Abstract:
A method of controlling the attitude of a boat at high speed through boat hull design involves a first step of forming a pair of high speed steps in the hull of the boat. The pair of high speed steps provide enough surface area to control ride attitude, while reducing the wetted area of the hull to decrease drag. A second step involves forming transition steps to provide a transition to the high speed steps as the boat accelerates. In addition to reducing drag, the method aids in turning and lifting of the hull by trapping air and water in the steps.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to a method of controlling the attitude of a boat at high speed through boat hull design, and a boat hull constructed in accordance with the teachings of the method.  
         BACKGROUND OF THE INVENTION  
         [0002]    The North American Space Agency (NASA) conducted a study as to the optimum attack angle for a motor boat. NASA found that the optimum attack angle was approximately 2 to 3 degrees. It has been found, however, that it is difficult to maintain an attack angle of between 2 and 3 degrees as a motor boat accelerates. This is particularly the case with motor boats powered by inboard jets, as the thrust line is higher than with motor boats powered by outboard motors. A lower thrust line allows greater leverage on the hull when trimming the drive to achieve the desired ride angle of the boat. The high thrust line of the jet is not nearly as effective in this regard because as the speed of a jet boat increases, hydrodynamic pressure builds near the stern making it difficult to maintain an effective planing attitude. This results in the hull running flat which creates a greater wetted surface area. The greater the wetted surface area of the hull, the more frictional water drag occurs resulting in poor handling and a loss of control of the boat.  
         SUMMARY OF THE INVENTION  
         [0003]    What is required is a method of controlling the attitude of a boat at high speed through boat hull design, and a boat hull constructed in accordance with the teachings of the method.  
           [0004]    According to one aspect of the present invention there is provided a method of controlling the attitude of a boat at high speed through boat hull design. A first step involves forming a pair of high speed steps in the hull of the boat adjacent to the stern on opposite sides of the keel between the chines to control the attitude of the boat at high speed. The length of the pair of high speed steps must be not less than 10% and not more than 30% of the length of the hull. The width of the each of the pair of high speed steps must be not less than 20% and not more than 40% of the chine to chine width of the hull. The depth of the each of the pair of high speed steps must be not less than 1% and not more than 5% of the chine to chine width of the hull. A second step involves forming at least one pair of transition steps in the hull of the boat adjacent to the pair of high speed steps on opposite sides of the keel and between the chines to provide a transition to the pair of high speed steps. The length of the pair of transition steps is not less than 10% and not more than 30% of the length of the hull. The width of the each of the pair of transition steps is not less than 20% and not more than 40% of the chine to chine width of the hull. The depth of the each of the at least one pair of transition steps being not less than 0.5% and not more than 2.5% of the chine to chine width of the hull.  
           [0005]    According to another aspect of the present invention there is provided a boat hull that is constructed in accordance with the teachings of the present method.  
           [0006]    With a boat hull constructed in accordance with the teachings of the above method, the wetted surface area of the boat is less at high speed, as will hereinafter be further described. This method also aids in turning and lifting of the hull by trapping air and water in the steps. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    These and other features of the invention will become more apparent from the following description in which reference is made to the appended drawings, wherein:  
         [0008]    [0008]FIG. 1 is a bottom plan view of a boat hull constructed in accordance with the teachings of the present method.  
         [0009]    [0009]FIG. 2 is a side elevation view of the boat hull illustrated in FIG. 1.  
         [0010]    [0010]FIG. 3 is an end elevation view of the boat hull illustrated in FIG. 1.  
         [0011]    [0011]FIG. 4 is an bottom plan view of the boat hull illustrated in FIG. 1, showing wetted surface area at low speed.  
         [0012]    [0012]FIG. 5 is an bottom plan view of the boat hull illustrated in FIG. 1, showing wetted surface area at high speed. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0013]    The preferred embodiment, a boat hull generally identified by reference numeral  10 , will now be described with reference to FIGS. 1 through 5.  
