Hazards resulting from it lower the navigation safety and decisively limit the possibility of using large driving surfaces necessary for for attainment of large navigation speeds.

In spite of the long realized need of constructing a novel device for wind drive deprived of these drawbacks, all hitherto performed attempts did not lead to the development of structures of practital importance. The various attempted structures in this field are illustrated in the patent specifications enumerated below.

Patents : 1. Poland, no. 70, 225, dated April 22, 1974, UDC B63H 9/06<BR> <BR> <BR> <BR> <BR> 2. Germany, no. 2, 431, 710, dated June 27, 1974, UDC BB63H 9/06<BR> <BR> <BR> <BR> <BR> 3. France, no. 2, 510, 969, dated Feb. 11, 1983, UDC B63H 9/04<BR> <BR> <BR> <BR> <BR> 4. France, no. 2, 524, 416, dated Oct. 7, UDC B63H 91'06<BR> <BR> <BR> <BR> <BR> 5. USA, no. 4, 674, 427, dated June 23, 1987, UDC B63H 9/04<BR> <BR> <BR> <BR> <BR> 6. USA, no. 4, 788, 924, dated Dec. 6, 1988, UDC B63H 9/04 7. USA, no. 4, 947, 775, dated Aug. 14, 1990, UDC B63H 9/00.

In all these structures, besides eliminating the heeling force of the wind drive, it was attempted to obtain the effect of aerodynamical unloading of the craft being driven.

Device for the lurch-free wind drive according to the present invention has the drive surface fastened crosswise on an extension arm in such rake that the force of wind acting on it is applied at the height of the centre of the hull's lateral resistance what makes it possible to eliminate completely the heeling moment. Besides solving the above-mentioned essential problem it has also other additional advantages of great practical importance. It can be utilized both in the racing, sports and @ touristic yachting as well as in sail transport of passengers and goods. There is also provided the possibility of applying it in cradles with a special strcture of skids. Below is given the subject and the features characterizing the structure according to the invention, which features are essentially different from structures applied in the art.

1. Extension arm, to which the drive surface is fastened, is mounted with its one end on the short mast of the extension arm socket placed vertically on the hull of the driven water craft in a bearing housing permitting rotation of the extension arm around the mast in a horizontal plane together with the drive surface to align it at the most favourable angle of attack <BR> <BR> <BR> against wind. The second end of the extension arm is supported<BR> on the centre of a transverse spar resting with its ends upon the auxiliary hulls.

The wide spacing of these hulls imparts a very high crosswise and lengthwise stability of the whole structure, independently of the position of the extension arm. This stability is transmitted by the mast of extension arm socket to the main hull, thus securing a quiet navigation even during violent surging. At the same time a broad base is obtained for < placing on it even a very large, multicomponent drive surface.

2. Each portion of the drive surface has preferably the shape of a triangle directed upwards with one vertex and downwards with two remaining vertexes and with the side between them. allem.

3. driving surface can be not-divided or - particularly in large water crafts - it can be divided into many portions.

Particularly preferable is a structure, in which it is composed <BR> <BR> <BR> <BR> of six portions. Three portions are situated linearly crosswise to the longitudinal axis of the extension arm in the vicinity of its. external end. The next portion is situated nearer to the <BR> <BR> <BR> hull and it is integrated with the main mast placed on the extension arm. The vertexes of all remaining portions of the driving surface are also underslung to the masthead. Due to this integration it is possible either to place the main mast aerodynamically inside the pocket at the edge of attack of the portion connected with it or to construct it together with this portion in the form of a wingsail. These four portions compose a primary set. Their rake is of such magnitude as to fulfill the demand that the axis of the common resultant of the wind pressure re passes at the height of the centre of resistance of the lateral hull.

The furthest from the hull, besides the above mentioned portions, is positioned an additional and greatest portion with a wide base. To balance the action of the wind power directed more upwards to the most inclined portion there is a sixth portion situated correspondingly next to the hull and in an almost vertical position.

