Patent Publication Number: US-9422036-B2

Title: Towable stream gauge platform having asymmetrical elastic harness

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/922,733 filed Dec. 31, 2013, which is incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     This invention relates to towable stream gauge platforms and in particular to a towable stream gauge platform having an asymmetrical elastic harness which causes a submerged hydroboard to pursue an upward twisting path toward the surface. 
     2. Discussion of the Prior Art 
     Floating towable stream gauge platforms are used to survey river courses and to gauge river and stream discharge rates using Doppler sonar measuring instruments. For purposes of brevity, and without being limiting, this disclosure will refer to towable stream gauge platforms as “hydroboards” or “boards” as they are commonly referred to in the art. 
     Hydroboards are modified forms of recreational boogie boards adapted to carry surveying equipment for measuring the contours or discharge rates of a body of running water. An aperture is provided centrally in the board in which a surveying instrument capable of measuring depth and velocity can be secured as with a band clamp. A hydroboard is usually towed using a flexible harness which is designed to accommodate the impact on the board of waves and currents. 
     A hydroboard will map the contours of a waterway by pulling it along the water&#39;s course. Alternatively, a hydroboard can be used to gauge discharge rates of a flowing body of water by retaining it from a stationary structure spanning the waterway being measured, such as a bridge. The hydroboard can be caused to traverse the waterway by crossing the spanning structure from one bank of the waterway to the other, during which the surveying equipment supported on the hydroboard measures water velocity at multiple depths. The sum of the measurements made as the equipment traverses the waterway gives a measure of the total flow. 
     A recurrent problem encountered when using hydroboards as described above is that the nose of the hydroboard may dip under the surface of the water in which case the hydroboard can rapidly submerge. Since the hydroboard is generally deployed at the end of a tow rope retained from in front of and above the board, the harness or tow line may snap resulting in not merely loss of the hydroboard but the expensive surveying equipment deployed on it. 
     Prior art hydroboards have typically been constructed using rigid polystyrene (or rigid polyethylene for boats). Thus, when the nose of a prior art hydroboard dips underwater, the board acts as an inflexible underwater sail causing the board to submerge rapidly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a hydroboard having an asymmetric elastic harness according to the invention; 
         FIG. 2  is a plan view thereof; 
         FIG. 3  is a bottom plan view thereof; 
         FIG. 4  is a sectional view of thereof taken along lines  4 - 4  of  FIG. 3 ; 
         FIG. 5A  is a side elevation view thereof; 
         FIGS. 5B-5D  are side elevation views thereof showing the rudder in different deployment configurations; 
         FIG. 6A  is a plan view of the front portion of the hydroboard showing the asymmetrical harness with the shock cord in a retracted position; 
         FIG. 6B  is a plan view of the front portion of the hydroboard showing the shock cord of the asymmetrical harness stretched out; 
         FIG. 7  is a close up perspective view showing a safety line collapsed when the shock cord is in a retracted position; 
         FIG. 8  is a close up perspective view showing the safety line stretched nearly to its full length when the shock cord is pulled forward under tension; 
         FIGS. 9A-9D  are side elevation views of the hydroboard shown submerged in a body of water and resurfacing; and 
         FIGS. 10A-10D  are front elevation views corresponding to  FIGS. 9A-9D  showing the hydroboard submerged and resurfacing. 
     
    
    
     DESCRIPTION OF THE ILLUSTRATED EMBODIMENT 
     Applicant&#39;s invention is a hydroboard having an asymmetrical elastic harness that seeks the surface when the board submerges. The asymmetrical harness causes a submerged hydroboard to pursue an upward helical path toward the surface. In addition, the hydroboard is sufficiently pliable that the board flexes into a helical shape better to follow the twisting path urged by the harness. 
     A hydroboard having an asymmetrical elastic harness according to the invention is referred to generally at numeral  10  in  FIG. 1 . With reference to  FIGS. 1-3 , the hydroboard  10  comprises a buoyant formed platform  12 . As seen in  FIG. 3 , a skin  14  is formed on the underside of the platform  12 . In one embodiment the skin  14  is formed from a closed cell backing  16  on which is mounted an HDPE coating  18  that provides a low friction protective working surface. Mount  20  is centrally located for securing a programmable control module (not shown), and a band clamp  22  is disposed in a central aperture  24  for securing surveying equipment (also not shown). Rudders  26 , secured by rudder rails  28 , steer the board straight. Handles  30  are provided midsection. Flexible, non-elastic long lines  32  are secured between front and rear pad eyes  34 ,  36  embedded in the top surface  38  of the board. It will be understood that, while long lines  32  are flexible in the nature of a cord or rope, they are not elastic in the sense that they do not stretch measurably lengthwise. 