         [0014]    This boat hull has been constructed in accordance with the teachings of the present method of controlling the attitude of a boat at high speed through boat hull design.  
         [0015]    Referring to FIG. 1, there is provided a boat hull  10  of boat  12  with a bow  14  and a stern  16 , chines  18 , and a keel  20 . Boat hull  10  is characterized by a pair of high speed steps  22  in hull  10  of boat  12  adjacent to stern  16  on opposed sides  24  of keel  20  and between chines  18  to control the attitude of boat  12  at high speed.  
         [0016]    The length  26  of pair of high speed steps  22  is not less than 10% and not more than 30% of the length  28  of hull  10 . Referring to FIG. 3, the width  30  of each of pair of high speed steps  22  is not less than 20% and not more than 40% of chine to chine width  32  of hull  10 . Referring to FIG. 2, depth  34  of each of pair of high speed steps  22  is not less than 1% and not more than 5% of chine to chine width  32  of hull  10 . In FIGS. 1 and 3, this chine to chine width is identified as “X”. In FIG. 2, the depth is indicated as a percentage of “X”.  
         [0017]    Referring to FIG. 1, at least one pair of transition steps  36  are provided for in hull  10  of boat  12  adjacent to pair of high speed steps  22  on opposite sides  24  of keel  20  and between chines  18  to provide a transition to pair of high speed steps  22 . Length  38  of pair of transition steps  36  is not less than 10% and not more than 30% of length  28  of hull  10 . Referring to FIG. 3, width  40  of each of pair of transition steps  36  is not less than 20% and not more than 40% of chine to chine width  32  of hull  10 . Referring to FIG. 2, depth  42  of each of pair of transition steps  36  is not less than 0.5% and not more than 2.5% of chine to chine width  32  of hull  10 .  
         [0018]    Referring to FIG. 1, each of pair of high speed steps  22  has a bow end  44  and a stern end  46 . Referring to FIG. 2, each of pair of high speed steps  22  increases in depth  34  from bow end  44  toward stern end  46 . The angle is preferably between 0.5 and 2 degrees. A change in the angle has the effect of altering the amount of lift exerted upon boat  12 . Beneficial results have been obtained with an angle of 0.75 of a degree.  
         [0019]    Referring to FIG. 5, high speed steps  22  will not have enough surface area  48  to control the attitude of hull  10  if length  26  of high speed steps  22  is less than 10% of chine to chine width  32  of hull  10 . Referring to FIG. 4, alternatively, there will be too much wetted surface area  48  which causes hull  10  to run flat and results in high frictional drag if length  26  of high speed steps  22  is more than 30% of chine to chine width  32  of hull  10 . Widths  30  of high speed steps  22  that are less than 20% of chine to chine width  32  of hull  10  are too narrow to effectively control the attitude of hull  10 . Widths  30  of more than 40% of chine to chine width  32  of hull  10  leave keel  20  too narrow to support the weight of hull  10  which results in high drag. Referring to FIG. 2, if depth  34  of high speed steps  22  is less than 1% of chine to chine width  32  of hull  10 , it results in hull  10  having a high drag. High speed steps  22  of depth  34  of more than 5% of chine to chine width  32  of hull  10  make it difficult to for high speed steps  22  to maintain contact with the water surface resulting in a loss of attitude control.  
         [0020]    Referring to FIG. 5, transition steps  36  will not have enough surface area  48  to control the attitude of hull  10  if length  38  of transition steps  36  is less than 10% of chine to chine width  32  of hull  10 . Referring to FIG. 4, alternatively, there will be too much wetted surface area  48  which causes hull  10  to run flat and results in high frictional drag if length  38  of transition steps  36  is more than 30% of chine to chine width  32  of hull  10 . Widths  40  of transition steps  36  that are less than 20% of chine to chine width  32  of hull  10  are too narrow to effectively control the attitude of hull  10 . Widths  40  of more than 40% of chine to chine width  32  of hull  10  leave keel  20  too narrow to support the weight of hull  10  which results in high drag. FIG. 2, if depth  42  of transition steps  36  is less than 0.5% of chine to chine width  32  of hull  10 , it results in hull  10  having a high drag. Transition steps  36  of depth  42  of more than 2.5% of chine to chine width  32  of hull  10  make it difficult to for transition steps  36  to maintain contact with the water surface resulting in a loss of attitude control.  
