US3650239A

US3650239A - Vehicle

Info

Publication number: US3650239A
Application number: US888386A
Authority: US
Inventors: Stewart P Gast
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-12-29
Filing date: 1969-12-29
Publication date: 1972-03-21
Anticipated expiration: 1989-03-21

Abstract

Vehicle, particularly for water travel, having two generally parallel spaced apart fins extending downwardly on either side of the central line of the hull to define a tunnel wherein the screw is mounted so that the relative water flow therethrough is substantially similar to water flow past a displacement-type hull and a pair of transverse steps extending oppositely transversely outwardly of the forward end of the fins so that relative water flow laterally of the tunnel will be substantially that produced by a planing type hull whereby water resistance is minimized while prop submersion is maximized.

Description

United States Patent Gast [451 Mar. 21, 1972 54] VEHICLE FOREIGN PATENTS OR APPLICATIONS [72] Inventor: Stewart P. Cast, 4600 Warrington Drive, 1,8 11/1957 g m New Orleans, La. 70122 Primary Examiner-Milton Buchler [22] F'led: 1969 Assistant ExaminerCarl A. Rutledge [21] APP] NOJ 888,386 AttorneyLachenbach & Lackenbach I [57] ABSTRACT [52] 11.5. Cl. ..115/39 vehicle, particularly for water travel, having two generally [5 1 1 '3" cl 5/16 parallel spaced apart fins extending downwardly on either side [58] Field of Search ..115/39; 1 14/56, 57 f the central line f the hull to d fi a tunnel wherein the screw is mounted so that the relative water flow therethrough [56] References Cited is substantially similar to water flow past a displacement-type hull and a pair of transverse steps extending oppositely trans- UNlTED STATES PATENTS versely outwardly of the forward end of the fins so that relative water flow laterally of the tunnel will be substantially that 835,530 11/1906 Huff 112/33 produced by a planing type bu whereby water resistancc is 1,163,075 12/1915 Fowler ..1 l minimized while prop submersion is maximized 3,469,557 9/1969 Wollard... ..115/39 3,515,087 6/1970 Stuart ..115/39 X 9 Claims, 5 Drawing Figures PATENTED MAR 21 I972 I FIG. 2

STEWART Pr GAST VEHICLE This invention relates generally to vehicles and, particularly, for vehicles adapted for travel on the surface of a liquid.

Boat hulls may generally be characterized as being of one of two varieties or types, namely, of the displacement type or of the planing type. The first or displacement type hull achieves lift and support entirely or substantially entirely from the static forces acting thereon in accordance with Archimedes principle. In other words, the amount of lift provided depends solely on the amount of water displaced by the hull. Hence, for a given gross boat weight, a given quantity of water will be displaced thereby. As the boat is moved through the water, the water being displaced must be physically pushed aside by the hull as it advances through the water. As the stern of the boat passes a given location, the water which has been pushed aside by the hull tends to rush back into the gap behind the stern so that both a lower pressure pocket is formed behind the boat together with substantial turbulence in an adjacent the pocket. Both the resistance of the water and the pressure differential between the bow and stern provide restraining forces against movement of the hull. However, since such a hull is generally smooth and the bottom of the hull towards the rearis gently curved upwardly, there is substantially smooth water-flow past the hull with little turbulence being created along the hull and, accordingly, a relatively low drag results. Such a hull is efficient at low speeds since the restraining forces at low speeds are only the inertial forces plus the low drag produced by the smooth or laminar fluid flow adjacent the hull. However, as speed is increased, increased turbulence provides rapidly increasing drag and high speeds become exceedingly difficult to attain. After a relatively moderate speed is reached, the addition of more power merely results in increased turbulence and very little increase in velocity.

in the second, or planing type of boat hull, lift is achieved by a combination of two types of forces. When the hull is stationary or moving or low speeds, then the lift is provided entirely or substantially entirely by the static forces of the water displaced by the hull. However, as the velocity of the hull through the water increases, the relative movement therebetween is utilized to generate dynamic lifting forces tending to raise the hull out of the water until, at high velocities, the boat planes so that the major or substantially all of the lifting force results from the dynamic forces. In the basic type of planing hull, the bottom is substantially straight back to the transom, as opposed to the rearward rise of the bottom to the transom conventionally utilized in displacement type hulls. The transom of the planing type hull is generally the full depth of the boat, rather than being shallow as in a displacement type hull. Since the transom and stem portions of the planing type hull project sharply and deeply into the water, a substantial drag is created, particularly at the transom, and the hull is fairly inefficient at low velocities. Given enough power, however, such a planing type hull will reach a point at which the water breaks away from the transom, to provide sufficient dynamic lifting forces that the hull is substantially out of the water and the boat may be said to be on a plane. From then on, the speed is limited only by the amount of power applied.

