EP0161953A1 - Ship comprising three semi-submersible floats - Google Patents

Abstract

1. Boat equipped with three semi-submersible floats (3-6; 5-8) connected to a deck (1, 2) via strut members (6; 8), one central float (3-6) being provided at the fore part of the boat and two side floats (5-8) being positioned symmetrically with respect to the longitudinal plane (S) of said central float, boat characterized in that a) the ratio of the ordinate (AI) of the curve of the areas (A1) of the boat at the crossing point (I) of the curves of the areas (A5) of the side float, on the one hand, and of the areas (A3) of the central float, on the other hand, to the maximum ordinate (AM1) of said curve of the areas (A1) of the boat is at least equal to 0.45 ; and b) the ratio of the sum of the volumes of the side floats combined, on the one hand, and of the volume of the central float, on the other hand, is between 0.3 and 1.7.

Description

The naval architect is today aware of several provisions in principle for making surface ships, the buoyancy of which is obtained by the adoption of several hulls. In particular, ship constructions supported by three hulls are already known.

The best known of these ships are fitted with hulls, of course partially submerged, but also partially emerged: this is the case of the arrangement represented in FR-A-1 414 492. Other ships, less known to the public, but of already old design, are equipped with fully submerged lift hulls: the arrangement shown in US-A-1 825 286 is an example of such vessels.

We also know, also, some achievements, and many more projects of surface ships of this second type, whose buoyancy is therefore ensured by several - two, three or four - fully submerged hulls, connected to the rest of the ship by partially submerged legs that participate in buoyancy. The useful part of such a vessel is disposed above the surface of the water and the assembly of a hull proper and of the part of the submerged leg is usually designated by the term "semi-submersible float ".

Studies of ships with "semi-submersible floats" have been developed in recent years with the aim of achieving economically viable achievements, and no longer just to define provisions which are fundamentally new in principle. The ships actually built are few and the experience acquired is incomplete.

This new concept is, however, promising with regard to the construction of ships. with good sea resistance and satisfactory stability. It is still necessary to manage to define the specific provisions allowing the obtaining of the resistance to the minimum advance and, consequently, the realization of economic ships as for their exploitation.

No known "semi-submersible float" vessel has nautical characteristics, in particular resistance to advancement, capable of making its operation economically attractive, which certainly explains the general drowsiness of all the projects under study.

The object of the present invention is, in particular, to optimize the relative shapes and locations of the semi-submersible floats, by defining such new particular provisions.

The invention therefore relates to a ship comprising three semi-submersible floats connected to a bridge by legs, a central float being arranged in front and two lateral floats being arranged symmetrically with respect to the longitudinal plane of the central float, such as the principle is disclosed in US-A-1,815,286, for example.

The main concern of the naval architect when designing a ship of this type is therefore to solve the problem of reducing the forward resistance, and more particularly the wave resistance, on which the previous projects stumbled and failed.

Admittedly, solutions have already been proposed for surface hull vessels, not semi-submersible IFR-A-1 414 492 defines the principles of provisions, which, for this type of vessel, allow the reduction of wave resistance .

You might think it was easy, obvious to those skilled in the art, to draw the lesson from FR-A-1 414 492 and, by applying it to a ship with "semi-submersible floats", as represented in US-A-1 815 286, to make a ship with "semi-submersible floats" having a low resistance to advancement, thereby becoming effectively attractive to the user.

But then, on the one hand, if this approach, which a priori is only intellectual and naturally requires the verification of real tests, had been so obvious, and taking into account, on the other hand, the economic interest of 'such a new realization, one must ask the following question: why did the past naval architects not propose this new type of ships ?.

