US 3842786 A
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States atent 1 [111 3,842,736 Uroshevich 1 Oct. 22, 1974 WATER-SKI TOWING DEVICE WITH Primary Examiner-Trygve M. Blix ATTITUDECONTROL  Inventor: Miroslav Uroshevich, 2505 Fleetwood Ave., Cincinnati, Ohio 45211  Filed: Jan. 2, 1974  Appl. No.: 429,528
 US. Cl. ll5/6.l  lint. Cl. ..A63c11/10  Field of Search 115/6, 6.1, 70; 114/16 A, 114/665 H  References Cited UNITED STATES PATENTS 2,387,907 10/1945 Hook 114/665 H 2,708,759 5/1955 Strawn l15/6.1 2,931,332 4/1960 Hebrank 115/70 3,062,172 11/1962 Moore 115/6.1 3,358,635 12/1967 McRee ll5/6.1
Assistant Examiner-Jesus D. Sotelo Attorney, Agent, or Firm-Gary M. Gron 5 7 ABSTRACT A water-ski towing device comprising a bouyant hull and a marine propulsion unit having a propeller mounted within a Kort nozzle beneath the hull. A tow bar is pivotally mounted to the stern of the hull between a horizontal ready position and a latched elevated running position. A transverse hydrofoil is mounted beneath the base of the tow bar through a pair of struts acting as vertical fins. The hydrofoil is adjustably positioned and oriented to urge negative pitch when the tow bar is horizontal and a lower degree of pitch when the tow bar is elevated to counteract the positive pitch produced by the propulsion unit. The hull of the device has a V-shaped bow section and permit a smooth roll into a turn.
16 Claims, 6 Drawing Figures PATENIEDBBTZZIHM SHEHIOF 3 PATENTEDUCTZZIBM .sum 20? 3 WATER-SKI TOWING DEVICE WITH ATTITUDE CONTROL The present invention relates to water-ski towing devices and more particularly to attitude control of this type of device.
In recent years there have been a number of significant developments in water-ski towing device. This type of unit comprises a bouyant hull andremote controlled propulsion unit steered through a rigid operator-gripped traction bar to pull a skier through the water. A development providing an efficient and stable propulsion unit for this type of device may be found in the copending application Ser. No. 403,440, filed Oct. 4, 1973, entitled Propulsion Unit for a Water-Ski Towing Device, M. Uroshevich et al inventors and of common ownership with the above application. An additional development is an improved tow bar assembly which adjustably latches the tow in an elevated running position. This is illustrated in copending'application- Ser. No. 405,896, filed Oct. 12, 1973, entitled Tow Bar Assembly for Water-Ski Towing Device, Richard T. Powers inventor.
These developments give excellent performance for a device of this type. However, one problem in handling does exist during the start-up condition. In a water-ski towing device the propeller providing the forward thrust must be suspended beneath the hull of the device to insure that the propeller is at all times submerged, even in choppy water. This placement of the propeller offsets it from the center of bouyance of the hull. The moment arm between the center of bouyancy and the line of thrust of the propeller causes a positive pitch for the hull. During running operation when the thrust of the engine is relatively stable this tendency toward a positive pitch is resisted by the weight of the skier on the tow bar which is latched in its elevated position. However, during the initial start-up position when the tow bar is horizontal and able to pivot in a vertical plane there is no mechanism for resisting the positive pitch. This is particularly aggravated when the engine is accelerated from idle to an output level sufficient to pull the skier out of the water. There is a strong positive pitch for the hull which in some cases is great enough to latch the tow bar in its elevated position. The operator must then push up on the handles to maintain a neutral pitch while he is attempting to reach a skiing condition.
The above problems are solved in one aspect of the present invention by a water-ski towing device comprising a bouyant hull and a propulsion unit supported by the hull. An aft extending operator-gripped tow bar assembly including a tow bar is pivotally mounted to the hull and displaceable between a generally horizontal and an elevated position. A flow-directing means positionedbeneath the hull is displaceable between a first position in which it urges a negative pitch for the hull and a second position in which it urges a lower degree of pitch. A means is connected between the tow bar assembly and the flow-directing means for displacing the flow-directing means in response to pivoting of the tow bar between its horizontal and elevated positron.
The above and other related features of the present invention will be apparent from a reading of the following description of the disclosure shown in the accompa- 2 nying drawing and the-novelty thereofpointed out in the appended claims. I
In the drawings: FIG. 1 is a side elevation view of a water-ski towing device having an attitude-control system embodying the present invention and shown in a running position;
FIG. 2 is a fragmentary side elevation view of the water-ski towing device of FIG. 1 shown in a start-up posi' tion;
FIG. 3 is a section view of the hull of FIG. 1 taken on line 3-3 of FIG. 1;
FIG. 4 is another section viewof the hull of FIG. 1 taken on line 4-4 of FIG. 1;
FIG. 5 is a fragmentary enlarged side view of the water-ski towing device of FIG. I particularly illustrating the attitude control device; and
FIG. 6 is an aft view of the attitude control device of FIG. 5 taken on line 6-6 of FIG. 5.
