OPEN SEA HYDROFOIL CRAFT

The present invention describes an open sea hydrofoil craft adapted to be used as a high-speed vessel for the transport of passengers and cargo, for recreation or various other applications, embodying a combination of advantageous characteristics of catamaran and hydrofoil vessels, whilst eliminating the drawbacks and limitations of the same.

In the state of the art of ship building three main well known categories of vessels are known. The presently proposed craft eliminates the following main disadvantages of the state of the art of all three well known categories of vessels enlisted herein below: First are mentioned the planning hull vessels of various types, that exhibit excessive fuel consumption due to wave making resistance that increases with the increase of speed and reaches a percentage of 60-70% of the factional resistance, thereby leading to the disproportionate increase of horsepower.

Secondly are mentioned the hydrofoil crafts, which are employed only in closed regions or in calm seas due to the limits imposed by the exposure of foils in the complex forces of waves and the resulting strokes that would be applied on the foils and accordingly on the ship as a whole. Further, hydrofoil type ships are not capable of transporting bulky and heavy items, such as automobiles, etc. and the exploitable space being provided is limited due to the requirements of engine rooms, pump stations, reservoirs, etc. Finally such ships cannot be adapted to employ modern propulsion highly efficient systems, such as water jet propulsion.

Thirdly, catamaran type vessels with the lateral floats on the sides thereof that do not have the capacity of being lifted during cruising, wherein such lifting might consequently lead to the minimisation of wetted surface that is directly related with the value of factional resistance. Catamarans also create wave making resistance and hydraulic strokes on the bottom of ship. Because of their design, catamaran vessels are further being subject to oscillations and vibrations with unanticipated consequences in the structural strength of the ship and of the installations thereof.

Various attempts have being made to avert drawbacks of catamarans. By way of example US-2,917,754 discloses a catamaran vessel construction wherein the lateral floats are made in a convertible flexible connection mode, so as to enable advantageous handling of the vessel when it is moved ashore.

It is an object of the present invention to effectively and advantageously overcome the disadvantages and drawbacks of the herein abovementioned vessel categories of the prior art, by providing an advantageous design based on the combination of catamaran and hydrofoil type vessels. The above principal object of the invention is being attained with an open sea hydrofoil craft, operating with propulsive obtained by modern water jet propulsion systems, wherein this craft comprises a pair of longitudinally, vertically extending lateral blades, in analogy to the side floats of catamarans, however with a complex curved configuration that enhances cruising characteristics and minimizes losses and an arrangement of horizontally extending lift producing foils serially arranged within the channel being formed between the vertically extending lateral blades, wherein these horizontally extending foils, in analogy with the foils of hydrofoil type craft adequately lift the vessel during cruising and being protected by the lateral blades provide the possibility of open sea cruising that is not attainable with hydrofoil crafts of the prior art. It is therefore the object of the present invention to provide an open sea hydrofoil craft that advantageously combines the advantages and eliminates the disadvantages of catamaran and hydrofoil type vessels, wherein the vessel proposed in the present invention displays diminished resistances of all kinds, e.g. of frictional resistances because of the substantially reduced wetted surface thereof during cruising, of air resistances being diminished due to the aerodynamic configuration of the bow and of the vertically extending lateral blades extending to thinned frontal edges and most importantly of the wave making resistances due to the specially designed curved configuration of the vertically extending lateral blades and also due to the design of the horizontally arranged lift producing foils. The vessel of the invention thereby attains high speeds with minimal fuel consumption even in adverse weather conditions.

These and other advantageous characteristics of the open sea hydrofoil craft of the invention will become evident in the description of a preferred embodiment following hereinafter.

The invention will be made apparent to those skilled in the art by reference to the accompanying drawings that present an illustrative, but not limiting embodiment of the invention.

Fig. 1 shows a perspective view focused on the bow, the bottom and the right side of an illustrative embodiment of the open sea hydrofoil craft of the invention.

Fig. 2 shows the craft of Fig. 1 in a perspective view focused on the rear right side thereof. Fig. 3 shows a perspective view of the upper and bottom configuration of the fore lift producing foil of the herein proposed vessel.

Fig. 4 shows a perspective view of the upper and bottom configuration of the lift producing foil located intermediately between the fore and aft lift producing foils of the herein proposed vessel. Fig. 5 shows a perspective view of the upper and bottom configuration of the aft lift producing foil of the herein proposed vessel.

Fig. 6 shows the naval constructional lines and theoretical frames of the conventional part of the vessel of the invention.

Fig. 7 shows the hydrostatic curve obtained with a test model vessel structure of the invention.

