Patent Publication Number: US-7905193-B2

Title: Trim tabs

Description:
BACKGROUND 
     The present invention relates to trim tabs mounted to the transom or underside the hull of a boat. In particular, the trim tabs are molded composite material elements shaped to provide light weight and enhanced lift characteristics. 
     Trim tabs typically have been in the form of flat stainless steel plates that are pivotally attached to the transom or hull of the boat. Trim tabs of different sizes are used, depending upon the size of the boat. 
     In one typical configuration, at least one trim tab is pivotally mounted on the left or port side and at least one trim tab is pivotally mounted on the right or starboard side of the transom. In other cases, a single center mounted trim tab is used. The trim tabs are raised and lowered by a drive mechanism. Earlier trim tab systems used mechanical jack screws to raise and lower the trim tabs. Currently available systems use either hydraulic or electromechnical actuators to raise and lower the trim tabs. 
     Trim tabs are used to provide additional boat control for reasons such as uneven load distribution in the boat, controlling bow attitude in various water conditions, and trimming the boat out of the water faster in conditions such as shallow water operation. Depending on the type of boat and the number and position of occupants, the attitude (or side-to-side angle along the keel) can tilt left or right. Trim tabs can improve boat performance by leveling the boat. Trim tabs can also be used to increase top end speed, to improve “hole-shot”, and to provide a drier ride by keeping the nose down and the boat up on plane. 
     SUMMARY 
     A trim tab features a tapered body that increases in thickness from a leading end to a trailing end and has a bottom surface with convex and concave sections. On the lateral edges of the trim tab, down-turned flaps extend the length of the trim tab. The contoured bottom surface and down-turned side flaps provide an increased bottom surface area that can provide an enhancement in lift characteristics for a given trim tab size. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective view of a stern of a boat with trim tabs mounted to the lower transom. 
         FIG. 1B  is a perspective view of a boat with trim tabs mounted to the lower transom and electric trolling motors mounted on the trim tabs. 
         FIG. 2A  is an exploded view of a trim tab assembly. 
         FIG. 2B  is an exploded view of a trolling motor assembly for mounting on the trim tab assembly. 
         FIG. 2C-2E  are sectional, top perspective, and front perspective views, respectively, of the trim tab and trolling motor of  FIG. 2B . 
         FIGS. 3A and 3B  show top and bottom perspective views, respectively of first embodiment of a molded trim tab with contoured bottom surface. 
         FIGS. 3C-3G  show top, bottom, rear, and sectional views of the trim tab of  FIGS. 3A and 3B . 
         FIGS. 4A and 4B  show top and bottom perspective views of a second embodiment of a trim tab having a similar chord length and greater span than the trim tabs of  FIGS. 3A and 3B . 
         FIGS. 5A and 5B  show top and bottom perspective views of a third embodiment of a trim tab having a similar chord length to trim tabs of  FIGS. 3A and 3B  and  4 A and  4 B, and having greater span. 
         FIGS. 6A and 6B  show top and bottom perspective views of a fourth embodiment of a trim tab having a span similar to the trim tabs of  FIGS. 3A and 3B  and having a greater chord length. 
         FIGS. 7A and 7B  show top and bottom perspective views of a fifth embodiment of a trim tab having a chord length similar to the trim tabs of  FIGS. 6A and 6B  and having a span similar to the trim tabs of  FIGS. 4A and 4B . 
         FIGS. 8A and 8B  show top and bottom perspective views of a sixth embodiment of a trim tab having chord length similar to the trim tabs of  FIGS. 6A and 6B  and  7 A and  7 B, and having a span similar to the trim tabs of  FIGS. 5A and 5B . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1A  shows the stem of boat  10  that includes a trim tab system. Mounted on transom  12  are outboard motor  14 , left trim tab assembly  16 L, and right trim tab assembly  16 R. 