The only answer to this question is that, in reality, the very concept of a ship with "semi-submersible floats" was and remains so unusual in shipbuilding, that the designers believed they had to rethink everything, imagine everything again, without to get hold of previous knowledge estimated to be of little interest. It is then that it must be considered that applying the teaching of FR-A-1 414 492 to US-A-1 815 286 is not obvious, but on the contrary, by realizing this application, the 'Man of the Trade overcomes a technical prejudice, which would normally make him discard the idea of this application, and perform an authentic act of invention, entirely not obvious, having involved a real inventive step.

It is this act of invention that the Applicant has performed by providing that, in this vessel, a) the ratio of the ordinate of the curve of the areas of the ship to the point of intersection of the curves of the areas of the lateral floats of a part, and the central float on the other hand, at the maximum ordinate of said curve of the areas of the ship is at least equal to 0.45; and, b) the ratio of the sum of the volumes of the lateral floats taken together on the one hand, to the volume of the central float on the other hand is between 0.3 and 1.7.

• - pour chaque flotteur, le rapport de la profondeur d'immersion du maximum de la courbe des aires des sections horizontales (soit TcL), au diamètre équivalent dudit flotteur est compris entre 0,6 et 1,4 ;
• - le coefficient de dissymétrie du navire est inférieur à 0,3 ;
• - l'allongement de chaque flotteur est compris entre 5 et 10 ;
• - au moins un aileron sensiblement horizontal relie chaque flotteur latéral au flotteur central ;
• - les deux flotteurs latéraux sont d'une part identiques, d'autre part distincts du flotteur central.

The following advantageous arrangements are also preferably adopted:

• - For each float, the ratio of the immersion depth of the maximum of the curve of the areas of the horizontal sections (ie TcL), to the equivalent diameter of said float is between 0.6 and 1.4;
• - the ship's asymmetry coefficient is less than 0.3;
• - the elongation of each float is between 5 and 10;
• - At least one substantially horizontal fin connects each lateral float to the central float;
• - The two lateral floats are on the one hand identical, on the other hand distinct from the central float.

The invention will be better understood, and secondary characteristics and their advantages will appear during the description of embodiment given below by way of example.

It is understood that the description and the drawings are given for information only and are not limiting.

• - la figure 1 est une vue, suivant flèche F de la figure 2, d'un navire conforme à l'invention ;
• - la figure 2 est une vue, suivant flèche G de la figure 1, du même navire ;
• - la figure 3 est une coupe suivant III-III de la figure 1 ;
• - les figures 4,5,6,7 et 8 sont les courbes des aires de navires conformes à l'invention, selon plusieurs variantes de réalisation distinctes.

Reference will be made to the appended drawings in which:

• - Figure 1 is a view, along arrow F of Figure 2, of a ship according to the invention;
• - Figure 2 is a view, along arrow G of Figure 1, of the same ship;
• - Figure 3 is a section along III-III of Figure 1;
• - Figures 4,5,6,7 and 8 are the curves of the areas of ships according to the invention, according to several different embodiments.

Reference is made below to certain concepts, the uncommon nature of which prompts definition, which is done in the attached annex, which is part of the patent application.

• - un corps entièrement émergé 1, comprenant un pont 2 et abritant le volume utile du navire (cales de transport, cabines, locaux divers)
• - une coque avant centrale 3, qui est oblongue possède un plan longitudinal vertical de symétrie S, et est entièrement immergée en dessous de la surface de l'eau 4 ;
• - deux coques latérales 5, qui sont disposées symétriquement par rapport au plan de symétrie S, en arrière de la coque centrale 3 sont identiques, et entièrement immergées ;
• - une jambe 6, qui s'étend verticalement, sensiblement parallèlement au plan de symétrie S et relie la coque centrale 3 à la face inférieure 7 du corps émergé 1 ;
• - deux jambes 8, qui s'étendent verticalement,sensiblement parallèlement au plan de symétrie S et, qui relient, chacune, une coque latérale 5 à la face inférieure 7 du corps 1 ;
• - deux ailerons sensiblement horizontaux 9, qui relient l'un, l'une des coques latérales 5, l'autre, l'autre coque-latérale 5 à la coque centrale 3.

