Patent Publication Number: US-6708642-B1

Title: Tri-sponson boat hull and method of making boat hulls

Description:
BACKGROUND OF THE INVENTION 
     The present invention is directed towards boat hulls, and in particular boat hulls having three sponsons. 
     Tunnel hull boat structures having a pair of longitudinal side channels that define a central tunnel in which is located a central sponson are known. Such boat hulls are typically configured so that the outer sponsons and central sponsons collectively sit in the water at low speed, however at higher planing speeds, the boat hull is partially supported by the surfaces of the side sponsons planing on the water and partially by air being compressed between the inside surfaces of the outer sponsons, the tunnel roof and the water surface. 
     Conventional tri-sponson boat design lacks versatility in that the designs are generally intended to be used in smaller pleasure-boat type applications and do not lend themselves well to being scaled to larger boats. Conventional designs also tend to lack versatility in that while a particular design maybe suitable for use in a specific environments, the same design may not be suitable for use in other environments. For example, a tri-sponson boat structure which may be quite efficient in smooth water conditions may not be suitable for rougher waters and a tri-sponson design intended for rougher waters may be inefficient in smoother waters. 
     Accordingly, there is a need for a tri-sponson boat hull that is scalable, and which can provide a smooth, efficient ride over a range of speeds and water conditions. There is also a need for an efficient method for manufacturing such a boat hull. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention there is provided a boat hull that includes an upper hull section, a pair of spaced apart substantially parallel elongated outer sponsons extending from a forward portion to a stern portion of a bottom of the upper hull section, the outer sponsons and upper hull section defining a tunnel therebetween, and an elongated center sponson extending along the bottom of the upper hull and positioned in the tunnel between and substantially parallel to the pair of outer sponsons and having a forward section with an upwardly extending trailing step wall defining an upward step in the center sponson, and an aft section that is located aft of the forward section, the aft section having an upwardly curved leading edge intersecting the step wall of the forward section. 
     According to another aspect of the invention, there is provided a boat hull that includes an upper hull section, a pair of spaced apart substantially parallel elongated outer sponsons extending from a forward portion to a stern portion of a bottom of the upper hull section, the outer sponsons and upper hull section defining a tunnel therebetween, the outer sponsons each having an inner wall extending substantially perpendicular to a water line, an outer chine and a bottom wall joining, bottom edges of the inner wall and the outer chine, the bottom wall being substantially planar aft of a leading edge thereof and angled upwardly from the inner wall to the outer chine, the upward angle of the bottom wall relative to the water line being less than that of the outer chine, and an elongated center sponson extending along the bottom of the upper hull and positioned in the tunnel between and substantially parallel to the pair of outer sponsons, the center sponson extending forwardly of the outer sponsons and having a upward step along its length with a portion of the center sponson leading the step having a greater depth than a portion of the center portion aft of the step, the center sponson being of lesser depth than the outer sponsons. 
     According to another aspect of the invention, there is provided a boat hull that includes an upper hull section having a substantially planar underbody, a pair of spaced apart substantially parallel elongated outer sponsons extending from a forward portion to a stern portion of the underbody of the upper hull section, the outer sponsons and underbody defining a tunnel therebetween, and an elongated center sponson extending along the underbody and positioned in the tunnel between and substantially parallel to the pair of outer sponsons. 
     According to still another aspect of the invention, there is provided a boat hull having an upper hull section, a pair of spaced apart substantially parallel elongated outer sponsons extending from a forward portion to a stern portion of a bottom of the upper hull section, the outer sponsons and upper hull section defining a tunnel therebetween, and an elongated center sponson extending along the bottom of the upper hull section and positioned in the tunnel between and substantially parallel to the pair of outer sponsons, the center sponson extending further forward and aft-ward than the outer sponsons. 