     An asymmetric harness  40  is now described in reference to  FIGS. 6A and 6B . It is seen that front retaining rings  42 L,  42 R are attached to front pad eyes  34  by short flexible ties  46 . Similarly, rear retaining rings  44 L,  44 R are attached to rear pad eyes  36  by ties  46 . Like long lines  32 , ties  46  are flexible, but not elastic and do not stretch lengthwise. Each of the retaining rings  42 ,  44  thus is freely movable about one of the pad eyes  34 ,  36  allowing it to rapidly shift position in response to forces imparted on it by shock cord  48  discussed below. 
     Shock cord  48  is a single length of elastic cord that stretches under tension. Shock cord  48  includes a lead end  50  and a fixed end  52 . A first length  54  of shock cord  48  passes from lead end  50  through left front retaining ring  42 L, left rear retaining ring  44 L, right rear retaining ring  44 R and right front retaining ring  42 R thereby forming a U-shaped configuration. A second length  56  of shock cord  48 , joined to the first length  54  at loop  58 , passes from loop  58  through right front retaining ring  42 R, right rear retaining ring  44 R and left rear retaining ring  44 L thereby forming an L-shaped configuration. A variable terminal length  60  of shock cord  48  extends from the left rear retaining ring  44 L to the fixed end  52  by a quick link  61 . The fixed end  52  is attached to an adjustable retention mechanism such as Prusik knot  62 . A Prusik knot is a type of friction hitch which can be used for sliding attachment to a rope or cord. Tension applied to the Prusik knot in a direction general parallel with the rope to which the Prusik knot is attached causes the rope to twist and the knot to seize the rope. Relaxing the tension releases the knot allowing it to be slid along the rope to a selected location. In the illustrated embodiment, it is seen that the fixed end  52  of the shock cord  48  can be attached to the long line  32  at any selected location. Attachment of fixed end  52  to the long line  32  closer to one of the front pad eyes  34  stretches the shock cord  48  thereby increasing the resistance to it being further stretched. Conversely, attachment of the fixed end  50  to the long line  32  closer to one of the rear pad eyes  36  relaxes the shock cord and reduces its resistance to further stretching. Thus, the resistance of the shock cord  48  can be adjusted by moving the Prusik knot  62  to which the fixed end  52  of the shock cord  48  is attached to a selected location along the long line  32 . While in the illustrated embodiment, first length  54  is shown passing from lead end  50  through the left retaining rings  42 L,  44 L and then through right retaining rings  42 R,  44 R, second length  56  passing from loop  58  first through right retaining rings  42 R,  44 R and then left rear retaining ring  44 L, and terminal end  60  attached to a long line  32  on the left side of the platform, it will be understood that this arrangement could be reversed from left side to right side to configure the elements of the harness in the mirror image of that shown in the illustrations with equal effect. Long lines  32  are provided on each side of the platform  12  to provide that option. 
     In the illustrated embodiment, the lead end  50  of shock cord  48  extends forward of left front retaining ring  42 L and is attached to one end  64  of a pull cord  66  with a quick link  68 . The loop  58  of the shock cord  48  is attached to the other end  70  of the pull cord  66  with a second quick link  68 . Quick links  68  are too large to pass through front retaining rings  42 L,  42 R, and therefore prevent either the loop  58  or lead end  50  of the shock cord  48  from retracting rearwardly through front retaining rings  42 L,  42 R. 
     A tow rope  72  is attached to the middle of the pull cord  66  such that pulling on the pull cord  66  with the tow rope  72  applies equal tension to the lead end  50  and to the loop  58  of the shock cord  48 . The shock cord  48  thus can be made to stretch and relax in response to pulling and releasing the tow rope  72  as seen in  FIGS. 6A and 6B . Application of tension to the lead end  50  and the loop  58  of the shock cord  48  causes the shock cord to extend from the lead end  50  along the entire length of the shock cord  58  to the fixed end  52  as indicated by the arrows in  FIG. 6A . The resistance to tension exerted on the loop  58  is greater than the resistance encountered from exertion of tension on the lead end  50  because pulling on the loop  58  stretches both the first and second lengths  54 ,  56  of the shock cord whereas pulling on the lead end  50  stretches mostly the first length  54  of the shock cord  48 . This asymmetric resistance to pulling the harness  40  impels the loop side  74  of the board, where the loop  58  is located, forward and upward with greater force than the lead end side  76 , on which the lead end  50  is located. 
