EP0199145B1 - Hydrofoil arrangement for a hydroplane-catamaran - Google Patents

Description

The invention relates to a catamaran with two spaced and substantially parallel to each other hulls, which are preferably connected to each other by a deck lying above water, and in the tunnel thus formed in the underwater area between the hulls are arranged transversely extending wings.

It is known that the cruising resistance of sliding boat catamarans can be improved by hydrofoil arrangements in the free space between the hulls, which carry part of the boat's weight when cruising.

Such arrangements have been described in European patent application 0 051 073 and in European patent application 0 094 673. In the last-mentioned publication, a pair of hydrofoils in a tandem arrangement is proposed, in which a larger main aerofoil is arranged near the center of gravity and an trim wing near the rear. Both wings are arranged in height so that they adjust approximately parallel to the water surface when the catamaran has adopted its favorable glide trim angle. The combined resulting dynamic buoyancy of all wings must attack lengthwise near the center of gravity of the length of the catamaran.

The known wing arrangement described above has proven itself. However, it still has certain disadvantages. At a speed at which the sliding state of the catamaran begins, the catamaran takes a certain trim angle with the usual shape of the boat hull, which has the consequence that the pressure resistance of the catamaran is greatly increased. Before the catamaran is partially lifted out of the water by the generation of dynamic buoyancy forces, there is a hump in the cruise resistance curve, an increase in resistance, known as "hump resistance". When the cruising speed increases, the catamaran reduces the trim angle and the cruising resistance drops again and then increases less sharply when the cruising speed increases.

The wing assembly according to European patent application 0 094 673 still has a relatively large "hump resistance" because the main wing lies in front of the length center of gravity of the catamaran and carries a greater load than the trim wings, which has the consequence that the induced Downward velocities in the outflow behind the main wing are quite large, and are greater in relation to the inflow speed at a lower cruising speed because the amount of water detected is smaller. With increasing speed, the induced downward speeds decrease in relation to the inflow speed. These downward speeds change the approach angle to the rear trim tab. The angle of the trim wing to the inflow is reduced (the higher the lift forces on the main wing and the lower the speed of travel, the more reduced) and the lift of the trim wings is reduced, with the result that the catamaran becomes more tense and the "hump resistance" becomes even greater than the wingless catamaran. For smaller catamarans with a large power reserve, the increased trim angle when traveling slowly, especially in very rough seas, is desirable because the bow is higher than the waves.

In larger vehicles, the design speeds of which are only slightly higher than the "hump resistance speed", this effect is undesirable because a higher drive power is required to drive through the "resistance hump". With slimmer boat half-bodies, the large "hump trim angle" is associated with higher resistance.

The invention has for its object to improve the generic arrangement of wings in a gliding boat catamaran so that the starting resistance occurring when starting the catamaran, "hump resistance", is reduced and thus the efficiency and maritime behavior, especially of larger catamarans be improved when driving in rough seas.

This object has been achieved according to the invention in that a main wing is arranged at a relatively short distance behind the center of gravity of the length of the catamaran and an trim wing is located at a greater distance in front of the center of gravity of the length of the catamaran, the main wing having a larger projected area than the trim wing has and the wings are localized so that the resultant of their dynamic buoyancy is in or in the immediate vicinity of the center of gravity of the length of the catamaran, and that the trim wing is arranged vertically approximately at the height of the keels of the hulls and the main wings above the keels , so that the wings have approximately the same relative immersion depth when the catamaran is traveling with a preferably optimal glide angle.

This wing arrangement according to the invention improves the conditions of the "hump resistance". The main wing is behind the center of gravity of the catamaran, creating a trim-reducing moment. It counteracts the glide boat body trim moment, whereby the induced downward speeds of the trim wing or the trim wing stumps have only a very slight influence on the main wing, because they carry only a small load and the induced downward speeds are load-dependent and because with a certain initial trim, the lift forces of the trim tabs in front of the center of gravity are reduced because they come closer to the surface. The influence of the induced downward speeds on the main wing is thereby reduced even more and the lift generation of the main wing is increased. The influence of the wing arrangement is therefore positive and stabilizes the trim. As a result, the hulls do not reach such large trim angles at approach speed, "hump speed", which results in a reduced drag hump. The new wing arrangement thus results in new physical wing lift conditions, which result in an increase in efficiency.

