Double flexible keel

Abstract

Water Craft or amphibious vehicle, includes a hull fitted with at least one elongate longitudinal keel; which may be extruded from natural or synthetic rubber. The keel has base, and at least two dependent keel members, which in steady state conditions slant downwards to port and starboard. If the keel is grounded, keel members deform elastically upwards against the base, absorbing shock. Keel members can be pushed down by water pressure, acting as dependent keels or. This may occur when cornering, or when planing. Stops act against stops on the base, so that when keel member is pushed downwards by water pressure, it cannot be forced beyond vertically dependent position. Alternatively, discrete keels may be provided on either side of the hull.

1 . A water craft having a longitudinal, elongate keel mounted to the underside of the craft, the keel comprising at least two elongate keel members, each keel member being movable from a first position in which it projects away from the underside of the craft by a first angle, to a second position in which it projects away from the underside of the craft by a second angle larger than the first, and means for biassing the keel members towards the first position, the arrangement being such that in use, when the keel is subjected to hydro-dynamic loading, at least one of the keel members is moved towards the second position so as to act as a dependent keel.  
     
     
         2 . A water craft as claimed in  claim 1 , in which the at least one of the keel members is moved towards the second position when the keel is subjected to a generally lateral hydro-dynamic loading.  
     
     
         3 . A water craft as claimed in  claim 1 , in which the keel members are arranged in pairs, the keel members of each pair projecting from the underside of the water craft in generally laterally opposing directions when the keel portions are in the first position  
     
     
         4 . A water craft as claimed in  claim 1 , in which each keel member is pivotably mounted to a base, the base being adapted to be mounted to the underside of a water craft.  
     
     
         5 . A water craft as claimed in  claim 4 , in which each keel member is formed integrally with its respective base.  
     
     
         6 . A water craft as claimed in any previous  claim 1 , in which each keel member is mounted separately to the underside of the water craft.  
     
     
         7 . A water craft as claimed in  claim 4 , in which the keel members are provided in pairs, with the keel members in each pair being pivotably mounted to a common base.  
     
     
         8 . A water craft as claimed in  claim 1  when dependent on  claim 5 , in which the keel members and their respective base(s) are extruded.  
     
     
         9 . A water craft as claimed in  claim 1 , in which the keel members are made from a resilient material.  
     
     
         10 . A water craft as claimed in  claim 9 , in which the resilience of the material biases the keel members to the first position.  
     
     
         11 . A water craft as claimed in  claim 9 , when dependent on  claim 4 , in which the keel members are provided in pairs, the keel members of each pair being pivotably connected to a base by means of a common hinge portion.  
     
     
         12 . A water craft as claimed in  claim 11 , in which an elongate hollow cavity is formed in the common hinge portion.  
     
     
         13 . A water craft as claimed in  claim 12 , in which the cavity is sealed to prevent water from entering the cavity, the arrangement being such that when hydro-dynamic pressure acting on the common hinge portion compresses the cavity, the keel members are moved towards the second position.  
     
     
         14 . A water craft as claimed in  claim 1 , in which each keel member has a first convex surface and a second concave surface and when the keel members are in the first position, the first surface is directed away from the from the underside of the water craft and the second surface is directed towards the underside of the water craft.  
     
     
         15 . A water craft as claimed in  claim 1 , in which each keel member is movable to a third position in which it projects from the underside of the water craft by a third angle which is smaller than the first angle.  
     
     
         16 . A water craft as claimed in  claim 1 , in which stop means are provided to prevent or resist movement of the keel members beyond the second position.  
     
     
         17 . A water craft as claimed in  claim 1 , in which the second angle is in a range from 80 to 100 degrees.  
     
     
         18 . A water craft as claimed in  claim 1 , in which the water craft is an amphibious vehicle.  
     
     
         19 . (canceled)