, roll, and yaw, have deep draft, must reduce speed in rough seas, are difficult to maneuver at slow speeds, drag appendages such as rudders for steering, require ballast for stability, carry cargo in the concentrated vapor zone near the water surface, must be strengthened to resist wave induced hull flexing, and compromise the shape of cargo areas to conform with the hydrodynamic imperative of moving mass through water.
Attempts to overcome the limitations inherent in conventional devices are shown in U.S. Patent No. 3,623,444 to Lang and U.S. Patent No. 3,430,595 to Tulleners. The present invention shares only a surface similarity to Lang and Tulleners. It is a large water plane area watercraft that relies on dynamic averaging of wave rise and fall over the long, high polar moment of inertia rails for pitch control. The Lang watercraft relies upon positioning the device's displacement volumes as far under the surface as possible to avoid vertical wave moments. It requires auxiliary horizontal stabilizers to dampen the device's pitch motion. The Tulleners watercraft depends upon an elevated pontoon parallel and above the displacement pontoon to create a vertical displacement force moment whenever the elevated pontoon noses into a wave. The Tulleners watercraft's pitch stability is highly dependent upon the wave heights encountered being compatible with the pontoon spacing selected.
The present invention, operating on different physical principles from Lang and Tulleners' inventions, differs in operating characteristics as well. Unlike Lang and Tulleners, the present invention increases in stability with speed, is highly insensitive to sea states up to its rated state, has a high tons per inch load rating, is highly stable in breaking beam seas, and being inherently stable, does not depend on auxiliary devices, like fins and pontoons to compensate for the watercraft's pitching.
Summary of the Invention
The present invention provides a displacement hull ship with a new configuration that distributes the displacement over a greater area of the sea thereby experiencing a greater number and phases of wave activity. This configuration coupled with limited reserve buoyancy distributed on rails with over fifty
• to one length to diameter ratios causes the ship to generally travel from wave trough to wave trough. Optimal length to diameter ratios run from 60:1 to 75:1. This ship is designed with wetted surface drag reduction through providing a laminar air flow between the hull surface and the surrounding water by utilizing pressure gradient control surfaces. Controlled differential fluid pressure creates lateral forces on the rail extremities generating turning moments for high speed ship direction control without the use of rudders or other appendages.
The advantages of the present invention over conventional devices are myriad. It provides a high speed displacement hull ship whose proportions are such that it can achieve exceptionally high speeds and maintain a constant level attitude in both calm and rough water. Multiple hulls with high length-to-width ratios minimize the amount of water disturbed during travel, and by minimizing the bow pressure wave, thus conserve horsepower and fuel and permit high speed travel. The hull's travel, from wave trough to wave trough, provides a stable horizontal ride achieving superior stability by dynamically averaging wave forces. The ship's weight is carried entirely by the displacement of its multiple hulls, without the use of lifting bodies or surfaces. The ship's upper structure is supported by the multiple hulls, elevating working and load carrying spaces above the water surface, providing greater clear spaces and reducing humidity and water condensation on interior surfaces. Aerodynamic and not hydrodynamic forces set design constraints. The ship's upper structure also permits bottom venting of heavy explosive gases.
The ship is not load sensitive and can adjust its reserve buoyancy and frontal area while underway or standing still in a minuscule period of time. It has a shallow draft which lends itself to beaching and off loading cargo or people in undeveloped areas without the need for harbors and docks. Inherent dynamic pitch and roll stability are achieved without the use of actively controlled fins or other powered balancing devices.
The invented device shares inherently low load sensitivity as measured in load tons per inch of draft with classic displacement hulls. Further, displacement is made variable through captured air housed underneath the rail keels.
In one embodiment, the device has at least two substantially parallel elongated displacement rails for supporting the device in the water. Each rail has a length greater than 50 times its average width taken across a plane perpendicular to the rails' axis of elongation. A superstructure is supported above the water level and connects the rails. The device preferably has a propulsion system for driving the device in a direction parallel to the rails' axis of elongation. The propulsion system can drive either one or more of the rails, or it can propel the superstructure.
