A variable trim trimaran

Abstract: This invention relates to a variable trim trimaran in which side floats (2) are provided that are connected to the central hull (1) by means of devices (3, 5) that allow them to shift vertically, wherein a deck structure (4) is provided that is connected to the central hull (1) and is so shaped as to cover at the top portion said side floats (2), so that they come to belong in the general outline of the trimaran itself.

Description: This invention relates to a variable trim trimaran. More particularly, this invention relates to a boat of the kind mentioned above, which in addition to be provided with means for adjusting the vertical shift of the floats so as to control the rolling motions of the boat itself, also has some further structural and/or functional devices that improve remarkably both the conditions and the possibilities of employing the craft. In US-A-3528380 a trimaran with spring center hull section is described, said trimaran having the features of the precharacterizing portion of claim 1. In a preceding patent application filed in the name of Prof. Alfredo Magazzù, granted on 18th February 1987, No. IT-A-1158613, a particular trimaran structure is disclosed wherein the connection between the side floats and the central hull is capable of allowing the floats themselves to be shifted vertically by automatic, semiautomatic or by manual action. Accordingly, the rolling motions of the boat as welll as the increase in the dynamic stability of the craft are obtained, under the same conditions, with respect to a conventional trimaran. The advantages stemming from the technical teachings of the patent mentioned above with respect to boats of that type already known, wich are endowed with floats that are connected rigidly to the central hull, can be put into evidence as follows: even when the hull is at rest, its floats are dipped till they receive a thrust which is set forth previously and can be adjusted independently of the average draft and of the attitude of the central hull; on increasing the speed of the craft, the hydrodynamic thrust generated by the floats themselves and/or the thrust given by any possible hydroplane fins present which are connected to the floats, causes the floats to be raised gradually and automatically (i.e., with no intervention on the pilot's part), so that the floats elude the hydrodynamic drag (partially in case they are finless or totally in case they are provided with fins), and this occurs independently of the draft of the central hull; adjustments of the transverse attitude of the craft can be obtained through the differential adjustment of the float height, and this operation can be performed in differently both when the boat is at rest and when it is in motion. The adjustment of the longitudinal attitude can also be obtained when the floats are fastened abaft with respect to the central hull, as is normally suitable; a significative increase in the overturning angle of the craft is obtained, and anyway a significative increase in the area subtended by the stability diagram, with the concomitant evident advantages as regards the dynamic stability (the work required to overturn the craft). This allows the float sizes to be reduced, under the same conditions, with respect to those required in the case of a conventional trimaran, with evident advantages in terms both of cost and of the motion drag, as well as of direct weight (the weight of the floats) and of indirect weight (lower stresses generated by the floats on the connecting structures and on the connections to the central hull); an initial behavior of the stability diagram is obtained which is perfectly in agreement with the operating requirements and the comfort requirements of the craft, this holding true both when the boat is at rest and when it is in motion; moreover, such diagram can be modified at will, by means of simple regulations of the control gains in order to keep into account the possible operative changing needs which are in connection, for instance to different load conditions; the almost complete elimination of the rolling oscillations is obtained on slight sea both when the boat is at rest and when it is in motion, this being a result of the remarkable controlling moments developed by the differential adjustment of the floats in comparison to the conventional antirolling fins employed on ships. However, the trimaran of the patent mentioned above shows a number of drawbacks which are particularly evident in the practical application of that solution on boats intended for commercial activities, like the transportation of passengers or other activities that ask for frequent docking, or frequent approaching to other boats or, anyway, asks for manoeuvering in crowded harbours. Indeed, the shape of the trimaran in question is somewhat not compact because of the presence of the side hulls (the floats) which come remarkably out of the general outline of the central hull, so that they are a remarkable encumbrance and obstacle during the operations mentioned above, because of the impossibility of taking the central hull, which is intended for housing people and/or materials to the approach zones. Moreover, the structure of the central hull which is necessarily narrow and subtle does not allow passengers and/or goods to be housed in the best way. In case of collision, the severe damage to one of the side floats and/or the damage to one of the articulated arms connecting the central hull and the floats and/or the damage to the systems that drive the floats compromise the lateral stability of the craft completely, and this can make it impossible, apart from the objective seriousness of the problem, to obtain the certification by the authorities if the craft is to be employed for commercial purposes and, in particular, for the public transportation of passengers. As a consequence, in spite of all advantages that the solution offered by the cited patent gives with respect to the prior art, a craft realized in that way is not competitive with respect to the craft employed at present. The main object of the present