The ship shown is a surface ship, of the type comprising three floats, known as a "trimaran". It is made up of:

• - a fully emerged body 1, comprising a deck 2 and housing the useful volume of the ship (transport holds, cabins, various premises)
• - A central front hull 3, which is oblong has a vertical longitudinal plane of symmetry S, and is fully submerged below the surface of the water 4;
• - Two side shells 5, which are arranged symmetrically with respect to the plane of symmetry S, behind the central shell 3 are identical, and fully submerged;
• - A leg 6, which extends vertically, substantially parallel to the plane of symmetry S and connects the central shell 3 to the underside 7 of the emerged body 1;
• - Two legs 8, which extend vertically, substantially parallel to the plane of symmetry S and, which each connect a lateral shell 5 to the underside 7 of the body 1;
• - two substantially horizontal fins 9, which connect one, one of the side shells 5, the other, the other side-shell 5 to the central shell 3.

• - l'ensemble d'une coque et de la jambe correspondante (coque centrale 3 et jambe 6, chaque coque latérale 5 et sa jambe 8) constitue un flotteur semi-submersible
• - chaque flotteur semi-submersible a une flottabilité positive, l'ensemble des trois flotteurs semi-submersibles procurant au navire sa flottabilité;
• - les coques 3,5 et leurs jambes 6,8 peuvent être constituées de réservoirs, de water-ballasts mais peuvent également être constituées de compartiments contenant les installations du navire ; ainsi, trois moteurs type "Diesel", un principal, deux de plus faible puissance, peuvent être installés dans la coque centrale 3 et dans les coques latérales 5, et entraîner des hélices propulsives ; de même, les jambes creuses 6,8 sont aptes à rendre possible le passage des nombreuses liaisons (câbles électriques, tuyauteries, accès ) reliant les coques 3,5 au pont 2 ;
• - les plans verticaux transversaux qui passent par les extrémités des courbes des aires immergées des sections transversales verticales des flotteurs semi-submersibles 3-6 et 5-8 sont repérés :
  • V 3 AR : plan passant par l'extrémité arrière de la courbe des aires du flotteur semi-submersible 3-6,
  • V 3 AV: plan passant par l'extrémité avant de la courbe des aires du flotteur semi-submersible 3-6,
  • V 5 AR : plan passant par les extrémités arrière de la courbe des aires des flotteurs semi-submersibles 5-8,
  • V 5 AV : plan passant par les extrémités avant de la

The following features are observed:

• - the whole of a shell and the corresponding leg (central shell 3 and leg 6, each side hull 5 and its leg 8) constitutes a semi-submersible float
• - each semi-submersible float has positive buoyancy, all three semi-submersible floats providing the ship with its buoyancy;
• - the hulls 3.5 and their legs 6.8 may consist of tanks, water-ballasts but may also consist of compartments containing the ship's installations; thus, three "Diesel" type engines, one main, two of lower power, can be installed in the central hull 3 and in the side hulls 5, and drive propelling propellers; similarly, the hollow legs 6,8 are able to make possible the passage of the numerous connections (electric cables, pipes, access) connecting the shells 3,5 to the deck 2;
• - the vertical transverse planes which pass through the ends of the curves of the submerged areas of the vertical cross sections of the semi-submersible floats 3-6 and 5-8 are identified:
  • V 3 AR: plane passing through the rear end of the curve of the areas of the semi-submersible float 3-6,
  • V 3 AV: plane passing through the front end of the curve of the areas of the semi-submersible float 3-6,
  • V 5 AR: plane passing through the rear ends of the curve of the areas of semi-submersible floats 5-8,
  • V 5 AV: plane passing through the front ends of the

curve of the areas of the semi-submersible floats 5-8, and it is noted that an overlap is made in the longitudinal direction, parallel to the plane S, of the relative positions of the central semi-submersible float 3-6 and of the lateral semi-submersible floats 5-8, the plane V 5AV being arranged in front of the plane V 3 AR.

