AN IMPROVED HYDROFOIL BOAT

Abstract

The invention involves a boat comprising—a hull (2),—a first hydrofoil (301) fastened to the hull (2) by means of a first fastening arrangement (302), and—a second hydrofoil (601) fastened to the hull (2) by means of a second fastening arrangement (503) which is separate from the first fastening arrangement (302),—wherein the second fastening arrangement comprises a strut (503) arranged to extend at least partly downwards from the hull (2), the second hydrofoil being fixed to the strut,—wherein that the boat comprises a motor pod (502) fixed to the strut (503),—wherein the strut and the motor pod are turnable in relation to the hull for steering the boat,—wherein the motor pod comprises a casing, a power supply assembly housed in the casing, and two propellers arranged to be driven by the power supply assembly,—wherein the propellers (5011, 5012) are counter-rotating.

Claims

1. A boat comprising a hull, a first hydrofoil fastened to the hull by means of a first fastening arrangement, and a second hydrofoil fastened to the hull by means of a second fastening arrangement which is separate from the first fastening arrangement, wherein the second fastening arrangement comprises a strut arranged to extend at least partly downwards from the hull, the second hydrofoil being fixed to the strut, wherein the boat comprises a motor pod fixed to the strut, wherein the strut and the motor pod are turnable in relation to the hull for steering the boat, wherein the motor pod comprises a casing, a power supply assembly housed in the casing, and two propellers arranged to be driven by the power supply assembly, wherein the propellers are counter-rotating.

2. A boat according to claim 1, wherein the second hydrofoil is located behind the first hydrofoil as seen in a direction of straight forward travel of the boat.

3. A boat according to claim 1, wherein the power supply assembly comprises two electric motors housed coaxially in the casing.

4. A boat according to claim 3, wherein the propellers are each arranged to be driven by a respective of the motors.

5. A boat according to claim 3, wherein the propellers are each arranged to be driven directly by a respective of the motors without a gear arrangement.

6. A boat according to claim 3, wherein the motors are positioned one after the other in a longitudinal direction of the motor pod.

7. A boat according to claim 1, wherein the casing is made in bronze.

8. A boat according to claim 1, wherein the diameters of the propellers are 180-350 mm.

9. A boat according to claim 1, wherein the casing has a cylindrical outer surface with a diameter of 80-140 mm.

10. A boat according to claim 1, wherein the casing has a cylindrical outer surface, wherein the ratio between the length of the motor pod (MPL) and the casing outer diameter (CD) is at least 5, preferably at least 7, for example around 9.5.

11. A boat according to claim 1, comprising a strut mounting arrangement for fixing the strut to the hull, wherein the strut is, by means of one or more strut bearings, pivotally connected to the strut mounting arrangement so that the strut and the motor pod may be turned in relation to the hull so as to steer the boat.

12. A boat according to claim 11, wherein the strut extends 0.7-2.0 meters between the one or more strut bearings and the motor pod.

13. A boat according to claim 1, wherein the strut is arranged to be tilted around an axis which is substantially horizontal when the boat is floating in an upright condition, and substantially lateral to a direction of straight travel of the boat.

14. A boat according to claim 1, wherein the second hydrofoil is located above the motor pod when the boat is floating in an upright condition.

15. A boat according to claim 1, wherein the second hydrofoil and the motor pod are at the same position along the strut.

16. A boat according to claim 1, wherein the strut comprises a lower strut part and an upper strut part, the second hydrofoil being mounted to the strut, between the lower and upper strut parts.

17. A boat according to claim 1, wherein the second hydrofoil is provided as a single component extending between two foil tips.

18. A boat according to claim 1, wherein a trailing edge of the strut merges into a fin on the motor pod wherein the ratio of the horizontal extension (DFH) of the fin to the maximum vertical extension (DFV) of the fin is at least 1.5.

19. A boat according to claim 1, wherein the motor pod is arranged to be more submerged than the first hydrofoil (301) when the boat is travelling straight forward, and when the hull is carried by the first and second hydrofoils.