         [0021]    While using the percentage range described above provides an improved ability to control the attitude of boat  12  at high speeds, more beneficial results are obtained by applying a narrower range of percentages. The benefit of the narrow range of percentages is that improved handling and control of the attitude of boat  12  at high speeds can be obtained. Using the narrower range of percentages results in less wetted surface area  48  on hull  10  of boat  12  resulting in less frictional drag yet allows for enough wetted surface area  48  for effective control of attitude of boat at high speeds. The narrower range of percentages will now be discussed with reference to FIGS. 1 through 5.  
         [0022]    Referring to FIG. 1, the length  26  of each of pair of high speed steps  22  is not less than 14% and not more than 22% of length  28  of hull  10 . Referring to FIG. 3, width  30  of each of pair of high speed steps  22  is not less than 26% and not more than 34% of chine to chine width  32  of hull  10 . Referring to FIG. 2, depth  34  of each of pair of high speed steps  22  is not less than 2% and not more than 4% of chine to chine width  32  of the hull  10 . Referring to FIG. 1, length  38  of each of pair of transition steps  36  is not less than 14% and not more than 22% of length  28  of the hull  10 . Referring to FIG. 3, width  40  of each of pair of transition steps  36  is not less than 26% and not more than 34% of chine to chine width  32  of hull  10 . Depth  42  of each of pair of transition steps  36  is not less than 1% and not more than 1.5% of chine to chine width  32  of hull  10 .  
         [0023]    With a boat hull constructed, as described, the wetted surface area of the boat is less at high speed. This results in less drag. However, the steps also aid in turning and lifting of the hull by trapping air and water in the steps.  
         [0024]    Examples will now be describe to assist in the successful application of the teachings of the method.  
       EXAMPLE #1  
       [0025]    Recommended dimensions for boat  12  having:  
         [0026]    a hull length  28  of 228 inches (19 feet)  
         [0027]    a chine to chine hull width  32  of 63 inches Length  26  of each high speed step  22  is not less than 10% of hull length  28  of 228 inches=22.8 inches and not more than 30% of hull length  28  of 228 inches−68.4 inches. Preferred is a narrower range of 14% of hull length  28  of 228 inches=31.92 and 22% of hull length  28  of 228 inches=50.16 inches. What is illustrated is 40 inches which is approximately 18%. Width  30  of each high speed step  22  is not less than 20% of hull width  32  of 63 inches=12.6 inches and not more than 40% of hull width  32  of 63 inches=25.2 inches. Preferred is a narrower range of 26% of hull width  32  of 63 inches=16.38 and 34% of hull width  32  of 63 inches=21.42 inches. What is illustrated is 18.9 inches which is approximately 30% depth  34  of each high speed step  22  is not less than 1% of hull width  32  of 63 inches=0.63 inches and not more than 5% of hull width  32  of 63 inches=3.15 inches. Preferred is a narrower range of 2% of hull width  32  of 63 inches=1.26 and 4% of hull width  32  of 63 inches=2.52 inches. What is illustrated is a slope which starts at bow end  44  at 1.5 inches which is approximately 2.4% and gradually increases in depth from bow end  44  toward stern end  46  to 2 inches which is approximately 3.2%.  
