Powerboat rooster tail depressor

Abstract

A powerboat with a rooster tail depressor (RTD) includes a hull, a propulsion subassembly on the hull, and a rooster-tail-suppressing subassembly on the hull. The propulsion subassembly propels the hull forwardly, producing a propulsion discharge that extends rearwardly of the stern. The rooster-tail-suppressing subassembly extends rearwardly of the stern over at least a portion of the propulsion discharge where it functions to suppress the formation of a powerboat rooster tail (e.g., for radar signature reduction and increased propulsion efficiency). Various embodiments include one or more of (i) a canopy having a downwardly facing surface that is arched (either curved or faceted), (ii) lift-to-drag ratio enhancing steps in the downwardly facing surface of the canopy, (iii) a rooster-tail-suppressing subassembly configured to enable articulation of the canopy in yaw and in trim, (iv) a skeg for enhancing maneuverability of the boat hull, and (v) a conveniently removable and/or retractable rooster-tail-suppressing subassembly.

Description

BACKGROUND OF THE INVENTION

1. Technical Field

This invention relates generally to the field of powered watercraft, and more particularly to powerboats, seagoing vessels, and the like that tend to produce a rooster tail when moving forwardly.

2. Description of Related Art

When the hull of a powerboat is driven forward, whether by propellers, water jets, or some other propulsion subassembly on the vessel, the propulsion subassembly often produces what can be called a propulsion discharge. As the hull is propelled forwardly, the propulsion discharge (i.e., water) is forced into the air rearward of the powerboat's stern. The resulting plume of water behind the powerboat is commonly referred to as a “rooster tail” because it reminds one of the tail of a rooster. Such a rooster tail increases in size with vessel speed and can become quite large.

One problem with powerboat rooster tails is that they can expose military vessels to the enemy. The rooster tail can create a serious radar signature that is useable by enemy fire control for acquiring, tracking, and attacking a vessel. Another problem relates to powerboat efficiency in that a large amount of energy is expended in creating the rooster tail. Thus, powerboat manufacturers and users need a way to alleviate the above drawbacks.

SUMMARY OF THE INVENTION

It is a primary object of the present invention to alleviate the foregoing concerns. The present invention does so by providing what may be called a “rooster tail depressor” (RTD). It is a rooster-tail-suppressing assembly on the hull that takes the form of a structure (e.g., a canopy) extending rearwardly of the stern and over the powerboat's rooster-tail-producing propulsion discharge. The RTD suppresses the propulsion discharge and thereby the rooster tail in a way that reduces the rooster tail radar signature while increasing powerboat efficiency.

To paraphrase some of the more precise language appearing in the claims and further introduce the nomenclature used, a powerboat constructed according to the invention includes a hull having a stern, a propulsion subassembly, and a rooster-tail-suppressing structure on the hull. The propulsion subassembly functions as means for propelling the hull forwardly, producing a propulsion discharge at the stern as it does so. The rooster-tail-suppressing subassembly (i.e., the RTD) includes a structure on the hull that extends rearwardly of the stern and over at least a portion of the propulsion discharge, where it functions as means for suppressing the formation by the propulsion discharge of the powerboat rooster tail.

The RTD recaptures a large amount of energy in the rooster tail that is otherwise lost. Recapturing this energy produces a significant gain in vessel lift, thereby reducing friction drag for a planing craft with an increase in propulsion efficiency. The RTD traps the vertical component of the propulsion discharge for vessel lift, while merely redirecting the horizontal component downward without braking the vessel and thereby reducing its forward velocity.

In one preferred embodiment of the invention, the rooster-tail-suppressing subassembly includes a canopy having a downwardly directed surface extending over at least a portion of the propulsion discharge. The downwardly facing surface is arched (laterally and/or longitudinally) and it may be faceted and/or curved. Another aspect of the invention concerns a means for enhancing lift-to-drag ratio, including steps in the downwardly facing surface of the canopy. Another aspect concerns articulation of the rooster-tail-suppressing subassembly in yaw and/or in trim. Still another aspect concerns a skeg connected to the rooster-tail-suppressing subassembly that functions as means for enhancing maneuverability of the boat hull. Yet another aspect concerns a rooster-tail-suppressing subassembly that can be removed from the transom or folded back into the hull to reduce overall length of the powerboat for storage or transport.