20. A boat according to claim 1, wherein the first hydrofoil is a submerged type hydrofoil.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Below, embodiments of the invention will be described with reference to the drawings, in which:

[0042] FIG. 1 shows a perspective view a boat according to an embodiment of the invention,

[0043] FIG. 2 shows a side view of the boat in FIG. 1,

[0044] FIG. 3 shows a view of the boat in FIG. 1 from in front of the boat,

[0045] FIG. 4 shown a vertical and longitudinal cross-section of a motor pod of the boat in FIGS. 1, and

[0046] FIG. 5 and FIG. 6 show respective side views of respective boats according to alternative embodiments of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0047] FIG. 1-FIG. 3 show a hydrofoil boat 1. The boat comprises a hull 2. As can be seen in FIG. 3, the hull 2 presents, when the boat is floating at rest, an imaginary vertical symmetry plane SP, and an imaginary horizontal plane HP coinciding with a waterline of the hull 2.

[0048] The boat comprises a first hydrofoil 301 fastened to the hull 2 by means of a first fastening arrangement 302. The first hydrofoil 301 is a submerged type hydrofoil. The first hydrofoil 301 has an adjustable pitch orientation so as to change the angle of attack of the first hydrofoil. The first hydrofoil 301 is connected to the hull by means of the first fastening arrangement 302. The first fastening arrangement 302 comprises two foil holding members 302. The foil holding members 302 are in the form of struts, herein also referred to as first struts. The first hydrofoil 301 may be, as exemplified in FIG. 2, in the direction of travel of the boat 1, located substantially at a center of gravity CG of the boat.

[0049] In some embodiments, the boat does not comprise an adjustable hydrofoil. In some embodiments, the boat comprises a surface piercing first hydrofoil.

[0050] The boat also comprises a second hydrofoil 601. The second hydrofoil 601 is a submerged type hydrofoil. The second hydrofoil is fastened to the hull 2 by means of a second fastening arrangement 503. The second fastening arrangement 503 is separate from the first fastening arrangement 302. The second fastening arrangement comprises a strut 503 arranged to extend downwards from the hull 2. The second hydrofoil is fixed to the strut. The strut is fastened to the hull at a stern of the hull. The second hydrofoil is located behind the first hydrofoil 301 as seen in a direction of straight forward travel of the boat. The second hydrofoil is arranged to support, in a hydrofoil driving mode, an aft part of the hull.

[0051] The hull 2 in this embodiment comprises a stern extension 201. The strut 503 extends through an opening or a recess (not shown) in the stern extension. In some embodiments, the strut 503 is mounted on a transom of the hull. In other embodiments, the strut extends through an opening in the hull, between the stern of the boat and the first fastening arrangement 302.

[0052] The boat also comprises a motor pod 502. The motor pod 502 is fixed to the strut 503. Thus motor pod 502 is provided below the stern of the hull. The motor pod 502 is located below the second hydrofoil 601 when the boat is floating in an upright condition. The length MPL of the motor pod is in this example 1000 mm

[0053] Reference is made also to FIG. 4. The motor pod comprises a casing 5021. The casing has a cylindrical outer surface. The diameter CD of the casing outer surface is in this example 105 mm. Two electric motors 5051, 5052 are housed coaxially in the casing. Two propellers 5011, 5012 are each arranged to be driven by a respective of the motors. The diameters PD of the propellers 5011, 5012 are in this example about 230 mm. The propellers 5011, 5012 are counter-rotating. The propellers are located behind the motors, as seen in a direction of straight forward travel of the boat. The propellers are pushing propellers. In some embodiments, the aft propeller may have a smaller diameter than the forward propeller. The propellers comprise blades which are mounted on propeller hubs. The combined length PHL of the propeller hubs is in this example about 240 mm.

[0054] In some embodiments, the propellers are pulling propellers. Thereby, the propellers are located in front of the motors, as seen in a direction of straight forward travel of the boat.

[0055] The motors are arranged to be powered by a power source such as a battery pack 504, shown in FIG. 2. Cables 506 for power and control of the motors are indicated in FIG. 4.

[0056] Each motor comprises a stator 5071, 5072. The stator is fixed to an inner surface of the casing 5021. Each motor also comprises a rotor 5081, 5082, fixed to a respective of two propeller shafts, 5091, 5092. An inner shaft 5091 of the shafts connects a forward motor 5051 of the motors to an aft propeller 5011 of the propellers. An outer shaft 5092 of the shafts connects a rear motor 5051 of the motors to a forward propeller 5011 of the propellers. The inner shaft 5091 extends through the outer shaft 5092.

[0057] The diameter MD of each motor is in this example 95 mm The length ML of each motor is in this example 180 mm The inner shaft has in this example a diameter of 20 mm The outer shaft has in this example a diameter of 35 mm.

[0058] In some embodiments, only one electric motor is housed in the casing, and one propeller is arranged to be driven by the motor.