FIG. 1 shows a water-ski towing device comprising a bouyant hull 10 having an upper housing 12 joined to it at a belt line 14. A marine-type propulsion unit 16 is mounted within'the hull and has a vertical output shaft (not shown) extending downward through a strut 17 to a propeller support housing 18 where it drives a propeller 20 through a right angle gearbox (not shown). As pointed out in the above-identified Uroshevich et al application, propeller 20 may be provided with an annular shroud 22 to improve its performance.
A water-ski tow bar assembly comprising a tubular tow bar 24 and a hand grip assembly 26 is pivotally mounted to the stern 28 of hull 10 by an adjustable latch mechanism, generally indicated at 30. The latch mechanism 30 is adapted to releasably maintain the tow bar 24 in the elevated position of FIG. I for running operation or freely movable in a vertical plane in the start-up position of FIG. 2 where the tow bar 24 is in' a generally horizontal position.
As pointed out above, the offset of the propeller 20 from the center of bouyancy of the hull 10 causes a positive pitch for hull 10. In accordance with the present invention this is compensated for by an attitudecontrol system, generally indicated at 32. The attitudecontrol system is described particularly in FIGS. 5 and 6 which show the cooperating features of the adjustable latching mechanism 30.
The adjustable latching mechanism 30 comprises a mounted on shaft 40. As stated in the above Powers ap- I plication, the tow bar 24 is adjustably positioned in its elevated position relative to a housing 42 by a threaded shaft 46 extending through housing 42 and. manipulated by a knob 48. A threaded end plug 50 fixed in the end of tow bar 24 is moved up and down by manipulating knob 48 to pivot tow bar 24 relative to housing 42 and adjust the height of hand grip assembly 26 in its latched position.
The lower end of housing 42 has a notch 52 which receives a shaft 54 mounted on a pivoting handle assembly comprising a pair of arms 56 and operator activated plate 57 pivotally mounted to plates 34 through shafts 58. A leaf spring 60 acting on shelf 62 resiliently urges shaft 54 into the notch 52. When plate 57 is depressed the shaft 54 swings out of notch 52 to permit housing 42 and tow bar 24 to swing to a horizontal position.
The attitude control system 32 comprises a support plate 64 extending downward from tow bar housing 42. A pair of vertical struts 66 and 68 are mounted to plate 64 by a bolt assembly 70. A plurality of aligned holes 72 in the aft portion of struts 66, 68 and corresponding holes 74 in the aft portion of plate 64 enable structs 66, 68 to be adjustably pivoted in different positions relative to plate 64 by simply inserting a removable bolt as sembly 76 between the particular set of holes.
The struts 66 and 68 have angled midsections 78, 80 respectively extending radially outboard for further control of the device, as described later. The lower ends 82 and 84 of struts 66 and 68 are secured to the outboard section of a platelike hydrofoil 86. As shown particularly in FIG. 6, the spans of hydrofoil 86 extend at least as far as the diameter of the annular shroud 22 for proper control. Vertical struts 66 and 68 are relatively thin so that they act as vertical fins to stabilize roll, while the hydrofoil 86 acts to control a pitch. Hydrofoil 86 is swung from its positive pitch relative to hull 10, shown in FIG. 2, to the lower almost neutral positive pitch of FIG. 1 by pivoting tow bar 24 from its horizontal position of FIG. 2 to its elevated latched position of FIG. 1.
When the water-ski towing device is to be operated the skier is positioned in the water with the tow bar in its horizontal position illustrated in FIG. 2. In this position the hydrofoil 86 is in a position in which it directs the propulsive stream from annular shroud 22 downward. Since the hydrofoil 86 is positioned aft of the center of bouyancy, it produces a reaction force F R on the hull that urges hull toward a negative pitch. As a skier accelerates the engine to provide propulsive force in a forward direction pulling the skier out of the water, the engine thrust acts to produce a reaction force urging a positive pitch but this is counteracted by the hydrofoil 86 urging a negative pitch. The reaction force F produced by hydrofoil 86 also acts about pivot shaft 40 of the adjustable latching mechanism 30. As viewed in FIG. 2, the force F produces a counterclockwise moment about shaft 40 to urge tow bar 24 toward its elevated position. This greatly improves start-up performance since the skier is literally lifted out of the water to a planning position. As the hull 10 gains speed in the water the water skier rises out of the water until he reaches his planing position on top of the water in which the tow bar is latched in its elevated position of FIG. 1. During the transition period the positive pitch of hydrofoil 86 (FIG. 3) which urges a negative hull pitch is reduced to a lower positive pitch thereby urging a slightly negative hull pitch (FIG. 1). Thus, as the water skier breaks the surface and the propulsive thrust requirements of the engine are reduced, the correction of the nose-up attitude is gradually and smoothly diminished to achieve a uniform and stable pitch for hull 10 during startup.
The adjustment of the struts 66 and 68 permit the pitch of the hydrofoil 86 to be adjusted to compensate for different pay loads in the hull 10, such as a difference in battery size used to start the engine, a change in skier size thus effecting the amount of pull provided by the engine, or simply a change in performance charaeteri'stics. This adjustment acts not only in the horizontal position of the tow bar but in its elevated latched position to provide in effect a trim tab functioning as a horizontal stabilizer for the hull 10.