• - la courbe A 5 à l'ensemble des deux flotteurs semi-submersibles 5-8,
• - la courbe A 3 au flotteur semi-submersible 3-6, et,
• - la courbe A 1 à l'ensemble des trois flotteurs semi-submersibles, c'est-à-dire au navire lui-même.

Figures 4 to 8 show the curves of the areas according to several distinct embodiments and corresponding, for each achievement:

• - curve A 5 to the set of two semi-submersible floats 5-8,
• - the curve A 3 with the semi-submersible float 3-6, and,
• - the curve A 1 to all three semi-submersible floats, that is to say to the ship itself.

• - la valeur AI de l'aire de la section transversale du navire (courbe A1) située dans le plan VI,
• - les valeurs maximales AM3 et AM5 des courbes A3 et A5,
• - la valeur maximale AM1 de la courbe A1.

Due to the above-mentioned overlap, the curves A 3 and A 5 have a point of intersection Í contained in a transverse vertical plane VI, located between the planes V 3 AR and V 5 AV. The following are also represented:

• - the AI value of the cross-sectional area of the ship (curve A1) located in plane VI,
• - the maximum values AM3 and AM5 of the curves A3 and A5,
• - the maximum value AM1 of the curve A1.

In the embodiment corresponding to FIG. 4, AI is substantially equal to AM3 and AM5. AM1 is therefore equal, substantially to any one of these three values. Curve A1 is flat between the V3AR and V5A7 planes. This is very favorable for obtaining a low wave resistance for the speeds corresponding to a Froude number of about 0.4 to 0.6 (curve A1 "balanced" between the front and the rear of the ship and free of accentuated hollows or peaks, particularly in the area of plane VI) In addition, the volume of the two lateral semi-submersible floats 5-8 on the one hand, and the volume of the central semi-submersible float 3-6 of on the other hand, are substantially equal (surfaces of the curves of the areas A3 and A5 substantially equal) which allows, in the trimaran arrangement adopted, to further minimize the wave resistance.

If the solution of the realization of figure 4 can appear from these points of view as an ideal solution, however, it remains obvious that other solutions, which may be less good, are also satisfactory.

Thus in the embodiment of FIG. 5, AM1 = AM5; AM3 is slightly lower than AM5 and AI / AM1 = 0.45. The volumes of the lateral 5-8 and central 3-6 semi-submersible floats are substantially equal. This is a limit realization, suitable for high speeds (Fn> 0.6), AI / AM1 having to be chosen in principle greater than 0.45 to allow the maximum reduction in wave resistance.

The embodiment of FIG. 6 is characterized by a strong imbalance in the volumes of the lateral semi-submersible floats 5-8 on the one hand, of the central semi-submersible float 3-6 on the other hand: the ratio of these volumes is equal to 0.3. Again, this is a lower limit below which you should not go down. Furthermore AI / AM1 is substantially equal to 1, which is satisfactory.

FIG. 7 represents an embodiment in which the volume of the lateral (and rear) semi-submersible floats 5-8 is equal to 1.7 times that of the central (and front) semi-submersible float 3-6. This achievement constitutes the upper limit not to be exceeded. Furthermore, AÍ is substantially equal to AM. The curve A1 is relatively flat between the vertices of the curves A3 and A5, from which a relatively low wave resistance is obtained for the speeds corresponding to Fn = 0.4 to 0.6.

FIG. 8 represents an embodiment in which the curve of the areas A1 of the ship has a high asymmetry. The ship's dissymmetry coefficient DIS is 0.3, which is the upper limit below which it is best to stay. The lateral semi-submersible floats (and aft} 5-8 are belly relative to the central submersible float, front 3-6.

