The main design requirements for sailboats are high speed and low costs. This especially applies to monohull sailboats with centreboard used for sporting and leisure purposes.

Background art

In Fig. 1a the "idealised" depiction of a single-sail sailboat is shown, the major components thereof being the hull 1, the rudder 2 attached to the hull 1 , the centreboard 3 that is retractable into the hull 1 , and a sail 4 disposed on a spar assembly consisting of a mast 5 and a boom 6. The sailboat also has rigging that is not shown in the drawing.

As a first step of designing a sailboat the hull 1 is designed, and then the centreboard box adapted for receiving the centreboard 3 can be dimensioned and positioned on the hull 1. Thereafter, the shape and dimensions of the rudder 2 are determined, followed by establishing the size of the sail 4 and the position of the mast 5 relative to the hull 1.

Sailboat design, therefore, involves choosing a specific rigging for a particular hull, and placing the mast at a fixed position.

The shape and dimensions of the hull 1 are determined by hydrodynamic considerations, while the mass of the hull 1 must be reduced to the possible minimum allowed by the particular rigging.

High speed is a fundamental design target. Speed can be increased on the one hand by reducing the mass of the hull 1 , and on the other, by increasing the sail area.

During sailing, the continually changing wind conditions that affect the stability of the hull 1 have to be taken into account. The mass and positioning of the crew are also factors affecting stability. In higher winds the crew must assume a position such that their centre of mass is as far to windward as possible from the boat's longitudinal axis.

This may be achieved in two ways: by "hiking", i.e. assuming a sitting position on the edge of the hull 1, or using the so-called "trapeze", a wire attached near the head of the mast 5 in order to be able to "stand" on the edge of the hull 1 by clipping the lower end of the trapeze to a trapeze harness. This "shifting" of the centre of mass calls for the hull 1 to be made wider.

However, a wider hull 1 means increased mass, and also that a larger part of the hull surface comes in contact with water, which makes the hull slower.

To overcome this difficulty, the so-called "skiff hull shape was invented. The most important characteristic feature of this hull type is that the lower part that is in contact with water is narrow, and it has a widening upper portion. The narrow lower portion results in a reduced surface area in contact with water, while the upper portion fulfils the above described requirements, i.e. the centre of mass is moved further away from the main axis of the boat. A further characteristic feature of such boats is that the hull has an open aft portion, having only a small protrusion adapted for attaching the rudder. Thereby, water entering the hull during sailing (due to high waves or capsizing) may leave the boat at the aft portion of the hull.

Figs. 2a-2c show cross sections of conventionally shaped hulls. In Fig. 2a the cross section of a conventional hull shape is illustrated, Fig. 2b and 2c, respectively, showing a monolithic skiff hull, and a skiff hull comprising a hiking frame 7.

Taking into account the design considerations of known sailboats, it can be maintained that the boat is designed for a given crew (for a given crew mass range): the position of the crew's centre of mass is determined relative to the longitudinal axis of the boat, and next the tilt angle of the mast (i.e. the range in which the mast can be adjusted in the direction of the boat's longitudinal axis), the dimensions of the sail and the length of the mast are determined. Typically, a single given rigging and a single mast step position are determined for a given hull.

Known solutions have the common drawbacks that a conventional sailboat is typically suited to be used by a single given crew with a given rigging, since the boat was designed with the parameters of the given crew in mind, and that conventional sailboats are costly.

Disclosure of invention

The single-sail monohull sailboat with centreboard according to the invention is based on the recognition that the components of the hull of a single-sail sailboat can be divided into two groups. The first group has those components which are functionally indispensable for the operation of the sailboat, while in the second group belong those components which can be "omitted". The functionally indispensable components are indicated in Fig. 1b with thick lines. These are: the bottom portion of the hull 1, being in contact with water, i.e. the so-called "main board" (which comprises the centreboard box and thereby allows for securing the centreboard), the part of the aft portion of the main board where the rudder 2 can be mounted, the attachment points of the mast 5, and a component, disposed above the main board parallel therewith, which allows for hiking. Therefore, between the main board and the portion allowing for hiking the hull 1 need not be a continuous body in order to obtain a structure - a sailboat - that is capable of sliding on water.

