Boat stabilizer

Abstract: A boat stabilizer (20) for attachment to the lower drive unit of a boat motor. The stabilizer comprises first and second lifting members (22,28) for positioning adjacent opposite sides of the drive unit and first and second arm portions (26, 32) for extension around the drive unit. The interior side walls (23, 30) of the lifting elements are spaced forming a slot therebetween for receiving the drive unit. The first and second arm portions (26, 32) are removably attached together and selectively movable toward and away from each other for varying the width of the slot, enabling the stabilizer to be adjusted to fit virtually any conventional outboard or inboard/outboard boat motor.

Description: This invention relates to boat stabilizers of the type that attach directly to the lower drive unit of a boat motor to provide lift to the stern of the boat. It is known that the stability, handling characteristics and safety of certain boats (e.g. recreational boats such as ski boats and bass boats) can be greatly improved by the addition of a lifting plate or member to the lower drive unit of the boat. Such plates or members (stabilizers) are typically designed to fit around either the front of the drive unit or the rear of the drive unit and over or adjacent to the anti-cavitation plate thereof. For example, US-A-2,963,000, 3,433,195 and 4,487,152 disclose stabilizers that extend around the front of the drive unit over the anti-cavitation plate thereof and function to lift the stern of the boat up and bring the bow down which causes the boat to plane off more quickly coming out of the "hole" and improves the overall ride and ability to control the boat. The shape of these types of stabilizers with respect to the drive unit to which they attach is very important. In addition to being held in the proper position with respect to the drive unit, the stabilizer must fit sufficiently tightly around the drive unit or it will be difficult to attach and/or lack sufficient strength. Unfortunately, the size and configuration of boat motor drive units and their corresponding anti-cavitation plates vary somewhat from boat to boat. It is impractical to design a separate stabilizer for each type of boat motor that exists. As a partial solution to the problem, certain two-piece stabilizers are available that consist of one lifting member for attachment on one side of the anti-cavitation plate and a second lifting member for attachment on the opposite side of the anti-cavitation plate. Although these stabilizers can fit most drive units irrespective of the size and configuration of the units, they do not have the structural integrity and strength of one-piece stabilizers and, as a result, are more easily damaged during use. For example, two-piece stabilizers may tend to break when they are stepped on by swimmers or skiers attempting to get onto the boat. According to the present invention there is provided a boat stabilizer for attachment to the lower drive unit of a boat motor, said stabilizer comprising a first lifting member having a first interior side wall for positioning adjacent to a first side of said drive unit and a first arm portion for extension around said drive unit; and a second lifting member having a second interior side wall for positioning adjacent to a second side of said drive unit and a second arm portion for extension around said drive unit toward said first arm portion, said second interior side wall being spaced from and opposing said first interior side wall and said first and second arm portions being attached together and selectively movable toward each other for decreasing the distance between said first interior side wall and said second interior side wall. Although the inventive stabilizer is effectively a one-piece unit and has the structural integrity and strength thereof, it is adjustable in width to fit the drive unit of virtually any conventional outboard or inboard/outboard boat motor. In one embodiment, the first and second arm portions are selectively slidably positioned one above the other in overlapping relationship. The first lifting member may include a first shoulder facing the second lifting member, and the second lifting member may include a second shoulder facing the first lifting member. When the arm portions are selectively moved toward each other as far as possible, the interior wall of the first arm portion directly abuts the second shoulder, and the second interior wall directly abuts the first shoulder. In order that the present invention will be more readily understood, the following description is given, merely by way of example, reference being made to the accompanying drawings, in which:- Figure 1 is an exploded perspective view of one embodiment of the adjustable boat stabilizer of the present invention. Figures 2 and 3 are bottom views of the right side and left side lifting members of the stabilizer of Figure 1, respectively. Figure 4 is a perspective view of a spacer bar of the stabilizer of Figure 1. Figures 5, 6 and 7 are a perspective view, a bottom view and a rear view of the stabilizer of Figure 1. Figure 8 illustrates how the stabiliser may be adjustable in width. Figure 9 illustrates a conventional boat motor and corresponding lower drive unit without a stabilizer attached. Figure 10 shows the boat motor of Figure 9 with the stabiliser attached. Figure 11 illustrates use of a torque equalizer in connection with the stabilizer