For the vessel shown in Figures 1 to 3 (semi-submersible floats 3-6 and 5-8 in solid lines in Figure 1), the coefficient of elongation of said floats is approximately equal to 7. To obtain a compromise between the wave resistance and friction resistance minimizing the total advance resistance, the shapes should be chosen so that the elongation coefficient is between 5 and 10.

Finally, to get the maximum benefit from this technique of semi-submersible floats, it is advisable, on the one hand, to immerse the floats 3-6; 5-8 at depths sufficient to decrease the movements of the ship and decrease the wave resistance, on the other hand to limit the immersion of said floats to depths making the construction of the ship-free from significant structural problems and preserving the surface wet to a reasonable value. This is the reason why the ratio TcL / Deq of the immersion depth of the maximum of the curve of the areas of the horizontal sections by the equivalent diameter is included, for each semi-submersible float, between 0.6 and 1.4 which corresponds to the dashed line drawings in FIG. 1: the drawing of the floats closest to the surface of the water correspond to TcL / Deq = 0.6 and that most distant from the surface of the water corresponding to Tcl / Deq = 1.4.

The definition of the vessel which has just been produced gives this vessel qualities of course, specific to all semi-submersible vessels, but also a new optimization of its resistance to advancement. For the first time, a semi-submersible ship has a performance substantially equivalent to that of a conventional surface ship of the same tonnage, which makes this technique viable.

In comparison with semi-submersible vessels of the catamaran type, the wave resistance is significantly lower because on the one hand, the elongation of the three semi-submersible floats can be more favorable than that of the two semi-submersible floats of a catamaran , on the other hand, the choice of the longitudinal overlap of the curves of the areas A3 and A5 makes it possible to avoid annoying interference between the flows along the central semi-submersible float 3-6 and the lateral semi-submersible floats 5-8, and, again, reduce the wave resistance. The very choice of the curve of the areas A1, preferably the flattest between the two vertices of the curves of the areas A3 and A5 and, in the vicinity of point 1, is, on this point, a guarantee of a significant reduction in the resistance to 'advancement.

It should also be noted that the recommended structure is particularly robust. We know that catamarans, for example, have generally fragile structures, given the very significant constraints that develop there. The new structure type "trimaran", which is proposed does not have this previously known fragility because on the one hand the ship is generally supported on 3 points instead of 4 for catamarans, on the other hand the fins 9 close the structure formed by the legs 6 and 8 and the hulls 3 and 5. Thus, the forces in the area of attachment of the legs 6 and 8 to the body 1 are much lower than those existing in the equivalent areas of connection of the floats of a semi catamaran -submersible at the central point of said catamaran.

The invention is not limited to the embodiments shown, but on the contrary covers all of them. your variants that could be brought to them without going beyond their framework or their spirit.

ANNEX

The main purpose of this annex is to clarify the definitions adopted for some of the terms used.

Vessel area curve

The submerged part of the hull of a ship is usually defined by the values of its successive vertical cross sections between the verticals passing through the submerged end points of the hull, called PPAV and PPAR in the direction of the length of the ship. The transfer, on the ordinate, of the areas of the cross sections and on the abscissa of the distances of said cross sections to a reference origin, makes it possible to establish the curve of the areas.

Volume of a semi-submersible float

This volume is equal to the area delimited on the graph representing the curve of the areas of the vertical cross sections, by this curve of the areas and the x-axis.

Semi-submersible float

An immersed body can be defined, at least partially, by horizontal sections.

The term semi-submersible float designates such a body with positive buoyancy, the curve of the areas of its horizontal sections (or water lines) having a maximum below the surface of the water at a depth TCL.

In such a float, the value of this maximum is preferably greater than twice the value of the area of the horizontal section at the waterline.

This maximum can be achieved for various depths of water lines. In this case, TCL designates the arithmetic mean of said depths.

Commonly, a semi-submersible float is constituted by the assembly of a totally submerged hull and a leg _' connecting it to at least the surface of the water.