The objective of the present invention is to provide a single-sail sailboat that eliminates the disadvantages of known sailboat types, namely, the problem of "one king of rigging only", while it has reduced mass and may be easily disassembled.

The inventive objective is fulfilled by providing a monohull single-sail sailboat with centreboard comprising a hull, a rudder attached to the hull, a centreboard retractable into the hull, a spar assembly consisting of a mast and a boom, and a sail disposed on the spar assembly, which sailboat is characterised by that it has an open hull consisting of a main board, aft support member(s) attached to the main board, forward support member(s) arranged parallel with the aft support member(s) and adapted for receiving a mast step supporting the mast, and hiking decks attached to the aft and forward support members and arranged to extend over the main board.

In a preferred embodiment of the single-sail sailboat according to the invention the aft support member(s) is (are) fixedly attached to the main board, while the forward support member(s) is (are) movably attached to the main board, and the hiking decks are fixedly attached to the aft support member(s), while the attachment between the forward support member(s) and the hiking decks is movable.

In another preferred embodiment of the single-sail sailboat according to the invention the main board is a closed body shaped to conform to hydrodynamic criteria that comprises a flat deck at the upper face thereof, with a rudder bracket being disposed at the aft edge of the main board and a centreboard box having an opening adapted to receive a centreboard being disposed near the centre of the longitudinal axis of the main board, with attachment members - dowels - adapted for attaching the aft support member(s) being disposed at the aft portion of the deck of the main board, where in the forward portion thereof attachment members - two pairs of rails - adapted for movably attaching the forward support member(s) are situated, and with the dowels situated at the aft portion of the deck of the main board having a threaded configuration, where the grooves forming the pairs of rails situated at the forward portion are terminated in respective openings at one of their ends, preferably their aft ends that face the dowels.

In a further preferred embodiment of the inventive single-sail sailboat the forward and aft support members are made from closed-section members, preferably aluminium tubes, the aft support member consisting of a flat bottom portion attached to the deck of the main board, an upper portion arranged perpendicular to the longitudinal axis of the main board, connecting portions adapted to connect the bottom portion and the upper portion, and a transverse stiffening member situated in the bottom portion, with bores arranged to be aligned with the attachment members - dowels - disposed in the deck of the main board being disposed in the bottom portion, and the forward support member consisting of a bottom portion, an upper portion arranged perpendicular to the longitudinal axis of the main board, connecting portions adapted to connect the bottom portion and the upper portion, and transverse stiffening members situated in the bottom portion, with bores adapted to facilitate attachment to the forward connecting members - pairs of rails - of the deck of the main board being disposed in the bottom portion, where the forward support member is arranged to receive a rotary mast, the upper portion of the forward support member being fitted with a bushing.

In an expedient embodiment of the inventive single-sail sailboat the aft and forward support members consist of multiple parts, the hiking decks are closed, water- sealed bodies, with fixedly arranged attachment members being disposed in the portions thereof attached to the aft support member(s), and with attachment members allowing movable attachment being disposed in the portions thereof attached to the forward support member(s), where dowels are disposed in the portions of the hiking decks that are attached to the aft support member(s), and grooves terminated in openings are disposed in the portions thereof that are attached to the forward support member(s).

In another expedient embodiment of the single-sail sailboat according to the invention the pair of rails formed in the deck of the main board and the grooves formed in the hiking decks have an identical, preferably T-shaped, configuration, the sailboat comprising further connecting members providing attachment between the hiking decks and the aft and forward support members, the connecting members being implemented as slotted cylindrical surfaces, with tube segments being attached to the cylindrical surface on both sides of the slot, and a base portion being attached to the cylindrical surface opposite the tube segments.

Brief description of drawings

An exemplary embodiment of the watercraft, particularly sailboat according to the invention is explained in detail referring to the attached drawings, where

Fig. 1 illustrates the typical configuration of a sailboat,

Figs. 2a-c show schematic views of a prior art sailboat type,

Fig. 3 is the axonometric view of the schematic arrangement of the sailboat according to the invention,

Fig. 4 is the top plan view of the sailboat shown in Fig. 3,

Fig. 5 is the side elevation view of the sailboat shown in Fig. 3,

Figs. 6a-c schematically illustrate the attachment of the sailboat superstructure to the main board of the inventive sailboat,

Figs. 7a-7b illustrate the schematic arrangement of the support members of the sailboat according to the invention,