     According to yet another aspect of the invention, there is provided a boat hull having a bow and a stern, the hull comprising an upper hull section, a pair of spaced apart substantially parallel elongated outer sponsons extending from a forward portion to a stern portion of a bottom of the upper hull section, the outer sponsons and upper hull section defining a tunnel therebetween, an elongated center sponson extending along the bottom of the upper hull section and positioned in the tunnel between and substantially parallel to the pair of outer sponsons, and a wing-shaped lift spoiler pivotally mounted between the pair of outer sponsons, the spoiler passing beneath an aft section of the center sponson and being adjustable to control trim of the boat hull during use. 
     According to another aspect of the invention there is provided a method of making a tri-sponson boat hull, including steps of (a) forming from reinforced fibre material, using an upper hull mold, an upper hull section having a substantially planar underbody; (b) forming from reinforced fibre material, using first and second outer sponson molds, an elongated first outer sponson and an elongated second outer sponson; (c) forming from reinforced fibre material, using a center sponson mold, an elongated center sponson; (d) arranging the upper hull section, first and second outer sponsons and the center sponson such that the first and second outer sponsons extend from a forward section to a stern portion of the underbody of the upper hull section, the outer sponsons and underbody defining a tunnel therebetween, and the center sponson extends along the underbody of the upper hull and is positioned in the tunnel between and substantially parallel to the first and second outer sponsons; and (e) securing the outer sponsons and center sponson to the upper hull using reinforced fibre material. 
     According to yet another aspect of the invention there is provided a method of making a boat hull that includes steps of layering up on a boat hull mold blended Kevlar (T™) and E-glass woven fabrics that are pre-impregnated with heat curable epoxy resin, and heat curing the layered fabrics. 
    
    
     Various other features of the present invention will be apparent from a consideration of the accompanying specification, claims and drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Like numerals are used throughout the drawings to refer to like components, in which: 
     FIG. 1 is a perspective view from the bottom showing a boat hull according to a preferred embodiment of the invention; 
     FIG. 2 is a further perspective view from the bottom of the boat hull of FIG. 1; 
     FIG. 3 is a front elevation view of the boat hull of FIG. 1; 
     FIG. 4 is a partial sectional view of the boat hull showing one of the outer sponsons; 
     FIG. 5 is a side elevation of the centre sponson of the boat hull; 
     FIG. 6 is a drawing representing sectional views of the centre sponson, taken along the lines A—A to G—G of FIG. 5; 
     FIG. 7 is a diagrammatic sectional view along the lines E—E of FIG. 5; 
     FIG. 8 is a diagrammatic sectional view along the lines G—G of FIG. 5; 
     FIG. 9 is a partial bottom plan view of the boat hull showing a forward end thereof; 
     FIG. 10 is a side elevation showing the relative positions of the boat hull and low speed and at a planing speed; 
     FIG. 11 is a partial bottom plan view of an aft-section of the boat hull showing optional aeration slots applied to the outer sponsons thereof; 
     FIG. 12 is a diagrammatic partial sectional view showing an aeration slot formed on one of the outer sponsons of the boat hull of FIG. 11; 
     FIG. 13 is a partial perspective view of the aft-section of the boat hull showing an optional lift spoiler; 
     FIG. 13A is a diagrammatic sectional view taken along the lines  13 A— 13 A of FIG. 13; 
     FIG. 14 is a perspective view of the boat hull showing optional aeration openings in a step in the center sponson and FIG. 14A is a diagrammatic sectional view of the boat hull showing the aeration openings and corresponding air passageways. 
     FIG. 15 is a partial sectional view showing the laminate construction of the boat hull in accordance with a preferred embodiment of the invention; 
     FIG. 16 is a partial plan view of a mold used to make an upper hull portion of the boat hull; and 
     FIG. 17 is a diagrammatic aft-end view illustrating construction of the boat hull. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to FIGS. 1-3, a boat hull  10  according to one preferred embodiment of the present invention includes an upper hull section  12  and a pair of spaced apart outer sponsons  14 ,  16  extending along a bottom of the boat hull such that a tunnel  73  is defined by the bottom of the upper hull section  12  and the pair of outer sponsons  14 ,  16 . A central sponson  18  extends along the bottom of the upper hull section  12  and is positioned in the tunnel area between the pair of outer sponsons  14 ,  16 . The outer sponsons  14 ,  16  and the inner sponson  18  each have a respective upwardly curved leading edge  20 ,  22  and  24 . The leading edge  24  of the centre sponson  18  extends forwardly of the leading edges  20 ,  22  of the pair of outer sponsons  14 ,  16 . The centre sponson  18  may, in a prefered embodiment, also extend further aft than the sternward ends of outer sponsons  14 ,  16 , which is convenient if a drive system is to be included in the centre sponson  18 . 
