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The present invention relates to the sector of watercraft and in particular to planing hulls characterized by particularly innovative shapes.

Traditional fast hulls have by now achieved a sufficiently known and standardized overall shape: the need to generate consistent forces of lift in order to guarantee a good rise of the bottom and reduce the resistance to advance has, ^' in fact, led to the construction of hulls with ample surfaces of the bottom characterized . in the stern part by reduced and longitudinally delimited deadrise, by edges that extend throughout or almost throughout the length of the hull, with said edges at a width almost corresponding to the width, of the hull.

On the other hand, in the field of fast hulls there is a continuous search for innovative shapes in order to achieve two main objectives:

increase of the performance of the keel, in terms of resistance to motion and efficiency;

- increase of the space available on board.

Multihulls represent in this sense an excellent solution: the interaction between the two hulls is in fact positive, and the resistance that derives therefrom is less than twice the resistance of the single hull. Furthermore, the distance between the hulls enables decks to be obtained of considerable width and an excellent stability (at least for small heeling angles) with the consequence of being able to increase considerably the size of the superstructure. The drawback-s are linked to the high frequency of the motions of roll, with consequent inconvenience for the passengers, and to the considerable widths that in various cases complicate the mooring manoeuvres.

The invention basically consists of a planing hull with quickwork (underbody) having innovative shapes that espouse the characteristics of the single hull with those of multihulls and enable the two objectives highlighted above to be approached.

, A better understanding of the invention will be obtained from the ensuing description and with reference to the annexed figures, which illustrate a preferred embodiment thereof purely by way of non- limiting example.

In the drawings: .

Figure 1 is- a perspective view of the hull according to the present invention;

. Figure 2 shows a cross section of the hull according to a plane of trace D-D indicated in Figure 1;

Figure 3 ^' shows a cross section of the hull according- to a plane of trace F-F indicated in Figure 1; ^'

Figure 4 shows a cross section of the hull according to a plane of trace E-E indicated in Figure 1;

Figure 5 is a top plan view of the same hull, in which the lift region P and the directional region D are visible;

' Figure 6 is a side view in which there appear the traces of the waterlines; Figure 7 is a view of the hull from the bow;

Figure 8 is a view of the hull from the stern;

. Figure 9 is a perspective view from beneath, from the bow;

Figure 10 is a perspective view from beneath, from the stern;

Figure 11 is a side view with trace of the cross sections; . -

Figure ^' 12 shows the cross sections of Figure 11 viewed from the bow;

Figure 13 shows the cross sections of Figure 11 viewed from the stern;

Figure 14 is a perspective from the bow, which shows the tunnel;

Figure 15 is a top plan view, which shows the tunnel from the inner side of the hull;

Figure 16 is a perspective view from the stern, from which the tunnel is clearly visible;

Figure 17 is a top perspective view of the tunnel from the bow;

Figure 18 shows sections with waterlines DWL and

WL1;

Figure 19 shows a. section with waterline WL2 ;

Figure 20 shows a section with waterline WL3;

Figure 21 shows a section with waterline WL4.

With reference to the figures, it should be noted that, conceptually, the bottom of the hull according to the present invention is characterized by five curves, which we define as "generatrices" and which develop in a longitudinal direction.

The . figures ^' contained in the annexed -plates of drawings show the pattern of said curves, generatrices of the hull, and the consequent edges that they determine.

The central edge, designated by the letter A, lies in the longitudinal plane of symmetry and coincides with the keel.

According to a first peculiar characteristic of the invention, said central edge A has a convex shape afore the cross section F-F, which is set in the point of inflection of the generatrix A, and a concave shape abaft the same cross section, becoming practically rectilinear and parallel to the baseline in the area abaft .

The intermediate edges B, closer to the longitudinal plane of symmetry, delimit a central part of the bottom referred to as "directional region" D in so far its bow shape is entrusted with the directional functions of the bottom.

The directional region D is made up of two distinct specular surfaces, joined together at the central edge A. Said surfaces determine in the bow part a V-shaped cross section, whilst starting from approximately one half of the length, proceeding towards the stern, the shape of the cross section changes without producing any discontinuity, "twisting", and continuing to connect up at the edge A to form a tunnel, the terminal shape of which, at the transom, is practically semicircular with concavity facing upwards. The two lateral hull surfaces, which are symmetrical with respect to the longitudinal plane and external to the directional region D, are referred to. as "lift · regions" P and are comprised between the edges B ^' and further lateral edges C that divide said lift regions P from the sides of the hull.

The function of said lift regions P is dual: in ^' their bow parts ^" · ^· they facilitate detachment of the threads and at the same time channel fluid towards the tunnel of the stern, increasing the pressure thereof. All this produces a reduction of the planing times. In their stern part, they perform the function of lift surfaces. In said area, the threads have transverse components of speed reduced as compared to the case of a conventional V-shaped hull, thus increasing the efficiency of the propellers that are set in said regions and are perpendicular to said threads .

The lift regions P are single-curvature surfaces that are segments in a transverse direction and curves in the longitudinal direction.

In the area afore, afore the cross section D-D, the directional region D joins to the lift , regions P to form two plane surfaces defined as "internal runners 1", and the lift regions join to the sides to form two practically plane surfaces defined as "external runners 2". The runners 1 and 2 meet at the stem.

The four surfaces (runners 1 and runners 2 on the right and on the left) are studied for facilitating planing.

As compared to conventional hulls of equal hull volume, draft, length and width of the sheer strake, the presence of the tunnel leads to an increase of the average width of the waterline plane and "verticalizes" the topsides. Said increase consequently produces:

- an increase in the transverse stability;

- a reduction of the motions of roll;

- an increase of the internal living space;

- a reduction of lateral wave formation; and

- a reduction of resistance to advance.

In the area abaft, alongside the tunnel the lift regions P can be considered almost as "independent" hulls and have dimensions such as to enable housing of the main motors, which are consequently installed at a distance from the longitudinal plane of symmetry greater than what occurs on conventional planing hulls. Advantageously, with the solution so far described according to the present invention, the manoeuvrability is improved and increased, in particular at low speeds.

With the hull shapes described above the dynamic behaviour of the hull, at . cruising speed, is such as to reduce formation of the stern wake resistance and hence the total resistance, thus improving the efficiency of the hull as compared to conventional ones of equal length and displacement, with consequent reduction in the power required and hence in the . associated consumption levels.

The hull ^" built according to. the example of embodiment that is described is made of welded light aluminium alloy of type 5083. To increase the overall strength, the edges A, B, C, are made from full pieces obtained by casting and subsequently machined and finished with machine tools and welded to the internal structures and to the metal plate of the bottom and of the sides.. From what has been said, the planing hull so far described has a hull shape that affords the following advantages :

- the average width of the waterline plane is greater than that of a conventional hull of equal displacement and equal . waterline length, ensuring an increase in the internal spaces that can be used for living, as well as an improvement of the stability to roll;

- the main motors are located at a distance apart greater than that of a conventional installation and hence provide an increase in manoeuvrability; and

- the bow shape affords good qualities of penetration and directionality.

As used herein, by "conventional hull" is meant the bottom of V-shaped planing hulls with dihedral angle variable and decreasing from bow (bow deadrise) to stern (stern dihedron or stern deadrise) .