US3760756A

US3760756A - Watercraft construction

Info

Publication number: US3760756A
Application number: US00100673A
Authority: US
Inventors: W Boden
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-12-23
Filing date: 1970-12-22
Publication date: 1973-09-25
Anticipated expiration: 1990-09-25
Also published as: NL178238C; FR2073489A1; CH533534A; NL7018618A; GB1298162A; CA930618A; DE2059087A1; FR2073489B1; SE377680B; BE760790A; NO136743C; NO136743B; DE2059087B2; NL178238B

Abstract

A hydrofoil has an elongated hull of a predetermined first volume and is provided with a bottom wall and a longitudinally extending center keel. Two or more stabilizing elements are provided on the respective lateral sides of the keel, flanking the same, and defining between themselves beneath the bottom wall of the hull at least one air channel which extends longitudinally of the hull and whose volume is equal to between substantially one-fifteenth and one-third of the volume of the hull itself. Various other features are also disclosed.

Description

United States Patent 1 Boden Sept. 25, 1973 1 WATERCRAFT CONSTRUCTION [76] Inventor: Wilhelm Boden, Kreis Eckemfoerde Schlei, Kopperby/ueber Kappeln, Germany [22] Filed: Dec. 22, 1970 [21] Appl. No.: 100,673

[30] Foreign Application Priority Data Dec. 23,1969 Norway 5087 [52] US. Cl ll4/66.5 R [51] Int. Cl B63!) l/38 [58] Field of Search 114/66.5 R, 67 A,

[56] References Cited UNITED STATES PATENTS Apel 114/665 R 3,148,652 9/1964 Canaui 114/6615 S Primary ExaminerGeorge E. A. Halvosa Assistant Examiner-Stuart M. Goldstein AttorneyMichael S. Striker [57] ABSTRACT A hydrofoil has an elongated hull of a predetermined first volume and is provided with a bottom wall and a longitudinally extending center keel, Two or more stabilizing elements are provided on the respective lateral sides of the keel, flanking the same, and defining between themselves beneath the bottom Wall of the hull at least one air channel which extends longitudinally of the hull and whose volume is equal to between substantially one-fifteenth and one-third of the volume of the hull itself. Various other features are also disclosed.

62 Claims, 10 Drawing Figures PATENTEU SEP 2 51975 SHEET 1 (IF 3 FIGJ INVENTORQ l/Eaneon 130020 BY: 1 /00! #h'll Pmmvinsimm 3.760.756

same or 3 FIG. 4 13 FIG. 5

INVENTOR KIM/Ivan 600:0

ATTORNEY PNENFED SEPZSBH sumanr's FIG. 7'

FIG. 8

FIG. ,9

FIG. IO

INVENTOR 0140061! 800cm 5 lion 1. 1H.

ATTORNEY 1 WA TERCHAW COMM/anon BACKGROUND OF THE INVENTION The present invention relates generally to a watercraft, and more particularly to a hydrofoil.

The use of the term hydrofoil as employed herein is intended to be understood in the broadest sense in that it includes a skimmer, that is a type of watercraft which skims over the surface or substantially over the surface of a body of water.

Such hydrofoils are already known. One type, with which the present invention is specifically concerned, is provided on the bottom wall of the hull at opposite lateral sides of the longitudinal center lines thereof, with stabilizing elements which are arranged symmetrically with reference to the center keel of the hull. The problem with these known constructions is that they require a rather significant propulsion effort, and also that they have a tendency to pitch and roll. This is true particular at higher speeds.

Attempts have been made in the prior art to avoid these problems by providing longitudinally extending stabilizing bodies on the bottom wall portion of the hull, such that two sets of these bodies are provided located at opposite sides of the longitudinal center line of the hull, with each side being composed of a plurality of stabilizing bodies and with the individual stabilizing bodies of each set receding in laterally outward and upward direction in stepwise manner. This is already an advantage over earlier constructions in that it makes watercraft of this type more resistant to the aforementioned problems and more maneuverable at high speed. Whereas these stabilizing bodies are elongated and of substantially planar configuration, another prior-art proposal suggests the use of elongated stabilizing bodies which are substantially of V-shaped cross-section. These begin in the region of the bow of the hull and end in the region of the stern. The longest body of each seteach set is composed of a plurality of bodies of different length-is closest to the center line of the hull. Here, the stabilizing bodies are configurated as displacement or water-displacement bodies which, however, disadvantageously influence the attainment of high speeds because they increase the resistance or drag of the ship during movement thereof through the water.

Finally, it is also known in this type of watercraft to provide in the region of the bow a forwardly projecting plate element the purpose of which is to advantageously influence the gliding or skimming of the craft. Again, however, experience has shown that this expedient does not have the desired effect and efiiciency, because the generally curved configuration of the remainder of the craft is not conductive to the skimming motion.

SUMMARY OF THE INVENTION It is, accordingly, an object of the present invention to overcome the aforementioned disadvantages of the art.

A more specific object of the invention is to provide an improved watercraft of the type under discussion which is not possessed of these aforementioned disadvantages.

A concomitant object of the invention is to provide such an improved watercraft which has a minimum drag or resistance to movement through water.

Another object of the invention is to provide such an improved watercraft which converts in a simple and inexpensive as well as reliable manner, and without the aid of auxiliary devices, the density of the water through which is moves to a lesser density by admixing water with air, in order to substantially reduce in this manner the surface friction resistance encountered during movement through the water.

In pursuance of the above objects, and others which will become apparent hereafter, one feature of the invention resides in a watercraft, particularly in a hydrofoil, which briefly stated comprises an elongated hull of a predetermined first volume having a bottom wall portion which is provided with a longitudinally extending center keel. At least two stabilizing elements are provided on this bottom wall portion exteriorly of the hull and flanking the center keel at opposite lateral sides thereof. These elements define between themselves beneath and together with the bottom wall portion at least one air channel which extends longitudinally of the wall and which has a second volume of between substantially one-fifteenth and one-third of the aforementioned predetermined first volume,

Preferably, the second volume should be one-sixth of the first volume.