     As shown in FIG. 3, the maximum depth of the centre sponson  18  is less than that of the outer sponsons  14 ,  16 . The boat hull  10  is arranged such that at rest and at lower speeds all three sponsons  14 ,  16  and  18  will typically sit in the water, whereas at higher speeds, under normal loading, the boat hull  10  will plane along on aft portions the outer sponsons  14 ,  16  with the centre sponson  18  positioned above the water. In this regard, line  26  in FIG. 3 shows an exemplary water line when the boat hull is at rest or at low speed, and line  28  illustrates an exemplary water line when the boat hull  10  is planing at high speed. 
     The components of the boat hull  10  will now be described in greater detail. In a preferred embodiment, the upper hull section  12  has a substantially planar bottom or underbody  38  along which the sponsons  20 ,  22  and  24  are positioned. Upper hull side walls  30 ,  32  extend upwardly from the starboard and port side peripheral edges of the underbody  38 . A curved bow portion  34  extends upwardly from a semi-circular front peripheral edge of the underbody  38  between the side walls  30 ,  32 . An upwardly extending transom wall  36  is located between the aft ends of the upper hull sidewalls  30 ,  32  along an aft peripheral edge of the underbody  38 . 
     The outer sponsons  14  and  16  are substantially identical, being mirror images of each other when viewed from the front of the hull. Each outer sponson  14 ,  16  has an inner side wall  40 ,  42 , an outer chine  44 ,  46 , and a bottom wall  48 ,  50 . Preferably, the inner side walls  40 ,  42  of the outer sponsons  14 ,  16  are substantially planar walls that form a perpendicular, or just slightly less than perpendicular, angle with the water line. The substantially planar bottom walls  48 ,  50 , are preferably upwardly angled from the inner sidewalls  40 ,  42  to the outer chines  40 ,  46 . The substantially planar outer chines  44 ,  46  extend at a higher dead rise angle than the bottom walls  48 ,  50 , but are not as sharply-angled relative to the water line as the inner walls  40 ,  42 . The leading edge portion  20 ,  22  of each outer sponson has a higher dead rise angles than the remaining aft portion of the sponson. The sponsons  14  and  16  are generally of a uniform depth along their respective lengths aft of the leading edges  20 ,  22  thereof such that the bottom surface of the underbody  38  lies in a plane that is parallel with the keelson of the outer sponsons  14 ,  16 . An intermediate longitudinal spray rail  52 ,  54  may be located along the bottom wall  48 ,  50  of each sponson  14 ,  16 . Similarly, a longitudinal spay rail may be provided along the outer chine  44 ,  46  of each of the outer sponsons  14 ,  16 . Longitudinal spray rails may also be located on the inner walls  40 ,  42 . 
     The outer sponsons are preferably configured such that the bottom wall  48  and outer chine  44  of the outer sponson  14  form one half of a V-shape, and the bottom wall  50  and outer chine  46  of the other sponson  16  form the other half of a V-shape, such that if the two outer sponsons were joined along the bottom edge of bottom walls  48  and  50 , the combined hulls would have a shape similar to that of a conventional V-shaped boat hull. Such a configuration can assist in improving the maneuverability of the hull  10 . 
     As can be seen in FIG. 3, in a preferred embodiment, the corner  60 ,  62  where the bottom wall  48 ,  50  of each outer sponson  14 ,  16  joins with its corresponding inner wall  40 ,  42  is inwardly upward angled. In this regard, the small corner portion  60 ,  62  of each sponson  14 ,  16  is angled in the opposite direction than the bottom wall  48 ,  50 . FIG. 4 shows the corner  60  of the outer sponson  14  in greater detail (corner  62  having the same configuration). In one preferred embodiment, the corner  60  is inwardly upwardly angled at approximately 45° relative to the plane of the water line. The inwardly upward chamfer of corners  60 ,  62  allow the boat hull to slide out on a high-speed turn with more ease than a 90° edge would typically permit. 
