The present invention relates to a vessel with a variable hull size according to the preamble of claim 1 .

The term "vessel" relates to all kinds of floating bodies , like ships , boats , sloops , canoes , pontoons and even submarines .

It is known in the art to build vessels with extensions , for example a swimming or diving deck or another recreational part of the vessel that can be extended when the vessel is anchored .

Such known extension provides the advantage that climbing aboard is easy, at least more easy than climbing up a ladder from the water . No other technical effect is obtained .

The invention aims at providing an improved vessel of the kind mentioned in the preamble .

The invention further aims at providing a vessel that can change between hydrodynamic properties .

The invention furthermore aims at providing a vessel that has optimum sailing behavior and sailing characteristics at different situations .

The invention also aims at providing a vessel that has sailing characteristics of a large vessel but that can moor at small j etties and berths .

The invention also aims at providing a vessel that has an improved buoyancy .

So as to obtain at least one of the above mentioned aims , the invention provides a vessel as mentioned in claim 1 . This vessel has the advantage that it may have a small size for example when mooring , whereas it may have a larger size when sailing . As a result , the sailing characteristics are largely improved whereas it can still moor at a small j etty or berth .

The vessel according to the present invention is admirable for private owners but for renting companies as well , since private owners can moor a vessel with great sailing characteristics at a relatively small j etty, and renting companies can dock more vessels at the j etties in their ports , whereas the long vessel fits more people .

In addition, a long vessel consumes less energy at the same speed than a short vessel . Especially for commercial shipping , this is a great advantage . Furthermore , a long boat has less draft and therefore sails more economically than a short vessel with the same mass , and as a consequence provides a more sustainable sailing .

Also , a long boat more easily stays horizontal at higher speeds . It also certainly has more prestige and provides more status to its owner .

On the other hand, a shortened vessel can maneuver more easily and it also can be transported easily on a trailer or other transport which is of high importance for pleasure craft .

The advantage of a shorter vessel furthermore is that it feels less empty when there are fewer people aboard . In addition, less costs are involved when placing the shorter or shortened vessel in a dry dock .

Such synergistic effects are highly advantageous .

The invention therefore relates to a vessel with a variable hull size , characterized in that it comprises a main hull with an outer hull and an inner hull , and wherein the main hull is provided with an intermediate receiving space between the outer hull and the inner hull for receiving at least part of an extension hull , wherein the intermediate receiving space and the extension hull are cooperatively engaged for repeated movement of the extension hull between a retracted position and an extended position . This provides a vessel , the hull of which can be moved between an extended position yielding a great length and a retracted position yielding a short length .

The effect of the extendibility of the hull is that the buoyancy is changed as well when changing the length of the vessel .

In the extended position the buoyancy is increased, allowing the vessel to carry more cargo . Since the buoyancy is increased, the vessel can carry more cargo at the same draft . On the other hand, a shortened boat has more draft , and thus can pass under lower bridges . In addition, larger cargo can be transported .

On the other hand, by retracting the extension hull , yielding a shorter length and less water displacement , the vessel will have a greater draft with the same weight . Hence , the vessel ' s maximum tonnage is less which lowers port dues and mooring costs .

A shortened boat with more draft also slips less quickly . On the other hand a longer ship, which is higher on the water, slips faster .

It is preferred that the receiving space is provided in the bottom and side walls of the main hull , since this ensures the complete hull is waterproof in the fully extended and the fully retracted position .

The waterproof capacity is further ensured when the receiving space is a continuous space .

Alternative embodiments for ensuring a required buoyancy are comprised of providing an increased pressure inside the receiving space , so as to keep out water . Another alternative embodiment comprises adding a water pump to remove any water that leaks into the receiving space .

The main hull and the extension hull may move directly over each other or a gliding systems , like ball guides , may be applied .

By providing the extension hull with a double hull profile , the stability of the vessel may be enhanced, although such will not be required if the vessel is a relatively small vessel , for example a pleasure yacht or a sloop . The double hull profile of the extension hull then comprises a first hull profile that is to be inserted in the receiving space of the main hull , and a second hull profile that is placed above the main hull or below the main hull . As a consequence , in such double hull profile embodiment , it is preferred that a first hull profile is embodied for insertion in the receiving space . The other hull profile , in case of a double hull profile , may be placed above the main hull ' s inner hull , that is on the inside of the vessel , or below the main hull ' s outer hull , that is below the vessel and in the water . For obtaining maximum free space within the vessel , it is preferred for the extension hull that one of the hull parts is placed below the main hull ' s outer hull part . For obtaining optimum hydrodynamics , it is preferred that part of the main hull is placed below the extension hull if the extension hull is at the stern side of the vessel . Hence , for obtaining improved stiffness in combination with an as large as possible usable volume inside the vessel , it is preferred that a second hull profile is embodied for positioning outside the main hull .

