WO2007045934A1

WO2007045934A1 - Sailboat with cruciform hull, dolphin nose bow bulb, asymmetrical pontoons and specialized usage deck

Info

Publication number: WO2007045934A1
Application number: PCT/GR2006/000056
Authority: WO
Inventors: Apostolos Kourtis
Original assignee: Apostolos Kourtis
Priority date: 2005-10-17
Filing date: 2006-10-12
Publication date: 2007-04-26
Also published as: GR1005248B

Abstract

This invention concerns the making of a sailboat of trimaran type of hull consisting of a cruciform hull (3a) that forms the central body equipped with a horizontal wing (1a) and hydrodynamic vertical structure (2a) for greater speed and volume capacity, a dolphin nose bulb (4a) at its bow for improved hydrodynamic efficiency and speed, asymmetrical / dynamically supported lateral pontoons (5a and 5b) for higher stability and speed, and finally, an open deck (10a) for meeting special functional requirements.

Description

SAILBOAT WITH CRUCIFORM HULL, DOLPHIN NOSE BOW BULB, ASYMMETRICAL PONTOONS AND SPECIALIZED USAGE DECK.

1. This invention concerns the making of a sailboat of Trimaran type of hull consisting of a cruciform hull which has a dolphin nose bow bulb laterally and by asymmetrical dynamically supported pontoons the central body's hull of which has the ability to configure into an open deck for specialized usage.

2. The henceforth conventional designing and engineering norm in the trimaran section of marine engineering are expressed with the following general approach called the 'existing work of art': a) By shaping of a central body which ensures the following vessel characteristics:

• Buoyancy (by virtue of its displacement)

• Hydrodynamics (via waterline coefficients, hull coefficients etc.) • Tonnage capacity (by provision of adequate internal volume)

• Steering (via rudder devices and appropriate fins) b) By shaping of two lateral vessels (pontoons) in both sides to the right and left of the central body to which they resemble, such pontoons being designed and built to a scale of 50% to 80% in comparison with the central body, thus ensuring the following vessel characteristics:

• Lateral stability (by a stabilizing moment)

• Hydrodynamics (via similar hydrodynamic hull coefficients)

• Steering (via auxiliary fins) c) By Interconnecting of central body with pontoons through transverse beams.

3. The so far conventional design and engineering trends face constraints of serious limitations as far as the optimization of Stability, Hydrodynamics and volume Capacity characteristics for the Trimaran type of sailboats.

4. The proposed invention that follows in this text description accompanied by appropriate figures, tackles the problem of reducing (or even eliminating) the aforementioned limitations, so that the performance and potential of a sailboat such as this "Trimaran" type may be improved. Brief description of figures:

5. The order of appearance of the figures is in equivalence with the text that follows: a) Concerning the Cruciform Hull proposal:

Fig.l shows the maximum transverse cross section (Ia) of the horizontal aerodynamic wing of the vessel's central body prior to its forming into a cruciform hull as well as the water line (WL).

Fig.2 shows the maximum cross section of the vertical hydrodynamic hull (2a) of the central body before being blended with the horizontal wing (Ia).

Fig.3 shows the combination of the above mentioned cross sections, i.e., of the wing (Ia) with hull (2a), which results in the shaping of the cruciform hull of the main body of the vessel (3a). b) Concerning the Dolphin Nose Bulb proposal:

Fig.4 depicts the bulb (4a), with its alphabetic symbols that denote groups of cross sections which define its two volume shape, (4b= nose, 4c=saddle, 4d=body), as well as the bow's profile curvature (4e) for sliding off through obstacles (S).

c) Concerning the Asymmetrical Pontoons proposal: Fig.5 shows a left side view of the pontoon (5a), with the hydrodynamic hard chine (A) of its hull. Fig.6 shows a bottom view of the same pontoon (5a) with the hard chine (A) of its hull, as well as its asymmetrical shape due to longitudinal bisection.