     As can be seen in FIGS. 1 and 2, the center sponson  18  includes a leading forward section  64  and a trailing aft section  66  that are joined at an intermediate upward step. The forward section  64  includes an upwardly curved leading edge  24 , terminates at an upwardly extending trailing step wall  68 , and has two sidewalls  65  and  67  that join at a common bottom edge and diverge in a upwardly direction such that the forward section has a generally V-shaped cross-section along its length. 
     The aft section  66  of the centre sponson  18  is formed from two elongated side walls  69  and  71  that join at a common bottom edge or keelson  72  and diverge in an upwardly direction such that the aft section  66  has a generally V-shaped cross-section along its length. At the forward end of the aft section  66 , the side walls  69  and  71  converge closer together and have a common upwardly curved leading edge that defines a forwardly tapering portion  70  that intersects with the step wall  68 . Thus, the leading portion  70  of the aft section  66  tapers in the forward direction much like a mini bow, and becomes deeper aft. The keelson  72  located aft of the leading portion  70  is substantially parallel to the plane of the bottom of the upper hull section  12 . 
     With reference to FIGS. 5 and 6, a preferred configuration of the centre sponson  18  will be explained in greater detail. FIG. 6 provides in diagrammatic form half sectional views of the forward section side  67  and the aft section side  69  taken along the lines A—A to G—G of FIG. 5 of the centre sponson  18 . As indicated by lines A-D in FIG. 6, the depth of the forward section  64  of the centre sponson  18  increases at a relatively quick rate moving aft from the leading edge  24 , after which the depth of the forward section  64  remains relatively constant until the forward section terminates at step wall  68 . The dead rise of the forward section  64  becomes shallower moving aft from the leading edge  24  to the step wall  68 . The forward section  64  reaches its deepest point just forward of the step wall  68  at approximately one third of the length of the center sponson back from its most forward point. 
     As can be appreciated from FIG. 6, the forward end  70  of the aft section has a dead rise angle that becomes shallower in the sternward direction, which is further exemplified in FIG. 7, which indicates by line E the dead rise of the aft section  66  right at the point where forward end  70  terminates at the step wall  68 , and FIG. 8 in which line G illustrates the shallower dead rise at a point trailing the leading edge  70  at which the aft section has reached a substantially uniform depth. 
     The configuration of the center sponson  18  is such that the forward section  64  (which is approximately one third the length of the centre sponson) acts as a wave breaker with the aft section  66  (approximately two thirds of the centre sponson) acting as a ride maker. In particular, the forward section  64  has very steep dead rise angles swelling to a large volume buoyancy body further aft. The forward section  64  is used to break or piece waves in heavy seas and yet, because of its large volume aft, creates a large amount of buoyancy. In this respect, the centre sponson  18  compliments the outer sponsons  14 ,  16 , which have relatively sharp dead rise angles and will cut through waves with ease. However, in heavy seas or large waves, the sharp forward sections of the outer sponsons  14 , 16  alone are not sufficient to generate buoyancy quick enough and thus the large volume buoyancy body provided by the forward section  64  of the centre sponson  18  combats the tendency that the hull would otherwise have to “stuff” (dive into another wave) or “pitch-pole” (roll end over end) when hitting large waves. 
     The forwardly tapering front end of the aft section  66  is much like a secondary bow and helps to channel the water coming around the forward section  64  and also helps to dissipate energy when the boat hull falls back into the water after riding over a wave, contributing to a smoother ride. The dead rise angle on the aft section  66  is relatively shallow aft of the leading portion  70 , providing good positive buoyancy which aids in softening the fall from waves by parting the water and channeling it towards the outer sponsons. In particular, the aft section  66  of the centre hull assists in creating a softer landing from a large wave by adding its buoyancy quickly and by dividing the large area between the outer sponsons into two smaller tunnels  74 ,  76  and partially trapping the air passing through such smaller tunnels  74 ,  76 . 