Maximum safety is obtained when the main hull itself is embodied as a watertight compartment providing the vessel with buoyancy . Even if some accident would occur , destroying the seals between the main hull and the extension hull , the main hull itself provides buoyancy . Actually, it provides increased buoyancy compared to the situation where the extension hull is in its retracted position for the total vessel' s total weight is that of the main hull only .

According to a main aspect of the present invention, the extension hull provides additional buoyancy to the vessel in the extended position . This is obtained according to the present invention by extending the extension hull at a position below the waterline of the main hull .

The present invention allows a new approach to environmentally friendly vessels . To that end, it is preferred that the vessel has an electric motor and batteries for powering said electric motor .

In this regard, an optimum weight distribution is obtained when the batteries are contained in the main hull and the electric motor is contained in the extension hull , the electric motor and the batteries being mutually operatively connected by electrical wiring . Such distribution of components allows for the vessel to remain stable at low and high speed . The relatively heavy batteries in the bow side of the vessel in combination with a larger length of the vessel in the extended position, ensure that the aft side remains low at high speeds . Such weight distribution thus provides increased safety .

A safe connection between the main hull and the extension hull may be easily obtained when the receiving space has an inner free dimension between an outer hull and an inner hull , with the proviso that a shoulder is provided at an outer edge of the receiving space with the result that the free dimension at the edge is less than the inner free dimension, and wherein part of the ex- tension hull that is received in the receiving space has a thickening at its end that is received in the receiving space , said thickening being larger than the free dimension at the edge . Such simply ensures that the extension hull cannot be removed from the main hull .

An improved waterproof embodiment is obtained when said edge is provided with an elastically compressible material . The elastically compressible material may be placed at the contact surface of the extension hull ' s thickening and the main hull' s shoulder , but also at a contact surface between the main hull ' s shoulder and an end position of the extension hull that may contact the said shoulder in the retracted position .

A further improvement may be obtained by connecting the extension hull to the main hull by means of a flexible sheet . Such provides for a covering of the connection between the main hull and extension hull . The flexible sheet is on the one hand connected to the main hull and on the other hand connected to the extension hull .

A further improvement in waterproof characteristics is obtained when the flexible sheet is waterproof . In such preferred embodiment , the flexible sheet provides a water tight connection .

The flexible sheet is securely stored in the retracted position if it is a harmonica folded sheet material .

A still further enhancement may be obtained when the flexible waterproof sheet is contained within the intermediate receiving space . This provides the advantage that the additional security is not visible from the outside .

In such embodiment , the waterproof flexible sheet is connected to the extension hull and the inner hull , providing optimum safety .

Hereafter, the invention will be further described by means of a drawing . The drawing shows in :

Fig . 1 a schematic view of a vessel according to the invention in an extended position,

Fig . 2 a schematic view of a vessel according to the invention in a retracted position, Fig . 3 a schematic view of a variant of the vessel according to the invention in a first position .

Fig . 4 a variant of a vessel in an extended position,

Fig . 5 a variant of a vessel of Fig . 4 in a retracted position,

Fig . 6 a variant of a vessel in an extended position,

Fig . 7 a variant of a vessel of Fig . 6 in a retracted position,

Fig . 8 a schematic detailed view of a combination of main hull and extension hull in a retracted position,

Fig . 9 a schematic detailed view of a combination of main hull and extension hull in an extended position,

Fig . 10 a variant of a vessel in an extended position,

Fig . 11 a variant of a vessel of Fig . 10 in a retracted position,

Fig . 12 and 13 a perspective view of a main hull and an extension hull ,

Fig . 14 and 15 an alternative embodiment of the vessel according to the invention, and

Fig . 16 and 17 another alternative embodiment of the vessel according to the invention .

The same and similar parts and features have been denoted by the same reference numerals in the figures . However , for ease of understanding the figures , not all parts that are required for a practical embodiment have been shown in the figures .

Fig . 1 shows a schematic view of a vessel 1 according to the invention . The vessel 1 mainly comprises a main hull 2 and an extension hull 3 . As shown in Fig . 12 , the main hull 2 comprises an outer hull 4 and an inner hull 5 . The main hull 2 is provided with an intermediate receiving space 6 , which is also clearly shown in Fig . 12 . The intermediate receiving space 6 is positioned between the outer hull 4 and the inner hull 5 for receiving at least part of the extension hull 3 , preferably for receiving at least part of the walls and the bottom element of the extension hull 3 . The intermediate receiving space 6 and the extension hull 3 are cooperatively engaged for repeated movement of the extension hull 3 between a retracted position as shown in Fig . 2 and an extended po- sition as shown in Fig. 1.