     Left trim tab assembly  16 L includes left trim tab  18 L, linear actuator  20 L (which includes actuator housing  22 L, actuator rod  24 L, and electrical cable  26 L), hinge  28 L, upper mounting bracket  30 L, and lower mount  32 L. Similarly, right trim tab assembly  16 R includes trim tab  18 R, linear actuator  20 R (which includes actuator body  22 R, actuator rod  24 R, and cable  26 R), hinge  28 R, upper mounting bracket  30 R, and lower mount  32 R. 
     Hinges  28 L and  28 R pivotally connect trim tabs  18 L and  18 R to transom  12 . Linear actuators  20 L and  20 R are connected between upper brackets  30 L and  30 R on transom  12  and lower mounts  32 L and  32 R on trim tabs  18 L and  18 R, respectively. Actuators  20 L and  20 R are, in one embodiment, electromechanical actuators that receive electrical power and provide feedback signals through cables  26 L and  26 R. 
     Trim tabs  18 L and  18 R operate in a trim range from about 0° (horizontal) to about 20° below horizontal. Trim tabs  18 L and  18 R can be individually adjusted within the trim range, or can be adjusted together by equal amounts. 
       FIG. 1B  shows the stem of boat  10  having a trim tab/trolling motor system that includes left trim tab/trolling motor assembly  40 L and right trim tab/trolling motor assembly  40 R. The embodiment shown in  FIG. 1B , trim tab/trolling motor assemblies  40 L and  40 R are generally similar to trim tab assemblies  16 L and  16 R shown in  FIG. 1A , and similar reference numerals are used to identify similar elements. 
     Assemblies  40 L and  40 R also include trolling motors  42 L and  42 R that are supported by trim tabs  18 L and  18 R, respectively. Lower mounts  32 L and  32 R, which connect to actuator rods  24 L and  24 R, are an integrated portion of trolling motors  42 L and  42 R, respectively. Thus mounts  32 L and  32 R in  FIG. 1B  mount trolling motors  42 L and  42 R to trim tabs  18 L and  18 R, respectively, as well as providing a connection to actuator rods  24 L and  24 R. 
     The trim tab/trolling motor system shown in  FIG. 1B  provides both a trimming function, and a trolling motor function. Trim tabs  18 L and  18 R operate in a trim range from about 0° to about 20° below horizontal. As in the embodiment shown in  FIG. 1A , trim tabs  18 L and  18 R can be individually adjusted within the trim range, or can be adjusted together by equal amounts. 
     When trolling is desired, trim tabs  18 L and  18 R are moved to a troll range, which is below the trim range. The troll range may be, for example, between about 20° to about 30° below horizontal. Trim tabs  18 L and  18 R are moved together to the same angle within the troll range, so that both trolling motors  42 L and  42 R are at the same elevation. During trolling, trolling motors  42 L and  42 R are electrically driven so that their propellers  44 L and  44 R rotate. The relative speed and direction of rotation of propellers  44 L and  44 R can be controlled to achieve movement of boat  10  forward or in reverse and to achieve steering to the left or the right. 
       FIG. 2A  shows an exploded view of trim tab assembly  16 L. Trim tab assemblies  1 L and  16 R are identical, and therefore  FIG. 2A  is representative of both assemblies  16 L and  16 R. 
     Hinge  28 L is attached to trim tab  18 L by bolts  50  and nuts  52 . Mounting screws  54  are used to attach hinge  28 L to transom  22  of boat  10 . 
     Upper mount  30 L is attached to transom  12  by mounting screws  56 . Fitting  58  is inserted into port  60  of mounting bracket  30 L to provide a passage for cable  26 L from actuator  20 L through transom  12  to the interior of boat  10 . O-rings  62  and  64  provide a seal around fitting  58 . 
     Upper mounting bracket  30 L includes three sets of actuator mounting holes  66 . Mounting pin  68  extends through one of the sets of mounting holes  66  and through passage  70  in the upper end of actuator housing  22 L to provide a pivotal connection between mounting bracket  30 L and linear actuator  20 L. C-clips  72  are attached to opposite ends of pin  68  to hold pin  68  in position. 