Fig. 8 shows the top pla view of the main board of an exemplary embodiment of the sailboat according to the invention,

Fig. 9 is the side elevation view of the main board shown in Fig. 8,

Fig. 10 is the top plan view of the centreboard box of the main board shown in Fig. 8,

Fig. 11 is a section taken along the line A-A of Fig. 10,

Fig. 12 is the rear view of the rudder bracket of the main board shown in Fig. 8, Fig, 13 is a side elevation view of the support member arrangement of the inventive sailboat,

Fig. 14 shows an underside view of the aft support member of the sailboat according to the invention,

Fig. 15 is an underside view of the forward lateral support member of the sailboat according to the invention,

Fig. 16 shows a top plan view of the bushing adapted for receiving the rotary mast of the sailboat according to the invention,

Fig. 17 is a sectional view of the main board shown in Fig. 8 taken along the line B-B,

Fig. 18 shows the top plan view of the hiking deck of the inventive sailboat, Fig. 19 is a side elevation view of the hiking deck shown in Fig. 18, Fig. 20 is a side elevation view of the connection member installed between the hiking deck and the lateral support member of the sailboat according to the invention, and

Fig. 21 shows the top plan view of the connection member illustrated in Fig. 20. Best mode of carrying out the invention

Fig. 3 shows an schematic axonometric view of the sailboat arrangement according to the invention, which consists of a main board 8, aft and forward support members 9, 10 attached to the main board 8, and hiking decks 11 that are attached to the aft and forward support members 9, 10 and are arranged to extend over the main board 8.

The main board 8 is a closed body, and it is the part of the watercraft that is in contact with water. To minimise the mass of the craft, the height of the main board is as small as possible, being preferably in the range of 10-20 cm. In the aft portion of the main board 8 a protrusion 12, referred to below as "rudder bracket", is situated rearward from the aft support member 9 (see Fig. 5). The protrusion 12 facilitates the mounting of the rudder assembly. An opening 14 (see Fig. 4) encircled by a protrusion 13 (see Fig 5) is situated on the portion of the main board 8 that extends between the aft and forward support members 9, 10. The opening 14 is adapted for receiving a centreboard, with the centreboard box being situated around the opening 14. The protrusion 13 is included for increasing the height of the centreboard box and thus providing better support for the centreboard.

The aft and forward support members 9, 10 are releasably attached to the main board 8. The respective upper portions of the support members have a widened configuration extending over the main board 8. A mast step 15, or in case of a rotary mast, two support points 16, 17 (indicated in Fig. 5 by empty circles), is/are disposed in the forward support member 10.

The block-shaped hiking decks 1 are releasably attached to the widened upper portions of the aft and forward support members 9, 10. The length of the hiking decks 11 (i.e. their dimension measured in a direction parallel with the longitudinal axis of the main board 8) is determined by the distance between the aft and forward support members 9, 10.

The height and width (i.e. the dimensions measured in a direction perpendicular to the longitudinal axis of the main board 8) of the hiking decks 11 are determined based on the following considerations: - the benches should provide comfortable seating for the crew,

- the height of the benches is chosen such that crew members may assume a seated position with their feet rested on the main board 8,

- each hiking deck should have a volume of 0.08-0.16 m ³ .

The hull of the sailboat is constituted by the main board 8, the aft support member 9, the forward support member 10, and the hiking decks 11.

It should be noted here that the relative position of the forward support member 10 and the main board 8 is determined by the rigging that is to be installed on the finished sailboat. Since the forward support member 10 is movably attached to the main board 8, several different types of rigging may be installed on the hull of the sailboat. The manner of attachment of the aft and forward support members 9, 10 is described in detail later on.

Since the inventive sailboat has been designed applying an attachment system corresponding to the forward support member 10, the sailboat itself can be divided into two parts, a main board and a superstructure, which are movable with respect to each other.

The attachment methods applied for constructing the sailboat according to the invention are illustrated in Figs. 6a-c. In the drawings, moving joints are indicated by empty circles, while filled-in circles indicate fixed joints.

