US20060254486A1

US20060254486A1 - Winged hull for a watercraft

Info

Publication number: US20060254486A1
Application number: US11/127,729
Authority: US
Inventors: Glynn Ashdown
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-05-12
Filing date: 2005-05-12
Publication date: 2006-11-16

Abstract

A hull for a boat, for example a sailboat, has a sharply angled front or bow with a curved center crest line providing a entry into the water during forward motion. Sides of the bow are concave. The main body of the hull is shaped as a semicircle in transverse cross section. The upper edge of the hull has a flare that extends laterally outward to form wings along both sides of the hull. The wings begin adjacent the front or bow and gradually increase in the extent of their lateral extension at a mid-position the hull and adjacent the stern. The stern has an angled end extending rearward at the bottom of the hull. A step is provided at the stern. The deck extends from the upper edge of the hull to the edges of the cockpit. The cockpit has curved inside surfaces and a center beam extending along the center of the boat, the center beam having sloping surfaces. An open transom permits water to flow from the cockpit.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a winged water surface craft hull, and in particular to a winged hull for a sailboat or powerboat or other watercraft utilizing a winged hull shape.
2. Description of the Related Art
People have been moving about on the surface of lakes and seas with success for perhaps 10,000 years or more. Ocean dwelling creatures, on the other hand, are the genetic result of a few million years of nature's evolutionary natural selection survival process and so have a significant ‘research and development’ head start when it comes to moving about in water. Thus, it is likely that large fast fish or water-based mammals are almost perfectly optimized for moving large bodies efficiently in the water. A better understanding of how whales, sharks, dolphins and other large-bodied ocean creatures move so effortlessly and rapidly in an incompressible fluid, and apparently with such low energy consumption, may be the best strategy to rapidly improve watercraft technology.
By definition surface watercraft operate at the interface of two quite dissimilar fluids—air and water. This interface can change from friendly light waves and winds, to powerful life-threatening squalls or even large tsunami-like water wave disturbances sometimes with little or no warning.
Most likely the safest and best watercraft operating today are modern naval craft and in particular submarines and aircraft carriers. The safest place at sea in a storm or major tidal wave is below the surface suggesting submarines have the greatest potential for survival of all watercraft. The modern aircraft carrier is probably the best adapted man-made surface watercraft, because it is designed to operate on the surface in hurricanes and is often forced to do so to avoid potential damage in port. Such large complex and costly military craft represent one extreme end of the spectrum in the current state of the art in watercraft. At the other end of the spectrum there remains the opportunity to develop low cost but much safer and more efficient watercraft designs to meet normal pleasure and transport needs.
Since many of us travel on water at least once in a while, and we put our lives at a higher level of risk when offshore in a surface watercraft, it would seem reasonable that in addition to the practice of carrying personal floatation devices and even life rafts on board, a watercraft should itself possess high levels of designed-in water survival capability.
The inventor suggests that watercraft design requirements should include some of the desirable capabilities listed below:

- 1. Unsinkable even with multiple hull breaches or when capsized,
- 2. Operable at some reasonable efficiency even after suffering multiple hull breaches,
- 3. Unsinkable even with hull severed in a catastrophic event through floatation of any major severed sections.

Meeting any of these requires that first the craft, together with occupants and maximum payload, be significantly lighter than water. Second, the craft must be designed to eliminate the possibility of any dangerous level of swamping, so that even after suffering one or more hull breaches, it can still operate at an adequate level of efficiency to return its crew and passengers to safety without outside help.
Amazingly enough, very few pleasure or even professionally crewed passenger surface craft operating today can meet the first two of these suggested basic survival requirements. Hardly any craft, including navy vessels, can meet the third requirement. Although many watercraft include some level of emergency floatation, most will become swamped and virtually incapable of normal operation, or navigation through the water after suffering a major hull breach or taking on large waves that filled the interior of the craft. This is because, even if the craft does not sink, the high level of swamping accepted in most designs will usually fill the craft, lowering it to the gunnels in the water. Such a swamped condition would make the craft difficult to move and may leave the craft and its occupants at the mercy of the seas.
A notable exception to this situation is the Boston Whaler surface craft. These boats are foam-filled, eliminating the quite common but very dangerous potential risk of water swamping the craft through displacement of the interior air with water following a hull breach or entry of large swamping waves.
This situation has prevailed in the industry over many years, most likely because use of floatation foam, balsa, cork or similar materials to eliminate swamping or sinking increases cost and reduces the hull volume available for crew and payload.
Whatever the reason for the current situation, sinking or swamping may be eliminated through a change in design priorities for watercraft, as amply demonstrated by the Boston Whaler. A craft using adequate foam or other floatation techniques may end up some 30% or so larger for the same payload. Although more costly, such craft will offer much improved safety for crew and payload, and a much greater chance of survival under all but perhaps the most severe sea conditions. As an important side benefit, a craft so designed could have potential for higher speed because of its approximately 30% increased waterline length.
A surface craft has the task of working well at the interface of both water and air under a wide range of weather conditions. This is a difficult task, and one not optimized in any large bodied living creature that comes to mind. Large fish and whales are believed to avoid the surface during storms. Seabirds trapped at sea during storms are typically forced to abandon flying and set down on the water surface using their wings slightly open to trap air and improve balance and flotation in a rolling seaway.
Clearly, fish and birds have evolved to a very high level of performance judged by their speed and maneuverability in their respective water or air environments. The inventor has attempted to draw clues for efficient underwater hull shapes from the body shapes of large fast-moving fish or mammals such as dolphins, sharks and killer whales. Similarly, the shapes of birds in flight offer valuable clues to optimizing above-water shapes. The further optimization of surface craft hull design to increase efficiency in moving through the water and to take advantage of the natural action of the water being displaced by the hull follows in the body of the text.
When it comes to the mechanics of moving efficiently on the water's surface there are several key characteristics of the large-bodied fast fish we may wish to emulate. The first and probably most important is the body shape. The large fish and mammals such as sharks and dolphins have hulls with a nominally circular cross section with maximum body diameter roughly in the middle and tapering more or less to a point towards either end. There is a well-defined sharp point at the front for water separation, a powerful but slender tail at the rear for propulsion and several fins attached to the main body. The round body shape will have very low roll resistance, the creature relying on its fins and tail for directional control and stability. This tapered circular hull shape permits the creature to move in water with the minimum of resistance and therefore the least amount of energy expended.
In keeping with fish shapes virtually all watercraft are tapered to a point at the bow, but are usually cut off straight at the stern, and thus are bullet shaped when viewed from above. This blunt cut-off at the stern is likely to increase stern wave generation and increase drag, when compared to a tapered stern. Interestingly, circular cross section tapered hulls, while used in submarines and torpedoes, are often avoided in surface craft, particularly powered craft, because of their low roll resistance. Rolling on a seaway is uncomfortable to people, and surface craft typically design-in higher roll resistance through a variety of different underwater shapes, such as flat bottoms or chines, to avoid excessive rolling or capsizing. However, most current watercraft designs, although possessing relatively high static and dynamic roll resistance when level or heeled at lower heel angles, often exhibit the potentially dangerous characteristic of reduced roll resistance with increased heel angle when heeled beyond some critical angle. This leaves such craft exposed to a higher risk of swamping or capsizing in heavy seas.
The current invention attempts to reverse this situation through a hull that has little or no roll resistance for low drag at normal heel angles, but through the use of extended wings built into the upper hull sides, exhibits dramatically higher roll resistance at higher heel angles. Thus, the winged hull of the current invention will resist dangerous over heeling and potential capsizing at extreme heel angles.
In general, sailboat hulls are more efficient than power boat hulls in moving through or displacing water with low resistance because they must operate in light winds. Power boats, on the other hand, can just increase engine power and bum more fuel to overcome hull design inefficiencies. Also, sailboats are widely considered safer in heavy weather and high seas because their deep keels and sails stabilize the motion of the boat greatly in comparison to most power boat designs.
Although these hull design principles are equally applicable to both power and sail craft, any hull design efficiency improvements are likely best demonstrated in a sailboat hull. Superior speed or lower fuel consumption in a power boat may be due to other factors such as engine efficiency. Sailboat hull efficiency is easily demonstrated in sailboat races through superior performance of the new designs over others of similar size under the same wind conditions.
Small to midsized sailboats are quite popular among recreational sailors who like to spend a day on the water racing or just sailing about, usually on protected bodies of water or near the shore. These recreational sailboats are often small enough to be brought to the water, for example, on a trailer pulled behind a vehicle. Many differing designs of small sailboats are available for the recreational sailor. These sailboats enable the recreational sailor to enjoy a day of sailing and potentially to compete against others in sailing contests, thus improving their craft handling and other sailing skills. The sailors that crew these boats may be experienced and expert sailors, but more commonly are occasional sailors who do not have all the skills and experience of a more seasoned sailor. Less experienced sailors are often unaware of and unprepared to handle the extremely hazardous conditions that can occur with little or no warning in squalls or storms.
A danger of many of the available smaller sailboats is that they may perform poorly in a seaway or under heavy air conditions. Speed of motion is critical in a surface craft because speed is required for control. Only when the craft is moving can the crew have any control on the direction and attitude of the craft. Once at rest the craft is entirely at the mercy of the wind and sea. Many sailors therefore prefer sailboats that are faster and more maneuverable, handle more smoothly, and perform well in a wider variety of weather conditions, making the day on the water safer and more enjoyable.