4. The lower corners of this largest portion are fastened to the ends of the transverse spar, preferably by means of two outriggers. Each outrigger has the form of a rod with one of the mentioned corners attached to its external end and equipped with a pull rod to pull this end of the outigger to the spar end. The second end of the outrigger is fastened slidably to the spar and is pulled with the second pull rod towards the same spar's end <BR> <BR> <BR> <BR> a parallelly to its longitudinal axis.<BR> and parallelly to its longitudinal axis.

Such design permits an additional adjustment to the momentary wind conditions of this portion of the driving surface; it is equivalent to the action of a spinnaker used in the hitherto known systems of sails. In the case of using a spinnaker the change of the role of its both edges of sail and of its lower corners is typical when changing the tack. The tightening to the spar end of the external end of the outrigger together with attached to it the corner of this portion of driving surface - which is actually the tack corner - makes it possible to stress strongly the edge corner, which is actually the edge of attack. By changing the choice of both pull rods of the edge of attack. By which the corner is fastened, in this case namely the sheet corner, a control of the veering of the sail surface and of its belly is obtained.

Also in a non-rotational manner the portion of driving surface adjacent to the hull is preferably fastened - this portion is a supplement of the above portion, mentioned in point 3.

5 and 6. All the remaining portions of the driving surface are fastened rotationally. In the portion integrated with mast the rotation axis is formed by the mast itself and an adequate stressing of the working surface is preferably obtained by fastening the boot heel to the mast, and by fastening the yeard arm to the kicking strap. In each of the remaining portions the stretching of the working surface is obtained by kicking the strap downwards with the use of a pull rod. By an appropriate approach of the fastening point of this pull rod to the tack corner the required location of the rotation axis of the given portion is obtained - namely before the centre of its surface, action warrants the leeward deflection of the trailing edge by the action of wind and a weathercocking of the sail in flutter. To heave up the surface of each rotary portion to the desired position the use conventional sheets is advantageous.

It is also designed - this design being especially useful in the case of single person navigation - a structure of the portion of the driving surface adjacent to mast. In this design the foreboom includes the mast and it has the sheet corner of the main portion of driving surface adjacent to mast fastened to the backward end and the tack corner of an additional portion fastened to the frontal end and serving as a slat. Such design makes possible servicing the set of these two portions with one sheet only. Additionally, the possibility of unloading the aftermast portion of the boom by means of a counterweight placed on the beforemast end of the boom. It is important - as in the case of other rotary portions of the driving surface - because of their considerable rake and the position of the point of gravity nearer to the sheet corner in relation to the axis of rotation and because of the natural tendency resulting from it to sink the sheet corner during light winds.

7 and 8. To preferably get rid of the difference in pressures on both sides of the lower portion of each portion of the driving surface, this surface was vertically divided into segments, the trailing edges of them being deflected leewards under the action of wind. These segments of the non- rotationally fastened portions of the surface have the shape of a triangle with vertex directed downwards. Vertexes of all these located are fastened to a horizontally slidable pull rod located below the segments. By sliding this pull rod in the wind direction a tension of edges is obtained in all segments, these edges being the edges of attack at the momentary tack, and also loosening of their trailing edges is obtained. Depending on the extent of the displacement of the pull rod a desired degree of this loosening is obtained, and thus - the degree of twist of the segment surfaces.

According to the above principles or to the principles given in point 9, the upper ends of the individual portions of the driving surface can be also divided into segments.

9. Segments in the rotationally mounted portions of the driving surface can have either the above given design or they can have a shape close to rectangular. In this case the lower edge of each segment segment stiffened with a small boom is connected with a pull rod to the common boom at one point placed adequately near to the frontal tack end of the given segment. In the space between each small boom and boom there is preferably <BR> <BR> <BR> <BR> <BR> unhooked a soft sealing surface, which limits the degree of<BR> twist of the segment surface under the action of wind and inhibits the formation of vortex around the lower edge of a segment. arm In the case when the water craft is being driven with device according to the present invention it is equipped with hydro-wings, it is preferablethat the mast of the extension arm socket, around which rotates the end of extension arm near to the hull, is firmly fastened to the main hull.