Fig.7 shows a front view of both asymmetrical pontoons left (5a) and right (5b), as derived from the bisection of an initially symmetrical with the hard chine (A), and their transverse cross sections (B) which form their deep V hull shape.

Fig.8 illustrates a view of the same pontoons as seen from the stern. Fig.9 illustrates in front view the configuration (9a) of the asymmetrical pontoons (5a and 5b) in the external sides of the Cruciform Hull (3a), either via direct connection (9b) or via short transverse beams (9c), the point where the wind (W) exerts its thrust on to the sail area (9d), as well as the roll angles of pontoon floatation, under buoyancy condition (WL-I) and under lift condition (WL-2). d) Concerning the Specialized Usage Deck: In a perspective point of view, Fig.10, part of the horizontal wing (Ia) and of the open deck (10a) are depicted, with their corresponding alphabetical symbols showing various forms, the head-rails / seats (C), the wheelchairs' recession (D), the corridors (E) and (E-I), the inclined planes (F) and the embarkation / disembarkation ramp (G). A. Cruciform Hull

6. The hydrodynamics and capacity characteristics of a Trimaran's central body are competitive with each other, since one can be optimized only at the expense of the other. Optimizing hydrodynamics therefore (by making the central body more slender) leads to a reduction of internal boat spaces, whereas increasing the boat's capacity, i.e., internal boat spaces leads to reduced efficiency hydrodynamics. As a consequence of this we have either extreme choices, (e.g., only in racing and cruising boats) or a compromise solution that is of mediocre design.

The essential idea of handling that limitation is a full / drastic compartmentalization that will satisfy the contradictory characteristics, that is Hydrodynamics on one hand and Capacity of the central body on the other. This is achieved through independent design for each body function as such: a) The shaping of a broad wing (Ia) along the horizontal axis, as in Fig.l, with emphasis on the achievement of the largest possible internal capacity and with the satisfactory provision of its aerodynamic shaping, since this will continuously function in the air high and above the water line (WL). b) Shaping of a narrow hull (2a) along the vertical axis Fig.2, with emphasis on its hydrodynamics optimization (minimum water line WL width) and an essential provision of its internal capacity (e.g. of a longitudinal walkway).

8. Those two independently designed but compatible bodies, i.e., the aerodynamic wing (Ia) and the hydrodynamic hull (2a) are blended into a single main hull (Fig.3) of cruciform cross section that from then on will be referred to as Cruciform Hull. 9. The above mentioned cruciform hull layout is expected to function in the following way: a) Hvdrodvnamicallv: Free from the demands of internal volume capacity and therefore of a small width at the waterline, this layout accomplishes the achievement of hydrodynamic parameters (e.g., prismatic hull coefficient, displacement coefficient, ratio of waterline length to waterline width, etc), that have a very favorable effect on the entire hydrodynamic efficiency of the boat, thus classifying it on the level of a "racing boat". b) With respect to volume Capaciv: Free from hydrodynamic demands and with an especially large width /internal volume of a horizontal wing, this layout allows for increased internal capacity so as to achieve more comfortable accommodation on a "cruise boat" level. c) Aerodvnamicallv: The carefully designed aerodynamics of the external shape of the horizontal wing (Ia), as an accommodation area (with the projection of small curved frontal surfaces into the wind, with thin leading edge and trailing edge and small thickness relative to the wing chord, etc), drastically reduces the parasitic wind drag at the central body and therefore in its aerodynamic characteristics (also due to its high sailing speed). d) Structurally: The large width of the accommodation area of the cruciform hull, i.e., horizontal wing (Ia) covers a big part of total width of the Trimaran leaving only a small empty space up to the pontoons. As a result of this the pontoons are much easier connected to the main body, either with their direct connection or through small transverse beams. 10. No equivalent application of the cruciform hull in sailing Trimaran boats has been implemented, although we may get that impression in some designs from the shape of transverse interconnection beams of rectangular cross section with the pontoons, which however, do not provide accommodation.