SUMMARY OF THE INVENTION

The present invention provides in one embodiment a hull for a sailboat, which has low drag and is safe, fast and fun under a significantly wider range of weather conditions than other craft of its size. The hull is shaped to more closely optimize the action of hydrodynamic forces of the water acting on the hull, and in effect work with, not against, the water to improve the motion, speed and stability of the boat. In general, the portion of the hull below the water line emulates a large fish to provide optimum hydrodynamic effects. At the same time, the portion of the hull above the water line more emulates seabird shapes to provide aerodynamic and hydrodynamic effects and other functions specific to optimum sailing performance.
Although this hull shares general shapes common to many other sailboat designs, particularly when viewed from a distance at the side or from above, there are key differences that result in critical safety and performance improvements that are the subject of this invention. These key hull differences may be visually evident when viewed up close, out of the water or, when underway directly from the bow or stern.
Specifically, the hull has a sharply defined water entry line with water-flow shaping surfaces extending from the water entry line at the bow. The shaping at the bow changes to a mid-portion of the hull having a generally semicircular transverse cross section to permit the boat to readily roll, or heel, when under sail.
The stern, or back of the hull, has an extension to provide an increased water line length for greater speed and to transfer weight forward, and shaped for minimum stern wave generation and low stern drag. Above the water line, the hull has extensions, or wings, extending from the upper sides of the hull. The extensions or wings are small to non-existent at the bow or front of the boat but extend to a greater length from the sides of the hull. The extensions or wings are shaped to contact the water surface only at large heel angles.
The crew space of an embodiment of the present hull has an open transom to permit any water entering the cockpit to exit the cockpit easily and automatically while the boat is under sail. The interior surfaces of the hull are shaped to provide seating surfaces and foot braces for the crew at a variety of heel angles while sailing. The deck surface extends over the extensions or wings at the sides of the boat to provide seating for the crew during large heel angles.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation illustration a design principle for a bow of a hull according to the present invention in front view;
FIG. 2 is a schematic representation illustrating a design principle of the bow of the present hull in side view;
FIG. 3 is a schematic representation of a design principle of a transverse cross section of a mid portion of the present hull below the water line;
FIG. 4 is a schematic representation of a design principle of the stern of the present hull, shown in side view;
FIG. 5 is a schematic representation of a design principle of sides of the present hull at and above the water line, in transverse cross section;
FIG. 6 is a schematic representation of a design principle for an upper bow of the present hull, in side view;
FIG. 7 is a perspective view of a sailboat including a sailboat hull incorporating the foregoing design principals of the present invention;
FIG. 8 is a view of the stern of an alternative embodiment showing a rearward tapering extension;
FIG. 9 is a bottom perspective wireframe drawing of the hull, slightly from the side;
FIG. 10 is a side perspective wireframe drawing of the present sailboat hull;
FIG. 11 is an enlarged end perspective view of the present sailboat hull showing the stern;
FIG. 12 is a top end perspective view of the sailboat hull showing the crew compartment;
FIG. 13 is a schematic partial view of a the interior construction of the hull in cross section;
FIG. 14 is a photograph of a prototype sailboat having a hull according to the principles of the present invention in bow view;
FIG. 15 is a photograph of the prototype sailboat in side view;
FIG. 16 is a photograph of the prototype sailboat in front view;
FIG. 17 is a photograph of the prototype sailboat broaching;
FIG. 18 is a photograph of the prototype sailboat generally from the rear showing a trough formed in the water;
FIG. 19 is a photograph of the prototype sailboat generally from the side;
FIG. 20 is a photograph of the prototype sailboat from the front and showing the shaping of the water at the bow;
FIG. 21 is a photograph of the prototype sailboat from the front quarter showing the boat sailing in light wind;
FIG. 22 is a perspective view of the present hull with a zebra stripe environmental mapping pattern overlaid thereon so enhance contours of the hull shape;
FIG. 23 is a photograph of the present sailboat shown from the front port side; and
FIG. 24 is the photograph of FIG. 23 on which is overlaid the Zebra stripe environmental mapping.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The sailboat hull of the present invention utilizes hydrodynamic shaping to provide a performance sailboat hull that moves quickly and efficiently through the water. A preferred embodiment of a more optimized hull is demonstrated in an 18 foot sailboat. A front portion of the hull has a shape to ease water entry and to shape the water flow at the front of the boat. FIG. 1 shows a schematic representation of the water entry portion of the present hull in transverse cross section (also see FIG. 14 that shows the present embodiment prototype sailboat from the bow view). FIG. 2 shows this same water entry portion of the hull in the longitudinal starboard side view. In particular, the water entry includes a relatively sharp edge 22 that slices into the water.
The sharp edge 22 is followed by a pair of outwardly angled concave surfaces 24. These outwardly angled concave surfaces 24 receive and direct the water that is sliced by the edge of the bow and direct it not only up and out but also impart a curve to the water flow at entry, as shown by arrows E. These curved water flows formed over the bow surfaces travel through the air in a ballistic path back to the water surface and tend to encourage the formation of vortices in the water on either side of the hull 20, as shown by arrows V. The vortices V, once started by the shape of the bow, continue to move along the two sides of the hull as the hull moves through the water (see FIG. 15 wherein the vortex, normally hidden under the hull side wings is in this instance clearly visible because the boat is rolled to weather rather than to leeward by the larger action of the seaway).
As mentioned, the water is displaced or splashed aside by the sharp bow and then follows a curved ballistic path back to the surface. The convex shape of the hull at the bow and along the sides of the hull under the wings is designed to approximate this ballistic path of the water being displaced by the hull at higher speeds, and therefore minimizes unnecessary re-contact with the water and associated unnecessarily higher drag.
The key characteristics of this unique hull shape are more clearly illustrated in FIG. 22 showing so-called zebra stripes, which are contour lines rendered by the 3D CAD software program used to develop the hull. These zebra stripes are generated by modeling in a so-called environmental mapping process which models light reflecting of the hulls surface from a grid of alternatively colored and white horizontal contrasting bars. The resulting wide zebra stripes exaggerate the hull surface contours and more clearly illustrate the lines of least curvature and therefore may predict the path that water could be expected to take as it is displaced by the moving hull.
FIG. 23 is a photograph of the prototype sailboat of the current invention underway from ahead and to the port side. This photograph clearly shows the wave shape generated by the hull moving through the water at moderate speed. As illustrated in FIG. 24, when narrow zebra stripes independently created by the computer generated environmental mapping of the hull such as shown in FIG. 22 are overlaid on the photograph of FIG. 23, it becomes apparent that the stripes do in fact closely map the actual path taken by water being displaced.
Furthermore, in comparing the zebra stripe model with other pictures of the boat underway at high speed but showing the entire side of the hull rather than just the front portions shown in FIG. 23, the zebra stripes appear to closely match the hull displacement wave shape not only at the sharply contoured bow, but also over the entire length of the hull.
As a result of carefully creating this sympathetic streamlined hull shape shown in FIG. 22, drag from water in contact with moving hull is minimized, and therefore the forces required from the sails to move the boat are also minimized. All drag from the moving hull in contact with the water takes energy from the hull and acts as a braking force. When compared with many existing hull designs a smoother more efficient water flow results with lower associated drag.
There are several other “winged” sailboat hull designs within the state of the art which properly require differentiation from the current invention. These winged designs fall in to a small group of exceptionally high performance boats that perform to a great degree like large windsurfers. One such design is the Australian 18 Skiff designed by Julian Bethwaite. This craft is sailed by experts only and is one of the fastest sailing dinghies in the world. The boat is very light and carries a massive sail area when compared with any other 18 foot boat. The high heeling forces from the sails are countered by crew on trapezes climbing up large hiking nets or wings built in to the sides and angled up from the deck. This technique gains extreme leverage from the crew hiking forces.
