BACKGROUND OF INVENTION: Boat manufacturers provide numerous systems for marine propulsion. One of the most recently developed and increasingly popular forms of propulsion, and one for which the present inventor was awarded U. S. Patent No.

4, 689, 026 (the contents of which are herein incorporated by reference), involves a marine surface drive system which incorporates surface piercing propeller technology beneath the hulls of high performance vessels of varying size. As with any fixed propeller system, such propulsion systems lack adequate directional control when reverse thrust is employed. Vessel propulsion systems are highly maneuverable when moving forward by placement of a steering rudder behind the propeller, the rudder placement is ineffective when the vessel is going backward because the rudder is no longer in the prop wash stream. To maintain control of a vessel while going backward, the vessel must move fast enough toforce water past the rudder in a reverse direction. However, this maneuver is not practical in all situations such as in close quarter maneuvering.

Solutions to this problem currently include the use

of different types of propulsion systems such as an outboard engine, stern drive system, steerable surface drive, thrusters or multiple inboard engines. The problem with these approaches is that the mechanical solution is complex and expensive. If a system could be devised to provide adequate steerage of a surface piercing propeller, fixed shaft drive system in both forward and reverse without adding an undue amount of complexity or cost and without a loss in forward speed, a longfelt need would be satisfied.

PRIOR ART : U. S. Patent #3, 407,774 addresses the issue of reverse maneuverability in a conventional straight inboard propulsion system by putting a rudder in front of the propeller which is connected to the rudder in the rear of the propeller. In the 774 patent the front rudder is always in the water and while the patentee stipulates that the drag is minimal, it is apparent there is some drag from this source, thus reducing forward speed. Furthermore, the approach of the 774 patent does not divert reverse flow into channels in the hull but rather diverts reverse flow off to the sides of the hull below the running surfaces. Finally, patentee does not contemplate raising the reverse flow rudder above the water, e. g. into a tunnel, for use in connection with a surfacing propeller. The steering system proposed by the 774 patent would be inappropriate for high performance vessels since the forces induced by the disclosed rudder construction would hinder vessel control at high forward speeds.

U. S. Patent #5, 359, 956 proposes a forward rudder which is connected to the rear rudder but in the case of the 956 patent reverse maneuverability is not enhanced

nor are there any references to channels in the hull which carry reverse flow. The 956 patent focuses on improved forward maneuverability and stability for skiers.

These patents fail to address the problem of reverse maneuverability in a single surfacing drive installation which uses a shaft driven system or a gearcase, positioned in a tunnel or behind a step created in the underside of the hull, and which does not rotate to create reverse steerage.

SUMMARY OF THE INVENTION The present invention is directed toward a marine propulsion system including an inboard engine coupled to a single shaft surface piercing propeller. The propulsion system may be disposed in a tunnel that runs longitudinally in the bottom of a marine watercraft. The propeller may be located within the tunnel or within a semi-enclosed area, is of the surfacing type and does not pivot for the purpose of steering the vessel. In one embodiment, a flat rudder is positioned behind the propeller, alternatively, a semicircular rudder is positioned above the propeller, as is commonly found in conventional inboards, jet drives or some fixed shaft surface drives. In addition there is a rudder in front of the propeller which is connected thru linkages to the rudder behind the propeller. The propulsion system of the instant invention further includes passages to either side of the front rudder which channel water flow to the sides of the hull for the purpose of steering the boat when backing down. The front rudder can be so positioned as to be parallel to the rear rudder or at 90 degrees to the rear rudder since either position will provide the required steerage characteristics, the controlling

parameter being the diversion of water to the side channels.

When operated in reverse mode, thrust generated by the propeller flows forward towards the bow of the boat.

The diverter directs a portion of this flow through channels in the hull. The diverter is mechanically coupled to the steering mechanism and is designed to turn in unison with the steering wheel. Because of the surfacing nature of the propeller, the diverter is not a source of drag when the vessel is on plane in the forward direction because it is above the propeller shaft and thus out of the flow of water to the propeller.

