Not Applicable
Not Applicable
1. Field of Invention
This invention pertains to boat hull structures. More particularly, this invention pertains to a hybrid hull structure which combines handling characteristics of a V-hull design with the speed and acceleration characteristics of a tunnel-hull design.
2. Description of the Related Art
Power boats display different operating characteristics depending on the shape of their hulls. Many hulls have been previously designed in an attempt to decrease the resistance of the hull moving across the water surface and to increase the directional stability of the hull while moving through or over the water. Attempts to achieve both of these objectives have often involved a compromise between decreased hull resistance and increased directional stability, due to the problems involved in achieving both of these advantages.
To decrease the hull resistance of a boat, one common hull design is a flat bottom, since it draws a low amount of water for its weight. The flat bottom hull is a classic example of a planing hull which tends to climb above the water to a full planing position from its at-rest displacement position. However, the flat bottom hull lacks directional stability, and the hull bottom is often subjected to impact from passing waves.
On the other hand, a more stable and softer riding hull in rough or choppy water is the V hull. The V hull typically has a V-shaped (or cathedral-shaped) cross-section with a low keel running from the bow to the transom. The V-shaped cross-section of the V hull is capable of cutting through waves and transitioning smoothly between an at-rest displacement position to a full planing position. Therefore, V hulls are capable of providing a smooth ride, seaworthiness and good handling and steering characteristics. However, because the V hull often has a wetted area (portion of hull contacting the water surface) larger than flat bottom hulls, the V hull provides considerably more resistance when moving, thus resulting in considerable loss of planing performance. The V hull typically displays lateral instability, slide slipping or tipping during turns as water pushes against the keel of the V hull. Also, the V hull is susceptible to capsizing in waves or choppy water when the hull direction is at an angle, that is, not perpendicular to the waves. Moreover, the increased resistance of the V hull often causes the bow of a V hull boat to rise considerably during acceleration, resulting in a temporary decrease in forward visibility during acceleration from the at-rest displacement position to the full planing position.
Attempts to decrease bow rise during acceleration while alleviating the problem of the V hull's tendency to tip over in turning situations have resulted in utilization of tunnel hulls. Tunnel hull boats utilize a large channel running along the middle of the hull with multiple sponsons that extend the entire length of the hull. Tunnel hull boats are designed to trap air underneath the boat hull as the boat moves through water, thereby compressing the air and lifting the boat above the water line defined by the boat's natural buoyancy. This lifting typically results in decreased bow rise during acceleration, and the effect of lifting the boat decreases the boat's resistance through the water, allowing for faster acceleration and greater boat speeds. Furthermore, the entrapment of air underneath the boat hull typically results in aeration of the water beneath the boat hull. This aerated water typically displays more desirable hydrodynamic characteristics than water that is unaerated, resulting in decreased boat hull resistance as the hull travels through the water and therefore increased hull speed.
Conventional tunnel hull designs have inherently sacrificed handling characteristics for higher speed performance. In particular, the performance of a conventional tunnel hull is load sensitive and sea state dependent. In other words, heavy loads detract from the air capturing and speed enhancing ability of tunnel hulls. Lighter loaded tunnel hull boats subjected to rapid acceleration are susceptible to poling, that is, capsizing end over end due to the lift provided by the tunnel hull entrapment. Also, as compared to the more traditional V hull, tunnel hulls are less stable in choppy water or in low-speed travel such as during acceleration from the at-rest displacement position.
Several devices have been developed in an attempt to combine the characteristics of multiple traditional hull designs to decrease hull resistance while increasing hull stability. Typical of the art are those devices disclosed in the following U.S. patents:
Of these patents, U.S. Pat. No. 3,996,869 (the '869 patent), U.S. Pat. No. 5,231,949 (the '949 patent), U.S. Pat. No. 5,265,554 (the '554 patent), and U.S. Pat. No. 6,216,622 B1 (the '622 patent) each disclose a substantially V-shaped central hull portion and a pair of adjacent sponsons. In each invention, the central hull portion and the sponsons begin proximate the bow of the hull and extend towards the stern. In both the '869 patent and the '949 patent, the inner walls of the sponsons are substantially vertical, and the sponsons are stepped upwardly at approximately midships, such that the rear portions of the sponsons are substantially horizontal, or parallel to the plane of the water surface. In the '622 patent, the hull includes mid hull sponsons and outer sponsons. The mid hull sponsons form longitudinal tunnels with adjacent central hull portions and outer sponsons. The outer sponsons engage and deflect side directed spray and wake downwardly, providing additional lift and decreasing or eliminating spray and signature wake. In each of these patents, the central hull and the sponsons form air tunnels which induce air beneath the hull and decrease frictional engagement of the hull with water, thereby improving the efficiency of the hull.