Brief Description of the Drawings
FIG. 1 is a perspective view of a high speed fish freighter according to the present invention with two fishing boats docked alongside; FIG. 2 is a top elevation view of the fish freighter of FIG. 1;
FIG. 3 is a front elevation view of the fish freighter of FIG. 1;
FIG. 4 is a front elevation view of a recreational cabin cruiser according to the present invention having a narrow main body and triangular rails;
FIG. 5A is a schematic representation of a rail according to the present invention traveling through idealized surface waves; FIG. 5B is a schematic illustration of the rail of FIG. 5A in which the idealized surface waves are shifted 180°;
FIG. 6 is a front cross-sectional view of a rail according to the present invention; FIG. 7 is a broken side elevation view showing the rail of FIG. 6;
FIG. 8 is a side elevation view showing the front portion of an alternative rail according to the present invention; FIG. 9A is a side elevation view of portions of a rail according to the present invention showing wetted surface drag reduction and navigational features;
FIG. 9B is a detail of the rail of FIG. 9A showing surface ribbing; FIG. 10 is a cross-sectional detail of the surface ribbing of FIG. 9B;
FIG. 11 is a top elevation view of the rail of FIG. 9A;
FIG. 12 is a detail of the ribbing on the rail of FIG. 11; FIG. 13 is a side elevation view of a rail according to the present invention showing the pivoting action of the bow and stern tips; and
FIG. 14 is a top elevation view of the rail of FIG. 13 showing the pivoting action of the bow and stern tips.
Detailed Description of the Invention
Traditional displacement hulls plow a furrow through the water while attempting to follow the water's wavy surface. Pitch, roll, yaw and excessive drag, and slamming, leading to crew and passenger discomfort and bending moments leading to hull fatigue are all traditionally suffered. The present invention substantially eliminates these traditional disadvantages. The present invention, in its preferred embodiment as shown in FIG. 1, has two rails, whose length to diameter ratios are 65:1 or 70:1, and whose preferred cross section is a vertical rectangle, of at least a 2:1 aspect ratio. The rails are positioned parallel to one another establishing a device beam to length ratio of about 1:3. The preferred embodiment has a superstructure attached to each rail by one or more legs joined at points that provide designed rail strengths and resonant frequencies. The leg heights elevate the superstructure above the mean water height at a ratio of 30 to 60 percent of beam width depending on the device's sea state rating. The superstructure, in the preferred embodiment, has substantially rectilinear surfaces providing clear conventionally shaped working spaces. The preferred embodiment utilizes modular components for ease of mass production.
FIGS. 1, 2 and 3 show an example of an embodiment of the present invention outfitted as a refrigerated fish carrier. The device has a starboard rail 2 and a parallel port rail 4 which support a superstructure 6.
The superstructure includes a set of six legs 8, three on each side. Three of the legs connect to the top surface of each rail and support a substantially flat platform 10 upon which the rest of the superstructure is built. The superstructure includes a cabin and bridge 12 near the front of the piatfόrm, a processing area and a hold 14 and a pair of engines 16. The rails operate as conventional displacement hulls to support the superstructure above the surface of the water whether the device is moving forward or standing still. The legs hold the superstructure above the water high enough to prevent any significant water contact with the platform.
In the example embodiment of FIGS. 1, 2 and 3, the freighter can be used as a short term dock for fishing boats. The device anchors in a location where boats are fishing and the fishing boats 20 tie up alongside a central portion of the rail. A crane 22 then moves fish caught by the fishing boats from the fishing boats into the freighter's processing and hold area 14. The fishing boats then move a short distance back to their preferred fishing site and the freighter moves to an area where other fishing boats are waiting or brings the fish to port. As explained below, the hallmarks of the device of the present invention are stability and high speed efficiency in both calm and rough water. Using the present invention as a pickup and delivery station allows the devices to concentrate on what they do best. The fishing boats, because of their reduced travel time, can spend more time fishing and the freighter, capitalizing on its stability and high speed, travels the long distance from the fishing areas to port.
The relative proportions of the freighter can better be seen in FIGS. 2 and 3. FIG. 2 is an elevational top view of the freighter. As shown in FIG. 2, the rails 2, 4 are parallel to each other and very thin and long. It is preferred that the length be at least 50 times greater than the diameter or average cross section of the rail, the longer the rail, the greater the stability in rough seas. However, longer rails are more expensive to produce because of the difficulty in maintaining structural integrity in very long and thin structures. It is presently preferred that the rails be approximately 65 times as long as their diameters to minimize cost while still obtaining good device stability. The superstructure 6 is substantially shorter than the rails. It is presently preferred that the superstructure be approximately one third the length of the rails. This prevents the weight of the superstructure from greatly affecting the motion of the bow or stern of each rail by concentrating most of the weight of the superstructure over the center of the rails. As mentioned above, the rails are displacement hulls and support the superstructure above the water with their own buoyancy. The device needs no fans, wings or forward propulsion to hold the superstructure above the water. FIG. 3 shows an elevational front view of the freighter. This view emphasizes that the rails 2, 4 are very thin in comparison with the other parts of the boat. The rails are spaced far enough apart to hold the entire device stable considering its substantial height. The bottom of the platform 10 which supports the structures on the superstructure, is raised high enough above the water level to prevent the superstructure from interfering with waves. Normally 20 percent higher than the maximum rated sea state for the device is sufficient. This accounts for abnormally large waves in the maximum sea state. The superstructure may span the entire distance between the rails or just a part of it. For stability, it is preferred that the superstructure be no wider than the rails and that its weight be centered between the rails.