The invention, in all its forms, provides a powerboat with a rooster-tail-suppressing RTD that significantly reduces powerboat radar signature while improving powerboat efficiency. The following illustrative drawings and detailed description make the foregoing and other objects, features, and advantages of the invention more apparent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 of the drawings is a pictorial view of a powerboat constructed according to the prior art that is shown being propelled forwardly as it produces a rooster tail extending rearwardly, with an X-Y-Z Cartesian coordinate system included for spatial reference purposes;

FIG. 2 of the drawings is a diagrammatic plan view of a powerboat having a first embodiment of a rooster-tail-depressing RTD constructed according to the invention, as viewed from overhead looking downwardly along a line of sight perpendicular to the X-Z plane of the Cartesian coordinate system;

FIG. 3 of the drawings is a diagrammatic cross sectional view of the powerboat and the first RTD embodiment as viewed in a vertical plane containing a longitudinally extending line 3-3 in FIG. 2 that is perpendicular to the X-Y plane of the Cartesian coordinate system;

FIG. 4a of the drawings is a diagrammatic cross sectional view of a faceted second RTD embodiment as viewed in a vertical plane containing a transversely extending line 4-4 in FIG. 2 that is perpendicular to the Y-Z plane of the Cartesian coordinate system;

FIG. 4b of the drawings is a diagrammatic cross sectional view of a curved third RTD embodiment as viewed in a vertical plane containing the transversely extending line 4-4 in FIG. 2;

FIG. 5 is a diagrammatic elevation view (similar to FIG. 3) of a fourth RTD embodiment that includes lift-to-drag ratio enhancement steps;

FIG. 6 is a diagrammatic elevation view of a fifth RTD embodiment that includes a thrust deflector on the transom of the vessel (i.e., a transom thrust deflector or TTD);

FIG. 7 is a diagrammatic plan view of a sixth RTD embodiment that can be articulated in yaw, about a pivotal axis that is perpendicular to the X-Z plane;

FIG. 8 is a diagrammatic elevation view of a seventh RTD embodiment that can be articulated in trim, about a pivotal axis that is perpendicular to the Y-Z plane; and

FIG. 9 is a diagrammatic elevation view of an eighth RTD embodiment that includes a skeg to enhance maneuverability and/or tracking.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 of the drawings shows a powerboat 10 constructed according to the prior art. The illustrated prior art powerboat 10 takes the form of a military vessel having a M-shaped hull 11 with a stern 12. As a propulsion assembly onboard the hull 11 (not shown) propels the hull 11 forwardly, the propulsion discharge it produces (i.e., water) forms a rooster tail 13. The rooster tail 13 has a radar signature that an enemy can detect. In addition, production of the rooster tail 13 consumes energy and thereby decreases vessel efficiency.

FIG. 2 of the drawings is a diagrammatic plan view of a powerboat 20 constructed according to the present invention. The powerboat 20 includes a hull 21 having a stern 22 with a transom 23. The powerboat 20 also includes a propulsion subassembly on the hull 21 that produces a propulsion discharge. The propulsion subassembly is not fully illustrated, but it may include known types and kinds of propellers and/or jets that are centered on a longitudinally extending hull axis 24 of the powerboat 20 extending parallel to the Z axis as shown in FIGS. 2 and 3. The propulsion subassembly is depicted diagrammatically by a propeller 25 in FIG. 2. Various propeller positions relative to the transom 23 are shown, including a water-jet propeller position furthest rearwardly of the transom 23 (i.e., toward the right margin of the drawing sheet on which FIG. 2 appears, in the direction indicated by an arrow on the Z axis of the Cartesian coordinate system).

The propulsion subassembly functions as means for propelling the hull 21 forwardly. In operation, the propeller 25 produces a rearwardly directed propulsion discharge (i.e., water) that propels the hull 11 forwardly (in a direction opposite the direction indicated by the arrow of the Z axis). The propulsion discharge is depicted diagrammatically in FIG. 1 by two rearwardly directed arrows near the propeller 25; it tends to form a rooster tail extending upwardly and rearwardly from the stern 22, as mentioned above with reference to FIG. 1 and as depicted diagrammatically in FIG. 3 by a broken line 26 shown extending upwardly and rearwardly from the propeller 25.

According to the major aspect of the invention, the powerboat 20 has a rooster tail depressor (i.e., an RTD) in the form of a rooster-tail-depressing subassembly extending rearwardly of the stern 22. The RTD functions as means for suppressing the formation by the propulsion discharge of the powerboat rooster tail (the broken line 26 in FIG. 3). A first RTD embodiment shown diagrammatically in FIGS. 2 and 3 includes a canopy 27 that extends rearwardly of the stern and over at least a portion of the propulsion discharge. The canopy 27 includes a downwardly facing surface 28 that deflects the propulsion discharge (i.e., the source of the rooster tail) downwardly as depicted diagrammatically by the two redirected arrows beneath the surface 28 in FIG. 3. The width of the canopy 27 parallel to the X axis, the length parallel to the Z axis, and the outline are all functions of the vessel size and speed in addition to being a function of propeller size, location, and function.