In a displacement type hull, since it sits relatively low in the water and the water flow is quite smooth over the bottom, the propeller may be positioned at any desired location and, even, close to the bottom and under the transom where the hull curves upwardly. At this location, the propeller is relatively well protected and can drive efficiently and quietly. On the planing type hull, the transom is generally deep and the propeller must extend substantially beneath the transom so as to be able to drive even when the hull is planing and substantially out of the water. When so positioned, the propeller is noisy, its efficiency is reduced and it is poorly protected against impact damage. As such, the planing type hull is generally only suitable for use with outboard engines or sterndrive units, either of which enable the lower unit to be readily raised for inspection and propeller replacement and repair or in racing boats where factors such as cost and ease of maintenance are of subsidiary importance. Further, the gearing necessary to drive propellers at such a location funher add to the high initial and maintenance costs of such drives. in the displacement type hull, however, the engine may be mounted inboard and only a straight drive shaft is required extending through the hull to the propeller or screw.

Having in mind all of the foregoing, it is a primary object of the present invention to provide a novel and improved boat hull exhibiting some of the advantages and characteristics of both displacement and planing boat hulls.

Another primary object of the present invention, in addition to the foregoing object, is the provision of new and improved boat hulls which are capable of planing.

It is another primary object of the present invention, in addition to each of the foregoing objects, to provide novel and improved boat hulls for use with inboard engines.

Still another primary object of the present invention, in addition to each of the foregoing object.,, is the provision of novel and improved boat hulls wherein the propeller may be positioned close to the bottom in a generally protected location.

Still another primary object of the present invention, in addition to each of the foregoing objects, is the provision of novel and improved boat hulls having a tunnel for directing a substantially-smooth flow of water past a propeller.

Still further, it is yet another primary object of the present invention, in addition to each of the foregoing objects, to provide novel and improved boat hulls having steps or discontinuities on either side of the bottom thereof for enabling the generation of planing type dynamic lifting forces as the hull moves relative to the water.

Another and still further primary object of the present invention, in addition to each of the foregoing objects, is the provision of novel and improved boat hulls combining features of both planing and displacement type hulls.

Yet still further, it is another primary object of the present invention, in addition to each of the foregoing objects, to provide novel and improved boat hulls having a bottom rising toward the rear of the transom at about the water line and means for enabling the hull to plane.

Still another primary object of the present invention, in addition to each of the foregoing objects, is to provide novel and improved boat hulls having a plurality of steps for providing planing type lift and a smooth tunnel for providing displacement type smooth flow of water past a propeller.

Still further, it is another primary object of the present invention, in addition to each of the foregoing objects, to provide novel and improved methods for lifting and driving boat hull.

The invention relates in the combination, construction, arrangement and disposition of the various component parts and elements incorporated in improved boat hulls constructed in accordance with the principles of this invention and improved methods of driving and supporting a boat hull in accordance with the principles of this invention. The present invention would be better understood and objects and important features other than those specifically enumerated above will become apparent when consideration is given to the following details and description, which when taken in conjunction with the annexed drawing, describes, discloses, illustrates and shows a preferred embodiment or modification of the present invention and what is presently considered and believed to be the best mode of practicing in the principles thereof. Other embodiments or modifications may be suggested to those having the benefit of the teaching herein, and such other embodiments or modifications are intended to be reserved especially as they fall within the scope and spirit of the subjoined claims.

IN THE DRAWlNG:

FIG. 1 is a side elevational view of a boat constructed in accordance with the principles of this invention;

FIG. 2 is a bottom plan view of the boat hull of the preceding figure;

FIG. 3 is an elevational cross-sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is an elevational cross-sectional partial view taken along line 4-4 of FIG. 2;

FIG. 5 is a partial, enlarged cross-sectional view taken along line 55 ofFlG. 2.

With reference now to the drawing, there is shown and illustrated therein a boat hull constructed in accordance with the principles of the present invention and designated generally by the reference character 10. As the hull may be associated or form a part of a boat of substantially any design or type, such as a runabout, cabin cruiser, fishing boat, and the like, without limitation, only the lower portion or the portion thereof which is adjacent or in contact with the water is shown, it being understood that the upper portion of the boat having the hull 10 may be constructed and arranged as desired, as aforesaid. Moreover, while boat hulls constructed in accordance with the principles of the present invention are particularly adapted for utilization with inboard engines, it is to be expressly understood that the hulls are not limited to utilization solely with inboard engines and may be driven by outboard engines mounted either at the transom or in a well which would position the propeller and lower unit thereof forward of the transom as will become apparent.