The sailboat according to the invention is configured based on the principle that a moving joint is applied as the bottom attachment point 18 connecting the forward support member 10 to the main board 8. In case of the variant illustrated in Fig. 6a, the attachment point 18 of the forward support member 10 and the bottom attachment point 19 of the aft support member 9 are equally movable along the main board 8, while the respective upper attachment points 20, 21 of the aft and forward support members 9, 10 are fixed joints, i.e. the hiking decks 11 are fixedly attached to the aft and forward support members 9, 10.

In case of the arrangement according to Fig. 6b, - in the same manner as illustrated in Fig. 6a - the attachment point 18 of the forward support member 10 is movable relative to the main board 8. The upper attachment point 21 , as well as the bottom attachment point 19 connecting the aft support member 9 to the main board 8 are fixed joints, while the upper attachment point 20 is a movable joint.

In the arrangement illustrated in Fig. 6c, the attachment point 18 connecting the forward support member 10 to the main board 8 and the upper attachment point 21 connecting the forward support member 10 to the hiking deck 11 are both moving joints, whereas both attachment points 19, 20 of the aft support member 9 are fixed joints.

It has to be noted, however, that other arrangements of fixed and moving joints may also be applied .

In case of the arrangement illustrated in Fig. 6c, the function of the aft support member 9 may be performed by a support structure consisting of two separated support portions 22, 23, where the support portions 22, 23 are attached to the main board 8 in a separated manner (see Fig. 7a). The support portions 22, 23 may also be implemented as closed profile members. The aft support member 9 arrangement consisting of the support portions 22, 23 has the further advantage that the support portions 22, 23 have smaller mass than the single-piece aft support member 9, and thereby the gross mass of the sailboat may be reduced further.

It is noted that also the forward support member 10 may have a multiple- component configuration (see Fig. 7b). Each hiking deck 11 is secured to the main board 8 by a respective support portion 24, 25, while the middle support portion 26 encompasses the mast step. In this arrangement the hiking deck 11 cannot be moved, the support portions 24, 25 being attached fixedly, whereas the middle support portion 26 is movable. In this configuration the sailboat according to the invention consists of a main board 8, two hiking decks 11, four support members - the support portions 22, 23, 24, 25 - and a "thwart" - the support portion 26 - movable along the longitudinal axis of the main board 8. Applying this configuration the mass of the sailboat may be reduced further.

In the above section the schematic configuration and the preferred embodiments of the inventive sailboat were described.

Fig. 8 shows the top plan view of the main board of an exemplary embodiment of the sailboat according to the invention. In the exemplary embodiment the fixed and moving joints illustrated in Fig. 6c are applied, i.e. the aft support member is fixedly attached, while the forward support member is movable.

The main board 8, as illustrated in Fig. 8, is a body having a length of 380 cm and a width of 90 cm that is shaped as a surfboard known per se. The bow section has a tipped configuration, while both the bow and stern sections have a slight upward arc (see Fig. 9). The upper portion of the main board 8 has a flat surface - the deck 27 - which extends from the aft edge 28 of the main board 8 towards the bow section W

9 thereof, terminating at a distance of approximately 80 cm from the bow tip. The deck 27 has two protrusions, i.e. a rudder bracket 29 and a centreboard box 30. The attachment members - dowels 32 - adapted for connecting the aft support member, and the attachment members - rails 33, 34 - adapted for the movable attachment of the forward support member are disposed on the deck 27. The standard height of the main board 8 is a= 16 cm (see Fig. 9).

Fig. 10 shows a top plan view of the centreboard box 30 of the main board 8. The centreboard box 30 protrudes approximately 4 cm above the deck 27 of the main board 8, and preferably has a depth of 20 cm. The centreboard box 30 comprises an opening 31 adapted for receiving a centreboard, with a block adapted for sail retraction being disposed on the main board 8 rearwards from the opening 31.

To allow for secure attachment of the block, this portion of the centreboard box 30 also has a reinforcing member 35. The section of the centreboard box 30 taken in the direction of the plane A-A is illustrated in Fig. 11 clearly showing the shape of the opening 31 , wherein the centreboard is moved in a direction tilted at an angle a towards the aft portion of the main board 8 with respect to the vertical direction. Thereby, the position of the centre point of the sailboat's lateral surface may be modified by retracting or lowering the centreboard.