     When a deployed hydroboard is riding on the surface of the water, the drag on the platform caused by the water is generally lower than the minimum tension required to pull either the loop  58  or lead end  50  forward off of the front retaining rings  42 L,  42 R. However, if the bow  78  of a deployed hydroboard becomes submerged as seen in  FIGS. 9A, 9B, 10A and 10B , the force of the water on the bow  78 , indicated by arrows A, will rapidly drive the platform further under water, as indicated by arrows B, and increase tension on the pull cord  66 , indicated by arrows C. As seen in  FIGS. 9C, 9D, 100 and 10D , the greater resistance on the loop side  74  of the platform  12 , as indicated by arrows D, relative to the smaller resistance lead end side  76 , as indicated by arrows E, increases tension on the end of the pull cord  66  on the loop side forcing that side upward and forward, as indicated by arrows F, relative to the lead end side  76 , forcing the platform to the water&#39;s surface S. In one aspect of the invention, the platform  12  is constructed using flexible expanded polyethylene foam beads such that the asymmetric forces experienced when the platform becomes submerged cause it to twist into a helical shape as seen in  FIG. 10C . The combined application of asymmetric pulling forces and flexure of the board causes it to pursue an upward helical path toward the surface of the water. Once tension is removed, as when the board surfaces, the shock cord  48  retracts (as seen in  FIG. 6A ) and tension is equalized between the two opposite sides. 
     With reference now to  FIGS. 6A, 6B, 7 and 8 , non-elastic safety lines  80  are connected between each front pad eye  34  and the ends  64 ,  70  of the pull cord  66  to limit the amount that the shock cord  48  can be stretched. In  FIG. 7  it is seen that the shock cord  48  is retracted and the safety line  80  is gathered loosely between the pad eye  34  and the quick link  68  interconnecting the lead end of shock cord  48  and pull cord  66 . In  FIG. 8 , it is seen that when fully extended the safety line  80  will prevent excessive stretching of the shock cord  48 . In the embodiment shown in  FIG. 7 , safety line  80  is connected to pad eye  34  by a quick link  68 . It should be understood that safety line  80  may be connected directly to pad eye  34 , long line  32 , retaining link  42 L or other gear in the immediate vicinity of pad eye  34 , such as tie  46  as shown in  FIGS. 6A and 6B . 
     With reference to  FIGS. 4 and 5A-5D , rudders  26  are provided on each side of the platform  12 . A rudder rail  28  is spaced laterally from and attached to the stern end of each side of the platform by forward and rear fasteners  82 F,  82 R. Each of the rudders  26  is slidably captured between one of the rudder rails  28  and the side of the platform. The forward end  84  of each rudder  26  is slidably affixed to the rudder rail  28  with a vertically-disposed retaining bar  86 . The rudder rail  28  is slidably captured in the control slot  88  formed between the transversely extending retaining bar  86  and the rudder  26 . An arced locking notch  90  is formed in the back end  92  of the rudder and similar forward sweeping arced position selection notches  94  are formed in the top side of each rudder  26 . The rudder  26  is thus movable between a stowed configuration  96  as shown in  FIG. 5A  and deployed configurations  98  as shown in  FIGS. 5B-5D . In the stowed configuration  96 , the forward end  84  of the rudder  26  is slid to a forward position along the rudder rail  28  and the rear rudder fastener  82 R is captured in locking notch  90 . The rudders  26  can be moved to selected deployed configurations  98  by moving the forward end  84  of the rudder  26  rearward along the rudder rail  28 , and maneuvering the rear rudder fastener  82 R into a selected one of the position selection notches  94  as seen. It can be seen that retaining bar  86  is mounted on rudder  26  at a slight angle from perpendicular to the longitudinal axis of the rudder in order to prevent the rudder from rotating to too great an angle relative to the platform  12  upon deployment. Rearward forces caused by flowing water impacting the rudders  26  will tend to push the back ends  92  of the deployed rudders backward and upward thereby urging the position selection notches  94  to remain around the ferrule  100  and securing the rudders in the selected position. It can be seen that each rudder has an overall planar geometry, and since the sides of the platform present flat surfaces  102  parallel with the longitudinal dimension of the board, any movement of the rudders  26  between the sides of the board and the rudder rails  28  will maintain the rudders  26  in parallel alignment with the sides of the platform  12  and help steer the hydroboard on a straight course. 
     An improved hydroboard having an asymmetrical elastic harness has the unique advantage over prior art hydroboards that it will tend to seek the surface upon becoming submerged in a moving body of water, thus reducing risk of loss of the hydroboard and the surveying equipment installed on the hydroboard. 
     There have thus been described and illustrated certain embodiments of a towable stream gauge platform having an asymmetrical elastic harness according to the invention. Although the present invention has been described and illustrated in detail, it should be clearly understood that the disclosure is illustrative only and is not to be taken as limiting, the spirit and scope of the invention being limited only by the terms of the appended claims and their legal equivalents.