Variants of the vessel 1 in the extended position are shown in Fig. 3, Fig. 4, Fig. 6, and Fig. 10.

Variants of the vessel 1 in the retracted position are shown in Fig. 2, Fig. 5, Fig. 7, and Fig. 11.

Fig. 2 shows a schematic view of the vessel 1 according to Fig. 1 in a retracted position. In this position, the extension hull 3 is substantially received within the intermediate receiving space 6 of the main hull 2.

The main hull 2 as shown in Fig. 1 and Fig. 2 has buoyancy of its own, since it is surrounded by walls 7, 8, 9, 10 that extend upwards from the inner hull 5. Fig. 3 shows a variant of the vessel of Fig. 1 since in the embodiment according to Fig. 3 the main hull has side walls 7, 8, 9 only. This provides the advantage that a continuous space is provided from the bow 14 to the stern 15 of the vessel, both in the retracted and the extended position.

The extension hull 3 has three side walls 11, 12, 13.

Fig. 5 and Fig. 6 show a variant of the vessel 1 in an extended and a retracted position, respectively. For completeness sake, a wind shield 14 and a skipper's seat 29 are shown in these figures. The windshield 14 is comprised of a first part on the main hull and a second part on the extension hull 3 that are slightly offset so as to enable a retractive movement of the extension hull 3 with respect to the main hull 2.

Fig. 6 and Fig. 7 show a variant of the vessel 1 in an extended and a retracted position, respectively, whereas a flexible sheet material 16 is connected to an end part 17 of the extension hull 3 and to an end part 18 of the main hull 2. The flexible sheet material 16 is a harmonica folded sheet material. It is easily pleated in the retracted position shown in Fig. 7 taking up as little space as possible. The sheet may be made of any water proof material that is able to withstand many retraction and extension movements of the vessel, for example polyvinyl chloride, which is available from many manufacturers, or, for example, hypalon which is a chlorosulphanated polyethylene.

Fig. 12 shows an explosion view of the vessel 1. The main hull 2 comprises an intermediate receiving space 6 for receiving walls 11 , 12 and floor element 20 of the extension hull 3 . The main hull 2 furthermore comprises a compartment 21 for receiving bottom part 19 of the extension hull 3 . This provides a stable coupling of main hull 2 and extension hull 3 . Fig . 13 more clearly shows the relative positions of bottom part 19 and floor element 20 of the extension hull 3 . At the stern 15 of extension hull 3 said bottom part 19 and floor element 20 are mutually coupled .

A schematic view of the bottom element 12 or the part 19 of the extension hull 3 received within the main hull 2 is shown in the retracted position in Fig . 8 and in the extended position in Fig . 9 . It is shown that the receiving space 6 has an inner free dimension between the outer hull 4 and the inner hull 5 . In this embodiment , a shoulder 22 is provided at an outer edge 23 of the receiving space 6 with the result that the free dimension at the edge 23 is less than the inner free dimension . A part of the extension hull 3 that is received in the receiving space 6 has a thickening 24 at its end 25 that is received in the receiving space 6 . The thickening 24 is larger than the free dimension at the shoulders 22 at the edge 23 . The extension hull 3 thus cannot be separated from the main hull 2 .

Fig . 10 and Fig . 11 show a variant of the vessel 1 in an extended position and a retracted position, respectively . In this embodiment , a single main hull 2 is provided with two extension vessels 3 , 3 ' ; one at each end 26 , 27 of the main vessel 2 . A flexible sheet 28 is connected to ends of the extension vessels 3 , 3 ' facing each other .

Fig . 14 and Fig . 15 show a main hull 2 that has buoyancy of its own, since it is surrounded by walls 7 , 8 , 9 , 10 that extend upwards from the inner hull 5 . However , a door 30 is provided in the wall 10 so as to allow easy passage from the main hull 2 to the extension hull 3 when it is in the open position according to Fig . 15 . The door 30 provides a water tight seal when it is in the closed position as shown in Fig . 14 .

Finally, Fig . 16 and Fig . 17 show a luxurious yacht 31 in an extended position and a retracted position, respectively . The advantages as indicated above are provided in each of these positions . Additionally, the platform 32 obtained by extending the ex- tension hull can be used as a recreational deck of as a landing platform for a helicopter , inter alia .

The invention is not limited to the embodiments as mentioned above and as shown in the drawings . The invention is limited by the claims only .

The invention also relates to all combinations of features described here independently of each other .