Boat hulls

Abstract

Power boat comprises hull having a keel line running from bow to stern which defines an axis of symmetry from which port and starboard hull portions of bottom surface extend to meet side walls. The stern of the boat is defined by a transom. A trim plate is mounted for pivoting about a transverse axis to alter the relative position of the bow in the water and control the wake-making or wake-shaping capability. A flat inclined surface slopes upwardly and sternwards from the transition point to form a water flow modifying part of the hull bottom surface. By rotating trim plate about hinge axis so that its trailing edge is lowered, the water flow encountering plate is deflected down and so the stern of hull can experience lift and the bow will “squat” or lower somewhat, with the keel line assuming a progressively lesser angle of attack to the surface of the water. This is accompanied by a change in shape of the wake (and some increase in drag). The wake shaping can thus be controlled to allow for more entertaining wake boarding or to allow for different skill levels of wake boarders. Conversely, rotating trim plate to raise its trailing edge tends to raise the angle of attack.

1 . A boat having an adjustable trim, said boat including: 
 (a) a hull with a bottom surface, side walls, transom, a keel line running from bow to stern defining an axis of symmetry from which port and starboard hull portions extend to meet said side walls,    (b) a water flow modifying part of the hull located towards the stern comprising an inclined portion of the hull which extends up relative to said bottom surface in a direction towards the stern from a transition point along said keel line, and    (c) located aft of said inclined portion a selectively moveable trim member with a surface for contacting water relatively flowing along said flow modifying part and wherein said moveable trim member can be selectively positioned to increasingly obstruct said water flow and thereby lift the stern and lower the bow in the water when the boat is travelling forward.    
   
   
       2 . The boat of  claim 1  wherein said inclined portion progressively widens from said transition point in the direction of the stern.  
   
   
       3 . The boat of  claim 2  wherein said inclined portion progressively widens to each and thereafter remains a predetermined width until reaching the trim member.  
   
   
       4 . The boat of  claim 1  wherein said inclined portion towards the trim member is recessed below the port and starboard hull portions on either side thereof.  
   
   
       5 . The boat of  claim 1  wherein the water flow modifying part of the hull further includes a flat surface which extends rearwardly in a direction towards the stern from the inclined portion and which is substantially parallel to the port and starboard hull portions on either side thereof.  
   
   
       6 . The boat of  claim 1  wherein the selectively moveable trim member comprises a plate.  
   
   
       7 . The boat of  claim 6  wherein said plate is moveable about an axis transverse to said keel line.  
   
   
       8 . The boat of  claim 7  wherein the axis is substantially in the same plane of the trim plate.  
   
   
       9 . The boat of  claim 8  wherein said transverse axis in provided by a hinge by which the trim plate is mounted.  
   
   
       10 . The boat of  claim 7  wherein the axis is displaced above the keel line and out of the plane of the trim plate.  
   
   
       11 . The boat of  claim 10  wherein said plate extends from a drum or cylinder which is selectively rotatable about the axis transverse to and above said keel line.  
   
   
       12 . The boat of  claim 11  wherein said plate is mounted so as to be substantially tangential to the drum or cylinder periphery.  
   
   
       13 . A boat hull of adjustable trim comprising: 
 a hull body having a bottom surface with first and second portions and extending rearwardly from a bow to a stern of the hull body, the bottom surface being substantially symmetrical on opposite sides of a vertical central plane that extends longitudinally of the hull body; and    a trim plate in the stern region rotatable by an actuator about an axis extending transversely of the hull body,    wherein—   (a) a keel line being a line of intersection between the said central plane and the bottom surface has a first segment forward of and a second segment rearward of a transition point partway along the keel line, the second segment of said keel line extending upwardly from said transition point and the second segment terminating adjacent to a leading edge of a bottom surface of the trim plate;    (b) the first portion of the bottom surface of the hull extends outwardly from the first segment of the keel line on each side of the central plane; and    (c) the second segment of the keel line being a centreline of the second portion of the hull bottom surface, that second portion extending outwardly from the keel line on each side of the central plane.    
   
   
       14 . The boat of  claim 13  wherein said second portion of the bottom surface is substantially flat or planar.  
   
   
       15 . The boat of  claim 13  wherein the second portion of the hull bottom surface extends transversely between steps that extend longitudinally and are equally spaced apart on opposite sides of the central plane, sections of the first portion of the hull bottom surface being located to port and starboard of the said steps so that the first portion of the hull bottom surface extends from bow to stern, the said steps and the second portion over at least a part of its length defining a recessed surface in the hull bottom surface between the port and starboard sections.  
   
   
       16 . The boat of  claim 15  wherein the trim plate leading edge extends across the width of the second portion of the hull bottom surface and across the gap between the two steps.  
   
   
       17 . The boat of  claim 13  wherein the selectively moveable trim a plate is moveable about an axis transverse to said keel line.  
   
   
       18 . The boat of  claim 17  wherein the axis is substantially in the same plane of the trim plate.  
   
   
       19 . The boat of  claim 13  wherein said trim plate extends from a drum or cylinder which is selectively rotatable about the axis transverse to and above said keel line.  
   
   
       20 . The boat of  claim 19  wherein said plate is mounted so as to be substantially tangential to the drum or cylinder periphery.