of Figure 1. The stabilizer 20 is designed for attachment to the lower drive unit of an outboard or inboard/outboard (stern drive) boat motor. As used herein and in the appended claims, "lower drive unit" (hereinafter "drive unit") means the portion of the boat motor connecting the actual engine to the propeller (sometimes called the motor post or propeller post). In outboard motors, the drive unit extends directly from the engine into the water. In inboard/outboard motors, the drive unit extends from the engine through the stern of the boat and into the water. The stabilizer 20 comprises first and second lifting members 22 and 28, having first and second interior walls 23 and 30 for positioning adjacent to the sides of the drive unit and integral first and second arm portions 26 and 32 for extension around the drive unit. The first and second interior side walls 23 and 30 are mirror images of one another and define : slot 34 therebetween. The first lifting member 22 and second lifting member 28 also each include an upper surface 35 and a lower surface 37. The first and second arm portions 26 and 32 are removably attached together and can be selectively movable toward or away from each other for decreasing or increasing the distance between the side walls 23 and 30. Attachment of the lifting members 22 and 28 together adds a great deal of strength thereto. Attaching the first and second arm portions 26 and 32 together greatly improves the structural integrity and strength of the stabilizer 20 as a whole. The lifting members 22 and 28 each include a nose portion 36, having a leading edge 42, a sweeping body portion 38 and a flap portion 40. The sweeping body portions 38 each include a first wing section 44 having a leading edge 46 and a second wing section 48 having a leading edge 50 and side edge 52. The flap portions 40 each have an exterior side edge 54, an interior side edge 56 and a trailing edge 58. As best shown in Figures 1, 5 and 7, the first and second lifting members 22 and 28 each taper downwardly (first negative dihedral) and outwardly (second negative dihedral) from their nose portion 36 toward their trailing edge 58 and side edges 52 and 54. The negative dihedral angles are formed with respect to the surface to which the members 22 and 28 are attached. To allow the lifting members 22 and 28 to be bolted to the anti-cavitation plate or other portion of the drive unit, they include openings 60, each counter-sunk at 62 to receive the head of the bolt, to improve the hydrodynamic performance and aesthetic appeal of the stabilizer. The lower surfaces 37 of the lifting members 22 and 28 each include an opening 64 and a plurality of openings 66 for receiving an adjustable torque equalizer (not shown by Figures 1-8). The nature and function of such a torque equalizer are discussed in connection with reference to Figure 11 below. A textured surface 68 is provided on the upper surfaces 35 of the lifting members 22 and 28, preferably on the flap portion 40 and may also be provided on the lower surface. Due to the excellent structural relationship between the members 22 and 28, the stabilizer 20 can be used as a step by swimmers and skiers to get in and out of the boat. The textured surfaces 68 prevent the bare feet of the swimmers and skiers from slipping. The textured surfaces 68 may also function to reduce the boundary layer effect and improve the hydrodynamic performance thereof. The arm portions 26 and 32 include upper surfaces 70, 80, lower surfaces 72, 82, front walls 74, 84, rear walls 76, 86 and interior walls 78, 88. In order to allow for a better fit on some drive units, the front wall 84 of the second arm portion 32 can be tapered downwardly from top to bottom toward the rear wall 86 thereof. As best shown in Figures 5-7, the first and second arm portions 26 and 32 are selectively slidably positioned to overlap one another. The lower surface 37 of the first lifting member 22 has a first recess 90 formed therein forming a first shoulder 92 facing the second lifting member 28. The upper surface 80 of the second arm portion 32 provides a second recess 94 forming a second shoulder 96 facing the first lifting member 22. The first and second recesses 90 and 94 have approximately the same shape and depth as the shape and width of the second and first arm portions 32 and 26 respectively. A plurality of first and second spacer bars 98(a)-98(d) and 100(a)-100(d) are removably attached to the interior walls 78 and 88 of the first and second arm portions 26 and 32 respectively, being removably attached together side by side between the interior walls 78, 88 and the shoulder 96 and 92. As best shown by Figure 4, the spacer bars 98 and 100 each include upper and lower surfaces 102, 104, end surfaces 106, 108, and exterior and interior side surfaces 110, 112. The exterior side surfaces 110 have upper and lower recesses 114, 116 which form a plurality of longitudinal grooves 118 when the spacers are attached together. Each spacer bar 98 and 100 is substantially rectangular in shape, has a length and height approximately equal to the length and height of the interior walls 78 and 88 of the arm portions 26 and 32 and is approximately 6.3 mm wide. The exterior sides 110 of the first of the spacer bars 98(a), 100(a) directly abut the interior walls 78, 88 of the arm portions 26, 32, while the interior sides 112 of the spacer bars 98(d), 100(d) directly abut the shoulders 96, 92. The spacer