Fig. 8 shows a cross sectional view of the vessel of the invention with the vertically extending lateral blades at the theoretical frames 0, 2, 4, 7, 8, the cross sectional view being taken along the section including the horizontally extending aft lift producing foil. Fig. 9 shows a constructional cross sectional view of the vessel being taken along the theoretical frame 3.

Fig. 10 shows a longitudinal side sectional view of the vessel being built for an illustrative cargo-passenger capacity.

Fig. 11 shows a perspective side view of a test model specimen of the vessel of the invention.

Fig. 12 shows a perspective bottom view of the test model specimen of the vessel of the invention.

Fig. 13 shows a perspective side view of the test model specimen of the vessel of the invention, wherein one may observe the theoretical naval frames and the advantageous curved configuration of the lateral vertically extending blades.

Fig. 14 shows the test model specimen of the vessel of the invention at a stationary condition within water, prior to lifting.

Fig. 15 shows a frontal view of the test model specimen of the vessel of the invention as it cruises within water, wherein wave making is apparently substantially eliminated.

Fig. 16 shows a side view of the test model specimen of the vessel of the invention during a turning around an angle of the order of 120°.

The open sea hydrofoil craft of the invention being depicted in Fig. 1 or 2 comprises a principal vessel infrastructure-hull A and an overlying superstructure D with a pair of lateral vertically oriented blades Bl, B2 mounted onto the hull A and extending longitudinally along the two sides of the hull A, wherein the interior surfaces of the blades B 1 , B2 that lie one opposite the other are planar.

A particular characterizing feature of the present invention is that the exterior surfaces of blades Bl, B2 have the configuration of a curve that dynamically changes in three dimensions x, y, z. Such curved configuration advantageously diminishes the resistances being encountered during cruising of the vessel and enhances the advantages obtained with the herein proposed open sea hydrofoil craft. The dynamically changing curved configuration of the exterior surfaces of blades Bl, B2 is characterized by that the fore ends of the interior and exterior surfaces of blades Bl, B2 converge to form vertically oriented thinned frontal edges (see Fig. 1, 14). The exterior surfaces of blades Bl ₅ B2 thereafter gradually diverge from the interior surfaces thereof towards the stern of the vessel defining a space 21 wherein engine rooms and reservoirs are being installed. Such dynamically changing curved configuration of the exterior surfaces of blades B1,B2 is being defined in three dimensions x, y, z, wherein axis x extends longitudinally along the vessel, axis y extends laterally along the vessel and axis z extends vertically.

The dynamically changing curved configuration of the exterior surfaces of blades B 1 , B2 conforms with the following variable parameters:

1. An angle φj formed by the bottom of each one of the blades Bl, B2 with y axis, wherein angle Cl) ₁ varies from a minimal value of the order of 5° at the stern and gradually increases to 90° close to the bow of the vessel.

This variable angle φi contributes in diminishing frictional and wave making resistances and in providing a substantially planar cruising of the vessel, whilst appropriately allowing for the creation of the space 21 for the engine rooms and fuel reservoirs (Fig. 1). Angle parameter φi also contributes in the creation of an arcuate longitudinally extending lateral edge 20 provided on the exterior surface of each one of the blades Bl, B2. 2. An angle φ ₂ formed by the curved section of the exterior surface of each one of the blades Bl, B2 with the vertically oriented axis z, wherein angle φ ₂ varies from a maximum value of the order of 30° at the stern and is gradually diminished to 0° close to the bow of the vessel.

This variable angular parameter φ ₂ is intended to provide a curved configuration of the exterior surfaces of the vertically extending blades Bl, B2 and create narrowed upper parts thereof, thereby diminishing the area and the volume of displacement of water effected by the vessel of the invention, thereby leading towards a sinking tendency of the vertically extending blades Bl, B2. This capacity is considered particularly advantageous for certain applications, wherein if the superstructure D is removed, a large and in the same time substantially low ship is obtained, which, if the case arises, might be lifted onto the water surface and cruise at very high speed.

The above angular parameter φ ₂ in combination with the angular parameter φi and the arcuate longitudinally extending edge 20 of blades Bl, B2 result in the sideward sliding movement of the vessel when turning around a curve and eventually in the vessel effecting such turning operation through displacement of the stern portion thereof. In this way, the vessel of the invention can attain a short turning circle even when cruising at high speed.