Fig. 12 shows the rear view of the protrusion - corresponding to the rudder bracket 29 - situated in the aft portion of the deck 27 of the main board 8. The function of the protrusion is to allow for the attachment of the metal fittings applied for conventional sailboat hulls. To allow for the attachment of the different metal fittings applied in a conventional manner for sailboats, the rudder bracket 29 comprises a reinforcing member 36.

It should be noted here that the rudder bracket 29 may also be configured to be removable, and may be mounted on the deck 27 of the main board 8 as a separate component.

The volume of the main board shown in Fig. 8 is approximately 0.4 m ³ . Assuming that the combined weight of the crew is 100 kg and the combined mass of the sailboat, including the hull, the centreboard and the rigging, is 50 kg, a volume of 0.4 m ³ provides enough buoyancy force for the secure floating of the sailboat.

The main board 8 is preferably made from a fibreglass composite material known per se, but a carbon composite material may also be used. The aft and forward support members 9, 10 of the sailboat described in relation to Fig. 3 may be made from aluminium tubes or other closed profiles.

Fig. 13 illustrates in side view the arrangement of the aft and forward support members 40, 41 applied for the sailboat shown in Fig. 8. Each support member consists of a bottom portion 38, an upper portion 39 arranged perpendicular to the longitudinal axis of the main board 8, and a connection element 37 which connects the bottom and upper portions 38, 39. The bottom portion 38 of the support members and the connecting portion 37 are made from aluminium closed profile having a section of 50x50 mm, while the upper portion 39 is made from aluminium tube having a length of 192 cm, a diameter of 0 60 mm and a wall thickness of 2 mm.

The support members 38 are secured to the deck 27 of the main board 8 such that the tube constituting the upper portion 39 is situated perpendicular to the longitudinal axis of the main board 8, with the hiking decks being attached to the upper portion in a manner described below. Thereby the lateral overhang of the support members, measured perpendicular to the longitudinal axis of the main board 8, is approximately 50 cm on both sides, as a result of which the gross width of the hull will be as much as 2 m.

Figs. 14, 15 show, respectively, a rear view of the aft support member 40 and an underside view of the forward support member 41 of the sailboat according to the invention, showing the arrangement of the section connecting the "base" portion of the aft and forward support members 40, 41 to the deck 27 of the main board 8.

The aft and forward support members 40, 41 are configured differently. The reason for the difference is that the forward support member 41 has to be arranged such that it may secure the mast step, and, in case of a rotary mast, such that it may receive a bushing providing the functionality of a second attachment point. Thereby, the forward support member 41 comprises two transverse stiffening members 42 to which a mast step known per se is attached. The bottom face of the mast step - against which the lower end of the mast is supported - should be situated as low as possible, but it must lie above the bottom plane of the transverse stiffening member 42. Thus, when the forward support member 41 is placed on the main board 8 the mast step does not come in contact with the main board 8. The distance between the transverse stiffening members 42 of the forward support member 41 is preferably 15 cm, which allows for a sufficient adjustment range for modifying the mast tilt angle. For the aft support member 40 it is sufficient to apply only one transverse stiffening member 43.

Each of the aft and forward support members 40, 41 comprises four bores 44 adapted for securing the support members to the deck 27 of the main board 8. This manner of the attachment of the support members is described in detail later on .

As it was mentioned above, the forward support member 41 is arranged to receive a rotary mast. Therefore, a bushing 45, illustrated in Fig. 16, is arranged perpendicular to the axis of the tube forming the upper portion 39 of the forward support member 41. The bushing 45 is preferably implemented as a tube segment having a length of 8 cm, diameter of 0 80 mm, and a wall thickness of 5 mm.

It should be noted that for the insertion of the bushing 45 the tube constituting the upper portion 39 of the forward support member 41 has to be cut in two, the resulting two pieces being welded together after making the cuts required for connecting the forward support member 41. Therefore the mast may be introduced into the mast step through the bushing 45 - producing the above mentioned supporting point - and thus an opening corresponding to the "mast-hole" found in conventional hull designs is obtained.

The support member illustrated in Fig. 13 - which is essentially identical to the aft and forward support members 40, 41 - preferably has a height of 38 cm. This implies that the mast is supported by the forward support member 41 at two points, one being situated at the bottom portion thereof (at the mast step), the other at the upper face of the bushing 45, at a height of approximately 39 cm. Since the upper point corresponds to the supporting point applied in relation to conventional rotary masts, the inventive sailboat may be equipped with any type of rigging. For protection against wear caused by mast rotation the bushing 45 comprises an insert that may be arranged to be replaceable.