bars 98 and 100 impart a great deal of structural integrity and strength to the stabilizer 20 by reinforcing the overlap connection between the arm portions 26 and 32. The spacer bars 98 and 100 are illustrated in Figure 1 as having openings 120 therethrough. Complementary bores 122 are formed through the interior walls 78 and 88 of the arm portions 26 and 32 and screw 123 can be inserted through the openings 120 into the bores 122. This means of attaching the spacer bars 98 and 100 to the interior walls 78 and 88 and to each other allows any number of the spacer bars to be removed and reattached at any time. Alternatively, the spacer bars 98 and 100 can be integrally molded or otherwise formed with the arm portions 26 and 32, and can be removed by cutting them off with a saw or other tool. This means of attachment is advantageous because it increases the structural integrity and strength of the connection. The grooves 118 formed by the recesses 114 and 116 in the exterior sides 110 of the spacer bars 98 and 100 facilitate the cutting or removing process by acting as saw guides. The grooves 118 also function to improve the hydrodynamic performance as well as the aesthetic appeal of the stabilizer 20. Although the arrangement shown in the drawings is preferred because of the structural integrity and strength it provides, the positions of the recesses and shoulders of the lifting members and arm portions can be varied if desired. Also, other sizes and numbers of spacers can be employed, if necessary. A pair of apertures 126 are disposed in the first arm portion 26 and a pair of elongated slots 128 are disposed in the second arm portion 132. The longitudinal axes 130 of the slots 128 extend from points 132 adjacent to the second shoulder 94 toward the first lifting member 22. Hexagonal recesses 134 open into the upper surface 70 of the first arm portion 26 over the apertures 126 and receive nuts 140. A pair of bolts 135 extend from the lower surface 82 of the second arm portion 32 and through the slots 128 and apertures 126. The head portions 136 of the bolts 135 abut the lower surface 82 of the second arm portion 32, and the threaded end portions 138 of the bolts 135 are threaded into the nuts 140 to attach the first and second arm portions together. The location of nuts 140 in recesses 135 improves both the hydrodynamic performance and the aesthetic appeal of the stabilizer 20. The longitudinal slots 128 allow the first arm portion 26 to slide toward and away from the second shoulder 96 while the arm portions are attached together, so that the distance between the first interior side wall 23 and second interior side wall 30 of lifting members 22 and 28 can be easily adjusted in fitting the stabilizer onto the drive unit. The upper surfaces 70, 80 of the arm portions 26, 32 include a plurality of grooves 142, 144 for improving the hydrodynamic performance of the stabilizer 20 and matching the grooves 118. The lifting members 22 and 26, including the arm portions 26 and 32 and the spacer bars 98 and 100, are formed of a material that is stable at both high and low temperature, strong and durable, preferably of high molecular weight plastics such as polypropylene and rubber copolymers. Such plastics have a very high strength-to-weight ratio. Referring now particularly to Figures 8-11, a method of attaching the stabilizer 20 to the drive unit of a boat motor will be described. A conventional outboard boat motor 150 is illustrated in Figures 9 and 10, connected to a transom portion 152 of the boat hull and includes a propeller 154 which is driven by a propeller shaft (not shown), the shaft being enclosed within a housing 156. A conventional anti-cavitation plate 160 which is disposed in a substantially horizontal position above the propeller to eliminate and reduce certain cavitation effects that would otherwise be created by rotation of the propeller. The boat motor 150 further includes a motor housing 162 and engine (not shown). The propeller 154, shaft, shaft housing 156 and anti-cavitation plate 160 form the lower drive unit 164, having front and rear ends 166, 168 and first and second mirror image sides 170, 172. The position of the stabilizer 20 with respect to the lower unit 164 is critical. Although the stabilizer can be attached on the lower unit at a variety of points above the propeller 154 in adjacent spaced relation therefrom as long as it is sufficiently submerged beneath the water to provide the desired amount of lift, it is preferably attached directly above, over or directly below the anti-cavitation plate 160. Typically, the anti-cavitation plate 160 will be 12.7 to 25.4 mm below the lowest point on the boat's transom/keel. Preferably, the first and second lifting members 22, 28 are bolted to the top of the anti-cavitation plate 160 on the first and second sides 170, 172 of the drive unit 164 respectively. When properly positioned, the side edges 52 of the second wing sections 48 and the side edges 54 of the flap portions 40 of the lifting members 22 and 28 will submerge in the water during turns made by the boat and as it rocks back and forth at cruising speeds. This causes the stabilizer 20 to act as a keel which prevents the back of the boat from skipping during the turns and reduces or eliminates rocking back and forth due to non-planar surfaces on the boat's hull. As shown in Figure 10, the stabilizer 20 is placed around the rear end 168 of the drive unit 164 over the anti-cavitation