The features of the instant invention therefore define a marine propulsion system for use in combination with a vessel, for example one having a planing hull, or a semi-displacement hull; in which a prime mover, such as an inboard engine or equivalent, is mechanically interfaced, for example via a shaft and strut system or a gearcase, with at least one non-pivoting/non-steering surfacing type propeller, a rear rudder and a forward rudder which are constructed and arranged to cooperatively provide steerage of the vessel. The forward rudder is positioned ahead of the non-steering surfacing propeller and is effective to divert water flow from the propeller when it is operating in the reverse direction. The forward rudder is further characterized as being positioned beneath the vessel so as to have the majority of its area above the surface of the water when the vessel is being propelled in the forward direction.

This is accomplished by positioning the forward rudder within a tunnel formed beneath the vessel or alternatively by placing the forward rudder aft of a step formed beneath the vessel. The hull may be particularly designed to incorporate water flow channels, termed

flutes, which are effective to direct a flow of water received from the forward rudder to one or more sides of the hull to provide controlled steerage when backing.

The flutes may be symmetrically or asymmetrically dimensioned, in accordance with the particular direction of propeller rotation, in order to effect straight backing. In an alternative embodiment, the forward rudder may be protected from incoming water flow from a forward direction by a shield positioned beneath it. In order to maintain directional control, the rear rudder and forward rudder are specifically constructed and arranged to cooperatively provide steerage by a system which provides coordinated movement thereof. In alternatively disclosed embodiments, the neutral position of the forward rudder is either parallel or perpendicular to the vessel's centerline. Lastly, the rear rudder may alternatively be characterized as having a single or dual blade configuration.

Accordingly, it is an object of the present invention to provide an effective yet uncomplicated means for steering the vessel in reverse without making the propeller itself steerable.

It is a further objective of the present invention to incur no appreciable loss in the forward speed of the vessel as a result of the installation of the reverse control enabling components.

It is still another objective of the invention to coordinate the reverse steering mechanism so as to work in concert with a surfacing propeller which is within a tunnel at the rear portion of the hull.

Yet an additional objective of the invention is to furnish water flow channels within the hull effective to carry the reverse flow of water, during the hull manufacturing process.

Other objectives and advantages of this invention will become apparent from the following descriptions taken in conjunction with the accompanying drawings wherein set forth, by way of illustration and example, are certain embodiments of this invention. The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 is a side view of a hull incorporating the instantly disclosed propulsion system.

Figure 2 is a partial cross-sectional view along the centerline of the hull.

Figure 3 is an isometric view of the bottom of the hull, shroud and single blade rudder.

Figure 4 is a stern view with single blade rudder.

Figure 5 is a partial bottom view showing backing straight.

Figure 6 is a partial bottom view showing backing to starboard.

Figure 7 is a partial bottom view showing backing to port.

Figure 8 is a partial isometric view of the bottom of a hull showing two blade rear rudder.

Figure 9 is a stern view showing a two bladed rudder.

Figure 10 is a partial bottom view of a twin blade rudder system showing backing straight.

Figure 11 is a partial bottom view of a twin blade rudder system showing backing to starboard.

Figure 12 is a partial bottom view of a twin blade rudder system showing backing to port.

Figure 13 is a partial bottom view of a perpendicular blade rudder system showing backing straight.

Figure 14 is a partial bottom view of a perpendicular single blade rudder system showing backing to starboard.

Figure 15 is a partial bottom view a perpendicular single blade rudder system showing backing to port.

Figure 16 is a partial cross-sectional view along the centerline of a craft depicting a drive system that is mounted aft of transom incorporating a forward rudder with no enclosed channels.

Figure 17 is a stern view of the craft of Figure 16.

Figure 18 is a partial bottom view of the craft of Figure 16, backing to starboard.

Figure 19 is an alternative embodiment of the present invention which utilizes a gear-case instead of a shaft and strut arrangement.

DETAILED DESCRIPTION OF THE INVENTION It is to be understood that while we have illustrated and described certain forms of the invention, it is not to be limited to the specific forms or arrangement of parts herein described and shown. It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown in the drawings and described in the specification.