The thus-obtained advantageous construction according to the present invention is further enhanced by additional features according to the present invention. Thus, according to an additional embodiment the top wall of the air channel, which is constituted by a corresponding part of the bottom wall portion of the hull, rises from the region of the stern towards the region of the bow of the hull in such a manner that when the watercraft is at rest in a body of water, the top wall of the air channel comes in contact with the water only in the region of the bow of the hull.

It is further advantageous according to the present invention that the width of the air channel have to the width of the hull (measured below the water line) less the width of the hull, a relationship of 1:1 and be at least equal to the total width of the hull measured below the waterline. However, the width of the air channel can also be somewhat greater. Thus, if the total width of the hull measured below the waterline is for instance 3 meters, then the width of the air channel would be 1.5 meters or perhaps even somewhat greater.

Also, the height of the side walls bounding the air channel measured over the entire active length, may amount to approximately one-third of the width of the air channel itself.

According to a further embodiment of the invention the height of these side walls is to decrease in the direction from the bow towards the stern of the hull, approximately in correspondence with the inclination of the bottom wall portion which also is declined in rearward direction, that is from the hull towards the stern. It is assumed for purposes of this consideration that the downwardly directed surfaces of the two stabilizing elements which flank the center keel of the hull are to be considered as located horizontally for purposes of measurement of these side walls.

The upright height of these side walls should be at least 15 cm in the region of the stern. This value may be less only in small ships, such as sporting craft or the like, preferably those having a total length of less than 6 meters.

Also, an embodiment of the invention provides that the total cross-sectional areas of all stabilizing elementswhich of course act in a buoyant capacity-which are immersed in water when the watercraft is at rest, correspond approximately at least to the crosssectional area of the air channel, measured substantially midway between the bow and the stern.

In order to increase and facilitate the whirlingtogether and admixture of water with the air it is further proposed to provide means--preferably in the bow region-which effect such admixture at high cruising speed of the watercraft. It is important that the proportion of air to water in such admixture be as high as possible. Means for this purpose may be drawn from a wide range of possibilities, for instance they may be in form of a plate which extends forwardly at an upward inclination from the bow at an angle of for instance between and 45 and which is provided with slots or other apertures. Another possibility is a grid-like metallic or non-metallic element which again preferably extends forwardly and upwardly at an angle of between for instance 10 and 45.

A somewhat similar effect is obtained if there is provided, in accordance with a further object of the invention, in the region of the bow at least one transverse connecting element which extends across the air channel between the two stabilizing elementsor the two innermost stabilizing elements, if more than two are provided-and which is of hydrodynamically advantageous configuration. Preferably, such an element should extend over at least half the width of the air channel. It can be connected to only one of the two stabilizing elements, that is it need not extend from one to the other of the stabilizing elements all the way across the air channel. It may be of generally wing-shaped configuration and may even be located outside of the air channel, being mounted at the outwardly directed sides of the stabilizing elements, or even of the hull itself. In this case there are preferably two such elements provided which are arranged symmetricaly with reference to one another.

A further important concept according to the present invention provides that at least two stabilizing elements project rearwardly beyond the stern of the hull. The projecting portions of these elements may be provided with a transversely extending plate which connects them, if desired.

Important for purposes of the present invention is also that depending upon the length of the watercraft, the bottom wall portion of the hull is inclined at an angle of between substantially 8 and 20 from the stern to the bow. Here, again, it is assumed for purposes of determining the measurement that the downwardly directed surfaces of the two stabilizing elements are oriented in horizontal position.

A further and very important concept of the present invention provides that at least one air supply conduit-- -preferably is of circumferentially closed crosssectionextends into the air channel. This air supply conduit may have one or more inlets in the region of the bow, laterally on the elongated hull, or at another place, for instance at the deck or the like. It will have at least one or more outlets which communicate with the air channel at a suitable location, for instance in the region of its first or leading third, its last or trailing third, or its intermediate third. Preferably the communication will be in the region of the ceiling of the air channel, but as a general rule the location where the outlets or outlet will be provided depends upon a determination where the incoming medium will have its most advantageous degree of effectiveness.

According to the invention the outlet opening or openings of the supply conduit or conduits may be configurated as nozzles, that is they may be tapered to slotshaped configuration in order to obtain an improved effect. If several air supply conduits are provided, there inlet openings may be distributed to various portions of the hull, for instance some of them may be located at the deck, some of them at the bow and others in a side wall of the hull. However it is to be understood that these inlet openings may also be located at other portions of the hull than those which have been mentioned, preferably such portions which are wetted by water, which means that they can also be located at or in the stabilizing elements.

In the region of the outlet opening or openings the air supply conduit may be so configurated as to project beyond the wall portion of the hull in which the outlet opening or openings will be provided. Thus, tubular portions of the air supply conduit or conduits may project out of the respective wall and at their free ends or in the region of their free ends may have one or more outlet openings which may be simple apertures corresponding to the cross-section of the tubular portion, or which may be configurated as slot-shaped or otherwise configurated nozzles. Such nozzles may be mounted and arranged on the center line or keel of the watercraft facing rearwardly towards the stern, or they may be inclined with reference to this center line at a desired angle. In fact, with reference for instance to the bottom wall portion of the hull these outlet openings may be oriented at a desired acute or obtuse angle-with reference to the direction of advancement of the watercraft-and they may also be made adjustable so they can be adjusted at the will of a user, preferably but not necessarily during the actual movement of the craft. However the necessary adjustment can be carried out in known manner, for instance by means of Bowden linkages or the like. For instance, the angular inclination of the outlets may be desired to be different during start-up than during cruising speed.

In order to obtain an increased supply of air through the air supply conduit or conduits, a source of compressed air may be provided, such as a compressed-air bottle, a compressor, or the like. This would for instance be used when for brief period of times top speeds are to be achieved, at which occasions the source will be connected with the air supply conduit or conduits.