Another advantage of the invention lies in the improved maritime behavior of the catamaran in rough seas, which is explained using an example. If the catamaran designed according to the invention runs into a wave crest, the dynamic buoyancy forces which act on the hull are greatly increased in the fore-region, which leads to an increase in the trim angle of the catamaran. This also increases the angle of attack of the main wing to the inflow, resulting in an increase in wing lift, which counteracts the increase in hull trim, since this force acts behind the center of gravity. The relatively small trim wings have only a small influence on the trim and the downward-induced velocities generated by them remain relatively small and have hardly any influence on the main wing. When the catamaran is moving, the wings have the same relative immersion depth, i.e. the same ratio of immersion depth to profile length. If the catamaran leaves a wave crest and enters a wave trough, the trim-reducing moment of the main wing will remain relatively small, since its lever arm is relatively small to the center of gravity of the dynamic buoyancy force and the change in the induced speeds due to the smaller area of the trim wing or the trim wing is insignificant remains.

The catamaran with the wing arrangement according to the invention therefore experiences much smaller trimming movements and vertical accelerations when traveling in rough seas than known designs, as a result of which its speed potential, its ability to drive fast in rough seas, is considerably increased.

In the catamaran according to European patent application 0 094 673, the sea behavior is comparatively different. The dynamic buoyancy forces, which arise when driving into a wave crest on the bow of the hull, are amplified by the dynamic main wing forces in order to generate a greater degree of disengagement of the catamaran, because both types of force attack before the center of gravity. The resulting higher trim angle increases the wing lift forces even more and reduces the rear trim wing forces due to the increased induced main wing speeds which overflow the trim wings at the rear. When the catamaran enters a wave trough, the dynamic forces of the hull forward and the main wing drop abruptly and the induced main wing speeds are greatly reduced as long as the ship's end is in the wave crest. Smaller induced downward speeds result in higher lift forces of the trim tabs at the rear. This creates a trim-reducing moment until the following wave crest is encountered in this unfavorable position. This results in stronger trimming movements in waves.

The catamaran according to European patent application 0 094 673 therefore experiences relatively stronger trimming movements when traveling in waves, which also results in a limitation of the maximum speed and relatively uncomfortable driving in the open sea. In contrast, the wing arrangement according to the invention significantly improves the sea behavior of a catamaran with supporting wings. In addition, the operation in waters with flotsam is considerably improved.

A further development of the invention is characterized in that the main wing extends over the entire width of the tunnel and that the trim wing preferably consists of two stumps which protrude from the opposite walls of the hull into the tunnel. The main wing has its maximum span here, which gives the highest levels of efficiency and enables high load absorption even at a relatively low speed. According to the objective of the invention, the trim wing must be much smaller than the main wing and, as a single wing which extends over the entire tunnel width, must have a small profile length and profile depth and thus have a critical rigidity and strength. In contrast, its training as wing stumps gives the advantage that the wing stumps have a much smaller span and can therefore be designed to be stiff and firm.

Another embodiment of the invention is characterized in that the trim wing is swept forward or backward toward the center of the vehicle and / or is angled upwards or downwards. The sweeping and angling of the trim tabs allows a gentler and undisturbed insertion, due to a gradual pressure build-up on the wing, into the water in waves. Flotsam is better rejected by the diagonally backward arrow shape and partly pushed down, which clears the way for the main wing and protects it.

Furthermore, the design can be such that the main wing sweeps forward or backward toward the center of the vehicle and / or is preferably angled upward or downward between 2 to 5 °. A slight bending of the main wing, which extends over the entire tunnel width, results in a higher bending stiffness of the wing, which is relatively thin in itself.

A sweep, especially in combination with an angle, results in a wing shape that can penetrate the water surface much more undisturbed and immerse again, which occurs periodically in the waves, in contrast to a flat, straight wing that extends across the entire width when it is immersed or immersed at the same time builds up a pressure field, which leads to bumps and strong splashing water.

According to a further development, the main wing can also consist of a pair of wing stumps. As a result, sufficiently small and stiff wings can be built for wide-tunnel and fast catamarans. Flotsam can be better discharged towards the center using the swept main wing stumps. The trim wing stumps preferably have a larger backward sweep than the main wing, and also a greater downward bend to repel flotsam down and toward the boat center to protect the following main wing from colliding with flotsam. The main wing is arranged relatively higher than the trim wing in relation to the keel, in such a way that the trim wing and main wing come to lie approximately parallel to the surface of the water with approximately the same relative immersion if the vehicle assumes its favorable glide trim angle while driving (depending on the shape of the half body and the wedge angle about 2 ° to 6 °). With this particular vertical wing arrangement, all wings have approximately the same relative immersion depth and can work at higher speeds in the so-called underwater hydrofoil surface effect, which is known to allow strong trim stabilization.