11. In the case when the water craft possesses no hydro- <BR> <BR> <BR> <BR> <BR> wings, to make it possible a natural change of the longitudinal hull's trimming in the moment of its entering into slide and during iring navigation on a high wave it is preferableto use a shearing housing of the lower mast end of the extension arm socket in the place of its connection with the hull around a horizontal axis perpendicular to the longiduginal hull's axis.

It is also advisable that the range of the thus-obtained freedom may heeling of the mast around this axis was limited - as need may be - by the use of for example of elastic pull rods or of a fluid spring with pressure valves. Due to the inclined mounting of the mast of the extension arm socket and resulting from it inclination of the longitudinal axis of the main hull in relation to the driving portion, a reduction of stresses is also <BR> <BR> <BR> obtained at the place of joining two portions of a water craft,<BR> namely of the driving portion with the driven portion.

12. It is preferable when the transverse spar is a two-part spar. By positioning its two arms at an angle it is possible to reinforce the structure with a pull rod joining the external ends of the two spar arms from below and to rise the central portion of the spar together with the extension arm's end resting on it to secure them against touching water surface during heavy surging. It is also possible to have a rotary coupling of both arms' ends besides the extension arms, what permits their piling backwards during rest along the extenstion arm.

13. Each auxiliary hull is attached to one of the two vertical ends of the transverse spar in a bearing housing permitting rotation of the extension arm in a horizontal plane around the mast. Due to such design it is possible to adjust the alignment of the auxiliary hulls to momentary needs, above all to the navigation direction of the water craft.

14. The auxiliary hulls are fastened to the the transverse spar's ends, either in the above bearing housing only or simultaneously in an additional bearing housing, too, what makes it possible to incline these hulls in a vertical plane, as described for the main hull in point 11.

15. In a structure with auxiliary hulls not aligned to the direction of navigation with pull rods from the main hull, each auxiliary hull has preferably a vertical plane of the direction stabilizer placed on the stern.

16. To obtain a high navigation stability of the whole water craft's direction, each auxiliary hull equipped with the above stabilizer of direction has preferably on its bow a plane of the bow rudder fastened to a vertical axis and connected with the main hull by means of pull rods placing it in a position parallel to the axis of the main hull, irrespective of the deviations of auxiliary hulls. The lower portion of the steerable plane is preferably curved backwards in such manner as to obtain the centre of plane advanced correspondingly by its rotation axis. In this structure, due to the freedom of rotation of the auxiliary hulls around the vertical spar's ends and to the angle freedom of rotation of the bow rudders exceeding the angle of 360°, it is advisable to place on the auxiliary hull it intermediate wheel driven from the main hull and to connect it with the driven wheel mounted on the rudder axis by surrounding them with a chain pull rod in gear with rudders.

17. Fastening of the ends of the above mentioned main hull's pull rods - permitting their movement on the preferably rotable wheel of the steering device - makes it possible to change the orientation of the steering bow rudders plane in respect to the main hull to have a very effective frontal steering of the water craft. Deflection of the frontal rudder creates automatically a lateral twisting force. As this force acts on the auxiliary hull bow, it causes its deflection and also its inclusion to the twisting action of the whole lateral surface of the auxiliary hull as well as of the direction stabilizer plane. This way of steering is particularly useful when these auxiliary hulls are being led in a continuous contact with water surface.

18 and 19. In a design different from that described in point 15, the auxiliary hulls have no direction stabilizer and no bow rudders, and to keep them in a position parallel to the main hull - independent of the changes in the extension arm position - serve two pull rods connecting each of the auxiliary hulls with the main hull.