In U.S. Pat. No. 4,165,703 (the '703 patent), issued to Donald E. Burg, a V hull having an air chamber substantially aft of midships and entirely beneath the waterline is disclosed. The '703 patent includes an air supply duct with a pressure control valve, providing injected air to the air chamber, thereby reducing the pad (wetted area of the hull during planing) and improving hull efficiency without substantially altering the V hull handling characteristics.
U.S. Pat. No. 4,587,918 (the '918 patent), also issued to Donald E. Burg, discloses a hull with one or more recesses that intersect the hull substantially beneath the waterline. In the '918 patent, each recess is bounded by catamaran-like sidehulls with bow shaped members located at the forward and aft portions of the recess. The fore and aft bow shaped members contact the water like small bow sections, thereby improving hull ride and handling characteristics. The keels of the sidehulls diverge to allow narrow or fine entry forward. Like the '703 patent, the recess of the '918 patent is supplied with pressurized gas to maintain a lift-augmenting, restrained pressurized gas layer under the hull.
Carl J. Anderson in U.S. Pat. No. 5,833,502 (the '502 patent) discloses a deep V-shaped forward section and a rear tunnel section extending longitudinally aft from midships. In the '502 patent, a vertically adjustable outboard motor is positioned at the forward end of the rear tunnel section. The center mounting of the engine in conjunction with the tunnel section of the hull reduces planing upon acceleration, improves center of gravity and reduces the risk to swimmers and water skiers from a rear mounted propeller.
U.S. Pat. No. 6,406,341 (the '341 patent), issued to Christopher S. Morejohn, discloses a shallow draft sports boat having a water tunnel in its bottom allowing one to place an outboard motor higher with respect to the hull of the boat than is conventional. In the '341 patent, the water tunnel is relatively short with respect to the overall length of the boat, has a small volume and is provided with a recess at its leading end. A vent communicates between the recess and a port in the transom above the water line to remove air entrainment from water that passes through the tunnel.
Finally, Ian A. Taylor, in U.S. Pat. No. 6,708,642 B1 (the '642 patent), discloses a hull having an upper flat bottom section and a pair of outer sponsons extending from a forward portion to a stern portion of the bottom of the flat bottom section. The pair of outer sponsons cooperate with the upper flat bottom section to define a tunnel, and an elongated center sponson extends along the bottom of the flat bottom section substantially parallel to the pair of outer sponsons. The center sponson has a forward section with an upwardly extending trailing step wall defining an upward step in the center sponson. An aft section of the center sponson has an upwardly curved leading edge intersecting the step wall of the forward section.
According to one embodiment of the present invention, is provided.
Another embodiment provides
The above-mentioned features of the invention will become more clearly understood from the following detailed description of the invention read together with the drawings in which:
A hybrid hull for increasing the directional stability of a boat hull while decreasing water resistance during planar movement is disclosed. The hybrid hull of the present invention, illustrated at 10 in the figures, combines the handling characteristics of a V hull design with the speed and stability of a tunnel hull design. Furthermore, the hybrid hull limits the possibility of poling by limiting excess air entrapment beneath the hull during high speed motion.
The stem 16 of the hybrid hull includes a transom 26 defining a rear surface of the hull 10. The transom connects rear edges of the port and starboard walls 21, 23 to the port side 22 and the starboard side 20. A lower portion 28 of the transom 26 is offset forward from a transom upper portion 30 by a transom recess 32. The transom recess 32 of the hybrid hull 10 decreases water resistance, thereby improving the efficiency of the hull 10. The transom recess 32 also increases the speed at which the hybrid hull 10 achieves its planing position during acceleration. As discussed in greater detail below, the configuration of the transom recess 32 offsetting the transom lower portion 28 forward from the transom upper portion 30 allows the bow 12 to rise as the hybrid hull 10 is propelled forward to achieve water-surface planing. In the illustrated embodiment, the transom upper portion 30 further includes a motor well 19 defined by a recessed portion of the transom upper portion 30. The motor well 19 is adapted to receive a conventional propulsive device, such as an outboard motor (not shown). Of course, those skilled in the art will recognize that the inclusion of the motor well 19 is not necessary to achieve the present invention.