[0059] The strut 503 holding the motor pod 502 is, by means of one or more strut bearings 5033, pivotally connected to a strut mounting arrangement 5034 so that the strut may be turned in relation to the hull. The strut mounting arrangement could be provided in the form of a bracket. The strut mounting arrangement is preferably fixed to the hull. Thereby, the strut with the motor pod may be controlled so as to steer the boat. Preferably, the strut 503 extends 0.7-2.0 meters between the one or more strut bearings and the motor pod 502.

[0060] The strut 503 is arranged to be tilted around an axis which is substantially horizontal when the boat is floating in an upright condition, and substantially lateral to a direction of straight travel of the boat. Thereby, the strut may be tilted clockwise or anticlockwise, as seen in the view of FIG. 2.

[0061] As can be seen in FIG. 4, the strut 503 comprises a lower strut part 5031 and an upper strut part 5032. The lower strut part extends between motor pod and second hydrofoil 601. The second hydrofoil 601 is mounted between the lower and upper strut parts. The second hydrofoil may be provided as a single component extending between two foil tips. The second hydrofoil is mounted to the strut at a region in the middle between the foil tips. The second hydrofoil extends through the strut. The second hydrofoil is sandwiched between the strut portions. The strut may have a streamlined cross-section, e.g. a foil-shaped cross-section, which could have a symmetrical shape. In this example, a rear portion of the second hydrofoil 601 is located behind a trailing edge of the strut 503. The lower and/or the upper strut parts may present a respective protrusion 50311, 50321 to support the second hydrofoil. The protrusion(s) may follow, in a chordwise direction of the second hydrofoil, the surface of the second hydrofoil. The fastening of the upper and lower strut portions to each other, and to the second hydrofoil, may be done in any suitable manner, e.g. with bolts and/or adhesive.

[0062] In some embodiments, a portion of the second hydrofoil 601 may extend behind and/or in front of the strut 503. Thereby, the second hydrofoil may extend partly through the strut.

[0063] As illustrated in FIG. 2 and FIG. 4, a trailing edge of the strut 503 merges into a fin 511 on the motor pod 502. The fin gradually decreases in height towards the propellers 5011, 5012. The ratio of the horizontal extension DFH of the fin to the maximum vertical extension DFV of the fin is in this example about 6.

[0064] As understood from FIG. 2 and FIG. 3, the motor pod 502 is arranged to be more submerged than the first hydrofoil 301 when the boat is travelling straight forward, and when the hull 2 is carried by the first and second hydrofoils 301, 601.

[0065] An aspect of the invention provides a boat according to any one of the following clauses. [0066] 1. A boat comprising [0067] a hull 2, [0068] a first hydrofoil assembly comprising a first hydrofoil 301 and a first fastening arrangement 302, the first hydrofoil 301 being fastened to the hull 2 by means of the first fastening arrangement 302, [0069] a second hydrofoil assembly, which is separate from the first hydrofoil assembly, comprising a second hydrofoil 601 and a second fastening arrangement 503, the second hydrofoil 601 being fastened to the hull 2 by means of the second fastening arrangement 503, and [0070] a motor pod 502 fixed to the first hydrofoil assembly, or to the second hydrofoil assembly, [0071] wherein the motor pod comprises a casing, a power supply assembly housed in the casing, and a propeller arranged to be driven by the power supply assembly. [0072] 2. A boat according to clause 1, wherein the casing has a cylindrical outer surface wherein the ratio between the length of the motor pod MPL and the casing outer diameter CD is at least 5, preferably at least 7, for example around 9.5. [0073] 3. A boat according to any one of the preceding clauses, wherein the diameter of the propeller 5011, 5012 is 180-350 mm [0074] 4. A boat according to any one of the preceding clauses, wherein the ratio between the length MPL of the motor pod and the diameter MD of the propeller is at least 3.0, preferably at least 3.7, for example 4.3.

[0075] 5. A boat according to any one of the preceding clauses, wherein the casing has a cylindrical outer surface with a diameter of 80-140 mm.

[0076] 1 6. A boat according to any one of the preceding clauses, wherein the power supply assembly comprises one or more electric motors, wherein the casing has a cylindrical outer surface, wherein the ratio between the casing outer diameter CD and the diameter MD of the respective motor is equal to or less than 1.20, preferably equal to or less than 1.15, for example 1.10. [0077] 7. A boat according to any one of the preceding clauses, wherein the casing is made in bronze. [0078] 8. A boat according to any one of the preceding clauses, wherein the power supply assembly comprises one or more electric motors wherein for each motor the ratio between the length ML of the motor and the diameter MD of the motor is at least 1.4, preferably at least 1.7, for example 1.9. [0079] 9. A boat according to any one of the preceding clauses, wherein the power supply assembly comprises one or more electric motors wherein the ratio between the length ML of each motor and the length MPL of the motor pod is at least 0.12, preferably at least 0.15, for example 0.18.