B. Dolphin Nose Bow Bulb

11. The addition of a "hemispherical" hydrodynamic bulb (with its unquestionable hydrodynamic benefits), into its sumberged bow part, as a rule is avoided in conventionally designed Trimaran hulls because: a) Structurally its shaping is very difficult and may be attempted only in "one of ship buildings and definitely not in line production (e.g. using molds, in which access is limited for their internal coating). b) Functionally, the separate bulb volume and its profile protruding from the ship's hull create at the WL level a kind of groove which may entrap floating objects such as ropes or foreign objects creating serious danger for sailing safety (especially in high speeds).

12. Tackling the aforementioned limitations the incorporation of a hydrodynamic bulb can be achieved, as long as the submerged bow part has a built in hydrodynamic bulb with the following characteristics: a) Dolphin nose bulb consisting of two volumes (4a). b) Discrete parts: Nose (4b), saddle (4c), body (4d) shaped by consecutive bulkheads of variable diameter (and not progressively varying from stern to bow) up to the final embodiment in the hull lines.

13. Entanglement danger of floating objects (S) at the bow is eradicated because the Dolphin nose bulb (4a) has been embodied in the bow profile hull without protruding in the longitudinal axis so that the floating objects can slide down and be diverted along the edge of the bow grapnel, (4e), just as in case of conventional designs without bulb. Thus applying a hydrodynamic bulb at the bow the safety factor is not degraded.

C. Asymmetrical Pontoons

14. The characteristics of lateral stability offered by the pontoons of a Trimaran are absolutely dependent upon their static parameters (i.e. the product of {pontoon displacement} times {arm moment of semi-beam of the ship}) defining the limits of the entire layout. Thus depending on the wind speed and the wind's lateral vector component in the ship's sailing area, the following take place: a) Correspondingly proportional increasing roll and pontoon immersion. b) Correspondingly increasing hydrodynamic resistance (and limitation of the maximum speed of the boat), c) Free-boards height exhaustion of the pontoon, of its reserve buoyancy and the ship's stabilizing moment levels (as a crucial part of its overall stability.) 15. This direct dependency of the lateral stability with the "pontoon displacement in relation to the arm moment on the semi-beam of the ship" imposes that whatever improvement (i.e., a moment arm increase and roll angle decrease during sailing) must be undertaken through the change of two specific parameters, that is either by the increase of the pontoon buoyancy or by the increase of the increase of the moment arm length (or with the combined increase of the two parameters thereof).

16. However these two specific conventional choices have the direct consequence of two new "side effects / aggravations" acting as follows: a) The increase of hydrodynamic resistance of the new larger pontoon (with the increased displacement) or b) The pronounced off center ship tendency for course deviation towards the leeward pontoon (with the longest moment arm).

Thus both the final size / displacement of the pontoons and its lateral in-between distance is a design compromise in the frame of these limitations. 17. We may tackle the above mentioned limitations (of lateral stability increase and roll decrease during sailing) as long as the pontoon design "in similarity accordance to the main body" and in their place we adopt the designing choice of Asymmetrical Pontoons (as in the group of Figures 5,6,7,8) with the following characteristics: a) Dynamically supported by a longitudinal hard-chine (A) b) With a longitudinally split boat hull (5a, 5b) c) With deep-V hull characteristics (B).

18. The placing (as in Fig.9), of the two asymmetrical pontoons (5a - 5b) as derived by the longitudinal bisection of a whole pontoon, (such pontoons having a displacement equal or smaller than a conventional one with a relatively small width and correspondingly a small Tonnage Per Inch - T.P.I.) in relation with the Trimaran's central body (3a) is accomplished as such:

A) With the flat sides of the pontoons facing inwards (9a) towards the main body with a counterbalancing incliantion "outwards" (i.e., equal in magnitude and opposite in direction of the Trimaran's angle of roll). B) By interconnecting the pontoons to the main body either directly (9b) or through short transverse beams (9c).