Because of the Australian 18's tremendous power-to-weight ratio, it is capable of very high speeds in strong breezes, and can plane upwind even in light breezes. These so-called “crash and burn” designs are often severely damaged in sailing accidents and collisions during racing. Their wings increase heeling moment of the crew as with the current invention, but are not normally intended to enter the water, and since the wings are just open nets mounted on angled frames they do not share the other important features of the current invention.
Several other slightly less extreme winged sailing dinghies exist in the state of the art, and most notably those from Bethwaite Design, the leading Australian racing dinghy design company. One such design with wings is the “79er” which like the Australian 18 is also a very high performance planing dinghy and, although not requiring a trapeze for hiking, is also designed for experts only. The 79er wings are an integral part of the hull, and therefore appear somewhat similar to the current invention when viewed from the stern. The 79er therefore also properly requires full differentiation from the current invention. As with the Australian 18, the 79er's wings have one primary purpose, which is that of increased crew leverage. The 79er's wings do not accomplish and are not designed to accomplishing the other design goals of the current invention, and as will be apparent from the following discussion, the present hull represents a departure from the 79er design.
In one embodiment, the front water line entry portion of the present hull continues for about the first one fourth of the hull length. Other fractions may also be use.
In side view, the water line entry portion 22, as shown in FIG. 2, has a curved shape with a substantial horizontal component to the curve. This traditional “spoon bow” curved shape 20 has a benefit over many modern “plumb bow” configurations in which the front edge of a hull is substantially perpendicular to the water line, and generally used to maximize waterline length (and therefore displacement speed potential). Waves hitting a spoon bow tend to lift the bow of the boat up to permit the boat to ride over the wave, whereas a plumb bow tends to push into the wave and generally results in more water washing over the deck and possibly into the cockpit. The effects of the water, and in particular a wave, are indicated in FIG. 2 as arrows W that tend to push the front of the hull up as indicated at arrow U.
The effect of the spoon bow shape then is to assist the boat in riding up over waves, and to keep the front of the boat riding high. This keeps the crew dryer and also facilitates movement of the hull up onto the water surface to help accomplish planing of the boat at speed. Although perhaps less ideal, particularly for in-shore craft, a hull with a plumb bow is also envisaged in a further embodiment and within the intended scope of this invention.
The foregoing describes the front portion of the hull. At a middle portion or main body 26 of the hull, the hull has a transverse cross section that is generally semi-circular, as shown in FIG. 3, or at least tending to a semi-circular shape. The semi-circular cross section permits the hull to roll readily about its longitudinal axis, offering little resistance from the water. The roll directions are indicated by the double-ended arrow R. Many boat hulls are built with structures to resist rolling, including squared or angled corners, so-called chines, channels, and the like. The present hull departs from this and offers the rounded cross section 26 so that it rolls easily, like a log in a log roll. This helps to minimize hull resistance in a seaway and therefore absorb less energy from the boat when rolling, leaving more energy available to propel the boat forward.
The hull is designed to work like the body of a large fish, which as previously noted has a nominally round body shape with very low roll resistance, relying for control and stability on its fins and tail. Similarly, this semicircular hull shape has almost no static roll resistance at rest, and any heeling force is only countered by the counterbalancing efforts of the crew, and the ballast weight and motion damping effects of the centerboard (or keel). However, roll resistance increases dramatically, even when at rest, once the heel angle is sufficient to place the vestigial side wings in the water.
The boat develops dynamic stability underway because of the lifting forces from the centerboard (an underwater wing similar to a fishes fin), and the lifting forces of the sails. These forces normally act in the same direction tending to roll the hull to leeward and are countered by the weight of the ballasted centerboard and the balancing efforts of the crew weight on the windward side of the boat. Thus, dynamic stability increases with speed in a similar way to that of a bicycle, which has no stability at rest, but can be easily held stable at speed the rider balancing with his movements to correct for roll.
The semi-circular shape of the mid-portion 26 of the hull may include variations in the radius of curvature, such as having a shorter radius of curvature at a portion midway along the hull and a longer radius of curvature in cross sections closer to the rear of the boat. This has a flattening effect that may tend to increase the capability of the hull to plane at speed and, to the extent that it is less circular aft, may also lend some level of increased roll resistance and stability for the crew.
A transition is made between the shape of FIG. 1 and the shape of FIG. 3 along the body of the boat, as will be apparent from a review of the later figures. This transition is gradual so as to provide as little disturbance to the water flow as possible. Similarly, the transition from the semi-circular shape of a shorter radius at a middle portion of the boat to a semi-circular shape of longer radius is also gradual.
As show in FIG. 4, at the stern 28 of the hull an extension 30 is provided that extends the lower portions of the hull beyond the upper portions of the hull. The extension increases the water line length of the boat. A boat hull that operates as a water displacement hull normally has a limit on the speed that the hull can obtain. The limit depends on the water line length of the hull, for example according to the following. The theoretical maximum speed for a boat with a single displacement hull is 1.34 (L_WL)^1/2, where L_WLis the length in feet of the hull at the water line. At this speed, the bow wave and stern wave coincide to form a continuous wave system and trap a displacement boat in its own wave. By increasing the waterline length, the boat can go faster while moving as a displacement hull.
In one embodiment, the present hull is 18 feet in length, although other length hulls are of course possible. The 18 foot sailboat in its present embodiment has a waterline length of approximately 17 feet, and therefore a maximum displacement speed of about 5.5 knots. This maximum displacement speed can be overcome as the boat climbs up on its own bow wave; that is, as the boat planes. By incorporating features that facilitate planing and in common with other planing craft, the present boat can exceed the speed limit for a displacement hull.
The extension 30 of the hull at the stern 28 also has the effect of moving the crew space forward, so that the weight of the crew is moved away from the stern and closer to the midway point between the bow and stern. The weight of the boat hull is also moved forward by the extension, which effectively trims off weight at the end of the boat. The boat rides better in the water as a result.
In a further embodiment intended to be within the scope of the present invention, the stern extension 30 may also run further aft as shown in FIG. 8. In this embodiment the stern hull extension is lengthened to allow the smooth “fish body” hull shape to continue aft until it rises above the normal waterline, and so more closely emulates the body shape of a large fish moving on the surface. In the first embodiment of the invention, the hull was cut-off at 18 feet to provide a convenient vertical mounting surface for the rudder. However, this vertical edge has the downside of creating a small stern wave when in motion as a result of water rushing in to fill the air space behind the vertical surface. The result is increased hull drag.
The inventor expects that extending the natural fish hull shape illustrated in FIG. 8 to completely, rather than partially, clear the waterline at the stern will further increase the efficiency of the hull. It is anticipated that the associated increase in wetted surface drag from further extending the stern may be more than offset by the elimination or at least further reduction in stern wave creation. With this added extension the hull becomes similar to the traditional so-called “double-ender” hull designs that have fallen out of fashion in larger craft, but remain the standard in man-powered canoes and rowing skulls.
So far, the discussion of the hull has addressed the shapes of the portion of the hull in the water. As noted, this portion of the hull emulates the body of a large fish, and as such is shaped for optimum movement through the water. In common with virtually all other sailboat designs the portion of the hull that normally lies above the water is of a shape designed to move efficiently through air, and so has shapes with low cross sectional areas presented to the wind as with a bird in flight. Surfaces above the water are therefore kept as flat as possible to reduce air drag. With the exception of the mast required to carry the sails, bluff surfaces are avoided since they carry a very high air drag burden. Clearly, a sailboat's sails act as the equivalent of wings on a bird and deliver the same lift and power functions.