plate 160 thereof. Although it is not as effective as the preferred embodiment described above, the lifting members can be connected together at the nose portions thereof and the slot for receiving the lower unit can be positioned at the opposite end allowing the stabilizer to slide on to the lower unit from the front side thereof. The stabilizer 20 can be installed in a very short time. First, the stabilizer 20 is adjusted to the proper width, so that the interior side walls 23, 30 should fit tightly against the first and second sides 170 of the drive unit 164 with the trailing edges 58 of the lifting members perpendicular to the drive unit. Although it is effective in all positions, the stabilizer is most effective (e.g. provides more lift) when it is positioned as far to the rear end 168 of the lower unit 164 as possible. The stabilizer was designed such that most drive unit housings will not entirely fill the center slot 34. This allows for adequate water flow into the cooling intakes. If the stabilizer 20 does not properly fit, it can be adjusted accordingly. As illustrated by Figure 8, the width of the slot 34 can be decreased from approximately 70 mm to 44.5 mm. This decreases the wingspan of the stabilizer from 356 mm to 330.4 mm. This width range allows the stabilizer to properly fit virtually any conventional lower drive unit. To decrease the width of the slot 34, the first lifting member 22 is first removed from the second lifting member 28 by removing the bolts 35 from the apertures 126 and slots 128 and separating the members. The appropriate number of spacer bars are then removed from each arm portion. For example, if the slot 34 is 12.7 mm too wide, two spacer bars are removed from each arm portion. If the spacer bars are fastened to the interior walls of the arm portion and to each other by screws, these are removed and the spacer bars are removed starting with the spacer bars closest to the interior walls 78 and 88 of the arm portions. In order to decrease the width of the slot by 12.7 mm, the spacer bars 98(a), 98(b), 100(a) and 100(b) are removed. In order for the arms to properly fit back together, an equal number of spacer bars must always be removed from each arm portion. If the spacer bars are integrally formed with the arm portions and each other, the spacer bars are removed starting with the spacer bars furthest away from the interior walls 78 and 88 of the arm portions. In order to decrease the width of the slot by 12.7 mm, the spacer bars 98(c), 98(d), 100(c) and 100(d) are removed. Once the proper width of the slot 34 is achieved, the members 22 and 28 are fastened back together and the stabilizer 20 is mounted to the anti-cavitation plate. Four holes are drilled through the cavitation plate using the openings 66 as guides and the stabilizer is bolted thereto. The stabilizer 20 forces the stern of the boat up and keeps the bow down. It gets the boat up on plane in less than half the normal time and eliminates the dangerous and burdensome cavitation and porpoising associated with many boats. Boats with the stabilizer of the invention can pull skiers up faster with less power and are more stable with improved control and ride. The stabilizer can result in a savings in fuel and an increae in top end speed. The stabilizer 20 functions by creating a higher water pressure on the lower surfaces of the lifting members which forces the stern of the boat up. The rear upward force, even at low speeds, keeps the bow down and causes the boat to plane in less time with less power. Unlike trim tabs, the stabilizer has a very low drag coefficient which brings out the hidden peak performance of every boat. Boats having the stabilizer 20 attached thereto handle, ride and track (even in turns) better. The stabilizer is easy to install, virtually indestructible and does not require any maintenance. The fact that it is adjustable in width allows it to be used in connection with boat motors having anywhere from one or two horsepower to three hundred horsepower and up. It can be used in connection with big or small runabouts, ski boats, bass boats, pontoon boats, inflatable boats and cruisers. The stabilizer allows boats to turn without cavitating and it allows for better stability and manoeuvrability at high speeds and reduces the annoying back-and-forth wander at low speeds. As in Figure 11, a torque equalizer 174 can be attached to the lower surfaces 37 of both lifting members 22 and 28. Using the openings 64 as guides, holes are drilled through the lifting members and bolts are inserted from the upper surfaces 35 of the lifting members through the openings 64 into corresponding openings 178 in the upper surfaces 180 of the torque equalizers. The torque equalizers can be positioned at various 10° angle increments (up to 40° right or left) to provide for maximum latitude and adjustment. Pegs 182 on the upper surfaces 180 of the equalizers are positioned in the appropriate openings 66 in the lower surfaces 37 of the lifting members. The torque equalizers function to neutralize tiresome and dangerous steering/propeller torque experienced by all boats. Boats having the stabilizer 20 and corresponding torque equalizers 174 attached thereto track straighter and are easier to control. It is the positioning and shape of the stabilizer 20 that allows the torque equalizers 176 to function so well. The torque equalizers 174 can be made of the same material that forms the stabilizer 20.