FIG. 4a is a diagrammatic elevation view of a canopy 32 on a second embodiment of the invention. The canopy 32 is faceted in the sense that it includes a downwardly facing surface 32A having a cross sectional shape in a vertical transverse plane parallel to the X-Y axis that is not continuously curved; it includes multiple line segments or chords instead.

FIG. 4b is a diagrammatic elevation view of a canopy 33 on a third embodiment of the invention. The canopy 33 is curved in the sense that it includes a downwardly facing surface 33A having a cross sectional shape in a vertical transverse plane parallel to the X-Y axis that is continuously curved. The shapes of the canopy 32 and the canopy 33 are functions of the propeller size, number, and location. Other considerations affecting their shapes include construction material and attachment design.

FIG. 5 is a diagrammatic elevation view of a fourth embodiment of the invention having a canopy 34 with a downwardly facing surface 34A that includes lift-to-drag ratio enhancement steps. The steps are designed to promote separation of the redirected rooster tail from the RTD as soon as possible. That is done to reduce wetted surface area and viscous drag. The steps also convert any forward motion of the propeller wake into thrust.

FIG. 6 is a diagrammatic elevation view of a fifth embodiment of the invention having a canopy 35 and an optional transom thrust deflector 35A (TTD) on the transom 23 of the hull 21.

FIG. 7 is a diagrammatic plan view of a sixth embodiment of the invention having a canopy 36 that is configured to be articulated in yaw (about a vertical pivotal axis that is perpendicular to the X-Z plane) as depicted by an arrow 36A. The canopy 36 can be articulated in yaw to control the direction of the rooster tail, enhance control of the vessel, and/or pivot with the propeller in the case of a propeller that articulates is yaw for steering.

FIG. 8 is a diagrammatic elevation view of a seventh embodiment of the invention having a canopy 37 that is configured to be articulated in trim (about a horizontal pivotal axis that is perpendicular to the Z-Y plane) as depicted by arrows 37A and 37B. The canopy 37 can be articulated in trim to control the amount of lift generated by capturing (i.e., depressing) the rooster tail and/or to articulate in trim with the propeller.

FIG. 9 is a diagrammatic elevation view of an eighth embodiment of the invention having a canopy 38 with a downwardly depending skeg 38A (or “rather”) attached. The skeg 38A (or “rather”) enhances maneuverability of the vessel and/or improves tracking.

Thus, the invention provides a powerboat having a rooster-tail-suppressing assembly that significantly reduces powerboat radar signature while improving powerboat efficiency. Various enhanced versions provide the additional benefits described. Although exemplary embodiments have been shown and described, one of ordinary skill in the art may make many changes, modifications, and substitutions without necessarily departing from the spirit and scope of the invention. As for the specific terminology used to describe the exemplary embodiments, it is not intended to limit the invention; each specific term is intended to include all technical equivalents that operate in a similar manner to accomplish a similar purpose or function, it being intended, for example, that the term “powerboat” includes any of various powered watercraft and seagoing vessels.

Claims

1. A powerboat comprising:

a hull having a stern;

a propulsion subassembly on the hull that functions as means for propelling the hull forwardly, said propulsion subassembly producing a propulsion discharge that extends rearwardly of the stern when the hull is propelled forwardly by the propulsion subassembly; and

means for suppressing the formation by said propulsion discharge of a powerboat rooster tail, including a rooster-tail-suppressing subassembly on the boat hull that extends rearwardly of the stern and over at least a portion of the propulsion discharge.

2. A powerboat as recited in claim 1, wherein the rooster-tail-suppressing subassembly includes a canopy having a downwardly facing surface extending over at least a portion of said propulsion discharge.

3. A powerboat as recited in claim 2, wherein the downwardly facing surface of the canopy is arched.

4. A powerboat as recited in claim 2, wherein the downwardly facing surface of the canopy is faceted.

5. A powerboat as recited in claim 2, wherein the downwardly facing surface of the canopy is curved.

6. A powerboat as recited in claim 2, wherein the downwardly facing surface of the canopy is arched laterally and longitudinally.

7. A powerboat as recited in claim 2, wherein the rooster-tail-suppressing subassembly includes means for enhancing lift-to-drag ratio, including steps in the downwardly facing surface of the canopy.

8. A powerboat as recited in claim 2, wherein the rooster-tail-suppressing subassembly is configured to enable articulation of the canopy in yaw.

9. A powerboat as recited in claim 2, wherein the rooster-tail-suppressing subassembly is configured to enable articulation of the canopy in trim.

10. A powerboat as recited in claim 2, wherein the rooster-tail-suppressing subassembly includes means for enhancing maneuverability of the boat hull, including an attached skeg.