     Lower mount  32 L is connected to trim tab  18 L by bolts  74  and nuts  76 . Lower mount  32 L has a pair of flanges  78  with four sets of mounting holes  80 . Mounting pin  82  extends through one of the pairs of holes  80  and through passage  83  in the lower end of actuator rod  24 L. C-clips  84  hold mounting pin  82  in position. By selection of different combinations of mounting holes  66  and  80 , linear actuators  20 L of different lengths and variations in transom configuration can be accommodated. 
       FIGS. 2B-2E  show actuator  20 L′ and trolling motor  42 L of left trim tab/trolling motor assembly  40 L, which is identical to right trim tab/trolling motor assembly  40 R. Assembly  40 L is generally similar to assembly  16 L shown in  FIG. 2A , except for the addition of trolling motor  42 L and the use of longer actuator  20 L′. Lower mount  32 L′ is an integrated portion of the housing of trolling motor  42 L, but is shaped to fit in the same location as lower mount  32 L of  FIG. 2A . Bolts  74 ′ and nuts  76  attach lower mount  32 L′ to trim tab  18 L. 
     Actuator rod  24 L′ is pivotally connected to lower mount  32 L′ by pin  82 . In the embodiment shown in  FIG. 2A , only one set of mounting holes are provided for pin  82  in lower mount  32 L′. Snap rings  84 ′ hold pin  82  in place. Also shown in  FIG. 2B  are nut  90 , washer  92 , and pin  94 , which are used to hold propeller  44 L in place on the drive shaft of trolling motor  42 L. 
     Motor power cable  96  exits lower mount  32 L′ through port  98 . As shown in  FIGS. 2D and 2E , port  98  is located at the forward end of lower mount  32 L′. Motor power cable  96  extends through a fitting (not shown) in transom  12  into the interior of boat  10 . 
     Boats vary in weight, length, speed, and performance, making the responsiveness of each boat unique. Therefore, the selection of size for trim tabs  18 L and  18 R is important in order to provide the performance and responsiveness. In the descriptions that follow, trim tabs of different sizes will be discussed. Two dimensions of interest are the chord length from the leading edge to the trailing edge of the trim tab, and the span, which is the distance from the inboard edge of the trim tab (nearest the center line of boat  10 ) and the outboard edge (furthest from the boat center line). 
     The embodiments shown in  FIGS. 3A and 3B ,  4 A and  4 B,  5 A and  5 B,  6 A and  6 B,  7 A and  7 B, and  8 A and  8 B show examples of trim tabs having two different chord lengths and three different spans. The trim tab shown in  FIGS. 4A and 4B  has the smallest chord length and span, and the trim tab in  FIGS. 8A and 8B  has the largest chord length and span. 
       FIGS. 3A and 3B  are top and bottom perspective views, respectively, of trim tab  18 A, which is the smallest sized trim tab group of six different trim tab sizes shown in  FIGS. 3A-8B .  FIGS. 3C ,  3 D, and  3 E are top, bottom, and rear views, and  FIGS. 3F and 3G  are sectional views of trim tab  18 A.  FIGS. 3A-3G  will be discussed collectively in describing the structure of trim tab  18 A. Trim tab  18 A may be used on either the left side or right side of boat  10 , and therefore may act as left trim tab  18 L or right trim tab  18 R in  FIGS. 1A  or  1 B. 
     In one embodiment, trim tab  18 A is an injection molded one piece trim tab formed of a polymeric material or a composite material that includes a polymeric material and a filler. For example, the polymeric material may be Plasticomp PA6-GF  50  that is 50% filled with long glass nylon. Carbon black may also be added to the polymer or the composite material to provide a black color. In other embodiments, other polymeric materials (with or without fillers) can be used, consistent with the strength requirements of the trim tabs. In still other embodiments, trim tab  18 A may be manufactured using a cast metal process, and/or may include metal (e.g., aluminum or stainless steel) stumpings. 