         [0028]    Length  38  of each transition step  36  is not less than 10% of hull length  28  of 228 inches=22.8 inches and not more than 30% of hull length  28  of 228 inches=68.4 inches. The Preferred range is a narrower range of 14% of hull length  28  of 228 inches=31.92 and 22% of hull length  28  of 228 inches=50.16 inches. What is actually illustrated is 41 inches which is approximately 18% width  40  of each transition step  36  is not less than 20% of hull width  32  of 63 inches=12.6 inches and not more than 40% of hull width  32  of 63 inches=25.2 inches. Preferred is a narrower range of 26% of hull width  32  of 63 inches=16.38 and 34% of hull width  32  of 63 inches=21.42 inches. What is illustrated is 18.9 inches which is approximately 30% depth  42  of each transition step  36  is not less than 0.5% of hull width  32  of 63 inches=0.32 inches and not more than 2.5% of hull width  32  of 63 inches=1.58 inches. Preferred is a narrower range of 1% of hull width  32  of 63 inches=0.63 and 1.5% of hull width  32  of 63 inches=0.95 inches. What is illustrated is a 0.75 inches which is approximately 1.2%.  
       EXAMPLE #2  
       [0029]    Recommended dimensions for a boat  12  having:  
         [0030]    a hull length  28  of 342 inches (28.5 feet)  
         [0031]    a chine to chine hull width  32  of 94.5 inches Length  26  of each high speed step  22  is not less than 10% of hull length  28  of 342 inches=34.2 inches and not more than 30% of hull length  28  of 342 inches=102.6 inches. Preferred is a narrower range of 14% of hull length  28  of 342 inches=47.88 and 22% of hull length  28  of 342 inches=75.24 inches. What is illustrated is 61.5 inches which is approximately 18% width  30  of each high speed step  22  is not less than 20% of hull width  32  of 94.5 inches=18.9 inches and not more than 40% of hull width  32  of 94.5 inches=37.8 inches. Preferred is a narrower range of 26% of hull width  32  of 94.5 inches=24.57 and 34% of hull width  32  of 94.5 inches=32.13 inches. What is illustrated is 28.35 inches which is approximately 30% depth  34  of each high speed step  22  is not less than 1% of hull width  32  of 94.5 inches−0.95 inches and not more than 5% of hull width  32  of 94.5 inches=4.73 inches. Preferred is a narrower range of 2% of hull width  32  of 94.5 inches=1.89 and 4% of hull width  32  of 63 inches=3.78 inches. What is illustrated is a slope which starts at bow end  44  at 2.25 inches which is approximately 2.4% and gradually increases in depth  42  from bow end  44  toward stern end  46  to 3 inches which is approximately 3.2%.  
         [0032]    Length  38  of each transition step  36  is not less than 10% of hull length  28  of 342 inches−34.2 inches and not more than 30% of hull length  28  of 342 inches=102.6 inches. The preferred range is a narrower range of 14% of hull length  28  of 342 inches=47.88 and 22% of hull length  28  of 342 inches=75.24 inches. What is actually illustrated is 60 inches which is approximately 18% width  40  of each transition step  36  is not less than 20% of hull width  32  of 94.5 inches=18.9 inches and not more than 40% of hull width  32  of 94.5 inches=37.8 inches. Preferred is a narrower range of 26% of hull width  32  of 94.5 inches=24.57 and 34% of hull width  32  of 94.5 inches=32.13 inches. What is illustrated is 28.35 inches which is approximately 30% depth  42  of each transition step  36  is not less than 0.5% of hull width  32  of 94.5 inches=0.47 inches and not more than 2.5% of hull width  32  of 94.5 inches=2.36 inches. Preferred is a narrower range of 1% of hull width  32  of 94.5 inches=0.95 and 1.5% of hull width  32  of 94.5 inches=1.42 inches. What is illustrated is a 1.13 inches which is approximately 1.2%.  
         [0033]    Where relative dimensions of the length of the hull have been provided above, it will be understood that trim tab, drives, swim platforms, etc. are not to be included in such calculations.  
         [0034]    It will be apparent to one skilled in the art that modifications may be made to the illustrated embodiment without departing from the spirit and scope of the invention as hereinafter defined in the claims.