Claims: A boat stabilizer (20) for attachment to the lower drive unit (164) of a boat motor (150), said stabilizer comprising a first lifting member (22) having a first interior side wall (23) for positioning adjacent to a first side (170) of said drive unit (164) and a first arm portion (26) for extension around said drive unit; and a second lifting member (28) having a second interior side wall (30) for positioning adjacent to a second side (172) of said drive unit (164) and a second arm portion (32) for extension around said drive unit toward said first arm portion (26), said second interior side wall (30) being spaced from and opposing said first interior side wall (23) and said first and second arm portions (26,32) being attached together and selectively movable toward each other for decreasing the distance between said first interior side wall and said second interior side wall. A boat stabilizer according to claim 1, characterised in that said first and second arm portions (26,32) are selectively slidably positioned one above the other in overlapping relation. A boat stabilizer according to claim 2, characterised in that said first lifting member (22) includes a first shoulder (92) facing said second lifting member (28), in that said second lifting member (28) includes a second shoulder (96) facing said first lifting member (22), in that said first arm portion (26) includes an upper surface (70), a lower surface (72) and a first interior wall (78), said first interior wall facing said second shoulder and in that said second arm portion (32) includes an upper surface (80), a lower surface (82) and a second interior wall (88), said second interior wall facing said first shoulder. A boat stabilizer according to claim 3, characterised in that said first and second arm portions (22,26) include upper surfaces (70,80) and lower surfaces (72,82), the lower surface (72) of the first arm portion having a first recess (90) forming said first shoulder (92), the upper surface (80) of the second arm portion having a second recess (94) forming said second shoulder (96). A boat stabilizer according to claim 3 or 4, characterised in that at least one first spacer bar (98) is removably attached to said first arm portion and is positioned between said first interior wall (78) and said second shoulder (96), said at least one first spacer bar having an exterior side (110) abutting said first interior wall (78) and an interior side (112) abutting said second shoulder (96) and in that at least one second spacer bar (100) is removably attached to said second arm portion and is positioned between said second interior wall (88) and said first shoulder (92), said at least one second spacer bar having an exterior side (110) abutting said second interior wall (88) and an interior side (112) abutting said first shoulder (92). A boat stabilizer according to claim 5, characterised in that there are a plurality of first spacer bars (98) removably attached to said first arm portion and removably attached together side by side between said first interior wall and said second shoulder, the first spacer bar closest to said first interior wall having an exterior side abutting said first interior wall and the first spacer bar closest to said second shoulder having an interior side abutting said second shoulder and in that there are a plurality of second spacer bars (100) removably attached to said second arm portion and removably attached together side by side between said second interior wall and said first shoulder, the second spacer bar closest to said second interior wall having an exterior side abutting said second interior wall and the second spacer bar closest to said first shoulder having an interior side abutting said first shoulder. A boat stabilizer according to any one of claims 1 to 4, characterised in that a plurality of first spacer bars (98) are integrally formed with said first arm portion (26), in that a plurality of second spacer bars (100) are integrally formed with said second arm portion (32) and in that a selected number of said first and second spacer bars can be removed from said first and second arm portions. A boat stabilizer according to any preceding claim, characterised in that said first arm portion (26) includes at least one aperture (126) extending between the upper and lower surfaces thereof, in that said second arm portion (32) includes at least one longitudinal slot (128) extending between the upper and lower surfaces thereof, the longitudinal axis of said slot extending toward said first lifting member and in that a bolt (135) extends through each aperture (126) and said longitudinal slot (128) and in that a nut (140) is threaded onto each bolt to attach said first and second arm portions together.

Inventors: TEMPLEMAN ARTHUR R, TEMPLEMAN, ARTHUR R.
Applicants: MARINE DYNAMICS INC, MARINE DYNAMICS INC.
Application year: 1991
Main classification: B63H21
IPC codes: B63H25, B63B39, B63H20, F02B61