     Trim tab  18 A includes leading end  100 , trailing end  102 , top surface  104 , bottom surface  106 , and side flaps  108  and  110 . Bottom surface  106 , shown in  FIG. 3B , includes convex central region  112  and concave side channels  114  and  116  positioned on opposite sides of convex central region  112 . Flaps  108  and  110  define the outer lateral limits of concave side channels  114  and  116 . Longitudinal ribs  118 ,  120 , and  122  are located on convex region  112 , and are generally positioned closer to leading end  100  than to trailing end  102 . In some cases, longitudinal ribs may not be necessary depending upon the performance requirements of the trim tabs. 
     On top surface  104 , hinge mounting platform  130  is located adjacent leading end  100 . Lower mount platform  132  is located adjacent trailing end  102 , and includes a pocket for receiving mount  32 L,  32 R,  32 L′, or  32 R′. Top surface  104  has a concave center section  133  that matches the general contour of convex region  112  on bottom surface  106 . 
     Hinge platform  130  includes a set of transverse ribs  134  and longitudinal ribs  136  that form a grid pattern. Mounting holes  138  extend through platform  130  to allow attachment of trim tab  18 A to hinge  28 L or  28 R. 
     Longitudinal ribs  140  and  142  extend rearwardly from hinge platform  130  to trailing end  102 . In addition, ribs  144 ,  146 , and  148  extend rearwardly from hinge platform  130  to mount platform  132 . Ribs  144 ,  146 , and  148  are located in the concave portion  133  of top surface  104 , with rib  146  being positioned along the center line of trim tab  18 A, and ribs  144  and  146  being positioned equal distances on opposite sides of central rib  146 . 
     Mount platform  132  includes parallel transverse ribs  150 , which extend between longitudinal ribs  140  and  142 . A trapezoidal section  152  of platform  132  is recessed to receive and locate lower mount  32 L,  32 R (or  32 L′,  32 R′). Mounting holes  154  in recessed region  152  provide passages for the holes used to attach the lower mount to mount platform  132  of trim tab  18 A. Recessed region  152  also includes a concave portion  155  that accommodates motor power cable  96  as it passes from motor  42 L,  42 R to port  98  at the front end of lower mount  34 L′,  34 R′. 
     Transverse ribs  134  and  150  on top surface  104  also provide stiffening of trim tab  18 A in the transverse or span direction. Longitudinal ribs  140 ,  142 ,  144 ,  146 , and  148  provide stiffening of trim tab  18 A in the longitudinal or chord direction. The use of molded ribs as part of trim tab  18 A achieves stiffening without adding unnecessary weight. As a result, the benefits of use of a polymeric or composite material (such as ability to form complex shapes to enhance lift, ability to use injection molding to reduce manufacturing costs, corrosion resistance, and light weight) can be achieved. In some cases, transverse ribs may not be necessary depending upon the performance requirements of the trim tabs. 
     The contour of lower surface  106  provides increased surface area, in comparison to a flat plate. As a result, greater lift is achieved with trim tab  18 A, than would be achieved with a flat plate trim tab having the same chord length and span. 
     Flaps  108  and  110  also assist in increasing lift by providing a lateral boundary to channels  114  and  116 . Flaps  108  and  110  prevent water passing through channels  114  and  116  from spreading laterally outward and off the sides of trim tab  18 A so that part of the lift effect is lost. 
     Convex region  112  has a minimum thickness at leading end  100  and has increased thickness or depth along the length until it reaches a maximum depth at trailing end  102 . This provides a transition from the hull of boat  10  to trim tab  18 A and channels  114  and  116  for water to flow without producing turbulence that could negate part of the lift effect of the trim tab. 