It is to be noted that, although in the above description the material of the aft and forward support members 40, 41 was specified to be aluminium, they may also be made from carbon fibre reinforced composite materials.

It is also noted that the base portion of the aft and forward support members 40,

41 preferably has a rubber coating.

As it has already been touched upon, the main board shown in Fig. 8 is arranged according to the principle illustrated in Fig. 6c, i.e. the aft support member 40 is movably attached to the deck 27 of the main board 8, while the forward support member 41 is fixedly attached. The support member 41 is movable because of the application of the pairs of rails 33, 34 built into the main board 8 and the hiking decks 11.

As pointed out in relation to Figs. 14 and 15, each of the aft and forward support members 40, 41 has four bores 44 disposed in their respective base portions, the bores 44 being adapted for securing the aft and forward support members 40, 41.

The bores 44 of the aft support member 40 are arranged above and concentrically with the dowels 32 situated in the aft portion of the deck 27 of the main board 8. The screws placed into the bores 44 of the aft support member 40 are introduced into the dowels 32, and the aft support member 40 is fixedly secured to the deck 27 of the main board 8 by tightening the screws. Once the aft support member 40 is secured, the midline of the tube that forms the upper portion 39 of the support member is preferably situated at a distance of 70 cm from the aft edge 28 of the main board 8.

The forward support member 41 is movable thanks to the application of the pairs of rails 33, 34 arranged in the forward portion of the deck 27 of the main board 8. The pairs of rails 33, 34 are essentially constituted by grooves 46 sunk into the deck 27. The configuration of the grooves 46 can be seen in Fig. 17 wherein it is shown that in order to secure the forward support member 4 in the groove 46 screws with a head configuration conforming to the shape of the groove 46 are applied. The insertion of the screws into the grooves 46 is allowed by openings 47, 48 disposed at one end of each of the grooves 46 constituting the pairs of rails 33, 34. To secure the forward support member 41 , first the screws are introduced into the groove 46 through the openings 47, 48 of the pairs of rails 33, 34, and then, through the bores 44 disposed in the base portion of the forward support member 41 , the forward support member 41 is pulled on the stems of the screws residing in the pairs of rails 33, 34, and is secured thereon applying nuts.

The length of the pairs of rails 33, 34 is preferably 35 cm, which provides enough room for adjusting the position of the forward support member 41 and thus also the position of the mast.

By establishing the location of the aft and forward support members 40, 41 on the deck 27 of the main board 8 the attachment locations of the hiking decks 49, as well as the location of the mast, are obtained. In a first approximation the hiking decks have the shape of a rectangular block (see Fig. 3). The hiking deck 49 applied for the embodiment illustrated in Fig. 8 is shown in Figs. 18, 19. The hiking deck 49 has the simple geometric shape of a rectangular block, preferably having a length of 220 cm, a width of 30 cm, and a height of 18 cm. It may be produced from flat sheets of any material, provided that it is water- sealed. It is therefore preferred that the hiking deck 49 is made from epoxy-fibreglass composite sheet, with internal stiffener ribs.

As it is clearly seen in the side elevation view shown in Fig. 19, the portions attached to the aft and forward support members 40, 41 are made thinner, the components adapted for securing the hiking deck to the other hull components being disposed at these portions. The hiking deck 49 is attached along the lines H and E, which lines H and E being identical to the positioning lines referred to in the description of the manner of attachment of the aft and forward support members 40, 41. The line H corresponds to the geometrical midline of the aft support member 40, the line E corresponding to the geometrical midline of the upper portion 39 of the forward support member 41. The hiking decks 49 are attached to the tubes forming the upper portion 39 of the aft and forward support members 40, 41.

To attach the hiking deck 49 to the aft support member 40, four dowels 50 are mounted at the aft end of the hiking deck 49 (see Fig. 18). Two parallel grooves 53 are formed in the forward portion of each hiking deck 49, the configuration of the grooves 53 being identical to the configuration of the groove 46 described above in relation to the attachment of the forward support member 41.

An opening 54 is disposed at the portion of the groove 53 distal from the edge 55 of the hiking deck 49. The function of the opening 54 is identical to the function of the openings 47, 48 described above.