     Referring to FIG. 9, the configuration of the outer sponsons  14 ,  16  and centre sponson  18  is such that the tunnel  73  formed between the outer sponsons  14  and  16  is essentially divided into two smaller tunnels  74 ,  76  by the centre sponson  18 . The tunnels  74  and  76  are provided with funnel-shaped forward ends that are designed to capture and channel frontal air into each channel  74  and  76 . FIG. 10 shows the boat hull  10  in a resting or low speed position  10  and in phantom lines as indicated by  10 ′ in a high speed planing position. At slow speed or when the craft is very heavily loaded all three sponsons are in contact with and are displacing water creating a very stable (almost barge-like) platform. At high speeds the boat hull runs on only the two aft sections of the outer sponsons  14 ,  16 . 
     In particular, at lower speeds, the aft end of the hull will generally be located deeper in the water than the forward end. As the boat hull speeds up, the air passing through the tunnel  74 ,  76  towards and into the aft sections is gradually compressed by the fact that the crafts altitude is lower aft and thus the roofs of tunnels  74 ,  76  are lower to the water. As the boat hull speed increases the compressed air lifts the aft sections of the vessel to escape, and thus works in conjunction with the planing that occurs at higher speeds to reduce the depth of the hull in the water, and thereby reduce drag. Accordingly, the act of planing and the additional lift from the “ram air” effect provided by air passing through the tunnels  74 , 76  keeps the draft of the boat hull very shallow. 
     With reference to FIG. 11, in one preferred embodiment of the invention aeration slots  78  are provided along the aft one-third of the outer sponson bottom walls  48 ,  50 . The aeration slots  78  act as aerators to reduce friction on the major planning surface of each of the sponsons  14 ,  16 . The slots  78  each define a respective downwardly opening passage across the sponson bottom  48 ,  50  that has a leading end  80  that communicates with an area outside of the hull structure and a trailing end  82  that communicates with the tunnel area  73  between the sponsons  14 , 16 . 
     By way of example, in the embodiment illustrated in FIG. 11, the aeration slots are each angled, with the outer facing end  80  forwardly facing, at approximately 30 degrees relative to the transom of the boat, although it will be appreciated that different angles could suffice. As illustrated in FIG. 12, each aeration slot  78  preferably has a leading substantially vertically wall  84  that intersects at an upper end thereof with a curved upper and trailing wall  86 . In one embodiment, the upper/trailing wall  86  has a very shallow “S” shape. When the hull  10  is planing in a forward direction as indicated by arrow  90  air, as indicated by arrows  88 , is drawn in from the outboard sides of the outer sponsons and down the aeration slots towards the fast flowing air passing through the tunnel  73 . The configuration of the walls  84  and  86  that define the aeration slot  78  forces much of the air out through the open bottoms of the aeration slots  72 , as represented by arrows  88 , and this air which escapes onto the aft planning surfaces mixes with barrier layer water and aerates the planning surfaces, thereby reducing drag. In one exemplary use, aeration slots may have a depth D of approximately 2 inches, and a width W of approximately 4 inches, however such dimensions are provided merely as an example as a range of differently dimensioned aeration slots could be used depending on the specific boat hull size and configuration. 