Fastening of the ends of the abve mentioned pull rods on the main hull permitting their appropriate displacement - as in point 17 - makes possible any changes in the orientation of each auxiliary hull in respect to the main hull, to use it for steering of the water craft. This way of steering - by changing position of auxiliary hulls - is particularly suitable when these hulls are equipped in hydro-wings and at higher navigation speeds they emerge above the water surface. In this design the appropriate portions of the hydro-wings surface take the role of the steering planes.

20. A full effectiveness of steering both auxiliary hulls - directly or by means of their bow rudders - is attained when they are situated before the main hull bow. On the contrary, when one of the auxiliary hulls is in a lateral position to the main hull, it as preferable to exclude it from being steered. To permit an independent switching on to steering and switching off both auxiliary hulls and their bow rudders as well as stern's rudder of the main hull, there is designed a optional steering device composed of rotating wheels, preferably placed coaxially with of the extension arm's mast socket of rotable wheels, namely of the driving wheel and of the intermediate wheels independently connected with them.

21 and 22. When the frontal steering is performed by the bow ruders, as described in point 17, there are the pull rod ends of the main hull's rudder connected to one of the intermediate wheels and to two remaining wheels correspondingly: to one the ends of the bow rudder of the main hull and to the other the ends of the bow rudder of the left hull. In a design decribed in points 18 and 19, it means when the frontal steering is performed independently by the auxiliary hulls by changing their position, then two intermediate wheels are correspondingly connected with the other pull rods' ends fastened with their second ends directly both to the right and to the left auxiliary hull. In both cases the stern rudder's pull rods are led action and the remaning rods as crossed pull rods. Such <BR> <BR> <BR> <BR> <BR> rudder. action of elements placed both before it and before its stern's <BR> <BR> <BR> <BR> <BR> ..... d.. 7.,.<BR> ruaaer.

To obtain simultaneously a high stability and a high turning ability, as need may be, all the mentioned elements are utilized jointly and according to established rules, namely: auxiliary hulls with their stabilizing planes, their bow rudder and the stern's rudder of the main hull. To obtain a common servicing of all these elements, the optional steering device is equipped with two additional intermediate wheels.

23. All the wheels have on their perimeters teeth, among which the stopping locks are introduced, independently of each other, to connect these wheels with the base integrated with the hull. The introduction of a stopping lock between teeth of the wheel corresponding to this lock prevents its rotation.

Alternately to these stopping locks there are also arranged locks connecting the individual intermediate wheels with the driving wheel. An introduction of any intermediate wheel betwwen teeth of a corresponding lock - to couple this wheel with the driving wheel - results in pushing forward the corresponding stopping look a depending on it. Such a design makes it possible to turn-on to the steering action of any steering elements and to stop them at turning-off in the resulting position.

Connecting with the base of an appropriate stopping lock of the driving wheel results, in case of need, in stopping all the elements which perform momentarily the steering operations. This possibility is of particular importance in the case of a one-man <BR> <BR> <BR> <BR> n ro. r<BR> n 1^b Ar 24. Connection of the end of the extension arm with the mast socket of the extension arm is preferably separable. It makes it possible to disconnect from the hull the driving portion of the main water craft. This is particularly advantageous in case of large or very large water craft, e.g. in case of difficulty in entering in full strength a port, a dock etc.. The driving unit can in that case be disconnected and-after having connected the extension ion arm with a pneumatic or rigid float - can be left at an external anchorage.

25. A rotational fastening of ends of the near-to-extension arm of a split spar to the connecting unit placed on the extension arm makes it possible to fold backwards both arms together with the auxiliary hulls and this slidable connection of the extension arm with its mast socket makes it possible to <BR> <BR> <BR> shift aft the folded unit to the main hull's stern. In this<BR> <BR> <BR> <BR> <BR> manner, a considerable reduction is obtained of the overall<BR> <BR> <BR> <BR> dimensions of the whole structure in the parking state.<BR> <P> 26. A connection of two steering-braking plates with the<BR> extension arm was also designed. The plates are fastened<BR> rotationally on axes aligned obliquely and convergently to<BR> outside. The plates are kept horizontally with pull rods. After loosening the pull rods of a corresponding plate, it becomes alignment @ in water to the vertical position. Its oblique aligment to the axis of the extension arm plate results - during the reverse motion of the water craft - in the formation of a force dowling down the extension arm towards that plate.