When the water-ski towing device is being maneuvered as by steering the hull 10 through the tow bar the curved chine on stem 28 makes it extremely simple to roll the hull 10 into a curve and thus provide a stable roll position for the hull 10. Since the vertical structs 66 and 68 have angled sections and act as vertical fins, they tend to stabilize the unit and act as a fin in the roll condition.
During straight-ahead operation the V-shaped bow section of the hull gives highly effective wave cutting performance thereby minimizing a tendency of waves to push the hull toward a positive pitch. Should this condition occur, however, the positive pitch in turn would produce a downward deflecting resultant force by the hydrofoil 86 which would in turn act to push the nose down and assume a neutral stable pitch. Thus it is seen that the hydrofoil 86 not only improves performance in the start-up position but during the running position.
The invention has been described in terms of a platelike hydrofoil 86 for controlling the pitch of the hull 10. It acts in effect as a flow director to produce this pitch control. It should be apparent to those skilled in the art that other types of flow directors, such as a pivotal section in shroud 22, may be employed to achieve the pitch control contemplated by this invention. Furthermore, other devices for interconnecting the tow bar to the flow-directing apparatus can be employed with equal effectiveness.
While the preferred embodiment of the invention has been described, it should be apparent to those skilled in the art that it may be practiced in other forms without departing from its spirit and scope.
Having thus described the invention what is claimed as novel and desired to be secured by Letters Patent of the United States is:
1. A water-ski towing device movable across water, said device comprising:
a bouyant hull having a bow and a stern;
a propulsion unit supported by said hull for accelerating water to provide a propulsive force for said hull;
an aft extending operator-gripped tow bar assembly pivotally including a tow bar mounted to said hull and displaceable between a generally horizontal and an elevated position;
means positioned beneath said hull and aft of said propulsion unit and displaceable between a first position for directing water flow in a direction producing a reaction force urging said hull toward a negative pitch and a second position for directing water flow in a direction producing a reaction force urging said hull toward a lower pitch; and
means connected between said tow bar assembly and said flow-directing means for displacing said flowdirecting means in response to pivoting of said tow bar between said horizontalfand said elevated positions.
2. A water-ski towing device as inclaim 1 wherein said flow-directing means comprises a hydrofoil displaceable between first and second pitches relative to said hull, thereby defining said first and second positions.
3. A water-ski towing device as in claim 2 wherein said connecting means comprises a strut assembly mounted on said tow bar assembly and supporting said hydrofoil beneath said hull thereby swinging said hydrofoil between said first and second pitches in response to pivoting of said tow bar.
4. A water-ski towing device as in claim 3 further comprising means for adjustably pivoting said strut assembly relative to said tow bar assembly thereby varying the first and second pitches of said hydrofoil.
5. A water-ski towing device as in claim 3 wherein said strut assembly comprises a pair of elongated plates extending downward from said tow bar to said plates, oriented to act as vertical fins and having sections angled toward the outboard portions of said hydrofoil.
6. A water-ski towing device as in claim 5 further comprising:
a downward projecting support plate secured to said tow bar assembly, said elongated plates being pivotally mounted to said support plate, said support plate and elongated plates having a plurality of spaced holes positioned to define aligned sets of holes for different pivotal positions of the elongated plates relative to said support plate; and
means forming a pin removably positioned in said aligned sets of holes thereby maintaining said elongated plates in said different pivotal positions.
7. A water-ski towing device as in claim 1 wherein said flow-directing means is in said first position when said tow bar is in its horizontal position and in said second position when the tow bar is in its elevatedposition.
8. A water-ski towing device as in claim 1 wherein said tow bar assembly comprises means for releasably maintaining said tow bar in its elevated position.
9. A water-ski towing device as in claim 1 wherein:
said propulsion unit has a line of propulsive force beneath said hull and displaced downward from the center of bouyancy of said hull thereby producing a reaction force urging a positive pitch for said hull;
said flow-directing means is positionedbehind said 11. A water-ski towing device as in claim 10 wherein:
said propulsion unit comprises a propeller positioned within an annular shroud; and
said hydrofoil has a span extending at least as far as the periphery of said annular shroud.
12. A water-ski towing device as in claim 11 wherein said connecting means comprises a strut assembly mounted on said tow bar assembly and supporting said horizontal stabilizer thereby swinging said hydrofoil between said first and second pitches.
13. A water-ski towing device as in claim 12 wherein said strut assembly comprises a pair of opposed elongated plates extending downward from said tow bar assembly to said hydrofoil, said plates oriented to act as vertical fins and having sections angled outward away from one another to the outboard portions of said hydrofoil.
14. A water-ski towing device as in claim 1 further comprising means for adjustably positioningsaid flowdirecting rneans in said first position.
15. A water-ski towing device as in claim 1 wherein said hull has a bow generally having a V cross-sectional shape thereby improving the wave penetration of said hull.
16. A water-ski towing device as in claim 15 wherein said hull has a stern with a uniformly curved crosssectional shape thereby enabling a skier to roll the hull into a turn.