FIG. 4 is a front elevational view of a second example embodiment of the present invention. This embodiment shows the device as a recreational cabin cruiser. The cabin 24 is typically approximately 8 meters long in a conventional recreational application and is suspended by legs 26 over a starboard rail 28 and a port rail 30. Again, the rails have enough displacement to maintain the superstructure out of the water even when the craft is at rest; The superstructure is narrower than the rails for enhanced stability. It is also preferred that each rail have enough displacement to support the entire weight of the ship, or in other words, that each rail have 100 percent excess buoyancy displacement. More than 100 percent excess buoyancy unnecessarily increases wave influences on the devices. The superstructure contains watertight compartments providing flotation when rails are optionally flooded to lower the superstructure nearer to or to rest on the water surface. The operator may choose to lower the superstructure for a variety of operating purposes.
Since the cabin 24 is typically 8 meters long, the rails should be approximately 24 meters long and should, accordingly, have a diameter of a little over 36 centimeters (the preferred length-to-diameter ratio being 65:1). However, since the cross section of the rails shown in FIG. 4 is an equilateral triangle, the equivalent to a 36-centimeter diameter for a triangle corresponds to each side measuring a little over 36 centimeters. For the device to be rated for two-meter waves, which would be sufficient for most coastline use, the legs 26 should suspend the cabin 24 about 2.4 meters from the water line, that is, 20 percent higher than the device's highest expected wave encounter.
One of the advantages of the peculiar design of the present invention can easily be seen from FIG. 4. As mentioned above, the triangular rails have an equilateral triangle cross section. Each side of the equilateral triangle is 40 centimeters long. Each rail has 100 percent excess buoyancy. This means that when the device is at rest, one half the volume of each rail will be submerged. In an upright equilateral triangle, this occurs when one third of the height of the triangle is submerged. The triangle is approximately 36 centimeters high, which means the draft of this recreational cabin cruiser is about 12 centimeters. A 12-centimeter draft is more common among canoes than seaworthy devices. The device can be docked and navigated in the shallowest of waters and beached directly on the shore. The device can be docked by beaching one rail; the passengers can simply climb down and walk to shore from the shore side rail of the boat. In addition to its extremely shallow draft, the very long, thin rail configuration of the present invention substantially frees the device from the effects of pitch and roll. FIGS. 5A and 5B show an example rail 34 floating in an idealized water surface wave 36. The wave has two crests 38 and 40 and two troughs 42 and 44. At the crests 38 and 40, the buoyancy of the rail pushes the rail up. Each rail is preferably at least 1-1/2 times the wavelength for the highest sea for which the device is rated. This minimum is the length illustrated in FIGS. 5A and 5B.
At the leading edge of each wave 36 before each crest 38, water moves upward. This pushes the rail surface upward. In a conventional short hull, the buoyancy of the bow causes the boat to move upward. Typically, oceangoing devices have reserve buoyancy of seven times the operating buoyancy, making them very reactive to the influence of wave forces. In the present invention, a leading edge of an incoming wave also pushes the bow of the rail upward, however, the buoyancy of the rail is small in its bow as compared to the rest of its length. The upward push of the leading edge of the oncoming wave is counterbalanced by the downward push of the falling water in the passing wave in other points along the length of the rail. Each wave creates equal amounts of heave and fall, or upward and downward force. By making the rail at least 1-1/2 times the length of the longest expected wave, the heave and fall balance each other out.across the length of the rail. The longer the rail, the less it is affected by heave and fall. As a result, the rail naturally travels flat through surface waves rather than over them as conventional hulls do. If the rail were maintained at the same length, but its diameter, and therefore its buoyant volume, were substantially increased, the rail would still be able to balance the effects of waves across its length. However, the leading edge of each wave would have a much greater effect on the pitch of the rail because the rail's buoyant bow would create more lift.
In the present invention, the rails are able to pierce through waves little affected by the waves' leading and trailing edges. It is not necessary to provide auxiliary pontoons to add buoyancy when a rail becomes significantly submerged. Because the aft ends of the rail hold the rail level, it is not necessary for the bow of the rail to have a downward pointing tip because the rail does not have to overcome its own inherent buoyancy, the buoyancy of the rail being spread out along its entire length. The rail simply rests on the water largely unaffected by weather conditions. The stability is enhanced by the speed at which the rail travels through the water. Accordingly, unlike a conventional ship, when rough seas are encountered, a device according to the present invention is not required to slow down.
The remarkable stability of the device makes it ideally suited for temporarily docking"smaller devices as shown in FIG. 1 or as a free floating platform without an independent source of propulsion. The stability In high seas together with the shallow draft and sleek hydrodynamic shape makes the present invention also very well suited for high speed travel. FIG. 6 shows a cross-sectional view of a single rail in an embodiment preferred for speeds over 50 knots and where a shallow draft is not the overriding concern.