Unlike other sailboats this hull has an additional similarity to birds, because of the built in vestigial wings on the upper hull sides. These wings act in a similar manner to a seabird's wings, which as noted previously are held slightly open when at rest on the water surface to trap air, and thereby both add buoyancy and improve stability when the seabird sits on a rolling sea. The wings are formed by flared sides that extend laterally from the upper portion of the hull. As shown in FIG. 5 (and in FIG. 16 which shows the wings extending from the sides of the craft), the flares or wings 32 are curved outward in a reverse curve from the semi-circular curve 26 of the hull bottom.
The wings 32 serve several key purposes, one of which is to provide a broader deck surface for the crew as with the 79er, enabling the crew to move outward from the center line of the boat. Such movement provides leverage for control of heeling movement, without the necessity of presenting an undesirably wider canoe body to the water. This is accomplished by the crew sitting on the sides of the deck over the wings. The wings 32 also provide a hull surface that contacts the water at higher heeling angles to oppose further heeling, or tipping, of the boat. These flares or wings 32 are not in the water while the boat is at rest or underway at normal heel angles, and although creating some increase in air drag because of the larger cross section and surface area presented to the air, do not increase the hull water drag.
The flares or wings 32 are at their greatest extent at the sides of the hull. The outward flare of the hull decreases to its minimum extent at the bow 34, as shown in FIG. 6. The presence of a flare at the bow of a boat has the effect of preventing the water from splashing up into the boat and so is used in many power boat hull designs. However, it also catches the force of an upwardly directed wave and can slow the boat down or lift the front of the boat more than desired if a particularly strong wave strikes the boat, possibly even enough to be flipped over by a large wave in very heavy seas. As such, the present hull has little or no flare 36 at the bow 34 and in the area of the front of the boat. The present hull therefore minimizes the braking effect of bow flare upon entering wave-fronts.
These principles of hull design may be combined in different ways to provide hulls of different shapes, all of which fall within the scope of the present invention. The hull can be longer or shorter as needed. As noted, one such hull has a length of 18 feet. However, the hull design principles described above may be extended to a hull of several hundred feet or more. The longer the boat, the more effective and efficient this hull shape will be. As boat length increases boat width does not need to increase in the same proportion. A boat 18 feet in length has typically about 6 feet maximum beam. A 72 foot boat might be about 16 to 18 feet wide. Therefore, hull width typically increases at a lower rate that the hull length increases. This is because the need for hull width is determined by the volume needs of occupants and payload, and watercraft volume typically increases at a greater rate than length.
As a result, a longer boat has the advantage of needing to move proportionally less water aside than a smaller boat, allowing for a lower rate of change of curvature of the hull. All this means proportionally less drag and therefore less energy needed to move the water aside to make way for the body of the boat. Furthermore, in very long boats, the differing hull shapes needed at the bow, middle and stern can begin to approach the ideal. In the present 18 feet length embodiment the bow, middle and stern are so close together that a best compromise shape is all that is possible.
The forgoing principles have been brought together in a hull shape for a small performance sailboat. FIG. 7 shows a sailboat 40 that includes a hull 42, a centerboard or keel 44, a rudder 46, and a mast 48 on which is mounted sails 50.
The sails 50 include a primary sail or mainsail 52 supported between the mast 48 and a boom 54 that extends from the mast 48, and a jib sail or jib 56 extending between the mast and the front or bow 58 of the hull 42. The front of the hull 42 has the bow 58 shaped according to the principles show in FIGS. 1, 2 and 6. The rear of the hull 42 has a stern 60 at the rear shaped according to the principles shown in FIG. 4. The hull 10 is symmetrical about a center line 62 through which the center board 44 extends.
In particular, the bow 58 of the hull 42 is shaped to present a sharp edge 64 for easy entry into the water. The hull surfaces 66 at the left side, or portside, and right side, or starboard side, of the edge 64 are concave and angled outward, as noted above. The sharp edge 64 defines the center line 62 of the hull 42 that runs from the tip of the bow 58 back to the stern 60. The shaping of the hull 42 changes smoothly from the sharp angle 64 at the front with the concave sides to the more rounded or semi-circular shape at the main body portion 68 of the hull. This change in shape is done gradually in longer boats according to this invention, but in the illustrated 18 foot boat, the change is less gradual since there is less hull length in which to make the transition. It is important, however, that no abrupt changes in hull shape be made so as to maintain the low drag, efficient performance of this boat.
Referring back to FIG. 7, the upper edge of the hull 42 is provided with a rub rail 72 where the deck is attached to the hull. The upper edge of the hull 42 is referred to as the gunnel or sheer. When the boat 40 is properly trimmed and sitting still in the water, the lower portion of the hull 42 is in the water and the upper portion of the hull is above the water line. The portions of the hull that are above the waterline are referred to as the topsides, and the minimum distance from the water-line to the gunnels or sheer line 72 is referred to as freeboard. The present hull has more freeboard than most comparable small sailboats. The extra freeboard together with the spoon bow and side wings permit the boat to operate in somewhat larger seas with less green water over the decks, and permits greater heeling before water enters the cockpit area. The hull 42 of FIG. 7 includes the wings 74 which are described as individual features in FIGS. 5 and 6.
The portion of the hull 42 just below the rail is shaped to provide the wings 74 extending laterally outward from the center plane of the boat. The wings 74 are formed to gradually increase in the extent of flare, from little or no flare adjacent to the bow 58, to an increasing extent of lateral projection from portions of the hull 42 at the middle and rear portion of the boat.
In common boating terms, a flare is an outward curve of a vessel's sides, usually near the bow. In the present invention, by contrast, the flare does not project much or at all near the bow of the boat, but instead has its greatest outward extension from hull's sides 78 at the back half of the boat. The flares are referred to as wings 74 in the present boat and are clear of the water while sailing on lower wind at a shallow heel angle. However, at larger heel angles, the wing 72 on the side of the boat toward which the boat is heeling (the leeward side) contacts the water where the buoyancy and drag of the wings in water resists further heeling and stabilizes the boat. In hull 42 of the illustrated embodiment, the boat heels readily to a fifteen degree angle or more from vertical without contact of the wings 74 with the water.
While sailing, the sailboat 40 heels over (or rolls to the side) as a result of the wind forces on the sails 50 and 52. With a small to moderate angle of heel, the bottom 68 and sides 78 of the hull are in the water, to present a relatively narrower, sleeker hull shape and thereby reduce water drag and enable more rapid movement through the water. The semi-circular shape of the mid-body and rear portion of the hull enables the boat to heel over easily to a fifteen degree or greater angle. The ease with which this boat heels when stationary or at low speeds may feel unsettling to less experienced sailors but is the key to a low drag high efficiency hull shape, and for a more experienced sailor could provides some of the excitement of sport sailing. An increased angle of heel beyond a desirable angle will result in the wing 74 contacting the water on the leeward, or downwind, side of the boat.
These vestigial wings on the upper hull sides provide at least four critical advantageous effects on the moving boat. First, and as with the 79er when the leeward side wing makes contact with the water due to excessive heeling it provides a sudden increase in the wetted surface of the hull and so a sudden increase in the resistance to forward motion on the side of the boat in contact with the water. The increased friction of the water on the added hull surface in the water on the leeward side causes the boat to slow and somewhat to leeward when the wing enters the water. This frictional slowing force is predominantly on one side of the boat and is in a direction to resist broaching of the boat, as follows.
As the wind blows against the boat 40, it exerts a turning force, or wind vane effect, on the boat, also termed broaching force. During high wind conditions, the broaching forces may be quite strong. For a wind powered craft, broaching normally causes the boat to “round up” or rotate toward the wind, while heeling heavily to leeward and then stalling and laying over at an angle in the water. In extreme cases the boat may experience a full knockdown, in which the boat is fully on its side with the sails in contact with the water. The additional hull contact with the water by the wing 74 on the leeward side creates drag that provides a force to counteract the broaching force. In a powerful wind gust then the sailboat 40 tilts over, the wings 74 scrub the water, and broaching is resisted. Furthermore, except in the case of extremely powerful wind gusts, a full broach or knockdown may be entirely prevented.