This make it possible - together with the action of the lateral surface of the main hull - an efficient steering in the reverse motion of the water craft to lead the driving surface through of wind line and to perform the operation of going-about. This emergency way of going-about can be useful in case of a lurch- free drive, particularly for a very rapid and light water craft.

For such water craft units the kinetic energy, even during a rapid navigation, can be insuficient to overcome the resistance rapid the very large driving surfaces of sails being set in flutter and to perform the operation of going-about in the navigation forwards.

Lowering of both plates makes it possible, as need may be, <BR> <BR> <BR> <BR> <BR> <BR> to rapidly and effectively set the water craft in a strongly braking drift.

27. The driving device according to the invention can also be applied in other vehieles, particularly in cradles. In this case the auxiliary cradles play the part of auxiliary hulls. Due to the fact that unloading of aerodynamic cradles during lurch- free drive decreases the skids ability to oppose to the drift causing force of cradles under the action of lateral winds, the skids are preferably equipped with longitudinal vertical planes which immerse into snow and play the part similar to that of the drop keels in a water sailing craft. The sharp lower edges of these planes are useful in the case of performing slides of the sailing cradles on a very strongly compacted snow or on ice. The depth of lowering the planes below the lower surface of skids is preferably controlled - as need may be - in dependence on the cradles' loading and on the type of snow.

The device according to the invention possesses many important advantages. Above all, it solves in a simple and efficient manner the crucial problem in sailing, namely that of the lurch-free wind drive of a water craft. It warrants a very high safety level of sailing, also in case of a two- and manyfold enlargement of the driving surface. It makes it also possible to obtain an aerodynamical unloading of the hull. The aerodynamical unlading was not utilized hither in the sailing hydrodynamic ractice, but it has a very important advantage over the hydrodynamic unlading, because it acts immediately and simultaneously with the increase of wind power, whereas the hydrodynamic unlading acts alwasy with a time-lag, because it increases only in parallel to an increase in the speed of the sailing craft. The elimination of the bow-loading and-lurching force together with an aerodynamical unloading of the hull facilitates the application of hydro-wings with the aim of lowering the navigation resistance.

All the above mentioned features of the driving device according to invention create the possibility of obtaining high speeds and very high accelerations, what contributes largely to the general attractiveness of sailing, particularly of sports sailing. Inclusion of the driving device according to the present invention into a water craft transforms it into an efficient trimaran with advantageous proportions exceeding in its useful characteristics all the hitherto known multi-hull designs. In the design according to the present invention was included an innovative steering system warranting a high direction stability and simulteanously a high turning ability.

The device according to the present invention exhibits a high versatility of applications. It adds to the sailing activities the possibility of a much better than hitherto utilization of natural environment and its protection. This is the result above all of two factors. The highly versatile <BR> <BR> <BR> <BR> <BR> efficiency of the design according to the present invention will lead to a more intensive implementation of the utilization of <BR> <BR> <BR> <BR> lead to a more intensive implementation of the utilization of<BR> <BR> <BR> <BR> <BR> <BR> two important factors of natural environment - namely of water<BR> and wind-for sports, recreational and touristic purposes as well as in the transportation of passengers and goods. The device according to the present invention is presented in Figures concerning the examples of patent execution. Fig. 1 presents a general view of the sailing water craft with a lurch- free drive and with a one-portion driving surface, whereas Fig.

2 presents a view of the same along the longitudinal hull axis.

In both cases is shown the transition of the wind driving power axis in the neighbourhood to the centre of lateral resistance.