The air inlet openings of the air supply conduit or conduits may also be made to be located outwardly away from the respective wall surface where they are provided. Thus, again tubular or otherwise configurated extension portions of the air supply conduit or conduits may project beyond such wall surfaces and be provided at or in the region of their free ends with the air inlet openings. They may be made telescopable and the cross-section of the tubular portions may diverge in direction towards the inlet openings, or putting it conversely, they converge in direction inwardly away from the inlet openings. The inlet openings may be subdivided into separate apertures if desired and they may also be configurated as nozzles. Similarly, the outlet openingsinstead of being configurated as nozzles-may be of convergent cross-section if desired.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a somewhat diagrammatic side view of a watercraft according to the present invention;

FIG. 2 is a front view of the watercraft in FIG. 1, looking towards the right-hand side, and providing a fragmentary enlarged detail view;

FIG. 3 is a view similar to FIG. 2 illustrating a further detail of the invention;

FIG. 4 is a fragmentary diagrammatic detail view illustrating yet another concept of the invention;

FIG. 5 is a front view of a detail shown in FIG. 4;

FIG. 6 is a view substantially analagous to that of FIG. 2 illustrating an additional embodiment of the invention;

FIG. 7 is a fragmentary diagrammatic side view of a watercraft according to another embodiment of the invention;

FIG. 8 is a diagrammatic view analogous to that of FIG. 2, but on a smaller scale, showing a further embodiment of the invention;

FIG. 9 is a diagrammatic view in explanation of another detail of the invention; and

FIG. 10 is a fragmentary diagrammatic side view of a portion of a watercraft incorporating still an additional concept of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Discussing now the drawing in detail it will be seen that the hull of the watercraft as illustrated in FIGS. 1 and 2, for instance, is generally identified with reference character H. The particular configuration of the hull as such is of no importance for purposes of the present invention, but of course, it is understood that in keeping with the specific type of watercraft involved the hull will be configurated along lines based upon hydrodynamic and aerodynamic principles which are well known in this field.

The hull H is provided with an air supply conduit 3 which in the illustrated embodiment extends from the bow of the hull H (at the left-hand side of FIG. I) towards the center of the hull, that is substantially midway between the bow and the stern which is identified at the right-hand side of FIG. 1 with reference numeral 38. At this midpoint the air supply conduit 3, whose air inlet openings 3' are visible in FIG. 2, communicates with an air channel 1 which is defined by the bottom wall portion of the hull H and by the

innermost pair

4a and 7a of stabilizing and buoyancy elements which are mounted on the bottom wall portion and which flank the longitudinal center line of the hull at opposite lateral sides thereof, to define with the bottom wall portion the longitudinally extending air channel 1. When the watercraft is in a static floating condition, then the bottom wall portion defines with reference to the surface of the body of water on which it floats a substan- 6 tially wedge-shaped air filled space 4 which is diagrammatically illustrated in FIG. 1 and which tapers in the direction from the bow towards the stem 38. Depending upon the speed of movement imparted to the watercraft from its static position, and depending upon the trim of the watercraft, the wedge-shaped space 4 will usually become larger, that is it will usually become higher in the region of the bow as the latter lifts out of the water.

According to the present invention this air channel 1 in which the wedge-shaped air cushion 4 is formed, will become filled during forward movement of the watercraft in dependence upon the travelling speed thereof-with a medium in form of air-water fog which, due to the admixture of profuse quantities of air with the water rushing through the channel 1, will form a medium of reduced density, thus corresponding to a reduction of the wetted surface area on the hull and resulting in a concomitant reduction of the surface friction resistance.

The necessary air volume in the channel 1 is obtained, according to the present invention, depending upon the travelling speed of the watercraft partially by the dynamic pressure of the air which is forced into the channel 1 during forward movement of the watercraft, and partially by a suction effect which develops at the outlet or trailing end of the channel 1 due to the ejection effect resulting from escape of the water-air mixture.

FIG. 2 shows that the watercraft illustrated is provided with two sets of stabilizing elements, each set being located at one lateral side of the center line of the hull. One of these sets is identified with

reference numerals

4a, 5a and 6a, and the elements of the other set are identified with

reference numerals

7a, 8a and 9a. In all cases the elements extend symmetrically with reference to the center line and from the region of the bow 3d (see FIG. 2) to the region of the stem 38. The longest ones of these elements, namely the

elements

4a and 7a, are closest to the keel and bound with one another the' channel 1.

As seen from the interior of the channel 1, the elements of each set (namely 4a, 5a and 6a, or 7a, 8a and 9a) recede laterally outwardly as well as upwardly in step-shaped formation as illustrated in the drawing. They are also of different height in laterally outward direction so that the respectively

outermost elements

6a and 9a are immersed in the water to the least extent as compared with the

elements

5a and 4a on the one hand and the

elements

8a and 7a on the other hand. The number of elements to be used-which theoretically could be two, namely the elements 4a and 7adepends upon the size of the hull. In any case, by this pro vision the watercraft is given its dynamic trim.

In FIG. 2 the height of the inner side walls bounding the channel 1, that is the inwardly directed surfaces of the

elements

4a and 7a, is identified with the doubleheaded arrow H. According to the invention this height H is to be greater in the front region of the hull than the similar height h which is indicated in FIG. 1 in the region of the stem 11 and which is to be no less than 15 cm. The height H according to the present invention should continuously decrease to the height h.

FIG. 3 shows that the combined cross-sectional areas F F F F F and F of the elements 40 9a, which becomes immersed beneath the waterline L when the watercraft is at rest, corresponds at least approximately to the cross-sectional area F of the channel 1, measured substantially midway of the hull as indicated by a comparison of the double-headed arrows l with the double-headed arrows in FIG. 1.

In FIGS. 4 and 5 I have illustrated means for facilitating at highspeed movement of the watercraft, admixture of the air with the water in order to efficiently form the air-water fog in the channel 1. Thus, a plate-shaped element 12 may be secured at the bow 13 and may project forwardly and at an upwardly inclined angle of between substantially and 45. It may be located partially below the waterline and may be provided with longitudinal slots 13 as illustrated in FIG. 5. It can also be located as indicated by the open-line representation 15 and may be inclined at a different angle as that illustrated, as already pointed out before. Naturally, the slots 13 could be provided with bores or other apretures of various different sizes and configurations, or

the plate 12 may be constructed as a grid or the likef In FIG. 2 I have illustrated a substantially wingshaped element which may be provided 'in lieu of or in addition to the element 12 of FIGS. 4 and 5, serving the same purpose. In FIG. 2 the wing-shaped element is identified with reference numeral 16 and is mounted on the inner side of the element 4a, being turnable as indicated by the arrow 17. A similar element 16 must also be provided on the inner side of element 7a. It is also possible, however, to provide a single such element which extends from the element 4a to the element 7a, being mounted on both of them for turning movement about a transverse axis in the direction as indicated by the arrow 17. Conversely, however, an element such as the element 16 may also be provided at the outer sides of, for instance, the stabilizing

elements

6a or 9a in which case again two such elements must be provided.