     With reference to FIGS. 13 and 13A, in a preferred embodiment the boat hull  10  includes an adjustable lift spoiler  92  which is located close to the stern of the boat hull  10  and extends between the inner sides  40  and  42  of the outer sponsons  14 ,  16 . The lift spoiler  92  preferably passes underneath the bottom of the center sponson  18  and is pivotally mounted at its opposite ends to the inner sponson walls  40 ,  42  such that its trim can be adjusted by means of an electrical, hydraulic or mechanical trim adjustment device  98  that is positioned in one or both of the sponsons  14  and  16  and which is controlled from a helm area of the craft into which the hull is incorporated. As indicated in FIG. 13A, the lift spoiler  92  preferably has a wing-shaped cross section with a larger forward end  94  and a tapering trailing end  96 . In addition to a neutral position, the lift spoiler  92  can be pivoted so that its leading end  94  is raised relative to the horizontal as indicated by phantom line  92 ″, or it can be adjusted so that the leading end  94  is lowered relative to the horizontal, as indicated by phantom line  92 ′. The trim of the lift spoiler  92  can be controlled manually from the helm so as to provide the boat operator with greater control of the trim of the hull during boat acceleration and planing. In an alternative embodiment, automatic trim control is provided for the lift spoiler, with a processing device being connected to receive information about the trim level of the hull from sensors located on the hull, and based on such signals control the trim adjustment device  98  accordingly. For example, if based on sensor input the processing device determined that the front of the boat hull has lifted up higher than a predetermined limit, the angle of the spoiler could be adjusted by the processing device to counteract against the lift and readjust the trim of the boat hull to a less steep angle. The processing device could also receive engine speed and or boat speed information to use in determining appropriate trim angle adjustments. 
     With reference to FIGS. 14 and 14A, in one embodiment of the present invention the boat hull  10  is provided with aftward facing aeration openings  100  on the step wall  68 . The aeration openings  100  are connected by one or more air passageways  102  that pass internally through the hull to one or more forward facing air intake openings  104  that are located at the bow of the hull  10  above the water line. During planing, air is taken in through the intake openings  104 , passes through passages  102  and exits through aeration openings  100 , as indicated by the arrows in FIG. 14A, in order to reduce the drag on the aft portion  66 . 
     The boat hull  10  can be constructed using a number of different conventional boat building materials including for example laminated layers of fibreglass in some applications, and steel or aluminum or wood in other applications. In one preferred embodiment, the outer sponsons  14 , 16 , upper hull section  12  and center sponson  18  are each formed from a laminate structure that includes layers of Kevlar (™) reinforced glass fabrics. In particular, with reference to FIG. 15, one preferred laminate structure used to make of the sponsons and upper hull of boat hull  10  is illustrated. A surface gel coat  111  which may be an apoxy or vinylester or other suitable material is first applied to an inner surface of a mold used to make the boat hull. The outer layer  112  of the boat hull in the illustrated embodiment is a surfacing scrim-cloth or mat, which is followed by a number of laminated layers of a Kevlar(™) E-glass hybrid fabric layers  113 . In the illustrated embodiment, three outer Kevlar (™)/E-glass fibre layers  113  are illustrated, however, more or fewer layers may be desired depending on the specific size and application of the corresponding boat hull. The outer laminate layers are provided over an end-grain balsa wood core  114 , the inner side of which is covered by a plurality of further Kevlar (™)/E-glass fabric layers  115 . Other core materials could be used in place of balsa, including for example, foams and honeycomb paper. 
     The next layer  116  is a Dacron (™) or similar peel ply fabric, which is followed by a breath-ply layer  117  to which an optional absorbent (bleeder) layer may be attached. 
     In a preferred embodiment, the Kevlar (™)/E-glass fabrics are pre-impregnated with “B” staged epoxy resin such that the laminated layers can be thermally cured at approximately 250-275 degrees ferenheit. The laminate structure is layered up on a mold with the surface gel coat  111  being applied to the mold surface, and then the subsequent layers laid up in the order shown in FIG.  15  and described above. Once layered up, a vacuum bagging film  118  having multiple vacuum fittings  119  positioned therein is placed over the entire inner structure of the laminated materials in order to compress the laminate structure against the mold in the direction indicated by arrows  120  when air is evacuated through fittings  119  as indicated by arrow  122 . Vacuum compression will typically compact the laminate during heat curing. 