Fig. 3 shows - for comparison - the action on sail of the wind power aiming in the known systems of sails to capsize the craft.

Figures 4-6 show a water craft with a six-portion driving surface according to the present invention; thus Fig. 4 shows the view from the hull side along the extension arm, Fig. 5 - perpendicularly to the extension arm, and Fig. 6 presents the top view. Fig. 7 is a general view of the auxiliary hull in the plane of the direction stabilizer with the device ofthe bow rudder and with the system of arranging the lower corners of the largest and non-rotational portions of the driving surface by means of an outriger. Fig. 8 is a view along the longitudinal axis and Fig. g. 9 is an end view of the auxiliary hull fastening to the vertical end of the transverse spar together with a system opf wheels and pull rods of the bow rudder of this hull.

Fig. 10 is an end view of a system of the sharply ended segments of the lower portion of the driving surface and Fig. 11 is a view of segments with a wide lower edge. Fingures 12 and 13 are <BR> <BR> the top views of the same, with arrows indicating the direction<BR> of wind flow through a palisade formed by surfaces of twisted segments. Fig. 14 is an end view of the system of wheels and of the linking and stopping locks, thus of the optional steering device. Fig. 15 is a top view of the steering-braking plates fastened to an extension arm structure, its left plate being <BR> <BR> kept in horizontal position and its right plate being lowered into water to vertical position along its axis. The action on right right plate of to force pushing the plate with its extension arm to the right and of a force formed during the reverse motion of the e extension arm is indicated. Fig. 16 is an end view, and Fig.

17 is the top view of a portion of the driving surface surrounding the mast with the pocket of its attack edge, including the additional portion of front slat and the foreboom on which these two portions are set. Fig. 18 is an end view of one of the rotary portions distant from mast of the driving surface together with the pull rod fastening it from below. Fig.

19 is a top view of the left half of the water craft in the parking state with the arm of the transverse spar folded and <BR> <BR> withdrawn together with the extension arm and auxiliary hull towards the main hull stern. Fig. 20 is a longitudinal view of the lower portion of the cradle skid with a vertical drop keel plane of a controlled depth of lowering them below the bottom surface of skids.<BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR> <P> Below there are explained three exemplary designs according to the present invention adjusted to the drive of water craft of various allocations. In these designs the device for lurch-free wind drive is equipped with a driving surface 1 disposed on the extension arm 2 mounted rotationally with one end on the mast of the extension arm socket 3 placed vertically on the main hull, and with the second arm resting - by means of a transverse spar <BR> <BR> <BR> <BR> 4 - on the auxiliary hulls 5 and 5' fastened rotationally to<BR> vertical ends of the transverse spar. The driving surface is situated in such a rake that the axis of wind action on it passes at the height of the centre of lateral resistance of the driven water craft, without evoking a hull lurching moment.

I. In this simplest exemplary design - of particular importance in the case of small one-man water craft - the driving surface 1 is a one-portion surface with its lower ends 6 and 6' joined directly to ends of the transverse spar and the thrust head underslung to the masthead of the main mast 7 placed on an extension arm. These auxiliary hulls have total freedom of <BR> <BR> <BR> <BR> <BR> revolution in the horizontal plane and they are positioned up to the navigation direction by the direction stabilizer surface 8.

In a more precise version of this exemplary design, the driving Iriving surface a is composed of two portions unhooked on the foreboom 9. Its main portion 10 surrounds the main mast 7 with its pocket. Its auxiliary portion 11 is placed before the mast and plays the part of a slat.

Both the main hull and the auxiliary hulls have a total freedom of inclination with their longitudinal axis positioned in the vertical plane by the shearing housing of them around the horizontal axes - 12 and 13, correspondingly - and in the plane vertical to their longitudinal axes. Steering of the water craft is done by means of bow rudder of the main hull. Arms 14 and 14' of the split spar are folded baekwards to parking state together with the auxiliary hulls and shifted together with the main mast laid towards the stern of the main hull.