Having in mind the foregoing, the boat hull 10 may be fabricated of substantially any desired material, including wood, plastic, metal, and the like, the combinations thereof and may comprise a bow portion 12 having a stem post 14 extending downwardly and rearwardly thereof into a keel 16 extending along the bottom 18 to a location 20 somewhat aft of amidship. The aft or stem portion 22 of the hull 10 may rise generally upwardly and rearwardly to the transom 24. Accordingly, as so far detailed and described, the hull 10 comprises generally a substantially conventional displacement type hull. The location 20'is approximately whereat the stem portion 22 starts to rise or curve upwardly toward the transom while the keel l6 and the bottom 18 generally forwardly of the location 20 until they rise towards the bow 12 may be generally straight in a fore and aft direction although curbed from side to side.

From each side of the location 20, a pair of generally parallel spaced apart fins 26 may be provided extending rearwardly under the stem 22 to define a tunnel 28 within which the propeller or screw 30 may be positioned and driven, as by means of a propeller shaft 32 extending through the hull 10 within the tunnel 28, to an engine 34, or the like positioned generally inboard of the hull 10 within an engine compartment or enclosure 36. The lower edges 38 of the fins 26 may be disposed generally in line with the bottom 18 forwardly of the location 20 to form a smooth continuation thereof which will not interfere or affect the smooth flow of water thereover. Accordingly, within the tunnel 28, as defined by the fins 26 rearwardly of the location 20, the bottom of the boat smoothly rises curvilinearly toward the transom so as to provide a profile substantially similar to that of a conventional displacement type hull and, therefore, the flow of water therethrough will be essentially smooth and along the hull bottom so as to break away only at the transom 24, as indicated in FIG. 1 of the drawing by that portion of the water designated by the reference character 40 and such smooth flow of the water through the-tunnel and past the propeller or screw 30 will occur substantially independent of the velocity of the hull 10. Generally laterally outwardly of the location on the outboard sides of the fins 26, the hull 10 may be provided with a pair of planing surfaces forming an extension of the bottom 18 and designated by the reference character 42 terminating at a rearwardly facing edge or step 44 which causes the water to break away from the hull 10 as the velocity increases, reducing drag and enabling the hull 10 to function substantially as it it was a planing type hull extending from the bow 12 rearwardly only as far as the steps 44. Hence, since the bottom 18 and the planing surfaces 42 generally forwardly of the steps 44 do not rlseupwardly towards a transom, the hull 10 may plane under the application of sufficient power, causing the water to break away from the hull 10 at the step 44 which, as heretofore pointed out, functions substantially as an apparent transom of a planing type hull so that the water outboard of the fins 26 will be at a lower level than that within the tunnel 28, as indicated in FIG. 1 by the reference character 46.

In accordance with the construction heretofore pointed out and in accordance with the principles of the present invention, the hull 10 may, when under way at any substantial speed, break away from most of the displacement type contact with the water and function substantially as a planing type hull, with the high velocity capable of being provided by such constructions under the application of sufficient power. However, in a manner substantially contrary to the conventional planing type hull, a small portion of the hull l0, namely, that portion thereof defined by the tunnel 28 effectively functions as a conventional displacement hull with the smooth flow of water therepast, enabling the hull 10 to be effectively powered by means of a conventional screw 30, drive shaft 32 and inboard engine 34 with the screw 30 being positioned within the rising portion under the stern of the hull. Moreover, at low velocities, since the entire hull is basically similar to a displacement type hull, with the exception of the step 44 and the fins 26, at such low velocity that the water does not break away from the step 44, the hull will exhibit the stability and seaworthiness of a conventional displacement type hull. Stated another way, in accordance with the present invention, the economical and seaworthy displacement type hull may be provided with means to enable the hull to shake off the speed limitations ordinarily inherent in such bulls and attain whatever speed may be achieved by the engine and screw through planing type operation, without losing the advantages of the displacement type hull. It is believed that the present invention is particularly suitable for use with larger craft, above, for example, approximately 25 feet in length, rather than the smaller runabout type of craft, although the invention may be utilized with such smaller craft to provide increased seaworthiness together with the attainment of substantial velocity, both in excess of those heretofore attainable.

