STABILIZED HULL FOR A KEELED MONOHULL SAILBOAT OR SAIL AND MOTOR BOAT

Abstract

The invention relates to boat building and can be used in the building and modification of sea-going high-speed keeled monohull sailboats or sail and motor boats with a high sail power to weight ratio, where a single, narrow, wave-penetrating displacement hull is used. To provide for the stable controlled movement of a keeled monohull sailboat or sail and motor boat in wave penetration mode, i.e. in a low wave/hydrodynamic resistance displacement mode, both when heeling and when upright (at the same time effectively counteracting heeling and rocking on all courses), and to provide for the damping of the energy of a broken wave and also for the ability of the boat to self-right to an even keel from a sail-on-water position, a stabilized hull for a keeled monohull sailboat or sail and motor boat is configured with an overall width of not more than 50% of the length of the hull and has, in the bottom part thereof, a vertically oriented narrow section (4) of low wave/hydrodynamic resistance, which runs longitudinally along the full length of the boat, is symmetrical about the centreline thereof and has a displacement segment (5) comprising a keel (8) with a heavy bulb, wherein the displacement of the segment is equal to the full unladen weight of the boat. The hull further comprises two narrow longitudinally oriented sponsons (6 and 7), arranged symmetrically in relation to the centreline of the boat, which do not bear the weight of the boat and which have a streamlined shape of low wave/hydrodynamic resistance. Said sponsons are situated above the waterline at the maximum width of the hull, forming two tunnel cavities (10) above the waterline to dampen the energy of a wave broken by the bow and the sponsons.

Claims

1. A stabilised hull of a monohull keeled sail/power-sail boat characterised by the hull total width not exceeding 50% of its length, which in its lower part is embodied with a longitudinally arranged, symmetrical in relation to the boat centerline and commensurate to its length, vertically oriented narrow section of low wave/hydrodynamic resistance, with a water displacement segment, including a keel with a heavy bulb, therein, the length-to-width ratio of that segment waterline is at least 7 times, with the segment water displacement corresponding to the fully loaded weight of the boat, therein, the narrow section is embodied with wave piercing lines, a high wave piercing stem, streamlined back lines, and a streamlined spatial widening in the upper front part thereof, it also includes two longitudinally oriented, symmetrical in relation to the boat centerline, sponsons, located above the waterline along the bottom surface of the hull at maximum hull width; in relation to the hull length, the sponsons may be located either closer to the stern, the middle or to the bow part of the hull, therein, the sponson length-to-width ratio is at least 7 times, with its own volume sufficient for parrying heeling under sail at submersion of the leeward sponson, but not sufficient for keeping the boat afloat, therein, the sponsons have a streamlined, spindle-shaped form with wave piercing front, streamlined rear and planing middle lines, forming above the waterline two tunnel cavities between the narrow section and each of the sponsons, of the size sufficient for dissipating the energy of the wave broken by the stem and the sponsons.

Description

[0040] FIG. 1 features the general view of the hull of a monohull keeled sail/power-sail boat 1 (the engine is not shown on drawings), where dimmed section 2 shows its wetted surface at no heeling under sailfor instance at sailing downwind or using the engine. The main elements are upper part of the hull 3, narrow section 4 with wave piercing displacement segment 5, right-hand 6 and left-hand 7 sponsons, keel 8 with a heavy bulb, rudder blade 9, two tunnel cavities 10, high front wave piercing stem 11.

[0041] The narrow section 4 is stabilised by keel 8 with heavy bulb and rudder blade 9 which ensures the boat steering capabilities. The boat's heavy equipment and the water and fuel reserves (if they are necessary) are located in the lower part of the narrow section 4, thus minimising the inertia moments of their weight at the hull movements. The segment 5 water displacement corresponds (within 80-100% range) to the fully loaded weight of the boat ready for travel, including the crew, the keel with a heavy bulb, the equipment and water and fuel reserves (if they are necessary), etc. Thus, the sponsons 6 and 7 do not take part in keeping the boat afloat.

[0042] The symmetric right-hand 6 and left-hand 7 sponsons are equally spaced from the boat centerline at the maximum hull width above the waterline. The location of the sponsons at the hull maximum width ensures a large lever arm of the sponson's displacement force, resisting heeling under sail and the hull swinging.

[0043] FIG. 1 shows the arrangement of the sponsons along the hull length closer to its stern; it is also possible to locate the sponsons closer to its middle or the front.

[0044] The installation angle of the sponsons in relation to the boat centerline (on FIG. 1, an angle of 10 degrees is shown) is appropriate for ensuring symmetrical water flow motion at submersion of the leeward sponson.

[0045] The narrow section 4 (FIG. 2) is long, narrow, with elevated forms of low wave/hydrodynamic resistance, relative elongation of the water line L/W WL of at least 7 times, thereby ensuring the displacement wave piercing mode and the laminarity of the water flow along its entire length, ensuring the cutting and passing of the wave along the narrow section with minimum impact on the boat speed. The high wave piercing stem 11 cuts the wave with minimum speed loss. In its front part, the narrow section 4 features a spatial widening 12 which reduces the pitching magnitude.

[0046] FIG. 3 shows sponsons details where symmetric right-hand 6 and left-hand 7 sponsons are made narrow, long, with elevated forms of low wave/hydrodynamic resistance, relative elongation of their shape (length-to-width ratio) of at least 7 times, thereby ensuring wave piercing and laminarity of the water flow along the entire length of the leeward sponson at its submersion under the impact of heeling under sail.

