Marine propulsion – Screw propeller – Having means to control flow around propeller
Reexamination Certificate
2002-01-31
2004-08-10
Basinger, Sherman (Department: 3617)
Marine propulsion
Screw propeller
Having means to control flow around propeller
C114S151000, C440S038000
Reexamination Certificate
active
06773316
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to boat hull designs, and more particularly a modified boat hull, which provides non-ventilating, dual aft thruster tunnels, which are completely submerged within a body of water when the boat is either stationary or moving at slow speeds, below plane speed.
2. Description of Related Art
Marine vehicle designs have included hulls which incorporate both fore and aft thrusters mounted within specifically designed housings or water channels. However, the housing inlets which are immersed within and receive water when the thruster is activated in a forward direction, thereby providing thrust from the transom, experience problems with ventilation of the channel due to the presence or ingestion of atmospheric air within the housing. This is because the conventional designs place the channel inlet, or opening which provides water access, above the water line of the boat hull, for example on the chine. A chine orifice which is in such close proximity to the water line, and generally above same, allows a substantial and undesired volume of air to be present in the channel when the thrusters are activated. Ventilation is extremely undesirable, as it results in a substantial reduction in power produced by thrusters, vibration of the motors, mechanical assemblies, and support structures, as well as increased noise.
Although prior designs have sought to improve the handling and maneuverability of boats in general, existing designs have failed to adequately address the problems and phenomena of ventilation when the boat is operating at low speeds. This is particularly true with vessels having wide beams, concomitant enhanced flotation and less chine submergence. This increases ventilation with respect to openings above the chine, which thereby increases the undesirable effects described above.
The prior art reveals a number of attempts directed toward increasing the maneuverability of marine vessels, including certain designs incorporating two or more aft thrusters. For example, U.S. Pat. No. 5,090,929 issued to Rieben, discloses a PAIRED MOTOR SYSTEM FOR SMALL BOAT PROPULSION AND STEERAGE. Rieben discloses a boat hull defining paired cylindrical bodies which house motors and propellers, and provide water channels therein. Rieben teaches of forward orifices which are located on the sides of the boat, providing water access. However, Rieben fails to appreciate or address the problems associated with the instant invention, in that the orifices are located above the chine line, thereby creating the ventilation and undesirable phenomena sought to be avoided.
U.S. Pat. No. 5,679,037 issued to Rieben discloses a STATIONARY SCREW INDUCTION SYSTEM. Rieben '037 discloses a specific system for improving performance of a watercraft, such as a canoe, and incorporates a cylindrical housing, with a helical-shaped induction channel to provide a specific form of increased propulsion. Rieben '037, however, does not address, nor was concerned with, the problems eliminated by the instant invention.
U.S. Pat. No. 4,843,988 issued to Clement discloses a STEPPED BOTTOM FOR BOAT. Clement teaches of a boat hull design incorporating stepped regions, substantially reducing the wetted bottom area of the boat, to eliminate unwanted frictional drag. Clement also discloses vent pipes through the hull of the boat, intended to introduce air flow to hull regions, thereby teaching away from the instant invention.
As has been described, the prior art does not address, or overcome, the aforementioned problems with thruster tunnel ventilation. Thus, there still exists a need for a modified hull design which eliminates the introduction or presence of air within aft tunnels when the vessel is operating at below plane speeds. A hull design is desired which increases the efficiency of the thrusters, and associated power output, by completely submerging the tunnels below the water line, and at the same time allowing for operational efficiency and maximizing hydrodynamic forces when the boat is accelerating, attempting to reach plane or exceeding plane speeds while cruising.
Accordingly, what is needed in the art is an improved hull design, providing for superior vessel performance, which eliminates ventilation within aft thruster tunnels, yet does not impede general performance of the boat when operating at relatively high speeds, for example, cruising. It is, therefore, to the effective resolution of the aforementioned problems and shortcomings of the prior art that the present invention is directed. However, in view of the boat and watercraft designs in existence at the time the present invention was completed, it was not obvious to those persons of ordinary skill in the pertinent art and marine industry as to how the identified needs could be fulfilled.
BRIEF SUMMARY OF THE INVENTION
The present invention contemplates an improved and modified boat hull that appropriates a design providing non-ventilating aft thruster tunnels. The tunnels are generally located on angles, for example between 35-40 degrees from the vessel keel. The hull incorporates a pair of such thruster tunnels, each of which extends from a strake orifice or water inlet opening located on the side of the hull, to a transom orifice or water outlet located at the opposing end of the tunnel. The strake opening is of a unique design, and is located beneath the chine, such that it is below the surface of the water.
The modified hull includes a strake step, or offset, from the side of the hull inboard, toward the keel line. The vertical face of the strake is extended to provide an efficient water inlet orifice, as well as to be compatible with the chine interface.
The novel hull also includes a chine step, which is a vertical offset from the chine line. The chine step then tapers angularly, and rearwardly, and ultimately terminates in close proximity from the transom. The upper planar surface of the chine step extends inboard from the chine line, and intersects with the vertical strake surface.
The instant design can also include a chine wedge, which constitutes a hook surface on the side of the vessel. The chine wedge provides a gradually flared surface, just preceding the chine step, which eliminates unwanted water spray from entering the strake orifice while cruising.
The modified hull includes a pair of symmetrical, opposing tubular tunnels located in the aft section of the vessel. Each said tunnel includes a generally cylindrical or tubular section which terminates at one end at the transom orifice. Each tunnel also includes a converging transition segment which terminates at the vertical strake surface, as described above.
The above-described design and specifications provides aft thruster tunnels which are completely submerged within a body of water when the vessel is either stationary or, alternatively, moving at slow speeds, when the boat is not on plane. The tunnels are thus filled only with water, thereby avoiding the presence or introduction of atmospheric air. This provides the optimum environment and conditions for operating the aft motors supported within the tunnels, providing optimum power and propulsion for precision handling of the watercraft. This design greatly enhances operator control of the vessel, for example, when docking the boat in close quarters, maneuvering in strong currents or through other boats in congested waterways, maneuvering the craft in conditions requiring quick and accurate navigation, as well as fishing and scuba diving activities.
Additionally, the design, while optimal at below plane speeds, must also be compatible with the general operation and performance of the boat when accelerating or cruising. The design does not negatively affect, or detract from, the operation of the boat when either achieving plane or operating at relatively high speeds. Once the boat achieves plane, the extended vertical strake face, operating in conjunction with the chine step, operates in a reverse fashion, to actually facilitate the introduction of ai
Basinger Sherman
Brunswick Corporation
Malin Haley & DiMaggio, P.A.
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