The cross section in FIG. 6 is rectangular, the height of the rectangle being approximately double it width. Because the rails have a 100 percent excess buoyancy, the cross section of the submerged portion of the rail is normally substantially square. It is preferred not only that the rail be kept small in diameter to distribute its buoyant effects over a very long length, but also that the rail be kept narrow. As the rail is pushed through the water, it must open the water to make space for the rail. This normally causes a large amount of drag. The rectangular cross section for the rail, shown in FIG. 6, reduces, compared to conventional devices, the distance the water must travel to pass by the rail and thereby the amount of power expended to open water for the rail.
As shown in FIG. 7, a broken side elevational view of the rail of FIG. 6, the rail includes a pointed bow tip 50. This tip opens the water more gradually, reducing water acceleration rates and therefore the volume of disturbed water through hull speed limiting bow pressure wave build up. Power consumption and drag are reduced commensurately. Preferably, the bow tip is ten times longer than the diameter of the rail. This ensures a gradual transition to ease the opening of the water. The bow tip in FIG. 7 is shown shorter than the preferred length. The rail also includes a stern tip 52. The stern tip reduces the drag of water closing around the rear of the rail as the rail leaves the water. The precise proportions of the bow and stern tips can be adjusted to accommodate the anticipated cruising speeds of the device. At higher speeds, a longer bow tip would be desired more than at lower speeds.
FIGS. 6 and 7 also show a tunnel 54 in the bottom surface of the rail 48. The tunnel is entirely submerged beneath the water. The water's entry into the tunnel is controlled by a set of flaps 56. As shown in FIG. 7, there is a pair of flaps 56A and 56B at the bow of the rail and a pair of flaps 56C and 56D at the stern of the rail. The flaps can be arranged so that they pivot from the upper surface of the groove, allowing or preventing water from flowing into the tunnel, as shown in FIG. 7. Air nozzles 58 are also supplied to the tunnel for pumping air into the tunnel. The position of the flaps controls the level of water within the tunnel. The air nozzles fill the part of the tunnel between the flaps with air, increasing the buoyancy of the rail.
The flaps, together with the air nozzles, allow the attitude of the device to be controlled. Moving all four flaps downward increases the volume of the tunnel filled with air. This makes the rail more buoyant raising it along its entire length. Moving the rear flaps up while maintaining the front flaps down causes the more buoyant front of the rail to move up relative to the rear of the rail. The flaps allow the device to be trimmed without using protruding rudders. The ride height of the device can also be adjusted.
It is preferred that the buoyancy of the rails be kept to a minimum. In the preferred embodiment, the rails have no more than a 100 percent excess buoyancy. This is thought necessary to prevent the device from capsizing if subjected to extreme side loading. However, as mentioned above, too much excess buoyancy increases the effect of surface waves on the attitude of the rails. Using the flaps 56A, B, C and D together with the air nozzles 58, the buoyancy of the rails can be adjusted to match its load. When the ship is lightly loaded, the flaps can be moved upwards, eliminating air from the tunnel 54. This reduces the frontal area of the rail and amount of water disturbed per. meter, optimizing device fuel efficiency when less than fully loaded. When the craft is fully loaded the flaps can be moved downward and the tunnel filled with air to maintain the designed reserve buoyancy under the heavier load. With the appropriate electronic control mechanism, the flaps can also be adjusted to trim the device maintaining its attitude when entering seas with extended wave periods. An electronic device coupled to level sensors can be used to. control the position of the flaps and the air supply volume in order to minimize short term variations in device attitude.
The flaps may be attached to the top of the tunnel and hinged as shown in FIG. 7, or they may be placed on tracks so that they slide up and down with respect to the tunnel or they may be mounted in any other fashion which allows them to be adjustable. Adding more flaps and air nozzles between the flaps allows the buoyancy of the rail to be controlled locally. This may offset the propulsion centerline of thrust variations discussed below. Because the rails move quickly through the water, and because the nozzle 58 supplies a steady stream of air, it is not necessary that the flaps seal against the inside edge of the tunnel to complement the hydrodynamic seal. However, if this is desired, it can be done using inflatable seals. The seals deflate when the flap is moved and inflate when the flap is located in position to seal the flap against the side walls. If a sliding flap is used, sealing might be easier. The front flaps may be integrated into the front surface of the bow point 50 to reduce drag or, as shown in FIG. 7, they may be located further back along the tunnel.