Thus, the present invention is a hull design that has inherent anti-broaching characteristics. In conditions that would cause a similarly sized sailboat to broach, round-up, or take a full knock-down this hull will heel hard to leeward, stall and come to a halt in the water abruptly while laying over with the leeward wing under the water (See FIG. 17 of the sailboat stalled during a moderate broaching gust). As can be seen from FIG. 17 of the boat in an actual wind gust stall, the crew have not lost control and are still in their normal crew positions in the cockpit (crew can often be thrown from their normal crew positions in a broach, particularly in a small sailboat or dinghy). Once a gust passes or the crew has time to release the pressure on the mainsail sheet the craft will tend to right itself and can be sailed out of the stalled condition.
A second effect of the wing 74 contacting the water is that the wing 74 changes the hull shape presented to the water from the easy to roll rounded shape of the lower hull to a shape similar to a fin. This fin shape must push the water out of the way to move through the water and so provides a strong resistance to further heeling or tilting. This shape change results in forces on a relatively long lever arm to resist further heeling once the wing 74 is in the water. With reference again to the 79er, this craft will also exhibit anti-broaching properties when its wings suddenly enter the water. But because the wings are much wider and increase in width much less gradually from the bow, they will have a much more extreme and less controlled effect when entering the water than the wings in the current invention. As mentioned previously the wings on the 79er are primarily for crew leverage to permit a more extreme sail plan be carried. The leeward wing is therefore not normally intended to be continuously in contact the water.
A third effect of the wing 74 in contact with the water is that the wing 74 provides floatation forces, or buoyancy. Not only does the floatation force resist movement into the water, but it also provides a righting force to bring the boat up to a lesser heeling angle. The righting forces are also exerted on a relatively long lever arm by virtue of the distance of the wing from the center of the boat. These effects combine to provide a strong righting moment to not only resist further heeling or rolling of the boat, but to bring the boat to a more upright position once sail forces are reduced either by releasing the sheets, or by wind forces dropping as happens after a powerful wind gust. As such, even though the present boat is a fast, sporty handling boat, the wings 74 provide resistance to rolling beyond a predetermined angle, or so-called over-heel. Consequently, the hull strongly resists capsizing and thus delivers an important increase in safety. Again referring to the 79er, its wings will also resist further heeling once in the water, but are generally much thinner with less buoyancy. Furthermore, since the 79er hull and wings is more like a thin saucer shape it will permit water to enter the large cockpit when heeled at higher angles so further reducing buoyancy and increasing heel. This is very similar to the action of a saucer floating on water that when tipped at just the right angle to bring the saucer's lip below the waterline will allow water to enter the saucer.
An added benefit of the wings in the current invention is that, because it resists over heeling, the leeward wing 74 serves as a guide to the extent of heel angle to strive for by the crew, in order to avoid the power loss that results from over-heeling. Once a wing is in contact with the water, but at less than broaching forces, a greater sail area is being presented to the wind than would otherwise be the case without the wings. With less wind power lost over the top of the sail, there is potentially greater power and therefore greater speed available to a crew skilled in counterbalancing the dragging force of the wing in the water to just match the heeling force of the sails without over heeling. In contrast the crew of a 79er would avoid the wings from being continuously in contact with the water because of the more extreme and somewhat uncontrolled braking affect of its wings in the water.
Finally, and key for improved hull efficiency at higher speeds, the underside of the wings preserve the convex shape started at the bow to continue to encourage vortex creation as the water moves back and up from the bow and provides the space needed to accommodate the flow of displaced water less impeded by the unnecessary re-collision with the widening hull common in most displacement surface craft. In contrast, the Australian 18 and the 79er hulls are not designed or shaped to generate vortices at the bow or continue to encourage and sustain them along the undersides of the wings. These hulls are designed to plane easily and so spend most of their time planing. In a planing condition the first 4 to 6 feet or even more of these hulls is often well out of the water and has no affect on the wave making of the hull. Both hulls are more dart or V-shape when viewed from above and the rear sections are quite flat to promote easy planning.
The wings 74 are readily apparent in FIG. 9, which is a bottom view of the hull 42 tipped to an angle as seen by the water during sailing. The main body 68 is rounded and extends up to the sides 78. From the sides 78, the wings 74 extend outward to provide the additional hull surface during over-heeling. The wing 74 has only a minimal extension from the side 78 near the front of the boat, as indicated at 80. At the midpoint and to the rear of the boat, the flare or wing 74 has a much greater extension, as is apparent at 82 and 84. By tapering the wing 74 from smaller to larger, a gradual change of shape is presented to the water to prevent strong resistance from the wing 74 contacting the water. The wings 74 are of a shape and structure so that the wings can be in contact with the water and the water can flow against the wings while the boat is in a normal sailing operation. For example, no abrupt shape changes are made that would disrupt the flow of water and unduly effect control or operation of the boat when the wing 74 contacts the water or enters the water.
As apparent from FIG. 9, the hull 42 has a widest portion at 86 approximately two-thirds of the way back from the bow 58 to the stern. From the widest portion 86 to the stern 60, a gradual inward tapering of the hull 42 is provided at the portion below the water line, at the gunnel 72 and the side portions 78. The widest portion 86 defines the over all width or maximum beam of the hull 42. It is also possible that the hull maintain this full width beam all the way to the stern instead of tapering to a narrower width.
The stern 60 is shaped to have a more flat or slightly rounded termination 88 at the portions below the water line and is angled at side portions 90 that extend from the rail or gunwale 72. The water line length of the boat is thereby greater due to the extension of the stern 60, which increases the maximum potential speed of the boat during displacement travel.
Still with reference to FIG. 9, the front of the hull 42 has sides 89 that spread the water after it has been pushed apart by the sharp edge 64. The sides 89 are at a relatively shallow angle relative to one another to provide a slicing effect at water entry. The rolling motion of the water discussed in conjunction with FIG. 1 forms two rolls or vortices of water that are moved apart from one another by the sides 89.
In a power boat version of this hull shape these rolls of water will normally be formed symmetrically on either side of the hull. In this sail powered version however the roll will be more pronounced on the leeward side of the hull because of the tendency of the hull to be pushed to leeward by the force of the wind. These rolls of water or vortices continue along the sides of the hull 42 as the boat moves forward, smoothing the movement of the boat through the water and changing the character of the wave along the sides of the hull during movement, particularly during fast movement.
The rolling motion of the water away from the hull and the shape of the hull creates a trough in the water and the hull moves along this trough. The trough shape in the water carries behind the boat and does not immediately close around the stern of the boat (see FIG. 18 wherein the stern wave is shown). This lessens the drag that would occur otherwise and is possibly removing or partially removing the stern wave trap that limits a displacement hull's theoretical maximum speed. At least as judged from early-on water testing carried out with the prototype, the trough shape appears to have the effect of lengthening the effective water line of the boat and so increasing the maximum displacement speed.
Further on-water testing is required to verify this potential breakthrough capability of the hull shape. FIG. 19 shows a prototype sailboat according to this invention in high speed travel in approximately 18 to 22 knots of wind, wherein the boat is traveling at an unmeasured speed perhaps somewhere between 8 to 11 knots, but in any event above the maximum displacement hull speed for an 18 foot hull. Since the hull is fully in the water over its entire length it appears to still be operating as a displacement craft.
At the time of writing it is not known for certain that this hull is in fact traveling above its normal maximum displacement speed as suggested by the photographs, nor what mechanism might be at work to accomplish this property of the hull. The inventor speculates two alternative general explanations for how this hull appears able to travel above the normal maximum displacement speed without obvious planing. First, although the hull appears to be in displacement mode because the entire hull is in the water, it may in fact be planing, or partially planning with inception of planing occurring at low hull speeds well before the normal maximum displacement speed is reached. Alternatively, the hull may be operating in a displacement mode but the vortices of water created at the bow, and encouraged by the convex shaped wing undersides, are separating from the hull surface after passing the widest point of the hull and traveling away from the hull at the stern. This might prevent, or at least inhibit, formation of the full normal stern wave, and thereby allow the hull to at least partially escape the normal displacement wave trap.