According to a further embodiment, the boat hulls are fully asymmetrical slide boat bodies with deep-V characteristics, the vertical side walls of the slide boat bodies, which are formed in mirror image, being arranged on the inside of the vehicle. This creates a flat, straight longitudinal tunnel that has little influence on the flow and thus allows the undisturbed parallel flow over the wings, which is necessary for effective wing lift generation. On the other hand, the Deep-V slide boat shape has proven to be the most successful slide boat shape for cruising. This good swell property is further improved by the damping effect of the wings, which results in lower accelerations when traveling in waves.

According to a further embodiment of the invention, the trim tabs can be adjusted in height and the trim tabs can be adjusted by pivoting them up and down. This adjustment of the angle of the trim tabs results in the advantage that the trim angle of the catamaran can be changed as desired while driving. This makes it possible, for example, to drive in approaching waves with a smaller than optimal trim angle in order to achieve smaller accelerations of the entire vehicle.

When cruising in the following lake, a higher trim angle is desirable in order to increase the ability to steer and to prevent "broaching", a course instability that can lead to capsizing. A trim angle swivel range of ± 30 ° from the horizontal position is desirable.

The angling of the trim tabs is also an advantage, in order to create a gentler entry and exit of the catamaran when cruising in rough seas.

When adjusting the wing, the wing remains unchanged in relation to the half-body baseline. Adjustment of the main wing to larger angles of attack may be desirable if it is important to swap out the vehicle when driving slowly and a lower hump resistance is desired due to a smaller power reserve.

According to another development of the invention, the invention is characterized in that the wing area of the main wing accounts for about 70% to 75% of the total wing area, that the main wing with its pressure center is about 8% to 15% of the length of the ship behind the length center of gravity of the catamaran and that the trim wing or the pair of trim wings is arranged at the keel line or base line with its pressure center at about 20% to 30% of the length of the ship before the center of gravity.

This arrangement has the advantage that under the conditions of trim balance according to the invention the front trim tabs are not arranged extremely far forward in the bow where they would be exposed to the strongest vertical accelerations at sea, which would also lead to severe trim fluctuations.

Furthermore, the design can be characterized in that a start-up wing with its dynamic lift center is arranged in height in or in the immediate vicinity behind the center of gravity of the catamaran so that it is completely submerged at the design speed of the catamaran. The approach wing can be arrowed forward or backward toward the center of the vehicle and / or angled up or down. This ensures trouble-free entry and exit when moving off without reducing the speed of the waves reached.

At lower speeds, there is a relatively high resistance before the catamaran starts to glide. The maximum resistance in the approach area is called the "hump resistance". A high resistance when driving slowly is particularly unfavorable for the drive propeller, which then has a very low efficiency and then requires more power from the drive machine at a reduced speed. If the prime mover is a diesel engine, a larger prime mover must be provided in order to come across the so-called hump resistor at a reduced speed. In the case of fast gliding, however, only part of the diesel engine power is required. A diesel engine is unfavorable in the underload range at high speed and higher consumption and shorter service life are the result.

It is therefore desirable to further reduce the catamaran's so-called "hump resistance". This is partially achieved with the wing arrangement according to the invention, but there are limits here because the dynamic lift forces of the wings increase with the speed square and the wing surfaces are designed for design speed. Larger wing areas would result in too much frictional resistance at high speed and possibly be pushed out of the water.

According to a further embodiment of the invention, the hump resistance can be further reduced in that a start-up wing with its dynamic lift center is arranged in height in or in the immediate vicinity behind the length center of gravity of the catamaran in such a way that it emerges from the water at the design speed of the catamaran is completely submerged. If such a third wing is arranged, it is preferably designed to be larger than the main wing and, in relation to the pair of tandem wings, be arranged higher above the keel line so that it completely emerges from the water at about medium speed and then has no effect. When driving slowly, the starting wing carries a higher load than the tandem wing pair and lifts the vehicle out of the water at a lower speed. This reduces the drag at slower speeds and in particular the "hump drag".

In order to prevent more unfavorable balancing, the approach wing must act in the immediate vicinity of the center of gravity, i.e. the resulting dynamic buoyancy must act in the center of gravity or in the immediate vicinity. Preferably, when using Deep-V-Planing half-bodies, the approach wing pressure center (the point of the wing through which the lifting force acts) should be between 1% to 5% of the length of the ship behind the length center of gravity, in order to compensate for the high trim angle that usually occurs at the hump resistance speed to counteract and thus keep the half-body resistance lower. The approach wing is preferably given a shape with a backward arrow and a V-shape or a curved shape with the lowest point in the median longitudinal plane of the plane, in order to enable the immersion and immersion in the swell at medium speed without interference.