FIG. 8 shows a side elevational view of a rail 56 suitable for compensating for the pivoting effect of the engines 16 of the embodiment of FIGS. 1-3. The bow tip 58 of the rail of FIG. 8 is configured in a conventional vee shape well known in recreational boats for developing lift to bring boats up on a plane. The vee shaped bow tip generates enough lift at the device's cruising speed to maintain the proper trim on the device. As shown, a vee shaped rail can also be built with a tunnel 60 and flaps 62 as described with respect to FIG. 7.
As shown in FIG. 7, the rail preferably has a bow and stern point which are tapered. The surfaces of the points are flat and move straight from the centerline of the rail to the edges of the rail. This provides a neutral attitude for piercing surface waves. In some instances, however, it may be desirable to alter the dynamics of the rail to compensate for other effects. If, for example, as in the embodiment shown in FIGS. 1 and 3, the main engines were located high upon the superstructure, there would be a tendency for the device to pivot downward. This can be compensated for either by providing additional thrust at the rails to balance the thrust provided up high upon the superstructure or by building a lifting force into the front of the rails by moving the center upward.
FIG. 9A shows the front portion of a rail adapted for high speed operation with reduced drag and additional navigational features. It is generally preferred that between the bow and stern tips, each rail 64 have a constant uniform cross section. The uniform cross section reduces drag by eliminating the need to open the water past the bow tip 66 and by eliminating flow irregularities. It is also preferred that the rail be free of protruding rudders, fins and wings. At speeds above 50 knots, these items create much drag. The bow tip preferably has a length ten times that of the rail's diameter; however, it is shown in FIG. 9 here with a steeper rake. At the tip of the bow tip there is long thin extendable boom 68. The boom can be drawn into the bow tip 66 for slow speed cruising and docking and extended when the rail is moving at high speeds. The features of the rail shown in FIG. 9A are specifically adapted for a cruising speed of approximately 52 knots. Since the present invention uses a much longer hull than a conventional boat and is capable 'of travelling at much higher speeds, the drag on the wetted surface of the hull becomes a significant factor.
At the tip of the boom 8 there is an air nozzle 70. The air nozzle helps open the water as the extendable boom travels forward. The air is ejected from the nozzle and it flows in the directions shown by the arrows. The high pressure air emitted at the boom tip expands upon exiting the tip and, because its pressure is higher than the surrounding water, it accelerates the water at the tip a substantial distance ahead of the bow taper. This provides a more gradual taper angle as needed to reduce acceleration of the displaced water at elevated speeds. The high pressure air acts as a bow taper extension. As the water and boom move with a relative speed, the air between the water and the boom is sheared. Shearing the air rather than the water significantly reduces the drag on the rail. It also provides a cushioning effect when rough seas are encountered.
At the rear end of the bow tip which contacts the rail there is a second nozzle 72 which extends around the entire circumference or perimeter of the rail. This air nozzle ejects low pressure air which travels along the entire length of the rail with the water, reducing or eliminating the wetted surface drag along the entire length of the rail. If a simple round rail or the triangular rail shown in FIG. 4 is used, the nozzle surrounds the entire perimeter of the rail and ejects a substantially even stream of air around the entire rail. While the craft is in motion, portions of the rail can be entirely submerged under the water while other portions of the rail are substantially above the local water level. Therefore, it is important that the entire perimeter of the rail enjoy the benefits of the air nozzle. The air ejected from the nozzle, in addition to reducing wetted surface drag, extends the apparent length of the rail with respect to the water closing about the stern of the rail by back filling the low pressure area.
The wetted surface drag on the rail of FIG. 9A is further reduced with a corrugated surface. The corrugated surface presents a series of elongated ribs substantially parallel to the rails' axis of elongation which is also substantially parallel to the flow of water. The preferred shape of the corrugated surface is shown in detail in FIG. 9B and greatly enlarged in cross section in FIG. 10. The corrugated surface presents a uniform series of vee shaped ribs 74 and valleys 76. The distance between ribs is preferably approximately 3/16 of an inch. The purpose of the corrugated surface is to trap air and reduce the amount of surface over which water flows. The valley between each rib serves as an air reservoir. By locating the ribs 3/6 or less of an inch apart, the air is more likely to be held within the valleys 76 between the ribs. As the water travels along the rail, it contacts only the ridges of the rail, greatly reducing the amount of wetted surface drag.
Water moving horizontally along the rail has a slight vertical component. At 52 knots, the vertical and horizontal components together result in water travel at approximately 5° upward from the horizontal. To ensure that the ribs best retain the entrained air, the ribs are offset downward from the horizontal by the same 5°, creating an action pumping air downward to match the surrounding water pressure. This can be best seen in FIG. 9B. This optimizes the wetted surface drag reduction for the device's rated cruising speed. A greater or lesser angle is preferred for lower and higher speeds, respectively. A higher speed craft would have ribs even more parallel to the rails' elongation axis. A slowmoving craft would not significantly benefit by ribs at all.