If a single element analogous to the element 16 is used, then the construction shown in FIG. 6 may be utilized. Here, the element is identified with reference numeral 18 and is mounted turnably on supports 19 provided on the inner sides of the

elements

4a and 7a. However, it is clear that the element 18 may also be shorter or somewhat longer than what has been illustrated in FIG. 6 and reference numeral 43 in-FIG. 6 shows that it is preferably although not absolutely necessarily provided with cutouts, apertures or the like.

Returning to FIG. 1 it will be seen that according to a further concept of the invention the bottom wall portion of the hull and the downwardly directed surface 21 of the element 70 (and of course also of the element 4a) define with one another an angle 20 which should be between substantially 6 and 20, it being assumed again that the surfaces 21 of

elements

4a and 7a are substantially longitudinally oriented.

As FIG. 1 also shows, the outlet end of the air supply conduit 3 (or conduits 3) is identified with reference numeral 22. It, or the several outlets 22, may be located as desired, either in the first third of the length of the channel 1, in the second third or in the third third (compare FIG. 1). If several conduits 3 are provided, one of them may have its outlet or outlets communicate with the first third of the channel, one or more with the second third, and so on. The outlet openings 22 may be configurated, as illustrated for instance in FIG. 7, in form of a nozzle 23 of substantially slot-shaped crosssection. This means that in the region 24 the crosssection of the channel 3 is substantially circular, but can also be of other configuration, and then decreases to the nozzle-shaped configuration 23 where the air enters the channel 1. It is also possible as shown in FIG. 1 to provide for instance a channel or supply conduit 3a which may for instance have its opening for inlet or air located at the deck of the watercraft, or at any other suitable location, and whose outlet 25 is located on the stabilizing element 7a, or the element 40. When air enters in the direction of the arrow 26, then it will exit at 25 below the downwardly directed surface 21 (compare FIG. 2) and will advance in the direction of the arrow 7 towards the stern of the watercraft, forming beneath the surface 21 an aircushion.

It is also possible according to an embodiment of the invention, and as shown in FIG. 3, to have the air outlet openings 30 located outside and beyond the bottom wall 29, in that the conduit is extended to the location 25. This is indicated by the broken lines in FIG. 3 and it will be appreciated that this projecting portion of the conduit will be configurated in streamlined shape so as to offer as little resistance and drag as possible. A similar outlet opening 3b is provided which is here formed with a telescopic extension 26a which may or may not be configurated as a nozzle. A suitable arrangement, as for instance a Bowden linkage or the like of known construction, may be provided for advancing and retracting the extension portion 26a during travel of the watercraft so that the length of the portion 26a can be selected at will and the point within the channel 1 at which it delivers a stream of air can similarly be selected freely at the will of an operator, thereby accommodating this arrangement to the prevailing operating conditions.

In the embodiment of FIG 3 the opening 25 and that of the extension portion 26a are inclined with reference to the longitudinal center line of the hull. However, they could also discharge vertically, that is in parallelism with the inner surfaces of the

elements

4a and 7a, respectively. Then again, they could also be arranged precisely at or on the center line.

In FIGS. 1 and 7 I have shown that with reference to the inclination of the bottom wall portion 29 from the bow towards the stern of the watercraft, the

channels

3 and 3a are inclined at an acute angle. This inclination can, however, be selected as desired and another angle may be chosen, such as that of a further air supply conduit 30 which is identified in broken lines in FIG. 1 and which defines an abtuse angle identified with reference numeral 30. Of course, the outlet openings, such as the outlet opening 31, are directed opposite the direction of forward movement of the watercraft.

In FIG. 7 I have illustrated that portions of the conduits or

channels

3, 30, etc. may also project beyond the respective wall surface at which their inlets are provided, and their cross section may then divergesuch as in the configuration of the funnel 32 shown in FIG. 7-so that a greater air quantity is scooped into the

respective conduits

3, 3a, etc. whereby increased pressure develops in these conduits and more air is ejected into the channel 1 or beneath the surfaces 21. Advantageously the portion 32 is telescopable and can be retracted or advanced (advance position as shown in FIG. 7) and this can preferably be done during movement of the watercraft. However, portion 32 can also be of one piece with the remainder of the

respective conduit

3, 3a. As also shown in FIG. 7, the

conduits

3, 30 may have more than one outlet opening, such as the openings 23 and 33. They may of course be located as desired to provide for instance even distribution of air in the channel 1. It is also shown in FIG. 7 that it is preferable to arrange a valve member, such as a turnably mounted plate 34 in the conduit 3. A Bowden linkage or similar means is provided for turning the plate 34 about a pivot axis in the direction of the arrow 35, so that the cross-section of the respective conduit (3 .in this case) can be completely closed, partially opened or completely opened, whereby the flow of air therethrough can be throttled at will. In addition a further plate 36 can be mounted in the channel 1 as shown in FIG. 2. Such a plate should preferably, but not necessarily, be apertured or be constructed as a gridwork. It has the purpose to maintain the air as close as possible to the bottom wall of the hull, and at the other hand it facilitates the admixture of air with water.

It is also advantageous according to the present invention that at least two of the stabilizing elements (one each located at opposite lateral sides of the center line of the hull) project beyond the stem 11 and terminate for instance in the region h. For instance they may extend to the arrows designating reference numeral 20.

The projecting portions of such elements may be connected by a connecting element as shown in FIG. 8. This may be in form of a plate which connects the projecting portions 712 and 4b, these designations having been chosen to indicate that these are portions of the

elements

7a and 4a which project beyond the stem 11. The connecting element is in form of a plate-shaped member 38 which extends between and connects the portions 7b and 4b as illustrated. The lower surface 39 of the element 38 is not located in a common general plane with the lower surface of the bottom wall portion 29 of the hull, but instead is located in a somewhat different plane. However, the

surfaces

29 and 39 could also be located in a common plane that is be located flush, and also the surface 39 could be located higher than the surface 29.