     In the laminated fibre construction method, each of the hull components, namely upper hull section  12 , outer sponsons  14 , 16  and center sponson  18  are each preferably layered up separately using different molds, and in this respect FIGS. 16 and 17 illustrate representative molds  124 ,  126 ,  128  and  130 , each of which is used for a separate corresponding component  12 ,  14 ,  16  and  18  of the boat hull  10 . Once each of the separate components have been layed up, vacuum compressed, and heat cured, their respective molds are subsequently assembled together after which further layers of Kevlar (™)/E-glass layers are used to secure the joints between each of the outer sponsons and the center sponson laminated portions adjoining them to the upper hull section  12 . Alternatively, the four component molds (outer sponsons, center sponson, and upper hull section) can be assembled together and then layed up and heat cured together, rather than separately. 
     The use of separate molds, which varies from traditional boat hull construction in which the boat hull is molded as a unified structure, provides versatility in that the same molds in manufacturing process can be used to make boat hulls of a wide range of sizes. In particular, upper boat hull mold section  124  preferably has an adjustable width as indicated by lines  132  in FIG. 16, and also an adjustable length, and the sponson molds  126 ,  128  and  130  each preferably have an adjustable length. For larger hull designs, the sponsons  126  and  128  can be spaced further apart, or can be spaced closer together for narrower hull designs. The flat underbody of the upper hull section  12  provides a design which is very ameniable to adjustment for different boat sizes as the top of the tunnel remains planer regardless of the relative positions of the outer sponsons. Because of the flat underbody, the relative position of the outer sponsons can easily be changed for different boat hull sizes to optimize the tunnel dimensions for a specific hull size and ram-air effect. Based on the desired speeds and load carry capability of the craft that incorporates the boat hull, an optimum sponson placement can be determined. Thus with the flat-bottom underbody and separate mold system described herein, using the same molds, different boat hulls having the same size can be made having different outer sponson placement locations to account for different intended uses of the boat hulls. 
     The Kevlar(™)/E-glass hybrid fibre layers may made of materials that are commercially available from Martintek of St. Jean sur Richelieur, Quebec including for example Martintek (™) product numbers 9009-127 single weave; product number 9037-127 double weave; or product number  9032-127  double weave, double weight fabrics. The Kevlar (™)/E-glass fabrics are preferably pre-impregnated with heat curable “B” staged epoxy resin, rolled and then placed in frozen storage until used to lay up the boat hull. Using heat curable “B” staged epoxy resin impregnated fabrics for the lamination process allows the lamination process to start and stop at will for several days without curing taking place, as opposed to traditional wet epoxy on site impregnation systems in which curing can occur within a few hours. Wet-catalyst curing systems typically require that the resin be applied to the fibre layers at the location that the boat is being made, thus introducing several subjective factors into the hull building process. Conversely, pre-impregnated thermal curing systems allow fabrics to be pre-impregnated in a highly-controlled process, thus resulting in a real-life production scenario in which consistent quality can be maintained, thus minimizing the need to design-in the redundancy (and hence excess weight) normally required in wet-curing systems. 
     The preferred composite materials described provide a lightweight, very strong hull which can be consistently produced in a high quality manner. It will be appreciated that this lightweight, strong design is particularly advantageous when used with the tri-sponson design described herein. However, such composite material construction could also be advantageously applied to other boat hull configurations including catamaran and single-hull designs. 
     It will be appreciated that a number of features of the present invention have been set out above and that not all embodiments of the present invention need include every feature set out above. The design provided by the present invention provides a great deal of versatility and can be applied to a large range of boat hull sizes from small pleasure craft to larger vessels such as coastal-patrol vessels. 
     When the laminate composite structure shown in FIG. 15 is used in the construction of the present boat, the compensate structure provides a very low radar signature. Angulation of the deck applied to the hull and use of radar absorbing paints can still significantly reduce the signature of boats which incorporate the boat hull of the present invention, as can engine shielding materials. Engine exhaust could be cooled by redirecting sea water through the water jacket, substantially reducing any heat signature. The use of jet drives (using an impeller to take water in and force it out the aft end of one more of the sponsons) could also be used in conjunction with a hull to vastly reduce sonar signals. Balistic Kevlar (™) could be molded onto the inside of the current composite structure to provide small arms fire protection. 
     Various features of the invention are set forth in the following claims.