With reference to Figures 1 and 2, a watercraft 1 is shown having a bow 2 and a stern 3, the general shape of which are not critical to the present invention. The craft incorporates a tunnel 4 that runs longitudinally fore and aft in the running surface 5 of the hull. While the shape of the tunnel is shown as being approximately square, this is merely illustrative as the invention may relate to other shapes as well. Within the tunnel is positioned a propeller 6, which is of a surfacing or

supercavitating design and is secured with a strut 7 and shaft 8 arrangement or any other suitable arrangement such as a gear-case 15 (as best seen in Fig. 19) to secure the propeller within the desired position in the tunnel.

The tunnel 4 extends from the stern of the vessel 3 forward toward the bow 2 for a distance adequate in length to house the propeller and the front rudder 9.

The front rudder 9 is mechanically connected via linkages 10 to the rear rudder 11 and both rudders move in unison, although not necessarily in a one-to-one relationship.

Referring to Figures 3 and 4, an isometric view of the bottom of the hull 2 is shown. The lowermost section of the hull, adjacent the propeller, defines a shroud which enhances the channeling of water flow. In this embodiment the single blade rear rudder 11 is shown aft of the propeller and within the tunnel area.

Now referring primarily to Figures 5, 6 and 7 (only Figure 5 is annotated), the hull contains water flow channels, also termed passages or flutes 12 and 16 which provide a path for the water flow which is generated in the reverse direction from the propeller 6. These channels are incorporated within the hull during the manufacturing process and are effective to divert the reverse flow of water so as to provide controlled steerage during backing of the vessel.

These passages may be covered or uncovered without altering the basic operating concept. The dimension of the flutes are asymmetrical, according to the particular propeller rotation. Reverse maneuverability is achieved by first reversing the rotational direction of the propeller. This creates a back flow of water which moves forward toward the bow of the boat and pushes the boat in a sternwise direction. When backing straight back the flutes are designed so as to produce equal thrust to

either side of the hull. This is not to imply that the channels are equal in size nor that the reverse steerage rudder is straight and parallel with the keel. On the contrary, testing has shown that in order to propel the vessel straight backwards the channels must be of different sizes and the rudder may need to slightly favor one side. As the operator turns the wheel to steer the stern of the vessel to starboard, as in Figure 6, the forward rudder 9 reduces the amount of water flowing to the flute on the starboard side of the hull 16 thus increasing the amount of water flowing through the port side flute 12 and in so doing, propels the hull in the starboard direction. The reverse situation results in steerage to the port direction as shown in Figure 7.

Now referring to Figures 8 through 12, an embodiment is illustrated wherein a rear rudder 20 with two blades is incorporated. The two-bladed rear rudder is positioned on opposite sides of the propeller and thereby defines a narrowed area for more precisely directing the flow of water emanating from rotation of the propeller.

The operation of the vessel parallels that described above in relationship to Figures 5-7. The relationship of the two-bladed rudder to the propeller and hull can best be seen in Figures 8 and, 9.

With reference to Figures 13 through 15 an embodiment is illustrated which employs a forward rudder that is arranged perpendicular to the direction of travel resulting in the function intended. When straight backing is desired the flow is diverted in a manner effective to equalize port and starboard directed forces.

When it is desired to back to starboard or to port, the rudders are rotated as shown in Figures 14 and 15 respectively.

As further described in Figures 16 through 18, an

additional embodiment of the invention locates the reverse flow forward rudder 9 behind a step in the hull.

As best seen in Figure 17, the step creates a damming surface 21 forward of the rudders and propeller which serves to guide the reverse flow to the port or starboard side of the vessel as desired. The rudder is free to rotate in such a manner as to create a flow of water to one side or the other thereby providing controlled steerage when backing.

Figure 19 depicts an embodiment of the invention in which a gearcase 24 is used to transmit power in conjunction with a forward rudder 9 for reverse maneuvering. This embodiment may be incorporated in any of the above described configurations as an alternative to the propeller/strut/shaft combination.

It is to be understood that while a certain form of the invention is illustrated, it is not to be limited to the specific form or arrangement of parts herein described and shown. It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown in the drawings and described in the specification.