Another embodiment of the invention is characterized in that the start-up wing and the main wing are connected by at least one support which is preferably arranged in the rear area of the wing. The support reinforces the two wings, which have to be made very thin for cavitation reasons, which creates a closed ring structure of the wing halves. The arrangement of the support in the rear wing area prevents the flow around the wing with the vacuum fields, especially behind the inflow edge, from being disturbed by the flow around the support. The support can also extend up to the tunnel roof of the catamaran, that is, be connected to it.

A further development of the invention is that the main wing and the trim wing are designed for high speeds and the starting wing for lower speeds. The approach wing is only used at slower speeds and may have a higher thickness ratio and greater curvature and pitch to create high lift forces at low speeds. The lower pair of wings is effective at high speed and generates sufficient lift forces with very thin and slim profiles that are favorable against cavitation. In the area of extreme speeds, the lower wing pair can also have fully cavitating wing profiles, making speeds over 60 knots possible.

Finally, the invention can be developed in such a way that the angles of attack of the wings can be adjusted or regulated individually or in combination. By increasing the position of the main wing and the approach wing, a higher lift can be achieved during slow travel in order to drive through the "hump resistance" with less power. By adjusting the angle of the trim tab while driving, a desired trim angle of the vehicle can be set or regulated, e.g. B. a smaller trim angle to drive into the waves or a larger trim angle to drive with the waves, which is cheaper. A height adjustment of the trim tabs, or Swiveling them gives a similar effect. The adjustment of a trim stump on one side alone can be used for a desired heeling, e.g. B. when the boat is cornering or when unwanted heeling is to be compensated.

Finally, the invention can be further developed such that two main wings and / or two trim wings and / or two starting wings are arranged one above the other.

• Fig. 1 eine Seitenansicht eines Katamarans im Wasser, ohne Fahrt,
• Fig. 2 den Katamaran gem. Fig. 1 bei Fahrt im Konstruktionsgeschwindigkeitsbereisch,
• Fig. 3 eine Unteransicht des Katamarans gem. Fig. 1 und 2,
• Fig. 4 einen Blick in den Tunnel des Katamarans gem. Fig. 1 - 3 von vorn,
• Fig. 5 eine besondere Trimmflügel-Ausgestaltung,
• Fig. 6 eine Seitenansicht eines Katamarans gem. Fig. 1 - 4 mit einem zusätzlichen Anfahrtragflügel,
• Fig. 7 einen Blick in den Tunnel des Katamarans gem. Fig. 6 und
• Fig. 8 eine Unteransicht des Katamarans gem. Fig. 6 und 7.

Embodiments of the invention are shown in the drawing. Show it:

• 1 is a side view of a catamaran in the water, without driving,
• Fig. 2 shows the catamaran. 1 when driving in the design speed range,
• Fig. 3 is a bottom view of the catamaran gem. 1 and 2,
• Fig. 4 shows a view into the tunnel of the catamaran. 1 - 3 from the front,
• 5 a special trim wing configuration,
• Fig. 6 is a side view of a catamaran gem. 1 - 4 with an additional approach wing,
• Fig. 7 is a look into the tunnel of the catamaran. Fig. 6 and
• Fig. 8 is a bottom view of the catamaran gem. 6 and 7.

The drawing shows in FIGS. 1-4 a sliding boat catamaran with two hulls 1, which are designed as fully asymmetrical half-bodies with a parallel tunnel in between. The side longitudinal walls of the hull that laterally delimit the tunnel are designated by 1a. In the tunnel there are a main wing 2 connecting the hulls 1 and two trimming wing stubs 3 lying opposite one another and projecting into the tunnel from the two hulls.

The larger main wing 2 is arranged a small distance behind the length center of gravity CG of the catamaran and the stumps 3 are arranged a greater distance in front of the length center of gravity. The combined resulting wing lift force of all wings is located under the CG focus or in its immediate vicinity.

The trim wing stumps 3 are arranged approximately at the level of the keel 6 so that they do not protrude too deeply below the lateral surface of the hull, which would make them sensitive to ground contact.

Fig. 5 shows in a partial representation similar to Fig. 4, a modified embodiment in which the trim stumps 3, of which only one is shown, are adjustable in height by pivoting.