19. This kind of asymmetrical pontoons as described in paragraph 17, (i.e., with characteristics of dynamic support, equipped with hard chine, deep V hull and a split boat configuration) have been used in powered Catamaran (twin hull speedboats), but not in Trimaran sailboats and certainly not in the present concept, i.e., going against the rule of similarity to the main body.

20. The above mentioned layout equipped with those pontoons is expected to function as follows: a) During the initial phase of the sailing departure and as soon as the boat (9d) is exposed to the thrust of the wind (W) as shown in Fig.9, there is a higher tendency for initial immersion due to the small TPI ratio of the pontoon, as well as adequate initial roll (WL-I) that relieves part of the pressure on to the sails, thus reducing the risk failure or strain, (in contrast with the conventional pontoons that from the very start show increased resistance to roll fluctuations). b) With the progressive speed increase and the appearance of the water sliding phenomenon of the leeward pontoon (dynamic support / lift) the gradual rising of the pontoon almost to the water level results to the immediate decrease in the Trimaran's roll in position (WL-2) that is to almost ¹A of the initial. Also it results to the decreased immersion / hydrodynamic resistance but also to the increase of the freeboards as well as the reserve buoyancy of the pontoon. c) The immersed internal flat vertical surface of at the time leeward pontoon, due to internal pressure drop (i.e., an equivalent increase in sub pressure) during sailing eliminates drift and functions as an adequate substitute of a boat keel and pontoon fins, thus rendering the design of direction fins unnecessary.

21. Other dynamic support applications of conventional pontoons which have been tried up to now, as in hydro-foils, do not provide - unlike the suggested one - a smooth and gradual transition from the static buoyancy condition to water sliding lift condition. Most importantly, they are extremely susceptible to damage because these finned hydrofoils are exposed to damage from the water environment.

D. Special Usage Deck 22. In each kind of "MonohuH" (single hull) or "MultihulT sail boat their conventionally designed decks for general usage and also the large rolling angles during sail make them suitable and safe only for specialized users (that is exclusively for sailors and familiarized passengers). It is very difficult and almost impossible in this kind of boats to have groups of "sensitive" people that do not possess the necessary abilities, experiences and familiarization as well as people with special needs. Thus these kind of people are practically excluded from these interesting activities.

23. However, depending on the size of a Trimaran designed on the basis of the above mentioned proposals and thanks to the unusually large horizontal wing of the Cruciform Hull, in combination with the mimmized rolling angles during sail, its special Layout and development is possible for covering specialized needs. Specifically, the boat becomes highly specialized for group activities, acquaintance and familiarization with "fast sailing", training in this field and also the "creative activity" of large groups (25+ people) consisting of: a) People with special needs (e.g., psychomotor difficulties) b) Elementary and high school students (educational programs) c) Elderly people (special programs) d) Sail men under training (open sea schools) δ

24. This specific specialized usage is achieved through the following design and building layout (as in Fig.10): a) Removal of any kind of "ceiling" of the main boat's horizontal wing (Ia), so that we have open air and uncovered areas functioning thus as a uninterrupted open deck (10a). b) In both external wing sides parallel to the longitudinal axis and facing to the internal side of the boat a symmetrical layout is formed consisting of two or three consecutive rows of side by side head-rails (C), according to the in force anthropometric / ergonomic regulations, etc. c) In the lower deck head-rails we have special recessions (also according to the in force anthropometric and ergonomic regulations) suitable for accepting and safely securing wheel chairs (D). d) In the external sides of the head-rails as well as in the internal deck floor we have three long longitudinal rolling corridors (E) for wheelchairs, whereas starting from the deck to the interior of the hull we have one more uninterrupted (El) corridor leading to the lavatories and service areas of the ship. e) The external longitudinal rolling walkays at the bow and stern are interconnected with the deck's internal walkway through transverse inclined planes (F), of similar specifications structures, concerning width, inclination, anti-skid surfaces, etc. f) At the four external corner areas of the open deck (bow starboard, bow port, stern starboard and stern port) four retractable ramps (G) suitable for safe boarding and disembarkation of the passengers at a port dock or a natural beach are installed.

