Abstract:
An oar system is provided that keeps the blade of the oar at approximately 90 degrees to the centerline or keel of a boat throughout the normal power producing stroke. This reduces the lost effort that is expended when operating oars whose blades are fixed to the oar shaft. A series of cables and pivotal attachment points holds the oar blade at the approximate 90-degree angle to the boat keel.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention pertains to an articulated oar system of the type which holds the oar blade at the optimum angle to produce the most efficient power stroke. 
         [0003]    2. Description of the Prior Art 
         [0004]    There have been many attempts over the past several thousand years to maximize the efficiency of moving a boat over the water. The Triremes of ancient times obtained very good speeds by using a short oar stroke, three rows of rowers atop one another and then with the help of sails, they obtained the speed necessary to ram another boat and crack its hull. This speed has been calculated to be 10 knots. 
         [0005]    In more modern times, there have been several patents issued that claimed to improve the efficiency of rowing. U.S. Pat. No. 4,383,830 used a variable oarlock position to keep the oar blade in nearly perpendicular position to the keel of the boat. The cost of the installation proved too expensive and was banned from competition. U.S. Pat. No. 4,383,830 shows an arrangement for using the feet to adjust the position of the oar lock to improve efficiency by keeping the oar blade more perpendicular to the keel of the boat. U.S. Pat. No. 3,677,216 shows a spring-loaded blade, which can be dragged through the water on the return stroke without removing it from the water. 
         [0006]    In neither case is there a suggestion that the oar blade should be kept at right angles to the keel. EP 1 391 379 A1 shows a means of rowing a boat in the direction of the rowers&#39; view and allows the oars to be nearly perpendicular to the hull, but that does not seem to be the primary purpose of the arrangement and it requires special sliding oarlock arrangements. 
         [0007]    Many oars and oarlock arrangements have been proposed for boats over the years. None have described an arrangement similar to that herein described. In racing shells in particular, it is important to conserve the energy used in moving the boat through the water. Each rower has a finite amount of energy that he or she may expend in a given period of time. 
         [0008]    It is therefore important that the effort put forth is used in the most efficient manner. Rowers are generally able to put forth the maximum effort during the time period when the oar is between −55 degrees and −35 degrees from a perpendicular to the keel extending through the oarlock. 
         [0009]    The arrangement herein described allows the oar blade to slip more easily through the water during this time period. The reason that this is accomplished is that the oar blade is held perpendicular to the keel of the boat and in moving away from and along the boat, the majority of water that is displaced by the oar blade is along the line of the keel of the boat and a minimum is displaced away from the boat. With a standard oar, the water that is displaced during this −55 to −35 degree angular sweep of the oar is away from the boat and only a fraction of the energy is converted into propelling the boat. 
         [0010]    A further object of this invention is to allow the rower to easily remove the oar from the water at the end of a stroke because he/she has the oar blade too deep in the water. This is accomplished by having the oar blade attached in such a manner that it can easily swing towards a parallel position with the current and thus is more easily extracted from the water. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0011]    The nature and characteristics of the invention will be more easily understood from the following description taken in connection with the accompanying drawings forming a part hereof in which: 
           [0012]      FIG. 1  is a front elevation view of the articulated oar system of the invention showing the position of the oar and the control arms and/or cables during the return stroke. 
           [0013]      FIG. 2  shows the plan view of the oar and other parts. 
           [0014]      FIG. 3  shows the blade portion of the oar assembly and the return spring. 
           [0015]      FIG. 4  is a view similar to  FIG. 3  except with a 90-degree rotation. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0016]    When referring to the preferred embodiment, certain terminology will be utilized for the sake of clarity. Use of such terminology is intended to encompass not only the described embodiment, but also technical equivalents, which operate and function in substantially the same way to bring about the same result. 
         [0017]    Referring now to  FIGS. 1-4  and more particularly to  FIG. 2 , it shows the oar system arrangement in plan view on a boat with the oar shaft  1  pivoting about a point  7  in the center of the oar shaft  1  and using an oarlock. This is the type of oarlock that allows the oar shaft  1  to rotate in a manner so that the center of the oar shaft  1  is over the point of rotation. On a parallel line with the center line of the hull of the boat  20  is an attachment point  10  for a cable or solid rod  2  to be attached, allowing the cable or rod  2  to rotate about the point  10  and which is also lifted with the oar shaft  1 . Such attachments are commercially available. The other end of this cable or solid rod  2  is pivotally attached at a point  8  to rods(s)  3  that can also be pivotally attached to the end of the oar shaft  1 , that is furthest away from the centerline of the boat  20 . Also attached at this point  8  is either a string or cable  5  that is attached to the outer end of an oar blade  4 . (There could also be multiple strings or cables for  2  and/or  5 .) The inner end of the oar blade  4  is pivotally attached to the end of the oar shaft  1 . As an alternate arrangement, the rod  3  can be rigidly attached to the oar blade  4  eliminating the need for the cable(s)  5 . A spring  12  supplies a force to the blade  4  so as to keep the cable  5  taught at the end of the return stroke. The action of spring  12  can be adjusted by the way that it is manufactured to supply force during all of the stroke or just at the end of the return stroke. 