[0080] 1 10. A boat according to any one of the preceding clauses, wherein the second fastening arrangement comprises a strut 503 arranged to extend at least partly downwards from the hull 2, the second hydrofoil being fixed to the strut. [0081] 11. A boat according to clause 10, wherein the strut is located behind the first fastening arrangement as seen in a direction of straight forward travel of the boat. [0082] 12. A boat according to clause 10, wherein the strut is located in front of the first fastening arrangement as seen in a direction of straight forward travel of the boat. [0083] 13. A boat according to any one of clauses 10-12, wherein the motor pod 502 is fixed to the strut 503. [0084] 14. A boat according to any one of clauses 1-12, wherein the motor pod 502 is fixed to the first fastening arrangement. [0085] 15. A boat according to any one of the preceding clauses, wherein a trailing edge of the strut 503 merges into a fin 511 on the motor pod 502, wherein the ratio of the horizontal extension DFH of the fin to the maximum vertical extension DFV of the fin is at least 1.5.

[0086] Where a stator of the motor is in contact with the casing, the ratio between the casing outer diameter CD and the diameter MD of the respective motor being equal to or less than 1.20, provides for an effective cooling of the motor by a relatively thin wall of the casing. Where a stator of the motor is in contact with the casing, and the casing is made in bronze, with the relatively high heat conductivity of bronze, the casing may provide an effective cooling of the motor.

[0087] An embodiment where the second fastening arrangement comprises a strut 503 located behind the first fastening arrangement as seen in a direction of straight forward travel of the boat, is illustrated in FIG. 1-3. An embodiment where the strut 503 is located in front of the first fastening arrangement 302 as seen in a direction of straight forward travel of the boat, is illustrated in FIG. 5.

[0088] Regardless whether the strut 503 is located behind or in front of the first fastening arrangement, the boat may comprise a strut mounting arrangement 5034 for fixing the strut 503 to the hull 2, wherein the strut is, by means of one or more strut bearings 5033, pivotally connected to the strut mounting arrangement so that the strut and the motor pod may be turned in relation to the hull so as to steer the boat.

[0089] The strut 503 may extend 0.7-2.0 meters between the one or more strut bearings and the motor pod 502. The strut may be arranged to be tilted around an axis which is substantially horizontal when the boat is floating in an upright condition, and substantially lateral to a direction of straight travel of the boat. The second hydrofoil 601 may be located above the motor pod 502 when the boat is floating in an upright condition. However, in some embodiments, the second hydrofoil 601 and the motor pod 502 are at the same position along the strut. The strut may comprise a lower strut part and an upper strut part, the second hydrofoil being mounted to the strut, between the lower and upper strut parts. The second hydrofoil 601 may be provided as a single component extending between two foil tips.

[0090] It should be noted that within the scope of the clauses, the second fastening arrangement may comprise two or more struts for holding the second hydrofoil.

[0091] An embodiment where the motor pod 502 is fixed to the first hydrofoil 301 is exemplified in FIG. 6. In some embodiments, e.g. where the first fastening arrangement 302 comprises a single strut, the motor pod 502 may be fixed to the strut.

[0092] It is understood that boat according to the clauses above may be provided in a variety of ways. For example, the power supply assembly may comprise two electric motors housed coaxially in the casing. The two propellers 5011, 5012 may each be arranged to be driven by a respective of the motors. The propellers 5011, 5012 may each be arranged to be driven directly by a respective of the motors without a gear arrangement. The motors may be positioned one after the other in a longitudinal direction of the motor pod. This is exemplified in FIG. 4. The propellers 5011, 5012 are preferably counter-rotating.

[0093] However, in some embodiments, the motor pod may comprise a single propeller arranged to be driven by a single motor.

[0094] The motor pod 502 may be arranged to be more submerged than the first hydrofoil 301 when the boat is travelling straight forward, and when the hull 2 is carried by the first and second hydrofoils 301, 601. The first hydrofoil 301 and/or the second hydrofoil may be a submerged type hydrofoil.

[0095] It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.