invention is that of realizing a trimaran whose floats are adjustable. according to what is already known from the patent mentioned above, said trimaran having a number of innovations of functional and structural character which can obviate all drawbacks mentioned above. Accordingly, a first object of the present invention is that of realizing a trimaran wherein the central hull has a deck which is capable of receiving the floats and of protecting them as a consequence in case of collision. It is a further object of the present invention the realization of a trimaran whose adjustable floats are so constructed as to compromise In a non-determinant way the stability of the craft In case of breaking and/or damaging of one of them. It is a further object of the present invention the realization of a trimaran provided with a dampening device of the pitch motion. Accordingly, it is a specific object of the present invention a variable trim trimaran comprising side floats connected to the central hull through devices that allow the floats themselves to shift vertically, a deck structure connected to the central hull shaped so as to cover at the upper part said side floats so that such floats do not exceed the upper deck contour when looking the trimaran in plan view, characterized in that said connection devices of the side floats to the central hull are provided above the sea level and comprise connection members which are rigidly connected to the floats and are hinged on the central hull at a point above the sea level, and devices for the automatic and/or manual and for passive variation of the attitude, said devices being arranged between the floats and the central hull or otherwise between the floats and the deck structure, in any case above the sea level, such devices being saved to regulation and/or control system of any type. In particular, such deck structure can be so realized as to be integral with the central hull or as to be separate from the same and connected structurally to it. According to the present invention, said devices for changing automatically and/or manually and/or passively the attitude of the floats can be provided between the floats and the central hull or between the floats and the deck structure. Further according to the present invention the floats are connected to the central hull by means of a plurality of connection members. Moreover, a plurality of devices can be provided for automatically and/or passively changing the attitude of the floats, whose number can be equal to or lower than the number of the connection members. Again according to the present invention, the single floats can be realized by means of total or partial foaming and/or by means of subdivision into watertight compartments. According to a further embodiment of the trimaran of this invention, two or more pairs of floats will be provided, each one being connected to the central hull according to one of the solutions disclosed above. In order to improve on the control of the pitching motions, a hydrodynamic fin can be provided according to the present invention, said fin being arranged at the bow of the central hull, which fin can be deflected totally in the active or the passive mode, in particular through a control device connected to sensors of the vertical direction and/or of attitude and/or of pitching velocity and/or of pitching acceleration, or said fin can be deflected partially by means of flaps or the like. This invention will be disclosed in the following according to some preferred embodiments of the same with particular reference to the enclosed drawings wherein: Figure 1 is a schematic bottom view of a first embodiment of the trimaran according to the present invention; Figure 2 is a front view of the trimaran of Figure 1; Figure 3 is a schematic bottom view of a second embodiment of the trimaran according to this in-vention; Figure 4 shows a detail of an embodiment of the trimaran according to the present invention; Figure 5 shows a detail of a further embodiment of the trimaran according to this invention; Figure 6 is a side view of a further embodiment of the trimaran according to this invention: Figure 7 is a bottom view of the trimaran of Figure 6; Figure 8 is a side view of a further embodiment of the trimaran according to this invention; and Figure 9 is a bottom view of the trimaran of Figure 8. With reference now to Figures 1 and 2, a trimaran is shown which is provided with a central hull 1 and with two floats 2, connected to the central hull by means of hydraulic cylinders 3 and the connections 5. The central hull 1 is provided with a deck 4 that extends over both sides of the hull 1, so covering the floats 2 which thus come to belong in the whole outline of the trimaran. As it would be impossible to realize such structural compactness of the trimaran if the floats 2 are of the adjustable attitude type by merely connecting the hull 1 and the floats 2 through a rigid deck, the solution disclosed herein allows the floats 2 to be independent of the base structure so that they are free of rising and lowering according to the automatic control logics, or in the passive mode and, at the same time, it is possible to avoid risks stemming from the damage of said floats 2 in case of approach or of docking. The solution suggested in Figure 3 is substantially similar to that disclosed with reference to Figures 1 and 2, with the only difference that the central hull 1 comes out of the deck 4 at the front position. The deck 4 can be so realized as to be com-pletely integral with the central hull 1 or to be separate from the same and structurally connected to it. For instance, the solution shown in Figure 4 allows the realization, from the structural viewpoint, of a hull beam which is capable of supporting the general stresses, in particular the flexural and the torsional stresses like those occurring in conventional hulls, with advantages in terms of weight, as the supporting structures of the deck 4 are just to be capable of supporting the local stresses, i.e. the stresses due to the superstructures or deckhouses (Ws) and of the carrying capacity (Wu). The structure shown in Figure 5 is also to support the stresses caused by the cylinders 3 which are connected to the deck 4, whereas the float 2 is hinged to the hull 1 by means of the connecting member 5. The result obtained is a boat which on the whole is lighter than the traditional boats of equal length and width, but the structural strength of such boat is at least equivalent to that of the traditional ones because, as already mentioned above, the supporting structures of the enlarged deck are not a part of the hull beam and do not take part in the general stresses. Moreover, as the boats are smaller than those of the traditional trimarans, the technique of connecting them directly to the deck 4 through the cylinders 3 gives rise to stresses in the deck 4 itself which are definitely reduced with respect to those of the normal floats. In order to prevent the damage of the connecting member 5 of a float 2 to the hull 1 in case of collision from compromising in a determinant way the stability of said trimaran, the solution shown in Figures 6 and 7 can be adopted, wherein a redundant system of connections 5 of the floats 2 with the hull 1 is realized (see Figures 6 and 7). Such redundancy can also be extended to said cylinders 3. Moreover, each float 2 will be realized so as to be scarcely permeated by any possible water pathways caused by collisions or any other similar accidents, by foaming the floats 2 themselves totally or partially, or realizing them as watertight compartments. Again Figures 6 and 7 show a system that allows the pitching motion of the craft to be dampened. It is made up of a hydrodynamic fin 6 arranged forwards of the hull 1, said fin being capable of deflecting totally so as to generate counteracting moments which are suitable to reduce the pitching motions of the craft, thus integrating in said function amlso the action of the floats 2. A further embodiment of the trimaran according to the present invention is that shown in Figures 8 and 9, wherein two pairs of floats 2′ and 2″ are provided, each one being connected to the central hull 1 by a plurality of connections 5. In such way, the safety coefficients of the solution shown n Figures 6 and 7 are further improved. The pairs of floats 2′ and 2″ can be employed for generating, in addition to the rolling motions obtained by lifting the floats of a given side and lowering the other ones or vice-versa, even the pitch moments, by lowering the forward floats and lifting the astern floats, or vice-versa, so obtaining changes in the longitudinal attitude and/or the dampening of the pitching oscillations. The results as regards this feature are definitely better than those which can be obtained by means of a sigle pair of floats, which pair is usually arranged astern. This invention has been disclosed with specific reference to some preferred embodiments of the same, but it is to be understood that modifications and/or changes can be introduced by those who are skilled in the art without departing from the scope of the invention as defined by the appended claims.

Claims: A variable trim trimaran comprising side floats (2) connected to the central hull (1) through devices (3, 5) that allow the floats (2) themselves to shift vertically, a deck structure (4) connected to the central hull (1) shaped so as to cover at the upper part said side floats (2) so that such floats (2) do not exceed the upper deck contour when looking the trimaran in plan view, characterized in that said connection devices (3, 5) of the side floats (2) to the central hull (1) are provided above the sea level and comprise connection members (5) which are rigidly connected to the floats (2) and are hinged on the central hull (1) at a point above the sea level, and devices (3) for the automatic and/or manual and /or passive variation of the attitude, said devices (3) being arranged between the floats (2) and the central hull or otherwise between the floats (2) and the deck structure (4), in any case above the sea level, such devices (3) being slaved to regulation and/or control system of any type. A trimaran according to claim 1, characterized in that said deck structure (4) is realized as an integral portion of the central hull (1). A trimaran according to claim 1, characterized in that said structure and/or deck (4) is realized as a separate portion with respect to the central hull (1) and is structurally connected to the central hull (1) itself. A trimaran according to anyone of the preceding claims, characterized in that the floats (2) are connected to the central hull (1) by means of a plurality of connection members (5). A trimaran according to claim 5, characterized in that a plurality of device (3) is provided for automatically and/or manually and/or passively varying the attitude for the floats, said devices (3) being equal in number to that of the connection members (5) or lower than the number of said connection members (5). A trimaran according to anyone of the preceding claims, characterized in that said floats (2) are realized by total or partial foaming and/or through subdivision into watertight compartments. A trimaran according to anyone of the preceding claims, characterized in that two pairs of floats (2) or more than two pairs of floats (2) are provided, said pairs being arranged in front of each other, the floats (2) of said trimaran being connected independently to the central hull (1). A trimaran according to anyone of the preceding claims, characterized in that a totally or partially deflectable hydrodynamic fin (6) is provided on the central hull (1), at the bow of the same. A trimaran according to claim 8, characterized in that said fin (6) is totally deflectable by means of a control device slaved to sensors of the vertical direction and/or of attitude and/or of pitching velocity and/or of pitching acceleration. A trimaran according to claim 8, characterized in that said fin (6) is partially deflectable by means of flaps.

Inventors: MAGAZZU ALFREDO, MAGAZZU', ALFREDO
Applicants: AEROMARINE SRL, AEROMARINE S.R.L.
Application year: 1991
Main classification: B63B1
IPC codes: B63B1