The limited experimental results so far may favor the second possibility because, as shown in FIG. 20, at even higher speeds, the bow does rises up, and clearly exhibits the inception of normal planing behavior. Also, as shown in FIG. 18 there is a trough evident in the water behind the boat which is not immediately filled in and remains behind the boat for several boat lengths. This trough has been observed under most sailing conditions with this hull, and may be supporting evidence that the vortices of displaced water are traveling away from the boat in such a manner as to reduce, inhibit or even eliminate stern wave creation.
The inventor has no special knowledge of vortices, but conjectures that the encouragement and creation of vortices may take more energy from the wave shaping forward sections of the hull, but reduces energy taken from the aft sections, with a net reduction in energy needed to displace the water with vortices versus without them. In other words, the total energy taken from the hull to first create and then sustain the vortices may be lower than the total energy needed to just splash or push aside the water in the somewhat chaotic manner occurring with most other hull shapes. Perhaps vortices then are capable of moving fluids in a more efficient manner than with normal fluid movement. This seems a reasonable possibility, since vortices once created tend to be self-sustaining, and naturally occurring vortices such as tornados or waterspouts usually only break up upon encountering obstacles or changes in environment sufficient to extract enough energy from the vortices to cause their collapse.
Returning now to the detailed hull description, the rolling vortices of water moving along the sides of the hull 42 move below the convex under surface of the wings 74. Any momentary tipping of the boat to the side may cause the rolling water to contact the wings 74, resulting in a stabilizing effect on the boat during movement. While being very tender at rest, the present hull provides increasing dynamic stability with increasing speed, and as such provides a very stable hull for the crew when underway at speed. This is due in part to wings 74 interacting with the rolling motion of the water at the sides of the hull 42, and due in part to the trough formed in the water by the vortex-encouraging shape at the front and upper sides of the hull 42.
In FIG. 10, the shape of the hull 42 at the bow 58 corresponds to the principle discussed in FIG. 2. The bow 58 and the portions of the hull below are shaped to help ride over waves rather than through them, providing better handling and crew comfort in a seaway. As stated, hull length affects maximum displacement hull speed in normal hulls and therefore the spoon bow potentially sacrifices some speed potential over a plumb bow because of the inherent reduction in waterline length. However, a traditional spoon bow is judged essential in a small sailboat, because it will usually be sailed in shallow waters and in close proximity to shorelines. A spoon bow allows the boat to be run up on a beach or shore or handle an unexpected grounding with much less potential for damage than a plumb bow. Also, during sailing, one occasionally strikes floating debris or even obstacles such as rocks and the like. Notwithstanding the foregoing advantages of a spoon bow particularly for small sailboats, a hull with a more vertical, or plumb bow, but with similar concave bow wave shaping surfaces and side wings, is envisaged in a further embodiment and encompassed within the scope of this invention.
The front portion of the hull 42 will naturally try to ride over the debris and rocks or at least lift up on them rather than striking these objects with a blunt blow and risking damage to the bow of the boat. Thus damage to the hull 42 is less likely as a result of the present bow shape. The main body 68 of the hull has the rounded bottom portion below the water line, as is apparent from the densely spaced contour line at the bottom of the hull from about midway to the stern 60. The cross-sectional shape of the hull is also apparent in the FIG. 10 by examining the section lines 87. The section lines 87 near the front or bow 78 have a sharp angle at the lower end indicating the sharply angled water line entry of the hull 42, whereas the section lines 87 near the middle portion and at the rear of the hull 42 have a rounded lower portion indicating the rounded shape that promotes ready heeling of the sailboat hull.
The shaping of the back sections of the hull 42 promotes planing on the water at higher speeds, rather than displacement motion. The bow shape provides lift in addition to slicing the water during forward motion. The lift is carried back along the hull so that the shallow rounding of the hull 42 from the main body 68 to the stern 60 permits the hull 42 to plane on the water upon reaching the planing speed. By providing a planing hull, the boat 40 is able to exceed its theoretical maximum displacement hull speed.
As with all other planing hull designs, planing speed occurs when the hydrostatic forces are just sufficient to lift the hull partially from the water, thereby reducing hull drag and also the amount of water needing to be displaced. Thus when a watercraft reaches its planing speed, the situation is equivalent to an aircraft just at the point of lift-off, the aircraft having reached its so-called “rotation velocity”, and above which the pilot may initiate take-off. In a sailboat any further application of power available from the sails will cause the hull to climb over its own bow wave and skim across the waters surface exactly like a windsurfer, increasing the speed of the boat beyond its theoretical maximum displacement hull speed.
FIG. 11 shows the stern 60 of the hull 42 from an end view. The stern 60 includes the stern sides 90 shaped with the upper edge at an angle, the sides 90 providing a connection between a rear panel 92 of the hull 42 and a step 94 that forms the extension of the hull below the water line and thereby increases the water line length. The step 94 has a horizontal top surface 96 and a vertical end surface 98. A rounded corner connects the vertical and horizontal surfaces 98 and 96. The step surface 96 provides a surface on which to kneel and stand to enter the boat, particularly useful for someone entering from the water. For example, someone swimming or falling from the boat may re-enter by climbing onto the step 94. As with other open transom boats with a stern step, a crew member who accidentally falls into the water may easily re-board via the step, turning a potential problem into an inconvenience.
Normally in boats of this size the boat crew would re-enter from the water at the sides. This can prove difficult under heavy conditions, since the boat may heel excessively as the person pulls his weight over the side. Furthermore, in a small dinghy or boat of this size, re-boarding from the sides can often result in capsize. In contrast, even a person weighing 300 pounds or more could enter from the stern without risk of significantly disturbing the boat's attitude in the water. The rudder 46 is typically mounted on or near the vertical end surface 98 at the stern 60 and may also provide a structure that can be grasped by the person in the water while pulling up to enter the boat. It is preferred that the top surface of the step 96 be provided with a texture, such as roughening, ridges or grooves, or the like to provide more sure footing for the person entering the boat from the water.
The wings 74 can be seen at the port side of the hull 42 in FIG. 11. Also apparent is the open transom. The rear panel 92 closes only the end of the hull body and does not close the end of the cockpit or crew area 100 of the boat. No transom board closes off the end of the cockpit 100 as is the case with many boats of this size. This eliminates the risk of swamping from a large wave entering the cockpit, because any water that gets into the cockpit 100 may flow out of the cockpit 100 at the stern 60 of the boat. The cockpit 100 is preferably shaped with a slope to enable the water to flow readily out the cockpit 100, so that the water from spray, splashes and waves does not remain in the cockpit. The step 96 is below the lowest point in the cockpit 100 to allow for easier boarding, and to permit the water to exit more readily, although it is also possible that the step may be even with the lowest point in the cockpit, just so long as water is not trapped in the cockpit 100.
The opening in the rear panel 92 for the cockpit 100 is in a widened W shape. This is the shape of the cockpit going forward from the stern 60. The W shape has outer walls or side walls 102 and a center beam 104. The side walls 102 of the cockpit 100 are curved inward to provide a lower back support for crew sitting sideways in the cockpit. The center beam 104 is angled up to a center ridge line 106 that runs the length of the cockpit 100. Crew members sitting sideways in the cockpit 100 can sit on one side of the center beam 104 and their feet against the side wall 102 on the other side with their knees over the center beam 104. The crew members are thereby braced between the sidewalls 102. The W shape of the cockpit floor is designed to work well for children 4 feet tall nearer the front, to adults over 6 feet tall nearer the stern.