[0047] The sponson has three types of lines in its designwave piercing 13 in its front part, planning (deep V) 14 in the middle part and streamlined 15 in the rear part. The sponson body is of streamlined spindle shape, having a volume sufficient for parrying the heeling under sail by the force of its displacement at submersion of the leeward sponson, and also for parrying the boat swinging at all sailing modes. At the same time, the sponson volume is not sufficient for keeping the boat afloatthus, at critical heeling when the boat is in sails on water position, the leeward sponson is fully submerged, thereby preventing the hull from tipping over into a stable lying position through the displacement body, as it happens, for instance, with catamarans and trimarans.

[0048] The absence of boat weight carried by the sponsons, and their location at the maximum hull width at a long distance from the boat centerline and above the waterline, are the most important conditions of functioning of the claimed stabilised hull, because only if the above conditions are all simultaneously met, then: [0049] the leeward sponson embodiment may be of small volume for an efficient resistance against heeling under sail, with narrow streamlined shape and with the length-to-width ratio of at least 7 times, thus having a wave piercing shape, thereby exerting little impact on the boat speed at its submersion due to heeling under sail; [0050] the narrow shape of the sponsons and their wide spacing allow two tunnel cavities 10 to be formed between the narrow section 4 and sponsons 6 and 7 where cavities 10 minimise the wetted surface at the boundary of the media and where, in cavities 10, the energy of the wave broken by the stem and the front lines of the sponsons is dissipated; [0051] with no heeling under sail (for instance, sailing downwind or using engine), the middle lines of such sponsons, located above the waterline and free of load, actively plane, thereby exerting minimum wave resistance to motion; [0052] at critical sails on water position, the small volume leeward sponson is not capable of carrying the boat weight and it submerges, thereby preventing the hull from tipping over the sponson, and the return to even keel occurs independently, just like in modern monohull keeled boats.

[0053] The claimed stabilised hull may be embodied, for instance, from fiberglass or other composite materials, wood, metal, polyethylene, or combinations thereof, and/or other materials used in shipbuilding.

[0054] FIG. 4 (front view) demonstrates the operating principle of the claimed stabilised hull (4.1, 4.2 and 4.3) and its comparison with the hull of a conventional monohull keeled sail/power-sail boat (4.4, 4.5 and 4.6) in various modes, where the action of the following forces is shown:

[0055] 4.1 and 4.4at travel without a heel under sail (sailing downwind or using engine),

[0056] 4.2 and 4.5at 20 degrees heel to portside under sail,

[0057] 4.3 and 4.6in sails on water position,

[0058] where:

[0059] C.sub.T is the gravitational force of the keel with a heavy bulb,

[0060] C.sub.BCsponson water displacement force,

[0061] C.sub.Bside of boat water displacement force,

[0062] C.sub.Bhull water displacement force, y-lever arm.

[0063] The size of the arrows showing forces are not proportional to their values.

[0064] In 4.1 and 4.2, the sponsons being located on maximum hull width ensure a large lever arm (y) of the sponson displacement force restoring moment (C.sub.BC), and the hull thereby efficiently resists heeling under sail and swinging. The C.sub.BC is proportional to heelthe more the heel the more the submersion of the leeward sponson.

[0065] The wave is pierced by the stem and front lines of the sponsons; the wave energy is dissipated in the tunnel cavities, without bumping against the hull horizontal elements. The narrow section and the submerged narrow leeward sponson move in the displacement wave piercing mode with a low wave/hydrodynamic resistance, and do not limit the boat speed. When there is no heeling under sail, the sponsons are planing on their middle lines, preventing dipping into the wave. When the speed increases, the planing sponsons create additional lifting force, which resists heeling.

[0066] 4.4 and 4.5. are featuring a conventional monohull keeled boat, where the lever arm (y) of the side of boat displacement force restoring moment (C.sub.B) is small, not exceeding one half of the width of the hull leeward side; so the restoring moment is also smallthe hull swings on the waves and excessively heels under sail. The waves are pushed apart by the stem, and then further by the wide hull, creating thereby a high wave resistance in the displacement mode and limiting the boat speed.

[0067] All other conditions being equal, the illustrated 20 degrees heel under sail will be reached for the hull in 4.5 at lower wind velocity, than for the hull in 4.2.

[0068] In 4.3, in the critical sails on water position, the leeward sponson displacement is not sufficient for keeping the boat afloat and it is fully submerged, shifting the displacement centre closer to the boat centerline. The hull displacement force (C.sub.B) is thus applied to the same point as in 4.6, ensuring in both cases the hull independent return to even keel.

[0069] For monohull keeled sail/power-sail boats, the claimed stabilised hull provides a combination of a narrow section with a single wave piercing displacement segment having a relative water line elongation L/W WL of 7 times or more (and, correspondingly, the use of the advantages of low wave/hydrodynamic resistance, high seaworthiness and motion stability) and at the same time (with a high sail area to displacement ratio of 7-10 m2 or more per tonne of displacement) an efficient stabilisation system (specifically, resistance to heeling under sail and swinging) for providing the hull static and dynamic stability at a better level, than in conventional monohull keeled sail/power-sail boats.

[0070] This results in rated speed increase of 2 or more times in the water displacement mode, or (which is similar) a 2-fold or more reduction of energy expenditure (sail or engine) required for moving the monohull keeled sail/power-sail boat from point A to point B.

[0071] At the same time, it ensures the following characteristics at the level of modern monohull keeled sail/power-sail boats: space and comfort of the living quarters and excellent steering capabilities.