3. Angles φ ₃ and φ ₄ formed by the herein above mentioned arcuate longitudinally extending lateral edge 20 of each one of the blades Bl, B2 with the horizontally oriented axis x passing from the naval frame of maximum breadth that is located close to the region of the middle of the length of the vessel. As shown in Fig. 2

whilst the head of the arc of the arcuate lateral edge 20 passes from the naval frame of maximum breadth, the side of the arc heading towards the bow and defining the angle parameter φ ₃ , as well as the side of the arc heading towards the stern and defining the angle parameter φ ₄ have a regularly increasing upward inclination and inward inclination ending at the thinned blade bow ends on the one side and at gradually relatively thinned rear portions of blades Bl, B2. The value of the angular parameters φ ₃ , φ ₄ depends on the overall constructional architecture of the vessel, that is aimed at the herein proposed arcuate longitudinal lateral edge 20 of the blades Bl, B2 being made to coincide at a large extent (from the middle towards the bow of the vessel) with the waterline under conditions of cruising at high speed. Such a configuration has proved to avert wave making resulting from changing values of pressures and speeds of water flow in contact with lateral blades Bl, B2 and thereby avert power losses associated with such wave making. Fig. 15 depicting the test model specimen cruising at high speed confirms the absence of wave making longitudinally along the exterior surfaces of the lateral blades Bl, B2.

The interior planar surfaces of the vertically extending blades Bl, B2 longitudinally extending along the sides of the hull A do form, in the direction from the bow towards the stern, an initially slightly convergent and subsequently a slightly divergent channel. It must hereby be noted that the combination of the dynamically changing parameters of the curved configuration of the exterior surfaces of lateral blades Bl, B2 in three dimensions x, y, z results in a smaller sinking volume of the lateral blades in comparison with the fixed section configuration of the lateral floats of conventional catamaran vessels, thereby achieving sinking of the vessel at a standstill condition, that substantially facilitates loading thereof. Such three dimensionally varying curved configuration of blades Bl, B2 provides a capacity of provision of usefully exploitable space close to the bow of the vessel, whilst the combination with the advantageously thinned blade frontal ends results in a substantial reduction of wave making and air resistances at the bow and also in the improvement of the trim of the vessel when stationary, thereby eliminating otherwise occurring possibilities of sinking of the bow end thereof. Trim of the vessel is additionally improved by the provision of the hull A advantageously extending beyond the water jet outlets at the stern of the vessel. It must

herein be noted that the vessel of the invention sinks when coming at a standstill in ports without creating the intense highly undesirable waves of conventional vessels, since the propulsive water jets thereof are disposed at a considerable depth.

The above mentioned lateral vertically oriented blades Bl, B2 are interconnected with an arrangement of lift producing foils Cl, C2, C3 extending laterally intermediately between the blades Bl, B2, all along the distance between opposite planar surfaces thereof, each one of the lift producing foils Cl, C2, C3 having a hydrofoil section with a leading edge oriented in the direction of the bow and being provided with vertically extending and longitudinally oriented, substantially parallel to the interior planar surfaces of blades Bl, B2, central supporting plates Cl ', C2', C3' respectively, wherein central plates Cl ', CT, C3' of the lift producing foils Cl, C2, C3 are fixedly mounted onto the hull A.

Each one of the vertically extending central supporting plates Cl ', C2', C3' respectively of the lift producing foils Cl, C2, C3 is perforated with apertures 10 through which water flows freely on either side of the supporting plates Cl ', C2', C3' thereby balancing pressures if any that may be due to a sideward inclination of the vessel.

Such pressure differentiation on the sides of plates Cl ', C2', C3' if they were not being provided with apertures 10, would lead, further to the deforming forces being exerted onto supporting plates Cl ', C2', C3', to the creation of torques tending to render an undesirable inclination of the vessel and delay the return of the same at the optimal horizontal condition.

Each one of the lift producing foils Cl, C2, C3 has a differentiated configuration and is located at a differentiated distance from the vessel's waterline during cruising and at a differentiated distance relatively to the lateral vertically oriented blades Bl, B2. hi particular, according to a preferred embodiment of the invention, the first fore lift producing foil Cl is located at a certain distance from the bottom edges of blades Bl, B2 and the third aft lift producing foil C3 is located at a level lower than the fore lift producing foil Cl with the distance thereof from the bottom edges of blades Bl, B2 tending to zero. Both the fore lift producing foil Cl and the aft lift producing foil C3 are being oriented perpendicularly onto the interior planar surfaces of blades Bl, B2, wherein, due to the differentiated distance of the fore lift producing foil Cl and of the aft

lift producing foil C3 from the bottom edges of blades Bl, B2, a counterclockwise rotational moment arises, such rotational moment increasing as the speed of the vessel increases. This rotational moment eliminates the otherwise successively occurring undesirable rising of the bow of the vessel and subsequent falling thereof as the vessel cruises at high speed, such bow rising and falling being associated with the undesirable periodical hard strokes of the vessel into the water mass and may also lead into a tendency of the vessel being overturned.