The system of ribs and air nozzles can also be applied to the legs which support the superstructure above the rails. When the rails pierce through tall waves, the legs are also partially immersed in the water. When traveling through the highest rate sea for which the device is rated, waves should frequently cover up to 80 percent of the length of the legs. FIG. 9A shows a portion of a leg 73 fastened to the rail 64, the rail has nearly horizontal ridges along its length and a long vertical nozzle 76 at its leading edge. It is preferred that the legs be kept as narrow as possible. As with the bow point, it is preferred that the legs flare at a rate no greater than 10:1.
FIG. 9A also shows navigational features of a preferred embodiment of the present invention for maneuvering the craft both at low and high speeds. In the bow tip, there is a set of pressurized air nozzles 78 which blow air laterally. It is preferred that both sides of the bow tip 78 include a set of nozzles. As the device moves through the water at high speed, it can be turned by blowing a large amount of air or water under pressure out of the nozzles on the side of the bow point opposite to which the device is to turn. The air expelled from the nozzles causes disruptions in the oncoming water increasing its acceleration rate and changing the bow pressure wave forces acting on the rail. This is analogous to moving the rails' bow point off center. The device's propulsive force pushes the device through the effectively offset bow point generating a turning moment. Steering can be done without the use of rudders or fins, both of which create continued drag.
FIG. 9A also shows a side thruster 80 for use at slow speeds. In a preferred embodiment, the side thruster 80 is a pair of propellers 82 and a shaft 84 which extends through the entire width of the rail. Each rail would have a pair of propellers at both the bow and stern ends. To change the heading of the device at slow speeds, a propeller in the appropriate direction is simply engaged, drawing water through the shaft and expelling it out the other side. Using four such propellers, two on each rail, the device can easily be pivoted within its own length. In addition, by operating all the thrusters in the same direction, the device can be moved sideways. This can be an advantage for maneuvering in small ports or when it is desired to beach the device. The device can be beached by propelling it sideways until one rail rests on the shore. Passengers or cargo can be unloaded from the top surface of the beached rail, using an extendable ramp on the top of the rail. To move the device back to open sea, the beached rail is raised off the shore and the trusters 80 are driven to draw the device away from the beach. The rails of the device can easily be raised and lowered, using the tunnel 54, flaps 56 and nozzle 58 described with respect to FIGS. 6 and 7. The combination of side thrusters and an inflatable tunnel allows even very large devices to beach in undeveloped areas. Landing boats are unnecessary. This is impossible with a conventional hull.
FIG. 11 shows the rail of FIGS. 9 and 10 in an elevational view from above. The top surface of the rail is also textured with a series of nonintersecting ribs 74 between valleys 76. On the top surface, there is no vertical movement upward of water flowing by the rail but, instead, general outward movement from the center of the rail towards the sides. The ribs are, as in FIGS. 9 and 9A, substantially parallel to the rails' axis of elongation and the flow of water over the rail. In addition, the ribs are preferably angled three degrees from the direction of elongation, extending toward the stern of the rail as they extend outward in a vee fashion. This is shown in greater detail in FIG.
•12. The bow point 66 and the boom 68 are similarly textured. The angle of 5 degrees has been chosen to optimize the drag reducing effect of the ribbing at 52 knots. However, a different angle can be used for optimizing different speeds.
The bottom surface of the rail is generally not ribbed, and, in the rail shown in FIGS. 6, 7 and 8, only a small portion of the bottom surface of the rail contacts the water. Most of the wetted surface drag on the bottom surface of the rail is eliminated by the tunnel 54, which would typically be filled with air, at least in part, when the device is operating at speed. The tunnel may be ribbed.
It is preferred that the device be operated completely without the use of conventional fins, rudders and trim flaps. All of these devices increase surface drag on the rail. If they are built large enough to effectively control the boat at low speed, they become hypersensitive at high speed. Similarly, if they are built as small as possible to minimize drag at high speed, they are ineffective at low speed. For low speed maneuvering, it is preferred that a set of thrusters, as described with respect to FIG. 9, be used. For high speed steering and trim, the tunnel flaps 56, described with respect to FIG. 7, together with the nozzles 78 in the bow point can be used. Alternatively or in addition, the bow and stern points can be made available.
FIGS. 13 and 14 show a rail 64 with a cone-shaped bow tip 78 and a cone-shdped stern tip 86. Again, while it is preferred that the bow tips have a length 10 times the cross section of the rail in order to more gradually open the water for the rail, they are shown here shorter for convenience. FIG. 13 is a side elevational view which shows the bow and stern tips directed straight out in a conventional operating mode. However,, as shown in dotted lines, the bow tip as well as the stern tip can be pivoted up or down to trim the attitude of the device. If the bow appears to be submarining excessively, the bow tip can be turned upward to present the underside of the bow tip 88 as a lifting surface. If the bow tip is planing excessively, the bow tip can be pivoted downward as shown in dotted lines to present the upper surface of the bow tip as a downward-pushing surface. The stern tip can be similarly adjusted. In FIG. 13, the stern tip includes a propeller 92 for propelling the device. Accordingly, moving the stern point not only presents submarining or planing surfaces to the flow of water, it also redirects the thrust, enhancing the effect of pivoting the stern tip.
