Waterski with improved torsional characteristics

Abstract

A water ski with improved torsional characteristics delimited on the upper side by the upper surface, on the bottom side by a concave surface and on the sides by curvilinear sidewalls. The ski has a tip at the front side and a tail on the rear side. On the central part of the ski, on the upper surface, a longitudinal groove is provided having a flat bottom surface connected with vertical longitudinal sides of the groove by rounded surfaces, wherein the groove decreases torsional and flexural strength, which depth and width reduce torsional and flexural stiffness of the central part of the ski. The width of the groove may be 30-80% of the width of the ski, and the depth of the groove may be 20-95% of the thickness of the ski.

1 - 5 . (canceled) 
     
     
         6 . A water ski with improved torsional characteristics, the water ski having a given thickness and a given width, comprising:
 an upper side having a curved upper surface;   a bottom side having a concave surface;   sides having curvilinear sidewalls configured to narrow a front end and a rear end of the water ski; wherein
 said water ski has a tip at the front end and a tail at the rear end, character-ized in that a central part of the water ski on the upper surface is provided with a longitudinal groove, the groove having a flat bottom surface connected with vertical longitudinal sides of the groove by rounded surfaces, wherein the groove decreases torsional and flexural strength of the central part of the water ski; and 
   wherein the groove has
 a width that is 30-80% of the width of the water ski; and 
 a depth that is 20-95% of the thickness of the water ski. 
   
     
     
         7 . The water ski according to claim  1 , having a given total length, wherein the groove is 20-50% of the total length of the water ski. 
     
     
         8 . The water ski according to  claim 7 , wherein the groove is 30-40% of the total length of the water ski. 
     
     
         9 . The water ski with improved torsional characteristics according to claim  1  or  2 , wherein the groove has a trapezoid cross-section. 
     
     
         10 . The water ski with improved torsional characteristics according to claim  1  or  2 , wherein the groove has a rectangular cross-section. 
     
     
         11 . The water ski with improved torsional characteristics according to any of the above claims wherein the ends of the groove are of the same or of a different shape and in that the ends of the groove are in the form of a semi-circle or angle. 
     
     
         12 . The water ski of claim  1 , wherein the width of the groove is 40-50% of the width of the central part of the water ski. 
     
     
         13 . The water ski of claim  1 , wherein the groove has a depth corresponding to 80-95% of the thickness of the water ski.