The boat 40 has a deck 108, that is also visible in FIG. 11. The deck 108 is on either side of the crew compartment, or cockpit, 100 and provides a seating surface for the crew while sailing at steeper heel angles. The deck 108 extends from the gunnel 72 to the cockpit 100 and is generally flat with a slight camber to direct water off the sides of the boat. The deck 108 extends fully over the wings 74 so that any crew sitting on the side portions of the deck with their feet under hiking straps running down the center of the cockpit floor has a strong lever arm for their body weight to help counterbalance the heeling force of the wind. The crew can sit upon the more outboard portion of the deck over the wings without having to hang over the edge of the boat as far as is common in many sailboats. This position is more comfortable and safer for the crew, with less chance of falling in the water.
For sailing conditions that require the crew to sit up on the side deck 108, the crew can place their feet under the hiking straps and resting either on the opposite sidewall 102 or on the center beam 104 on the same side on which they are sitting. The center beam 104 thereby provides a stable foot position for the crew in this position as well. As the wind conditions change, the crew may move to several different positions in the cockpit 100 and on the side deck 108 for optimum sailing position, facilitated by the unique W shaping of the cockpit.
Turning now to FIG. 12, the cockpit 100 when viewed from above has a elliptical shape with a elliptical shaped edge 110 where the deck 108 and cockpit 100 meet. The cockpit 100 provides the interior space of the boat for the crew during slower sailing or in lighter wind where the heel angle is less. The elliptical shaping of the cockpit 100 reduces the swamp volume of the cockpit over the more common rectangular shape. Perhaps more importantly, the elliptical shape also forces the majority of the water toward the stern, aiding in tilting the boat aft to assist rapid draining out of the boat at the open transom. Also as a result of the elliptical shape of the cockpit, the deck 108 has a wider seating surface for the crew at the midpoint of the boat for greater crew comfort.
The cockpit surface 104 may have open-able panels 112 for storage within the hull 42. For example, an insulated ice chest opening 112 may be provided for storage of chilled drinks for the crew in the center beam 82. It is also preferred that a storage compartment beneath a panel 112 be provided for emergency equipment such as a whistle, lifesaver, rope and the like. Of course, other openings for storage or the like are also possible in the center beam 104, in the sidewalls 102 or in the deck 108. Such cockpit openings should be of relatively small volume and also drained into the trunk to prevent build up of weight due to water trapped in these enclosures.
The deck has a forward portion 108 on which or in which is mounted the mast 48 for the sailboat.
With reference to FIG. 13, the hull 42 is formed of a lower hull piece 120 and a deck or upper hull piece 122. The cockpit 100 may be formed in one piece with the deck piece or may be separate. Although these pieces may be of several different materials, in a preferred embodiment the lower hull piece 120 and the upper hull piece 122 are formed of composite fiberglass and foam sandwich that is molded and shaped to the appropriate shape.
Between the lower and upper hull pieces 120 and 122 is an interior space 124 for the boat 40. Preferably, this space 124 includes floatation materials, such as foam blocks, air bladders, wood blocks or the like. In a particularly preferred embodiment, the interior space 124 is filled with a combination of spheres 126 of polystyrene foam and a (pour-able) plastic foam 128 filled in the spaces between the spheres 124. Because polystyrene is much lighter than typical marine floatation foam, the effect of the polystyrene spheres is to reduce the total weight of the combined floatation material, without leaving air cavities that may be displaced by water in a hull breach. Almost the entire interior space 124 within the boat 40 is filled with this combination of spheres and foam. A small space or cavity is left at the bottom of the hull to allow water from condensation to collect and subsequently be drained. Also a few places are left unfilled to accommodate beverage storage boxes and emergency equipment storage.
The combination of spheres and foam is designed to remain embedded and securely attached to the hull or deck. The spheres of polystyrene and the foam have excellent buoyancy; if the boat were completely fractured apart in a catastrophic collision, the spheres and foam combination would for the most part remain intact and provide powerful floatation forces even to a such a badly fractured hull. The expanded plastic foam 128 between the spheres 126 bonds the spheres 126 in place. This light and strong floatation material, present in almost the entire hull in a preferred embodiment, virtually eliminates the risk of water entering the interior space 124, even in the event of a severe hull breach.
In addition to its powerful floatation properties, this mix of polystyrene spheres and foam adds strength to the overall structure, and permits the craft to tolerate multiple sharp object hull penetrations with a low short-term risk to overall hull integrity and crew safety. Such a structure might even absorb bullets in craft designed for military applications. During manufacture, the polystyrene spheres 126, together with the flotation foam, may be preformed in multiple sections to fit in to the various cavities of the hull interior, and then be bonded in place to the hull or deck.
In one embodiment, the spheres are about two to four inches in diameter, although other sizes are envisioned and are encompassed within the scope of this application. Mixed sizes of spheres can be provided as well. A combination of smaller spheres and larger spheres may be included together to provide greater packing density, or to best fit the specific hull interior cavities. The present invention encompasses the use of non-spherical foam pieces in place of the spheres, or in addition to the spheres. These non-spherical pieces can be oval, oblate, square, rectangular and many other shapes. They may also be complex shapes, such as to fit into specific spaces within the interior space of the hull. Within the scope of this invention, these shapes are encompassed within the term sphere.
The spheres are preferably of expanded polystyrene, although other types of foam or other buoyant material are also possible for use as spheres. Hollow plastic spheres may also be substituted as desired, although these carry a greater risk of water uptake through puncture or osmosis. The foam filler may be liquid foam that expands as it cures, such as an expanding urethane liquid foam material. It is also contemplated to use foam particles, flakes, granular foam or other material as the filler instead of, or in addition to, the liquid foam. The preferred filler material is pour-able, although this is not necessary. In an alternative embodiment, the spheres and/or the foam fill may be made of or include wood particles or other buoyant materials. The foam material should be a so-called closed cell foam to reduce water absorption.
The spheres and foam fill may entirely fill the interior space of the hull or may be provided only at portions of the hull. It is preferred that sufficient spheres and foam be provided in each major section of the hull that a catastrophic breakup of the boat will still leave all major portions of the hull floating. Persons involved in such a disaster will have large buoyant pieces of the boat to cling to, and so increase their chances of survival.
The present boat is nearly impossible to sink. The hull is strong enough to take hard impacts without being breaking apart. Even a major hull breach should not result in sinking of the boat, but will only reduce the speed at which the boat can sail, so that the crew can return to port safely. If a catastrophic event occurs, such as a high-speed impact from another boat that fractures the hull into multiple pieces, each major piece should remain floating, providing surviving crew with flotation pieces to cling to until rescued.
The use of the polystyrene spheres 126 with the foam fill 128 reduces the total weight of floatation material that would be otherwise needed to fill in the interior hull space. The result then is a light boat that is essentially a solid object, leaving little or no air inside the hull for water to displace following any hull breach.
Thus, there is shown and described a hull for a sailboat (as shown in FIG. 21 from the starboard side) which is essentially a solid object that is lighter than water, and so does not rely on interior air for floatation. Therefore, unless trapped under a heavier object, the described hull is almost impossible to sink. Furthermore, the hull shape is designed to move through the water with low resistance, and incorporates side wings to provide wide hiking and seating surfaces, and to powerfully aid stability at speed through increasing roll resistance with increasing heel angle. The unique hull shape is designed to encourage and aid the creation of vortices along the sides of the boat using the water that must be displaced anyway. These vortices in-turn stabilize the boat by making contact with the side wings at higher speeds and heel angles. The present boat is sufficiently fast that the size of the sails can be reduced compared to boats of similar size, yet still retain adequate speed from the wind. The smaller sails make sailing easier for the crew, particularly in heavy weather, and make for a lighter boat. The result is a safe, high performance hull designed, in this first embodiment, in a sports boat that can operate in heavier sea and weather conditions than other boats of its size.
Although other modifications and changes may be suggested by those skilled in the art, it is the intention of the inventor to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of his contribution to the art.