6 and 7 show the additional arrangement of a starting wing 4 in the catamaran version according to Fig. 1 - 4. The approach wing 4 is arranged with its dynamic buoyancy center in the immediate vicinity behind the longitudinal center of gravity CG of the catamaran so that it is completely submerged from the water at the design speed of the catamaran. The approach wing is also swept back towards the center of the vehicle. Between the main wing 2 and the approach wing 4, a support 5 is arranged in the central plane of the boat, which is connected to the two wings in the rear area thereof and has a streamlined cross section.

Claims (14)

1. Catamaran with two hulls which are arranged spaced apart from one another and substantially parallel to one another, and which are preferably connected together by a deck which lies above the water when the boat is travelling, and in whose tunnel, which is thus formed, transversely extending hydrofoils are arranged in the underwater region between the hulls, characterised in that a main hydrofoil (2) is arranged at a relatively small distance behind the longitudinal centre of gravity of the catamaran, and a trimming hydrofoil (3) is arranged at a greater distance away from the longitudinal centre of gravity of the catamaran; the main hydrofoil having a larger projected surface than the trimming hydrofoil, and the hydrofoils being localised in such a way that the resultant of their dynamic lifting forces is located in, or directly near to, the longitudinal centre of gravity of the catamaran, and that the trimming hydrofoil is arranged vertically, approximately at the height of the keels (6) of the hulls (1), and the main hydrofoil is arranged higher above the keels, so that when the catamaran is travelling, the hydrofoils have approximately equal relative submersion depth, with preferably optimum gliding angle.

2. Catamaran according to claim 1, characterised in that the main hydrofoil (2) extends over the entire width of the tunnel, and in that the trimming hydrofoil consists of two stub hydrofoils (3) which project out into the tunnel from the oppositely-facing walls of the hulls (1).

3. Catamaran according to claim 1 or 2, characterised in that the trimming hydrofoil (3) extends forwards-swept or backswept in relation to the middle of the vessel, and/or is bent angularly upwards or downwards.

4. Catamaran according to one of the preceding claims, characterised in that the main hydrofoil (2) extends forwards-swept or backswept in relation to the middle of the vessel, and/or is bent angularly upwards or downwards, preferably between 2 to 5°.

5, Catamaran according to one of the preceding claims, characterised in that the main hydrofoil (2) consists of two stub hydrofoils which project out into the tunnel from the oppositely-facing walls of the hulls (1).

6. Catamaran according to one of the preceding claims, characterised in that the hulls (1) are fully asymmetrical hydroplane hulls with deep-V-characteristic, wherein the vertical longitudinal side walls (1a) are arranged towards the common central longitudinal plane of the boat.

7. Catamaran according to one of the preceding claims, characterised in that the trimming hydrofoil (3) is adjustable as regards its height.

8. Catamaran according to claim 7, characterised in that the trimming hydrofoil (3) is pivotable upwardly and downwardly.

9. Catamaran according to one of the preceding claims, characterised in that the hydrofoil surface of the main hydrofoil (2) amounts to approximately 70 % to 75 % of the total hydrofoil surface, and in that the main hydrofoil (2) is arranged with its centre of thrust approximately 8 % to 15 % of the ship's length behind the longitudinal centre of gravity of the catamaran, and in that the trimming hydrofoil (3) is localised at the height of the keel line and/or base line, with its centre of thrust at approximately 20 % to 30 % of the ship's length in front of the longitudinal centre of gravity.

10. Catamaran according to one of the preceding claims, characterised in that a starting hydrofoil (4) with its dynamic lifting centre in, or directly adjacent behind, the longitudinal centre of gravity of the catamaran is arranged at such a height that at the design speed of the catamaran it is entirely above the water level.

11. Catamaran according to claim 10, characterised in that the starting hydrofoil (4) extends forwards-swept or backswept towards the middle of the vessel, and/or is angularly bent upwards or downwards.

12. Catamaran according to claim 10 or 11, characterised in that the starting hydrofoil (4) and the main hydrofoil (2) are connected together by at least one support member (5) which is preferably arranged in the rear region of the hydrofoils.

13. Catamaran according to one of the claims 10 to 12, characterised in that the main hydrofoil (2) and the trimming hydrofoil (3) are designed for high speeds, and the starting hydrofoil (4) is designed for lower speeds.

14. Catamaran according to one of the preceding claims, characterised in that the angles of incidence of the hydrofoils are adjustable and/or controllable, individually or in combination.

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