Equivalent diameter

It is often difficult to distinguish the leg from the fully submerged shell to which it is connected. It is then advantageous to refer to the diameter Deq of a circle whose surface is equal to that of the maximum cross-section of the semi-submersible float (leg ⁺ hull fully submerged).

Elongation of a semi-submersible float Elongation is the ratio of the length of the curve of the areas of vertical cross-sections to the equivalent diameter of this semi-submersible float.

Coefficient of asymmetry

• x, l'abscisse, repérant la position d'une section transversale verticale, mesurée à partir d'une origine 0 située à l'abscisse médiane de la courbe des aires. L'abscisse médiane de la courbe des aires est l'abscisse de la section transversale verticale qui sépare le navire en deux volumnes égaux.
• A(x), la valeur de l'aire de la section transversale verticale correspondant à l'abscisse x ;
• V , le volume total de la partie immergée du flotteur
• Xav , abscisse de l'extrémité avant de la courbe des aires.
• Xar : abscisse de l'extrémité arrière de la courbe des aires
• xmax : plus grande des deux valeurs Xav et Xar

The curve of the areas of the vertical cross sections of a float extends along the total length of this float, that is:

• x, the abscissa, locating the position of a vertical cross section, measured from an origin 0 located at the median abscissa of the curve of the areas. The median abscissa of the area curve is the abscissa of the vertical cross section which separates the ship into two equal volumes.
• A (x), the value of the area of the vertical cross section corresponding to the abscissa x;
• V, the total volume of the submerged part of the float
• Xav, abscissa of the front end of the area curve.
• Xar: abscissa of the rear end of the area curve
• xmax: larger of the two values Xav and Xar

The longitudinal asymmetry of the float corresponds to the differences in values of the areas of vertical cross-sections corresponding to abscissas x and (-x), symmetrical with respect to the origin of the abscissas.

est une représentation de cette dissymétrie. Elle a les dimensions d'un volume et il est possible, et naturellement préférable, de la transformer pour obtenir un coefficient sans dimension. Il suffit, pour ce faire, de la diviser par le volume V du flotteur. Avec

le coefficient de dissymétrie DIS d'un flotteur est défini par l'égalité :

The amount

is a representation of this asymmetry. It has the dimensions of a volume and it is possible, and naturally preferable, to transform it to obtain a dimensionless coefficient. To do this, simply divide it by the volume V of the float. With

the dissymmetry coefficient DIS of a float is defined by the equality:

Claims (6)

1. Ship comprising three semi-submersible floats (3-6; 5-8) connected to a bridge (1,2) by legs (6; 8), a central float (3-6) being arranged forward and two lateral floats (5-8) being arranged symmetrically with respect to the longitudinal plane (S) of the central float, characterized in that a) the ratio of the ordinate (AI) of the area curve (A1) of the ship to the point of intersection (I) of the area curves (A3 and A5) of the lateral floats on the one hand, and the central float on the other hand, at the maximum ordinate (AM1) of said curve of the areas (A1) of the ship is at least equal to 0.45; b) the ratio of the sum of the volumes of the lateral floats taken together on the one hand, to the volume of the central float on the other hand is between 0.3 and 1.7. 2. Ship according to claim 1, characterized in that for each float, the ratio of the immersion depth of the maximum of the curve of the areas of the horizontal sections (TcL), to the equivalent diameter (Deq) of said float is between 0 , 6 and 1.4. 3. Ship according to any one of claims 1 and 2, characterized in that its asymmetry coefficient (DIS) is less than 0.3. 4. Ship according to any one of claims 1 to 3, characterized in that the elongation of each float is between 5 and 10. 5. Ship according to any one of claims 1 to 4, characterized in that at least one fin (9) substantially horizontal connects each lateral float (5) to the central float (3). 6. Vessel according to any one of claims 1 to 5, characterized in that the two lateral floats (5-8) are on the one hand identical, on the other hand distinct from the central float (3-6).

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