The hiking decks 49 are attached to the aft and forward support members 40, 41 applying the connecting member 56 described in relation to Fig. 20 that is preferably made from stainless steel and consists of two portions, a base portion 57 and a cylindrical surface 58 portion disposed above the base portion 57.

As seen in Fig. 21 , two bores 59 are disposed in the base portion 57, with the distance between the bores 59 being the same as the longitudinal distance between the dowels 50 mounted in the aft portion 51 of the hiking deck 49. Thereby, a connecting member 57 may be secured to each of the two pairs of screws situated at the aft portion 51 of the hiking deck 49. A respective connecting member 56 may also be attached to each of the grooves 53 situated in the forward portion 52 of the hiking deck 49 utilising the screws, having the above described special head configuration, applied for securing the aft and forward support members 40, 41 to the deck 27 of the main board 8. Each of the connecting members 56 is secured to a respective groove 53. Two screws, positionable at a predetermined distance, preferably at 9 cm from one another applying nuts placed on the upward facing end of the screws, may be slid into each groove 53. After securing all of the four connecting members 56 to the hiking deck 49 in a manner that the distance between the aft and forward connecting members 56 is the same as the distance between the aft and forward support members 40, 41 , the hiking deck 49 is pushed sideways on the laterally protruding ends of the aft and forward support members 40, 41.

In order that the attachment of the hiking deck 49 is made firm, i.e. that the hiking deck 49 could not be moved in the direction of the main board 8 or in a direction perpendicular to the longitudinal axis of the main board 8, the connecting members of the hiking decks 49 have to be firmly secured. As it is seen in Fig. 20, the upper portion of the connecting member 56 is slotted such that a tube segment 61 , 62 is welded to each side of the opening 60, with the inside diameter of the tube segments 61, 62 preferably being 8 mm, and one of the tube segments 61 , 62 having an internal threading. Applying the tube segments 61 , 62 and a screw, the two halves of the cylindrical surface 58 may be pulled closer to each other, and the aluminium tubes forming the upper portion 39 of the aft and forward support members 40, 41 can be slid into the appropriate portion - i.e. the cylindrical surface 58 - of the connecting members 56, and thus the connecting members 56 may be firmly pressed against the aluminium tubes by tightening the screws introduced into the tube segments 61 , 62 situated above the cylindrical surface 58. Thereby, the hiking deck 49 may be secured to the laterally protruding ends of the aft and forward transverse support members 40, 41 applying the connecting member 56.

The above described manner of attachment has the advantage that, since the distance between the hiking decks 49 and the main board 8 can be adjusted within a given range, the maximum width of the sailboat may be as large as 199 cm, the minimum width thereof being determined the width of the aft and forward support members 40, 41.

We would like to point out that the connecting members 56 are applied "in pairs" because of the following considerations: on the one hand, in the event of malfunction of any one connecting member 56 the structure remains safe, and on the other hand, such an arrangement improves load distribution.

It should be noted here that, since the arrangement of the rudder assembly, centreboard, spar assembly and sails applied for the sailboat according to the invention is known per se, they are not described in the present specification.

The sailboat according to the invention has the advantage that, thanks to the arrangement of the movable forward support member, it may be used applying any type of rigging. Further advantages are the following:

- it has reduced mass

- it can be produced with low costs

- it consists of multiple separate components, and thereby the components may be replaced independently of one another,

- it can be transported easily.

List of reference numerals

1 hull

2 rudder mount

3 centreboard

4 sail

5 mast

6 boom

7 hiking frame

8 main board

9 aft support member

10 forward support member

11 hiking deck

12 protrusion

13 protrusion

14 opening

15 mast step

16 support point

18 attachment point

19 attachment point

20 attachment point

21 attachment point

22 support portion

23 support portion

24 support portion

25 support portion

26 support portion

27 deck

28 edge

29 rudder bracket

30 centreboard box

31 opening

32 dowel

33 pair of rails pair of rails

block

reinforcing member connecting portion

bottom portion

upper portion

aft support member forward support member transverse stiffening member transverse stiffening member bore

bushing

groove

opening

opening

hiking deck

dowel

aft portion

forward portion

groove

opening

edge

connecting member base portion

cylindrical surface

bore

opening

tube segment

tube segment