FIG. 14 shows the same rail 64 in an elevational top view. In addition to pivoting up and down as shown in FIG. 13, the bow tip 78 and stern tip 86 may be pivoted from side to side. This allows the device to be steered. To steer the device to the starboard side, the bow and stern tips are both moved towards the starboard side, or upwards as shown in FIG. 14. To steer the device to the port side, the bow and stern tips are moved to port. As in FIG. 13, the rail of FIG. 14 includes a propeller 92 which is connected to the end of the stern tip, moving the propeller, starboard or port, increases the steering effect. While pivoting the bow and stern tips provide adequate maneuverability at moderate speeds, it is preferred that the thrusters 80 be retained for slow maneuvers. In addition, it is not necessary that both the bow and stern tips pivot. At high speed, the device can be controlled merely by pivoting either the bow tip or the stern tip. Conventional mechanical and hydraulic drivers can be used for controlling the position of the tips. The effect of each tip can be equalized by providing strain gauges in the legs. If the leg nearest a tip is, for example, experiencing more strain than other legs, then the amount of pivot on that tip can be altered. The device of the present invention can be propelled in a variety of ways. Turbojet or propeller aircraft type engines may be mounted to the rear of the superstructure, as shown in FIGS. 1 through 3. However, this high centerline of thrust will tend to rotate the device downward. This can be overcome using any of the trimming techniques discussed above. That is either by adjusting the flaps 56 in the tunnel 54 or by biasing the bow and stern points in the appropriate directions. The device may also be propelled by propellers at the ends of the rails as shown in FIGS. 13 and 14. However, at high speeds, the aerodynamic drag on the superstructure will tend to rotate the bow of the device out of the water. Again, this can be countered using the trimming techniques discussed above. Ideally, the thrust centerline should be somewhere between the superstructure and the rail. However, the exact location of this optimum centerline will vary depending on the speed of the craft and the water conditions. The hydrodynamic drag on the rails will increase faster than the aerodynamic drag on the superstructure. This effect can be compensated for by providing thrust both at the superstructure and on the rails and adjusting the relative contributions of the engines to control the trim of the device. The device can also be propelled by some type of propeller located at the front or bow end of the tunnel 54 and the rail. This propeller draws water into the rail and thrusts it towards the stern of the rail through the tunnel. Drawing water into the rail reduces the amount of water which must be opened to accommodate the rail as it moves through the water, further reducing bow pressure wave drag. In addition, the influence of the flaps 56 within the groove 54 would be greatly increased. Additionally, the device
•can be propelled by a ducted propeller located in the stern of the rail supplied with water drawn in through NACA ducts leading to a pressure bell before the propeller.
The device of the present invention is well suited for virtually any application served by a conventional type hull device. FIGS. 1 to 3 show the device adapted for use as a fish freighter. The device is equally well suited for hauling other kinds of freight. It is especially valuable for freight which is sensitive to large pitching and rolling motions and which must be transported quickly. FIG. 4 shows the device adapted for use as a recreational cabin cruiser. As a cabin cruiser it offers greater speed, a shallower draft, and lower fuel consumption than a conventional boat.
Any of the devices described above may be fitted with anchors attached to the superstructure. Preferably, there is one anchor at each end of the superstructure to reduce the anchor line swing experienced by traditional devices. Because of the freedom of the present invention from heave and fall, the excess anchor line weight of traditional devices may be eliminated. If the invention is to be used as an anchored platform only, then a similar anchoring system may be used.
The invention may be utilized in both powered and nonpowered forms. In a nonpowered form, the invention provides a rough water stable platform that shares the low load sensitivity and other beneficial features of the invention in powered form. Examples of nonpowered forms are floating airplane runways, piers, and open ocean platforms. These may be constructed in modular units for on-site assembly.
The present description is limited to only a few embodiments of the invention and variations thereon. For example, any of the nozzles described as air nozzles could provide some other fluid, whether in liquid or gas form, to achieve the same beneficial wetted surface drag reduction effects. The inventor intends in no way to limit the scope of the invention to the illustrated embodiments. The invention should be limited only by the following claims.

Claims

1. WHAT IS CLAIMED IS:
1. A displacement hull device comprising: at least two elongated, substantially
5 parallel displacement rails for supporting the device in the water, the rails having a length greater than fifty times greater than their average width taken across a plane perpendicular to their axis of elongation; and
10 a superstructure above the rails and connecting the rails, the superstructure being connected so that it is above the water when the device is in use.