     Longitudinal ribs  118 ,  120 , and  122  are also tapered so that they are of greater thickness at their trailing end then at their leading ends. Ribs  118 ,  120 , and  122  provide additional strengthening to trim tab  18 A without disrupting flow past bottom surface  106 . 
     Flaps  108  and  110  extend generally downward and slightly outward. In one embodiment, the angle of flaps  108  and  110  with respect to the top plane defined by platforms  130  and  132  is about 70°. Flaps  108  and  110  are resilient and can deflect slightly outward during an operation, which can result in additional lift capability. 
     In one embodiment, trim tab  18 A shown in  FIGS. 3A-3G  has a nominal size of about 9 inches by 9 inches. In other words, the chord length is about 9 inches, and the span is about 9 inches. 
       FIGS. 4A and 4B  show trim tab  18 B, which has a similar chord length to trim tab  18 A, but a greater span. In one embodiment, trim tab  18 B is a 9×12 trim tab having a nominal chord length of about 9 inches and a nominal span of about 12 inches. 
     Trim tab  18 B is generally similar in structure to trim tab  18 A, except that it includes two additional ribs  160  and  162  located within concave region  133  and generally follow the converging contour of region  133  as it extends from leading end to trailing end. Rib  160  is located between rib  140  and rib  144 . Rib  162  is located between rib  142  and rib  148 . Ribs  160  and  162  provide additional stiffening, generally in the longitudinal direction. 
       FIGS. 5A and 5B  show top and bottom perspective views of trim tab  18 C. Trim tab  18 C has the same chord length as trim tab  18 A and  18 B, but has a larger span. In one embodiment, trim tab  18 C has a nominal chord length of about 9 inches and a nominal span of about 18 inches. 
     The structure of trim tab  18 C is generally similar to trim tab  18 B, except for a greater span. As a result, ribs  140 ,  142 ,  144 ,  146 ,  148 ,  160 , and  162  are spaced apart by larger distances. 
       FIGS. 6A and 6B  are top and bottom perspective views of trim tab  18 D, which has the same span as trim tab  18 A, but has a longer chord length. In one embodiment, trim tab  18 D has a nominal chord length of about 12 inches and a nominal span of about 9 inches. 
     Platform areas  130  and  132  of trim tab  18 D are similar to platform areas  130  and  132  of trim tab  18 A. Ribs  140 ,  142 ,  144 ,  146 , and  148  are longer in trim tab  18 D, to accommodate the longer chord length. Bottom ribs  118 ,  120 , and  122  are also longer in trim tab  18 D than trim tab  18 A. 
       FIGS. 7A and 7B  are top and bottom perspective views of trim tab  18 E has a span which is similar to trim tab  18 B, and a chord length similar to trim tab  18 D. The same rib structure is provided in trim tab  18 E as in trim tab  18 B, but the lengths of the longitudinal ribs are greater because of the longer chord length. In one embodiment, trim tab  18 E has a nominal chord length of about 12 inches and a nominal span of about 12 inches. 
       FIGS. 8A and 8B  show top and bottom perspective views of trim tab  18 F, which has the same span as trim tab  18 C and the same chord lengths as trim tabs  18 D and  18 E. The rib in trim tab  18 F is similar to that shown in trim tab  18 C. The lengths of the longitudinal ribs are greater to accommodate the greater chord length of trim tab  18 F. Trim tab  18 F may have a nominal chord length of about 12 inches and a nominal span length of about 18 inches. 
     As illustrated by trim tabs  18 A- 18 F, wide range of different trim tab sizes can be achieved using the same basic trim tab design. In each trim tab, the bottom surface has a contour that includes a central convex region and concave side channels located between the concave region and the side flaps. As a result, each of the trim tabs  18 A- 18 F provides enhanced lift characteristics, while offering a lightweight structure. In some cases, the use of longitudinal ribs on both top surface  104  and bottom surface  102 , and transverse ribs on top surface  104  can provide stiffening to ensure structural integrity without sacrificing the benefits of the trim tab structure. 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.