It is also advantageous that the air oulet openings such as those identified with reference numerals 23, 33 and the like can be adjusted in their angular-orientation with reference to the elongation of the channel 1, so that the air which is ejected from these openings will contact the surface of the water at an angle which can be freely selected in accordance with prevailing requirements and considerations.

The arrow 40 in FIG. 7 indicates that it is also possible to provide an air inlet opening for the conduit 3 where a compressor or a bottle of compressed air or the like can be connected. This may for instance be desirable if insufficient air enters through the funnel 32 when the motion of the watercraft first begins. In this case air can then i be forcably introduced from the source supplied for this purpose, with the plate 34 being first used to close the cross-section of the conduit 3 in order to prevent the escape of such air through the inlet opening of the portion 32. Thus, such compressed air fulfills the function with ordinarily newly incoming air fulfills which enters during movement of the watercraft into the inlet opening or openings of the

conduits

3, 30.

Of course, the air outlet opening or openings, such as the one identified with reference numeral 33, could also be divergent as indicated at 32 for the inlet open- In FIG. 9 I have illustrated, and this is also shown in FIG. 1, that the surface 41 of the element 9a (and of course also conversely the same surface of the element 6a) should not rise as strongly towards the bow of the hull, as does the bottom wall portion 29 thereof. This means that the height of the inner walls 42 of the

elements

7a and 4a increases more rapidly in the direction towards the bow than the surface 48 increases in the same direction.

It is also advantageous if the inclination of the bottom wall portion 29 is such that no part of this bottom wall portion will become wetted by contacting the water when the watercraft is at rest in the water.

In the region 42 of the valve at least one hydrodynamically configurated connector may be located between and connected to the

elements

4a and 7a. This connector may be configurated such as the element 16 or as the element 18 of FIG. 6. It may be made immovable or it may be turnable about a substantially horizontal pivot axis, and a suitable arrangement, such as a Bowden linkage or the like, may be provided for effecting such turning even while the watercraft is in motion.

The plate 18 may be provided with the illustrated cutouts 43 in form of slots, apertures or the like, or it may be provided with projections and/or depressions, all having the purpose to facilitating admixture and turbulence of water with air.

It is clear from what has been said and illustrated that the inlet opening to the various air supply conduits may be located wherever desired, for instance also on superstructures or the like, and that the outlet openings may be provided in the bottom wall portion bounding in part the channel 1, or at another suitable location as previously discussed.

In FIG. 10 I have shown that a damping element 46 may be provided which is either stationary or turnable and which may be located at one side of the bow (with a similar elements being located at the other nonvisible side) for damping the movement of the watercraft with reference to the water through which it advances. Of course, this element 46 may have various different configurations and it may for instance also be located lower than illustrated so that it is actually located below the bow and projects laterally to both sides thereof.

In FIG. 8 I have illustrated a keel 46 which according to the present invention should reach to above the waterline of the hull in the static condition of the watercraft, meaning that at the bow it should extend far enough upwardly so that in that region it is not contacted by the water when the craft is not in motion.

Returning to FIG. 2 is it pointed out that according to another concept of the invention the height of the strips defined by laterally adjacent ones of the stabilizing elements, for instance the

elements

7a and 8a, or the elements and 9a, and so on, should be greater in the region of the bow of the hull than in the region of the stem 38. This distance is identified with a doubleheaded arrow 46 in FIG. 2 and the concept is also evident from FIG. 1. It will be noted that the distance of the

lines

38 and 39 is greater in the region of the bow than in the region of the stern and the same is true for the

lines

49 and 50.

Finally, it is also pointed out that according to another concept of the invention the construction of the channel 1, and particularly the width of the channel 1 should be dependent upon the length of the hull and should amount to approximately one-sixth of that portion of the lateral surfaces 42 which are wetted during movement of the watercraft. During such movement, and as a result of the raising of the bow out of the water, not the entire length of the surfaces 42 is in the water, but only perhaps two-thirds of this length. Thus, the width b of the channel 1 is to amount to approximately one-sixth of this length as indicated in FIG. 2.

Insofar as any features have been identified as known or conventional, for instance the use of means for making adjustments during movement, such as Bowden linkages or the like, it is not believed necessary to describe these in detail because they are well known and are expedient which will readily and thoroughly offer themselves to those having ordinary skill in the art.

It will be understood that each of the elements de scribed above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in a watercraft, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. In a watercraft, particularly a hydrofoil, in combination, an elongated hull of a predetermined first volume having a waterline and a bottom wall portion provided with a longitudinal extending center keel; and at least two stabilizing elements provided on said bottom wall portion exteriorly of said hull and flanking said center keel at opposite lateral sides thereof, said elements defining between themselves beneath and together with said bottom wall portion at least one airchannel which extends longitudinally of said hull and has a second volume of between substantially onefifteenth and one-third of said predetermined first volume, the transverse width of said airchannel being at least equal to half the transverse width of said hull at the level of said waterline, and said stabilizing elements having downwardly directed bottom faces which are recessed in the form of a plurality of steps located under the level of said bottom wall portion and extending in direction upwardly and outwardly of said hull so as to compensate for the unsteadying influence of said air-channel.

2. In a watercraft as defined in claim 1 wherein said airchannel has a second volume of substantially onesixth of said first volume.

3. In a watercraft as defined in claim 1, said stabilizing elements each having an upright inner surface facing the interior of said airchannel, and wherein each of said surfaces has a height which corresponds at least substantially to one-third of the transverse width of said airchannel.

4. In a watercraft as defined in claim 1, said watercraft having a bow and a stern; and wherein said bottom wall portion is upwardly inclined from said stern towards said bow such that with said hull stationary said bottom wall portion is below said waterline only in the region of said bow.

5. In a watercraft as defined in claim 4, said stabilizing elements each having an upright inner surface facing the interior of and laterally bounding said airchannel; and wherein the height of said surfaces increases in direction from said stern towards said bow of said watercraft.

6. In a watercraft as defined in claim 1, said stabilizing elements each having an upright inner surface facing the interior of and laterally said airchannel; and wherein said surfaces each have a height which in the region of a stern of said watercraft is equal to at least 15 cm.