25. The active participation of such groups of people in that kind of sailing activity is achieved at the very minimum through the simultaneous movement of the entire group from one side of the ship's head rails to the other and vice versa at the captain's command, whenever necessary. This functions simply as the movement of a "smart ballast". It should be noted that the participating passengers in such an activity does not require any special training (only a couple of drills before departure should be enough) and can be executed within a timeframe of 60+ sec so that every one can have ample time to respond in this activity.

Advantages. 26. Under similar sea conditions when compared to a conventional Trimaran of equivalent displacement and size, the following advantages are associated with the proposed four design aalternatives: a) Due to the implementation of Cruciform Hull: • Improved Hydrodynamics (increased speed)

• Increased volume capacity (Improved accommodation) b) Due to implementation of Dolphin Nose Bow bulb:

• Improved Hydrodynamics (increased speed) • Abolishment of side effects of conventional bulb (Sailing safety) c) Due to implementtion of Asymmetrical Pontoons:

• Reduced rolling angles (increased travel comfort)

• Smaller hydrodynamic resistance (increased speed)

• Increased reserve pontoon buoyancy (improved stability) d) Due to the implementation of a Deck of Specilaized Usages:

• Increased capacity (larger number of passengers on board)

• Specialized activities support, (i.e., for persons of special needs).

Claims

1. Sailboat of crucifoπn hull with dolphin nose bow bulb, asymmetrical pontoons and a specialized usage deck characterized bv the fact that on one hand the central body (3a) is of cruciform cross section, consisting of the superstructure's horizontal wing (Ia) above the waterline (WL), with such a wing having great width for increased volume capacity, and on the other hand by the vertical hull (2a) being especially narrow particularly in its waterline and its sub-water area aiming at reduced hydrodynamic resistance and by the fact that the two volume dolphin nose hydrodynamic bulb (4a) is embodied in the bow sub-water area part of the hull and that such a bulb is curved longitudinally, shaped by successive bulkheads varying in diameter and defined by discretely shaped parts of nose (4b), saddle (4c) and body (4d), with the bulb not protruding outside the bow's profile (4e) thus precluding it from interfering with floating objects (S), and by the fact that the cruciform hull being the central part of the vessel is laterally supported by two asymmetrical pontoons (5a-5b) which are those floating parts as a result of the longitudinal bisection of a dynamically supported vessel equipped with longitudinal water sliding surfaces - hard chine - (A) and a cross section of a deep-V hull angle (B), with such pontoons having their inboard flat surface (9a) facing towards the inner portion of the vessel (3a) and attached with it either directly through the horizontal wing (9b) or through small length transverse struts (9c) so that for a wind thrust (W) acting on to the sail area (9d), the initial roll position (WL-I) of the vessel is reduced to position to (WL-2), and by the feet that the horizontal wing of the cruciform hull (Ia) via the removal of its top can be transformed into an open deck of large surface area (10a), appropriate for cultural, social, athletic, therapeutic, educational and other activities or specialized uses (such as the in-group participation of people of special needs on wheel chairs), through appropriately placed and oppositely feeing head-rails / seats (C) with special recesses (D) for safely receiving and securely tying the wheelchairs as well as longitudinal corridors for the free movement of the wheel chairs (E - El) being interconnected with each other through the corresponding transverse inclined planes (F) and finally of external retractable ramps (G) placed at the four outmost points of the open deck ( bow / stern starboard and port) for the passenger and wheelchair boarding or disembarking.