15 2. The device of claim 1 comprising a propulsion system which propels the device in a direction parallel to the rails' axis of elongation.
3. The device of claim 2 wherein the rails 20 collectively have a buoyancy approximately equal to 5% to 200% greater than that required to support the entire device.
4. The device of claim 1 wherein the device is 25 adapted for use in water having waves and the lowest position of the main body is raised over the rails to a height greater than the height of a typical wave in the environment.
30 5. The device of claim 1 wherein the superstructure has a central main body supported above the rails by legs and wherein the length of the main body is approximately one third the length of the rails.
35 -27- 6. The device of claim . wherein the rails have a triangular cross section wit! a bottom side parallel to the water surface.
7. The device of claim 1 wherein at least one of the rails has a pointed tip at one end, the tip having a length aproximately ten times the average width of the rail.
8. The device of claim 1 wherein at least one of the rails has a pointed tip at one end and wherein the tip is capable of articulation with respect to the rails' axis of elongation for steering the device.
9. The device of claim l further comprising an extension boom extendable forwards from a rail's forward end to reduce drag at high speeds.
10. The device of claim 9 wherein the extension boom has an air nozzle at its forward end for ejecting fluid.
11. The device of claim 1 wherein at least one rail has one or more nozzles near an end of the rail for ejecting fluid at pressure substantially perpendicular to the rails' axis of elongation and parallel to the water surface, thereby generating a steering moment.
12. The device of claim 1 wherein the bottom surface of at least one rail has at least one elongated open tunnel surface running substantially from one end of the rail bottom surface to the other.
13. The device of claim 12 wherein the tunnel has a depth approximately one third the height of the rail and a width greater than one fourth the width of the rail.
14. The device of claim 13 wherein the tunnel has a horizontal opening at one end of the rail and the rail has a trim panel for adjusting the size of the horizontal opening.
15. The device of claim 1 wherein at least one rail has a fluid ejection nozzle near the rail's bow, the nozzle ejecting fluid around substantially the entire periphery of the rail for reducing wetted surface drag on all elongated surfaces of the rail.
16. The device of claim 15 wherein the at least one rail has a series of grooves extending out from the rails' exterior surface.
PCT/US1991/000485 1990-01-23 1991-01-23 High stability displacement hull device WO1991011359A1 (en)

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US46856590A 1990-01-23 1990-01-23
US468,565 1990-01-23

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1994025334A1 (en) * 1993-04-28 1994-11-10 Helmut Borcherdt Watercraft
US7047896B2 (en) 2001-11-30 2006-05-23 Van Dijk Jac W Multi-hulled vessel
WO2010020026A2 (en) * 2008-08-22 2010-02-25 Goes Batalha Alexandre Support vessel for offshore activities
US8555734B2 (en) 2005-08-22 2013-10-15 Technology Investment Company Pty Ltd Stabilising means

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Publication number Priority date Publication date Assignee Title
US3075489A (en) * 1960-10-28 1963-01-29 Thompson Ramo Wooldridge Inc Method and apparatus for reducing drag on submerged vehicles
US3430595A (en) * 1967-02-20 1969-03-04 Harry Werner Tulleners Watercraft
US3447502A (en) * 1967-07-14 1969-06-03 Litton Systems Inc Marine vessel
US3595191A (en) * 1968-10-11 1971-07-27 John Wakelam Grundy Ships and boats
US4227475A (en) * 1977-04-15 1980-10-14 Mattox Darryl F Waterborne sidewall air cushion vehicle

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3075489A (en) * 1960-10-28 1963-01-29 Thompson Ramo Wooldridge Inc Method and apparatus for reducing drag on submerged vehicles
US3430595A (en) * 1967-02-20 1969-03-04 Harry Werner Tulleners Watercraft
US3447502A (en) * 1967-07-14 1969-06-03 Litton Systems Inc Marine vessel
US3595191A (en) * 1968-10-11 1971-07-27 John Wakelam Grundy Ships and boats
US4227475A (en) * 1977-04-15 1980-10-14 Mattox Darryl F Waterborne sidewall air cushion vehicle

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1994025334A1 (en) * 1993-04-28 1994-11-10 Helmut Borcherdt Watercraft
US7047896B2 (en) 2001-11-30 2006-05-23 Van Dijk Jac W Multi-hulled vessel
US8555734B2 (en) 2005-08-22 2013-10-15 Technology Investment Company Pty Ltd Stabilising means
WO2010020026A2 (en) * 2008-08-22 2010-02-25 Goes Batalha Alexandre Support vessel for offshore activities
WO2010020026A3 (en) * 2008-08-22 2010-10-28 Goes Batalha Alexandre Support vessel for offshore activities

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