7. In a watercraft as defined in claim 1, said watercraft having a bow, a stern and said hull being normally submerged to said waterline when stationary, and said stabilizing elements each having a cross-sectional area which is at least in part submerged when said watercraft is stationary; and wherein said airchannel terminates midway between said bow and said stern.

8. In a watercraft as defined in claim 1; and further comprising admixing means for admixing and agitating air and water passing beneath said bottom wall during cruising movement of said watercraft.

9. In a watercraft as defined in claim 8, said watercraft having a bow, and said admixing means being provided in the region of said bow.

10. In a watercraft, particularly a hydrofoil, in combination, an elongated hull of a predetermined first volume having a bottom wall portion which is provided with a longitudinally extending center keel; at least two stabilizing elements provided on said bottom wall portion exteriorly of said hull and flanking said center keel at opposite lateral sides thereof, said elements defining between themselves beneath and together with said bottom wall portion at least one airchannel which extends longitudinally of said hull and has a second volume of between substantially one-fifteenth and onethird of said predetermined first volume; and at least one wing-shaped agitator member mounted in said airchannel and extending transversely of the same.

11. In a watercraft as defined in claim 10, wherein said agitator member is provided in said air-channel in the region of a stern of said watercraft.

12. In a watercraft as defined in claim 1 1; and mounting means mounting said agitator member stationarily with reference to said hull.

13. In a watercraft as defined in claim 1 l; and mounting means mounting said agitator member for turning movement about an axis extending transversely of the elongation of said hull.

14. In a watercraft as defined in claim 10; and mounting means mounting said agitator member on one of said stabilizing elements, said agitator member extending from said one stabilizing element towards but short of the other of said stabilizing elements.

15. In a watercraft as defined in claim 14; and further comprising an additional agitator member mounted on the other of said stabilizing elements and extending towards but short of said one stabilizing element.

16. In a watercraft as defined in claim 15, wherein said stabilizing elements'are spaced from one another longitudinally of said airchannel.

17. In a watercraft as defined in claim 14; and further comprising an additional agitator member also mounted on'said one stabilizing element but spaced from the first-mentioned agitator member longitudinally of said airchannel, said additional agitator member also extending towards but short of said other stabilizing element.

18. In a watercraft as defined in claim 1, said stabilizing elements each having an inner side facing said airchannel, and an outer side; and further comprising at least a pair of wingshaped agitator members each mounted on the outer side of one of said stabilizing elements and projecting in direction outwardly therefrom.

19. In a watercraft as defined in claim 14, wherein said airchannel has a predetermined transverse width; and wherein said agitator member extends from said one stabilizing'element across at least half of said predetermined width.

20. In a watercraft as defined in claim 1, said watercraft having a bow and a stern; and wherein said bottom wall portion is upwardly inclined in direction from said stern towards said bow at an angle of between 6 and with reference to said stabilizing elements.

21. In a watercraft, particularly a hydrofoil, in combination, an elongated hull of a predetermined first volume having a bow, a waterline and a bottom wall portion provided with a longitudinally extending center keel; at least two stabilizing elements provided on said bottom wall portion exteriorly of said hull and flanking said center keel at opposite lateral sides thereof, said elements defining between themselves beneath and together with said bottom wall portion at least one airchannel extending longitudinally of said hull and having a second volume of between substantially onefifteenth and one-third of said predetermined first volume, the transverse width of said airchannel being at least equal to half the transverse width of said hull at the level of said waterline and said stabilizing elements having downwardly directed bottom faces which are recessed in the form of aplurality of steps located under the level of said bottom wall portion and extending in direction upwardly as well as outwardly of said hull so as to compensate for the unsteadying influence of said airchannel; and air supply conduit meansprovided on said hull and having inlet means facing in direction substantially towards said bow and outlet means at least in part communicating with said airchannel.

22. In a watercraft as defined in claim 21, said outlet means being configurated as outlet nozzle means.

23. In a watercraft as defined in claim 21, said airchannel having a leading portion, an intermediate portion and a trailing portion as seen with reference to the direction of forward movement of said watercraft, and wherein said outlet means communicates with at least one of said portions.

24. In a watercraft as defined in claim 23, wherein said one portion is said leading portion.

25. In a watercraft as defined in claim 23, wherein said one portion is said trailing portion.

26. In a watercraft as defined in claim 23, wherein said one portion is said intermediate portion.

27. In a watercraft as defined in claim 21, said air supply conduit means comprising a plurality of air supply conduits each having at least one inlet and at least one outlet, all of said outlets communicating with said airchannel and said inlets being spaced from one another and located in different regions of said watercraft.

28. In a watercraft as defined in claim 21, said outlet means comprising at least two outlets one of which communicates with said airchannel, and the other of which is provided outside said airchannel at least substantially in the region of the waterline of said watercraft.

29. In a watercraft as defined in claim 21, said outlet means comprising at least two outlets; and further comprising at least one telescopic tubular extension portion telescoped into said air supply conduit means and extendable and retractable through at least one of said outlets while said watercraft is in motion.

30. In a watercraft as defined in claim 21, said outlet means comprising at least two outlets provided laterally of and inclined with reference to said center keel.

31. In a watercraft as defined in claim 21, said outlet means comprising at least two outlets provided in and spaced longitudinally of said keel.

32. In a watercraft as defined in claim 21, said outlet means being inclined at a predetermined angle with reference to said bottom wall portion and to the elongation of said hull.

33. In a watercraft as defined in claim 21, said outlet means being inclined at a predetermined angle with reference to the elongation of said hull and facing towards the stern of said watercraft.

34. In a watercraft as defined in claim 21, said air supply conduit means comprising a main portion and at least one tubular portion projecting from said main portion beyond said hull and being provided with said inlet means.

35. In a watercraft as defined in claim 34, said tubular portion having a passage provided with an inner end communicating with said main portion and with an outer free end provided .with said inlet means; and wherein said passage has a cross-section which converges in direction from said inlet means towards said inner end.

36. In a watercraft as defined in claim 21, said air supply conduit means comprising at least two air supply conduits; and wherein at least one of said air supply conduits comprises at least two conduit branches each having at least one outlet.

37. In a watercraft as defined in claim 21, said air supply conduit means comprising a plurality of air supply conduits each having at least one inlet; and wherein all of said inlets are located at least substantially on a common level of said hull.