         [0018]    One arrangement allows the cables or rods  2  to be in tension during the entire power portion of the stroke. At the end of this stroke, the oar shaft  1  and blade  4  are as shown in the  FIG. 2 . At this point the oar is normally lifted from the water to return to the starting point  11 . The dashed lines indicate the relative position of the oar shaft  1  and blade  4  and the cable  5  at 0 degrees and −55 degrees from a perpendicular to the keel (not shown) of the boat  20 . Should the rower fail to promptly lift the oar shaft  1  from the water at the end of the stroke, the blade  4  will pivot about the point  6  and therefore prevent the rower from being struck by the handle end of the oar shaft  1  as would occur with a fixed blade submerged in the moving water. This most often happens when the rower has set his oar blade too deeply in the water. 
         [0019]    By use of the above-described system, the blade  4  is properly kept at approximately 90 degrees to the centerline of the keel of the boat  20  during the power-producing phase of the stroke producing maximum efficiency. Instead of the blade  4  pushing water away from the boat  20  at the beginning of the stroke, it slides away from the boat  20  with little resistance and all of the power that the rower is able to put to the oar shaft  1  results in thrust to the oarlock and the boat  20 . This action is determined by the relative distances of the pivot point  10  to the pivot point  7  and the pivot point  8  to the pivot point  6 . These distances normally would be equal, but there may be advantages to making them slightly unequal so that instead of a perfect parallelogram, the blade  4  is more open or closed at the beginning and end of the stroke. This will result in a different action, which will either push the oar shaft  1  toward the oarlock or pull it out away from the oarlock. This will affect the feel of the oar in the hands of the rower. Changing the length of rod or cable  2  relative to the length of the oar shaft  1 , past the oarlock, results in a similar action. 
         [0020]    If the oarlock is of the type most commonly used today, that is an oar shaft that rotates about a fixed post, the same desired action can be obtained by finding that point in space that allows the cable or other system mentioned above the control the position of the oar blade  4  in the manner desired. The attachment point for the cable or rod  2  nearest to the blade  4  can be definitively located. The points in space for the point  8  when the blade is perpendicular to the keel can be calculated using simple trigonometry and the appropriate attachment point for the cable or rod  2  near the oar lock can be determined using well known appropriate formulae. 
         [0021]      FIG. 2  shows a plan view of the arrangement, wherein  1  is the oar shaft,  2  is the parallel cable or rod,  3  is a spacer piece to which the cable or rod is attached,  4  is the blade of the oar,  5  is another rod or cable that attaches the blade to a spacer piece  3 ,  6  is a hinge or flexible joint,  7  is the position of the oar lock or pivot pin,  8  is the attachment point of the cables or rods  5  that connect the blade  4  to the outrigger for the oar lock,  9  is the tip of the blade and  11  is the position of the flexible joint or hinge at the most rearward position of the oars motion. (Approximately −55 degrees from a vertical to the keel.) 
         [0022]      FIGS. 3 and 4  show the essential parts of the oar assembly. The spacer piece  3  is shown attached to the oar blade, but it also may be attached to pin  6  of the hinge by means of a fork arrangement. The length of the part  3  is a compromise between the various stresses and ease of operation. The shorter part  3  is, the higher the stresses in the cable and part  3 , the longer that it is, the lower the stresses, but then the assembly becomes more difficult to handle. 
         [0023]    It is easily imagined that bar  3  if attached to the blade  4  could be extended on the other wide of the blade  4  and another cable attached to it. In such an arrangement the oar blade  4  is always perpendicular to the keel of the boat, but now can be used to propel and to reverse the direction of the boat. This is especially important when the boat is used for pleasure and backpressure on the blade  4  is important to maneuver the boat. 
         [0024]    Another arrangement would be to have a rod in compression (not shown) held along the oar shaft in such a manner as to resist the movement of the blade and yet release it at the end of the stroke. 
         [0025]    It will thus be seen that structure has been provided with which the objects of the invention are achieved.