Further to the general shape distinctions heretofore pointed out between conventional planing and displacement type boat hulls, the weight distribution preferably differs between the two hull types for maximum efi'tciency and seaworthiness. More particularly, in the displacement type hull, the lifting forces acting on the hull result from static forces and therefore are substantially uniformly distributed and the center of displacement therefore occurs slightly aft of midships. Hence,

the center of gravity is preferably also located slightly aft of midship. In a planing type hull, however, the lifting forces at speed or on plane are result of dynamic forces and are concentrated nearer the transom and the center of displacement is generally well aft of midships. Hence, the design center of gravity is preferably located well aft of midships to accommodate the dynamic lifting forces. The deep transom of the planing type hull results in the center of displacement being further aft than would be true of a displacement hull even when at rest or at low speeds and proper design may, therefore, result in proper fore and aft trim or attitude both at low speeds and at planing speeds. However, positioning the center of gravity aft does adversely affect the seaworthiness of the hull.

With hulls according to the present invention, at low velocities or at rest the hull is substantially a displacement hull with the center of displacement being slightly aft of midships and, therefore, the center of gravity may be slightly aft of midships to provide proper fore and aft trim and good seaworthiness. When the hull reaches planing speed, the lifting forces are concentrated on the step and the center of displacement remains slightly aft of midships so that proper fore and aft trim or attitude is maintained. In other words, the effective bottom is shortened, the rear of the steps functioning as an effective or apparent transom, and the efiect is similar to moving the" center of gravity apparently rearwardly to provide the proper weight distribution for planing without adversely affecting the seaworthiness of the basic hull. Yet further, if desired, the roof of the tunnel may comprise a slight downward curve behind the propeller to thereby deflect the discharging stream of water downwardly to afford some additional lift to the rear of the boat.

While the invention has been described, disclosed, illustrated and shown in terms of an embodiment or modification which it has assumed in practice, the scope of the invention should not be deemed to be limited by the precise embodiment or modification herein described, disclosed, illustrated and shown, such other embodiments or modifications as may be suggested to those having the benefit of the teaching herein, beingintended to be reserved especially as they fall within the scope and breadth of the claims hereto appended. I claim:

1. In a displacement type boat hull having a bottom which rises at the stern toward the transom the combination of at least a pair of generally parallel spaced apart fins extending generally vertically downwardly of the bottom of the hull generally between a location beneath the transom and the location whereat the bottom starts to rise toward the transom and at least one step extending generally downwardly of the bottom generally laterally outwardly of said fins at said last mentioned location, said step causing the water to break away from the hull rearwardly thereof at an elevated velocity to provide lift to said hull similar to that provided by a planing type hull, said fins defining a generally centrally disposed rearwardly open tunnel for directing a generally smooth flow of water, isolated by said fins from the wake produced by said step, generally upwardly and rearwardly therealong similar to flow along a conventional displacement type boat hull, enabling a displacement type boat hull to plane at elevated velocities to eliminate the speed limitation generally considered inherent therein and generation of the high speed characteristics of a planing type boat hull to enable the hull to attain the maximum velocity the power plant is capable of producing while retaining the low speed characteristics, basic economy and seaworthiness of such displacement type hull.

2. The boat hull defined in claim 1 further comprising a screw disposed within said tunnel for propelling said hull through the water.

3. Boat Hull defined in claim 2 wherein the lowermost edges of said fins extend generally straightly rearwardly of said last mentioned location and further comprising a keel extending from a forward portion of the hull rearwardly no farther than said last mentioned location.

4. A boat hull comprising, in combination, a bottom having a rearward portion rising generally upwardly towards a transom having a depth substantially less than the maximum depth of the hull, a pair of fins extending generally downwardly in laterally spaced apart relationship beneath said rising portion to define therebetween a tunnel through which water may flow smoothly along said rising portion so that a propeller disposed within said tunnel may remain submerged in water, and a pair of steps extending generally transversely outwardly adjacent the forward ends of said fins defining rearward facing steps so that water may break away from the bottom of the boat hull there at and enable the hull to attain a planing attitude even while water continues to flow smoothly through said tunnel.

5. Boat hull defined in claim 4, wherein said fins extend substantially entirely from the location wherein the bottom begins said rise towards the transom to substantially adjacent said transom.

6. Boat hull defined in claim 4 wherein the lower marginal edges of said fins comprise the continuations of the bottom of the hull forwardly of said rising portions.

7. Boat hull defined in claim 4, wherein the bottom edge of each of said fins comprises an extension of the hull bottom forwardly of said rising portion.

8. Boat hull defined in claim 4, further comprising a screw disposed within said tunnel for driving said hull through the water.

9. Boat hull defined in claim 4, wherein said tunnel is generally centrally laterally disposed beneath said rising portion.