38. In a watercraft as defined in claim 21, said air supply conduit means comprising a plurality of air supply conduits each having at least one inlet; and wherein said inlets are located on different levels of said hull.

39. In a watercraft as defined in claim 21; further comprising at least one adjustable throttling element mounted in at least one of said airchannel and air supply conduit means for throttling the flow of air therethrough at the will of an operator.

40. In a watercraft as defined in claim 39, wherein said throttling element is mounted in said air supply conduit means.

41. In a watercraft as defined in claim 40; and further comprising an additional throttling element adjustably mounted in said airchannel for throttling the flow of air through the same at the will of an operator.

42. In a watercraft as defined in claim 41, said additional throttling element being a tumable apertured plate.

43. In a watercraft as defined in claim 21, said outlet means comprising outlet nozzles mounted for displacement between a plurality of positions in which they are respectively inclined at different angles with reference to the elongation of said air-channel.

44. In a watercraft as defined in claim 21; and further comprising a source of compressed air connectable with and disconnectable from said air supply conduit means at the will of a user.

45. In a watercraft as defined in claim 35, wherein said tubular portion is of one piece with said main portion.

46. In a watercraft as defined in claim 21, said air supply conduit means comprising at least one air supply conduit having a cross-section which diverges in direction towards said outlet means.

47. In a watercraft as defined in claim 21, said elements each having a downwardly directed surface which is upwardly inclined in direction from said stern towards said bow at a first angle; and wherein said bottom wall portion is upwardly inclined in direction from said stern towards said bow at a second angle which is greater than said first angle.

48. In a watercraft as defined in claim 21, said watercraft having a stern; and wherein said bottom wall portion is upwardly inclined from said stern towards said bow such that said bottom wall portion is above said waterline in its entirety.

49. In a watercraft as defined in claim 21, said elements having a combined buoyancy so selected as to float said hull when said watercraft is stationary.

50. In a watercraft as defined in claim 21, said watercraft having a stern; and further comprising at least one connecting element extending between and connecting said elements in the region of said bow within the confines of said airchannel and having a configuration selected for providing minimum hydrodynamic drag.

51. In a watercraft as defined in claim 50, wherein said connecting element is fixed.

52. In a watercraft as defined in claim 50; and further comprising mounting means mounting said connecting element for pivotal displacement about an axis extending transversely to the elongation of said airchannel.

53. In a watercraft as defined in claim 21; and further comprising at least one motion-damping element provided on said hull and projecting laterally of the same in the region of said bow.

54. In a watercraft as defined in claim 21, wherein said keel tapers gradually rearwardly of said bow from an inclined to a substantially horizontal orientation, and also tapers transversely of the elongation of said hull at least to the region of the lateral center of gravity of said hull.

55. In a watercraft as defined in claim 21, wherein the height of said stepped recesses is greater in the region of the bow of said hull than in the region of the stern of said hull.

56. In a watercraft as defined in claim 55, wherein said height decreases continuously in direction from said bow towards said stern of said hull.

57. In a watercraft as defined in claim 21, wherein at cruising speed of said watercraft only a predetermined fraction of the longitudinal extension of said bottom wall portion comes in direct contact with the water; and wherein said airchannel has a transverse width which corresponds substatially to one-sixth of said fraction 58. In a watercraft, particularly in a hydrofoil, in combination, an elongated hull of a predetermined first volume, said hull having a waterline, a bow, a stern and a bottom wall portion extending between said bow and said stern and being provided with a longitudinally extending center keel; and at least two stabilizing elements provided on said bottom wall portion exteriorly of said hull and flanking said center keel at opposite lateral sides thereof, said elements having respective first portions defining between themselves beneath and together with said bottom wall portion at least one airchannel extending longitudinally of said hull and having a second volume of between substantially onefifteenth and one-third of said predetermined first volume, and respective second portions which project longitudinally beyond said stern by a predetermined extent, the transverse width of said air-channel being at least equal to half the transverse width of said hull at the level of said waterline, and said elements further having downwardly directed bottom faces which are recessed in the form of a plurality of steps located under the level of said bottom wall portion and extending in direction upwardly as well as outwardly of said hull so as to compensate for the unsteadying influence of said air-channel.

59. In a watercraft as defined in claim 21; and further ocmprising a connecting plate extending between and connecting said second portions with one another.

60. In a watercraft as defined in claim 59, said bottom wall portion and said connecting plate each having a downwardly directed surface; and wherein said surfaces are located at least substantially in a common plane.

61. In a watercraft, particularly a hydrofoil, in combination, an elongated hull of a predetermined first volume having a bow and a bottom wall portion which is provided with a longitudinally extending center keel; at least two stabilizing elements provided on said bottom wall portion exteriorly of said hull and flanking said center keel at opposite lateral sides thereof, said elements defining between themselves beneath and together with said bottom wall portion at least one airchannel which extends longitudinally of said hull and has a second volume of between substantially onefifteenth and one-third of said predetermined first volume; and admixing means mounted in the region of said bow for admixing and agitating water which passes beneath said bottom wall during cruising movement of said watercraft, said admixing means comprising an apertured plate projecting forwardly from said bow in the direction of cruising movement of said watercraft at an upward angle of between substantially 10 and 45.

62. In a watercraft, particularly a hydrofoil, in combination, an elongated hull of a predetermined first volume having a bow and a bottom wall portion which is provided with a longitudinally extending center keel; at least two stabilizing elements provided on said bottom wall portion exteriorly of said hull and flanking said center keel at opposite lateral sides thereof, said elements defining between themselves beneath and together with said bottom wall portion at least one airchannel which extends longitudinally of said hull and has a seocnd volume of between substantially onefifteenth and one-third of said predetermined first volume; and admixing means mounted in the region of said bow for admixing means comprising a grid-shaped

Claims

1. In a watercraft, particularly a hydrofoil, in combination, an elongated hull of a predetermined first volume having a waterline and a bottom wall portion provided with a longitudinal extending center keel; and at least two stabilizing elements provided on said bottom wall portion exteriorly of said hull and flanking said center keel at opposite lateral sides thereof, said elements defining between themselves beneath and together with said bottom wall portion at least one airchannel which extends longitudinally of said hull and has a second volume of between substantially one-fifteenth and one-third of said predetermined first volume, the transverse width of said airchannel being at least equal to half the transverse width of said hull at the level of said waterline, and said stabilizing elements having downwardly directed bottom faces which are recessed in the form of a plurality of steps located under the level of said bottom wall portion and extending in direction upwardly and outwardly of said hull so as to compensate for the unsteadying influence of said air-channel.