In Fig. 1, R _a denotes the frictional resistance of the water mass and R _b denotes the lifting capacity of the vertically extending lateral blades Bl, B2. Whilst both the fore and aft lift producing foils Cl, C3 are oriented perpendicularly onto the interior surfaces of blades Bl, B2, the intermediate lift producing foil C2 comprises two identical portions C2a, C2b symmetrically extending on one and the other side of the vertically extending central supporting plate C2' by means of which the intermediate lift producing foil C2 is connected to the hull A. The symmetrically oriented identical portions C2a, C2b form an obtuse angle so as to render an overall configuration of inverse V of the intermediate lift producing foil C2. The abovementioned intermediate lift producing foil C2 is located at a certain distance from the bottom edges of the blades Bl, B2, higher than the fore and aft lift producing foils Cl, C3 thereby producing, in addition to the lift effect, a laminar flow with the water masses being directed towards the centre of the channel being formed in between the vertically extending blades Bl, B2 thereby enhancing the kinetic energy thereof.

The intermediate lift producing foil C2 is preferably located at the end of the slightly convergent portion of the channel being formed in between blades Bl, B2, whereby the span of the intermediate lift producing foil C2 is less than the span of either the fore lift producing foil Cl or the span of the aft lift producing foil C3.

The horizontally extending lift producing foils Cl, C2, C3 are protected by excessive sea waves, that do not up today permit employment of hydrofoil crafts in open seas, by means of the vertically extending blades Bl, B2 within which they are enclosed, whilst through these blades Bl, B2 the lifting effect is being transferred to the overall structure of the vessel. It is hereby noted that the connections of the horizontally

extending foils to the vertically extending lateral blades and to the hull of the vessel consist a substantially strengthened overall structure of the vessel.

The arrangement of the three lift producing foils horizontally extending along the direction of axis x, with the differentiated height of mounting and differentiated design thereof is aimed at obtaining an optionally laminar flow through the channel being formed between the interior surfaces of vertically extending lateral blades Bl, B2. In particular:

According to a preferred embodiment of the invention the fore lift producing foil Cl is provided with a complex bulb structure 11 extending longitudinally along the bottom of the lift producing foil Cl underneath the central supporting plate Cl ' thereof, wherein the abovementioned complex bulb structure 11 protrudes afore the leading edge of the fore lift producing foil Cl and acts so as to smoothly guide the water mass onto this fore lift producing foil Cl and avert hydraulic strokes thereupon. Fins 11a, l ib are also being provided on either side of the complex bulb structure 11 longitudinally along the bottom of the fore lift producing foil Cl, wherein these side fins l la, 1 Ib lag behind the forwardly protruding bulb structure 11 along only a portion of the length of foil Cl, and act so as to damp wave making and to enhance the effect of the centrally oriented protruding complex bulb structure 11. It is additionally noted that the fore lift producing foil Cl acts so as to handle both longitudinally and sideward acting torques, thereby playing the role of stabilizing blades of conventional vessels.

The intermediate lift producing foil C2 with the afore mentioned characteristic configuration of an inverse V contributes in the optimization of laminar flow characteristics, but it is otherwise not absolutely necessary in obtaining the desired lifting effect that may be obtained only by means of the combined effect of the fore and aft lift producing foils Cl, C3.

The aft lift producing foil C3 comprises an arrangement of three conically shaped fins 12 protruding afore the leading edge thereof, wherein a first one of the three conically shaped fins 12 lies longitudinally along the central supporting plate C3' and the other two conically shaped fins 12 lie symmetrically along one and the other side of the aft lift producing foil C3, rightwards and leftwards relatively to the central supporting plate C3', wherein all these three conically shaped fins 12 protrude afore the leading edge

of the aft lift producing foil C3 and act so as to eliminate turbulent vortices resulting from the wake of the preceding lift producing foils Cl, C2 and smoothen pressures and speeds of the water masses falling onto the aft lift producing foil C3.

A characteristic feature of the vessel of the invention as becomes evident from the test model specimen thereof being depicted in Fig. 11 is that the hull A does not come in contact with the sea surface whilst the craft is cruising and has a substantially planar square cross section thereby providing enhanced cargo loading capacity.

The invention is not limited in the illustrative preferred embodiment described hereinabove, but is limited as set henceforth in the appended claims.