The top edge 29 of the transom lower portion 28 is connected to the lower edge 31 of the transom upper portion 30 by a spray deflector 18 defining a surface configured substantially parallel to the plane defined by an at-rest displacement waterline 38. The spray deflector 18 serves to limit the upward spray of the wake resulting from the forward propulsion of the hybrid hull 10 through water. In the illustrated embodiment, a plurality of additional spray deflectors 25, 27 extend aft from the transom lower portion 28. As illustrated, these deflectors 25, 27 define a series of step-shaped protrusions extending aft from the transom lower portion 28. It is appreciated that other shapes can be used in various configurations to accomplish the present invention. To this extent, it is understood that inclusion of the additional spray deflectors 25, 27 is not necessary to achieve the present invention.
The keel 14 is interrupted by a tunnel recess 34 at a point 36 located between the at-rest displacement waterline 38 and a full planing waterline 40. The tunnel recess 34 defines a longitudinal passageway running from the keel point 36 and extending aft toward the stem 16. The tunnel recess 34 is provided with a vertically tapered forward end such that the tunnel recess 34 opens substantially upward into the hybrid hull 10. This configuration is designed to limit the entrapment of frontal air into the tunnel recess 34 while the hybrid hull 10 is in a full planing position. The tunnel recess 34 intersects at 42 with the transom lower portion 28, such that the aft portion of the tunnel recess 34 adjacent said transom lower portion 28 is open. In the illustrated embodiment, the configuration of the tunnel recess 34 relative to the at-rest displacement waterline 38 and the full planing waterline 40 is such that the tunnel recess 34 is completely submerged when the hybrid hull 10 is in an at-rest displacement position and partially submerged when the hybrid hull 10 is in a full planing position. However, those skilled in the art will recognize other possible configurations between the tunnel recess 34 and the at-rest displacement and full planing waterhnes 38, 40 which can be used without departing from the spirit and scope of the present invention.
In
Referring to
The tunnel recess 34 further serves to reduce the frictional wetted area of the hybrid hull 10, as compared to a typical V-hull design. The pad 56′ of a typical prior-art V-hull is illustrated in
A further embodiment of the hybrid hull is illustrated at 10″ in
A damper 68 is movably positioned proximate the interface between the tunnel recess 34″ and the ballast cavity 66. The damper 68 serves to regulate the flow of water out of the ballast cavity 66 and to limit debris from entering the ballast cavity 66. In the illustrated embodiment, the damper 68 comprises a screen hinged to the interface between the tunnel recess 34″ and the ballast cavity 66. Of course, those skilled in the art will recognize other devices suitable for use to accomplish the damper 68. In the illustrated embodiment, a piston 70 connects the damper 68 to the ballast cavity 66. The hybrid hull 10″ includes controls (not shown) for the piston 70 sufficient to allow a user to selectively position the damper 68 between an open and a closed position. Those skilled in the art will recognize other devices and configurations suitable for use in limiting the inward flow of debris to the ballast cavity while regulating the outward flow of water. To this extent, it is appreciated that the damper 68 may be fixed to substantially cover the interface between the tunnel recess 34″ and the ballast cavity 66 without departing from the spirit and scope of the present invention.
Another embodiment of the hybrid hull is illustrated at 10′″ in
In this embodiment, the air duct 62 partially fills with water when the hybrid hull 10′″ is in an at-rest position. As the hybrid hull 10′″ is propelled forward, the damper 68 restricts the flow of water from the air duct 62, and the partially water-filled air duct 62 acts as a forward counterbalance to limit bow rise during acceleration. As the hybrid hull 10′″ achieves a full planing position, the air duct 62 empties, thereby decreasing the hull weight proximate the bow 12′″ and increasing the speed capabilities of the hybrid hull 10′″. With the air duct 62 empty, the user is able to selectively position the damper 68 to an open position, thereby allowing air to fill the tunnel recess 34 and dissipating any hydraulic suction which may result from water within the tunnel recess 34. Once the hybrid hull 10′″ achieves planing position, the air duct 62 allows air to flow into the tunnel recess 34 and beneath the stem 14, where the additional air provides additional aeration to the water beneath the hybrid hull 10′″.
From the foregoing description, it will be recognized by those skilled in the art that several embodiments of a hybrid hull have been provided. The hybrid hull of the present invention combines the handling characteristics of a V hull design with the speed and acceleration characteristics of a tunnel hull design. The transom recess feature of the hybrid hull decreases water resistance while increasing the speed at which the hybrid hull achieves its planing position during acceleration by encouraging rapid bow rise and allowing more immediate lift to planing position than the traditional V hull design.
While the present invention has been illustrated by description of several embodiments and while the illustrative embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicant's general inventive concept.