2. In a watercraft as defined in claim 1 wherein said airchannel has a second volume of substantially one-sixth of said first volume.

5. In a watercraft as defined in claim 4, said stabilizing elements each having an upright inner surface facing the interior of and laterally bounding said air-channel; and wherein the height of Said surfaces increases in direction from said stern towards said bow of said watercraft.

10. In a watercraft, particularly a hydrofoil, in combination, an elongated hull of a predetermined first volume having a bottom wall portion which is provided with a longitudinally extending center keel; at least two stabilizing elements provided on said bottom wall portion exteriorly of said hull and flanking said center keel at opposite lateral sides thereof, said elements defining between themselves beneath and together with said bottom wall portion at least one airchannel which extends longitudinally of said hull and has a second volume of between substantially one-fifteenth and one-third of said predetermined first volume; and at least one wing-shaped agitator member mounted in said airchannel and extending transversely of the same.

12. In a watercraft as defined in claim 11; and mounting means mounting said agitator member stationarily with reference to said hull.

13. In a watercraft as defined in claim 11; and mounting means mounting said agitator member for turning movement about an axis extending transversely of the elongation of said hull.

16. In a watercraft as defined in claim 15, wherein said stabilizing elements are spaced from one another longitudinally of said airchannel.

17. In a watercraft as defined in claim 14; and further comprising an additional agitator member also mounted on said one stabilizing element but spaced from the first-mentioned agitator member longitudinally of said airchannel, said additional agitator member also extending towards but short of said other stabilizing element.

19. In a watercraft as defined in claim 14, wherein said airchannel has a predetermined transverse width; and wherein said agitator member extends from said one stabilizing element across at least half of said predetermined width.

20. In a watercraft as defined in claim 1, said watercraft having a bow and a stern; and wherein said bottom wall portion is upwardly inclined in direction from said stern towards sAid bow at an angle of between 6* and 20* with reference to said stabilizing elements.

21. In a watercraft, particularly a hydrofoil, in combination, an elongated hull of a predetermined first volume having a bow, a waterline and a bottom wall portion provided with a longitudinally extending center keel; at least two stabilizing elements provided on said bottom wall portion exteriorly of said hull and flanking said center keel at opposite lateral sides thereof, said elements defining between themselves beneath and together with said bottom wall portion at least one air-channel extending longitudinally of said hull and having a second volume of between substantially one-fifteenth and one-third of said predetermined first volume, the transverse width of said airchannel being at least equal to half the transverse width of said hull at the level of said waterline and said stabilizing elements having downwardly directed bottom faces which are recessed in the form of a plurality of steps located under the level of said bottom wall portion and extending in direction upwardly as well as outwardly of said hull so as to compensate for the unsteadying influence of said airchannel; and air supply conduit means provided on said hull and having inlet means facing in direction substantially towards said bow and outlet means at least in part communicating with said air-channel.

35. In a watercraft as defined in claim 34, said tubular portion having a passage provided with an inner end communicating with said main portion and with an outer free end provided with said inlet means; and wherein said passage has a cross-section which converges in direction from said inlet means towards said inner end.

42. In a watercraft as defined in claim 41, said additional throttling element being a turnable apertured plate.

57. In a watercraft as defined in claim 21, wherein at cruising speed of said watercraft only a predetermined fraction of the longitudinal extension of said bottom wall portion comes in direct contact with the water; and wherein said airchannel has a transverse width which corresponds substatially to one-sixth of said fraction

58. In a watercraft, particularly in a hydrofoil, in combination, an elongated hull of a predetermined first volume, said hull having a waterline, a bow, a stern and a bottom wall portion extending between said bow and said stern and being provided with a longitudinally extending center keel; and at least two stabilizing elements provided on said bottom wall portion exteriorly of said hull and flanking said center keel at opposite lateral sides thereof, said elements having respective first portions defining between themselves beneath and together with said bottom wall portion at least one airchannel extending longitudinally of said hull and having a second volume of between substantially one-fifteenth and one-third of said predetermined first volume, and respective second portions which project longitudinally beyond said stern by a predetermined extent, the transverse width of said air-channel being at least equal to half the transverse width of said hull at the level of said waterline, and said elements further having downwardly directed bottom faces which are recessed in the form of a plurality of steps located under the level of said bottom wall portion and extending in direction upwardly as well as outwardly of said hull so as to compensate for the unsteadying influence of said air-channel.

61. In a watercraft, particularly a hydrofoil, in combination, an elongated hull of a predetermined first volume having a bow and a bottom wall portion which is provided with a longitudinally extending center keel; at least two stabilizing elements provided on said bottom wall portion exteriorly of said hull and flanking said center keel at opposite lateral sides thereof, said elements defining between themselves beneath and together with said bottom wall portion at least one airchannel which extends longitudinally of said hull and has a second volume of between substantially one-fifteenth and one-third of said predetermined first volume; and admixing means mounted in the region of said bow for admixing and agitating water which passes beneath said bottom wall during cruising movement of said watercraft, said admixing means comprising an apertured plate projecting forwardly from said bow in the direction of cruising movement of said watercraft at an upward angle of between substantially 10* and 45*.

62. In a watercraft, particularly a hydrofoil, in combination, an elongated hull of a predetermined first volume having a bow and a bottom wall portion which is provided with a longitudinally extending center keel; at least two stabilizing elements provideD on said bottom wall portion exteriorly of said hull and flanking said center keel at opposite lateral sides thereof, said elements defining between themselves beneath and together with said bottom wall portion at least one airchannel which extends longitudinally of said hull and has a seocnd volume of between substantially one-fifteenth and one-third of said predetermined first volume; and admixing means mounted in the region of said bow for admixing means comprising a grid-shaped admixing member. and agitating water which passes beneath said bottom wall during cruising movement of said watercraft, said admixing means comprising a grid-shaped admixing member.