II. In this examplary design the driving surface is composed of f four portions, 15, 16, 17, and 18, and its can be supplemented with portions 19 and 20. Fastening of the extension arm is inclined to the main hull, as it was in the previous design. On the contrary, the auxiliary hulls equipped, as in the previous design, with the planes of the direction stabilizer, are re fastened in a non-inclined manner and on each of them there is fastened the bow rudder 21. Steering is accomplished by means of these rudders and of a bow rudder with the use of an optional steering device equipped with a driving wheel 22 and with intermediate wheels 23, 24, and 25 coupled with the driving wheel. Coupling of each of these wheels with the driving wheel is accomplished by means of a corresponding coupling lock, 26 or 27 or 28, with a simultaneous automatic switching-off of the corresponding stopping lock 29, 30 or 31.

In a more sophisticated variant of this design, to obtain a still higher precision of keeping direction and steering, it is advantageous to include in the steering operations the changes in position of the auxiliary hulls performed from the main hull by means of pull rods connected additionally by means of two <BR> <BR> <BR> <BR> <BR> lilt'. ermediate wheels mounted in an optional steering device. A by inclined fastening of the auxiliary hulls in the vertical plane is facilitated in this case. This design is<BR> particularly suitable for large and very large water craft with numerous staff. This concerns mainly yachts for sea tourism and water craft for the sailing transportation of passengers and goods. <BR> <BR> <BR> <BR> <BR> <P> III. The third exemplary design is distinguished by the<BR> introduction of hydro-wings both into the main hull and into the auxiliary hulls. These hulls are in principle mounted in a non- inclined position. To allow only for the fitting of the hulls to the surface of the strongly fluctuating waves during a slow navigation it is preferable to fasten the hulls in an inclined manner and with a possibility of blocking this inclination when passing-at higher speeds-to navigation on hydro-wings in hydrodynamic displacement. The auxiliary hulls have no planes of the direction stabilizer and no bow rudders. Their situating in parallel to the main hull and their steering is performed by means of the stern rudder of the main hull, as in the previous design, by using an optional steering device. This design is above all suitable for the very rapid stunt and sports units of the water craft.

In all the he above exemplary designs it is advantageous to use a vertical division of the lower portions of the driving surface <BR> <BR> <BR> -above all of the portions 19 and 2JD-into inclined segments 33 or 34. To obtain a better aerodynamic efficiency it is advantageous also to o divide into segments the portions in the neighbourbood of the masthead of the above driving surface. In all ? the rotationally fastened portions of the driving surface, because of their rake, it is useful to apply load of a counterweight 35 to the tack end of the boom end to prevent sinking of the heavier sheet end of the boom during a light breeze. The elastic pull rods can be used ofr the same purpose.

Very advantageous - particularly in the case of a one-man <BR> <BR> <BR> <BR> <BR> sailing and in the case of steering with the stern rudder of the<BR> main hull only - is adding of the steering-braking plates 39 and 39' to the deck equipment.

To mount the extension arm in the desired position it is advantageous to use three boat tackles; one tackle pulling the extension arm to the bow and two tackles pulling it in the direction of stern, to the left and to the right side, correspondingly. When the hull is narrow, is it preferable, <BR> <BR> <BR> <BR> <BR> <BR> aiming at shifting more away the points of the side tackles, to<BR> fasten two extension arms beyond the ship's sides.<BR> <P>One can also apply an optional steering device to mount the extension arm supplied with an additional transmitting wheel and <BR> <BR> <BR> <BR> <BR> <BR> connected with the extension arm. This is a preferable way,<BR> <BR> <BR> <BR> <BR> <BR> particularly in the case of one-man sailing.<BR> <P>In the case of dividing into segments the portions of the<BR> driving surface adjacent to the masthead it is advantageous to<BR> given to these segments the trapeze shape and to hang the semgnets of the masthead on the year or on the gaff hung to the masthead.