Claims

1. A hull for a boat, comprising:

an exterior hull surface of the hull having a shape that is symmetrical about a longitudinal center line;

a bow portion of said exterior hull surface having a water entry edge, said water entry edge defining a curve having a horizontal and a vertical component, said bow portion including sidewalls having a concave shape on either side of said water entry edge;

a main body portion of said exterior hull surface connected to said bow portion, said main body portion having a semicircular shape in transverse cross section; an upper edge of said exterior hull surface having a deck portion connected thereto; and

first and second wings of said exterior hull surface extending laterally from opposite sides of said hull below said upper edge, said first and second wings having a greater extent of lateral extension at a mid-portion of said hull than at said bow, said first and second wings being structured to permit water to flow against the wings while under normal sailing operation.

2. A hull as claimed in claim 1, wherein said first and second wings taper from a full lateral extension at sides of a midpoint of said hull to a slight lateral extension adjacent said bow.

3. A hull as claimed in claim 1, further comprising:

a stern of said exterior hull surface defining a rearward extension of said exterior hull surface at a lower portion thereof and having an endwardly tapering sidewall between said upper edge and said lower portion.

4. A hull as claimed in claim 3, wherein said stern includes a step, said step including a horizontal step surface extending transversely across stern and a vertical surface below said step surface defining a rearmost surface of said hull.

5. A hull as claimed in claim 1, further comprising:

a stern of said exterior hull surface defining a rearward extension of said exterior hull surface, said rearward extension being tapered to said longitudinal center line and rising to above a water line of the hull.

6. A hull as claimed in claim 1, further comprising:

a cockpit formed in said deck, said cockpit defining interior side surfaces extending from said deck, said interior side surfaces being curved inwardly and being adapted for a crew member to sit leaning against said interior side surfaces; and a center beam extending longitudinally of said hull in said cockpit.

7. A hull as claimed in claim 6, wherein said deck includes side deck portions laterally of said cockpit, said side deck portions overlaying said wings, said side deck portions being adapted for a crew member to sit upon.

8. A hull as claimed in claim 1, further comprising:

foam spheres in an interior space between said exterior hull surface and said deck; and

foam material filled between said foam spheres, said foam material bonding said foam spheres in place.

9. A hull as claimed in claim 8, wherein said foam spheres are of polystyrene.

10. A hull as claimed in claim 1, wherein said hull is a sailboat hull.

11. A hull as claimed in claim 1, wherein said hull is a powerboat hull.

12. A hull for a sailboat, comprising:

a main body portion of said exterior hull surface connected to said bow portion, said main body portion having a semicircular shape in transverse cross section;

an upper edge of said exterior hull surface having a deck portion connected thereto; and

first and second wings of said exterior hull surface extending laterally from opposite sides of said hull below said upper edge, said first and second wings having a greater extent of lateral extension at a mid-portion of said hull than at said bow, said wings extend from both sides of said hull, said wings tapering from a full lateral extension at sides of a midpoint of said hull to a slight lateral extension adjacent said bow;

a stern of said exterior hull surface defining a rearward extension of said exterior hull surface at a lower portion thereof and having an inwardly tapering sidewall between said upper edge and said lower portion, said stern including a step, said step having a horizontal step surface extending transversely across stern and a vertical surface below said step surface defining a rearmost surface of said hull;

a cockpit formed in said deck, said cockpit defining interior side surfaces extending from said deck, said interior side surfaces being curved inwardly and being adapted for a crew member to sit leaning against said interior side surfaces;

a center beam extending longitudinally of said hull in said cockpit;

said deck including side deck portions laterally of said cockpit;

said side deck portions overlaying said wings, said side deck portions being adapted for a crew member to side upon;

foam material filled between said foam spheres.

13. A hull for a boat, comprising:

an outer hull of fiberglass;

an inner hull of fiberglass, said inner hull being mounted in and connected to said outer hull to define an interior space there between;

foam spheres in said interior space; and

a foam material between said foam spheres in said interior space, said foam material bonding said foam spheres in place.

14. A hull as claimed in claim 13, wherein said hull is a sailboat hull.

15. A hull as claimed in claim 13, wherein said hull is a powerboat hull.

16. A hull as claimed in claim 13, wherein said inner hull includes a deck and a cockpit.

17. A hull for a boat, comprising: an exterior hull surface of the hull having a shape that is symmetrical about a longitudinal center line;

a bow portion of said exterior hull surface having a water entry edge, said water entry edge including a front edge defining a substantially straight line that is substantially perpendicular to a water surface as said hull is floating on the water, said bow portion including sidewalls having a concave shape on either side of said water entry edge;

first and second wings of said exterior hull surface extending laterally from opposite sides of said hull below said upper edge, said first and second wings having a greater extent of lateral extension at a mid-portion of said hull than at said bow.

18. A hull for a boat, comprising:

an outer hull portion having a bow and stern;

a cockpit in said outer hull portion, said cockpit having a shape in transverse cross-section generally in a shape of a W, said W shape extending generally from said stern to at least crew seating area of said cockpit; and

a deck extending from outer edges of said cockpit to upper edges of said outer hull.

19. A hull for a boat as claimed in claim 18, wherein said cockpit has a generally elliptical shape when viewed from above, said W shaped being defined in part by a beam extending along a central axis of said parabolic shape.

20. A hull for a boat as claimed in claim 18, wherein said outer hull portion includes wings extending laterally from both sides of said hull portion, said wings gradually increasing in extent of extension from said sides beginning with a minimal lateral extension adjacent said bow and a greater extension at a position midway between said bow and said stern, said deck defining seating surfaces above said wings.