HK1058655B - Hull and propeller arrangement - Google Patents

Description

Hull and propeller arrangement

Technical Field

The present invention relates to a hull and propeller arrangement.

Prior Art

For water craft, in particular for speed motorboats, semi-submerged propellers are known, i.e. the blades of the propeller are alternately in a water position and a submerged position when the propeller is rotating, when the boat is travelling at high speed. For a given hull and a given shaft power, a semi-submerged propeller is able to drive a boat at a much higher speed than a completely submerged propeller. This improves performance in the case of semi-submerged propellers, since the resistance to converting the rotational power of the power source into hull thrust is much less than for conventional fully submerged propellers.

In order to reduce the hydrodynamic drag, it is desirable to have as few components in the water as possible while the boat is traveling. Considering the propulsion structure of the ship, this requirement is met to a large extent if the components that do not contribute to the direct power transmission are located outside the water flow. Considering a propeller, this is achieved if only the propeller blades are in direct contact with the water, while the propeller hub is located above the water surface.

US patent US 3793980 describes a system with a semi-submerged propeller by which the propeller hub is located outside the water flow at high speed in a controlled manner, while only the propeller blades are in direct contact with the water.

When the ship is planing, the hull acts on the water with a force pressing down on the water, the hull being supported by the water by means of a reaction force, so that the contact area between the hull and the water is smaller than when the ship is running at a displacement speed. At very high speeds, the contact area is relatively very small and is located at the aft-most portion of the hull. If the hull is designed to have multiple contact areas while planing, at least one contact area is located aft-most of the hull. If the motion of the vessel is disturbed, for example by the vessel running on surface waves, there is then a rotational movement in the rowing direction, the rotational centre often being located close to the rear contact area between the hull and the water. This movement causes the semi-submerged propellers, which are at a distance from the rear contact area in the longitudinal direction, to move substantially upwards and downwards. This means that during movement the size of the part of the propeller that is located in the water changes. Sometimes the propeller is lifted completely out of the water. The vertical movement of the propeller relative to the surface of the water results in an interruption of the propulsion of the ship, the source of which is poorly utilized.

When a ship having a conventional semi-submerged propeller structure travels at a relatively low speed just above the speed range for transition from moving propulsion to planing propulsion, the water level associated with the hull is elevated in a position immediately aft of the hull. This means that the propeller located in this region is surrounded by water at this speed and loses its semi-submersible mode of operation. At the moving speed of the boat, the propeller also loses its semi-submersible mode of operation.

In a conventional motorboat, the position of the or each propeller is at a distance from the drive shaft introduction hole, i.e. the position at which the drive shaft projects from the inside of the hull to the outside. In order to fix the propeller in the radial direction, it is therefore customary to provide a drive structure next to the propeller, which has a bearing fastened to a structure, for example in the form of a bearing bracket, which is in turn fastened to the hull. The drive structure must therefore be mounted at the drive shaft inlet and in close proximity to the propeller. This conventional structure with bearings for the propeller and corresponding fastening structures requires the use of a plurality of constructional parts and, in contact with the water flow, constitutes a source of resistance during propulsion.

Object of the Invention

It is an object of the present invention to provide a hull and propeller arrangement for a water craft that reduces interference with the propulsion of the craft.

It is another object of the present invention to provide a hull and propeller arrangement for a water craft that reduces drag during propulsion of the craft.

It is a further object of the present invention to provide a hull and propeller arrangement for a water craft which enables efficient propulsion over a greater range of speeds than conventional hull and propeller arrangements.

Another object of the present invention is to provide a hull and propeller structure for a water craft that can simplify the driving structure of each propeller.

Description of the invention

The object of the invention is achieved by providing a hull and propeller arrangement provided with two propellers which are semi-submerged at high speed of the vessel and arranged in such a way that only the propeller blades or a part thereof are submerged at high speed of the vessel, characterized in that the hull is provided with a belly and two streamlined nose parts extending substantially in the longitudinal direction of the hull, each nose part having an outer shape at its rear end with an end edge extending at least partly substantially perpendicularly to the longitudinal direction of the nose part, that each propeller is located close to the tail of the respective end edge, that a part of each propeller extends in radial direction beyond the defining surface of the respective nose part, that the belly and nose parts are arranged in such a way that a rear bearing area for the vessel is formed on each nose part at high speed of the vessel, the rear bearing area is mainly formed by a part of the surface of the respective projecting part which is situated immediately in front of the end edge and at the lowermost part of the projecting part, and a front bearing area is formed on the belly part, whereby the vessel is supported by water flowing through the bearing area, on which the hull is held up with force.

The position of each propeller immediately aft of an end edge on the aft end of a projection from the hull means that the propeller is close to a surface that acts as a bearing surface at high speed, which in turn means that the rotational movement of the vessel in the pitch direction, for example due to the vessel driving into waves, causes only a small vertical movement of the propeller. This in turn allows the propeller blades to move very little relative to the water surface and thus any disturbance in the propulsion of the ship is very small.

The position of each propeller immediately aft of the respective end edge on the aft end of the respective projection also means that substantially only the propeller blades are in contact with the water flow even when the watercraft is traveling at relatively low speeds just above the speed range for transition from mobile to flight propulsion.

According to one embodiment, the propeller is semi-submersible at moving speeds, at least at relatively high moving speeds, by virtue of its size and positioning.

According to the invention, each propeller is provided with a hub which is designed as a relatively sharp hub edge at the intersection of the rear defining surface and the peripheral defining surface. The hub edge is effective to separate the water flow from the propeller.

The end edge on each projection effectively separates the water flow from the projection.

The protruding part has a cross-section near the propeller, which cross-section is at least partly substantially shaped like a portion of a circle, the centre of which radially substantially coincides with the centre of the propeller. The radius of the circle is substantially equal to the radius of an imaginary circle formed by the intersection of the propeller blades and the propeller hub when the propeller is rotated. As a result of this, the surface of the flowing water that has left the projecting portion meets in a controlled manner substantially with the periphery of the propeller hub.

According to the invention, the drive shaft abuts against the propeller hub through the location of the introduction hole of the hull, which simplifies the mounting of the propeller, since no additional bearings and corresponding fastening structures outside the hull are required.

Brief description of the drawings

In the drawings:

figure 1 is a perspective view, from the side, and to some extent from below, of a motorboat equipped with a hull and propeller arrangement according to the invention;

fig. 2 is a perspective view, seen somewhat obliquely from below, of the aft part of a motorboat equipped with a hull and propeller arrangement of the invention;

fig. 3 is a perspective view, from below, in part, of the aft portion of a motorboat equipped with a hull and propeller arrangement of the present invention;

FIG. 4 shows an enlarged view of the rear portion of the motorboat shown in FIG. 1;

FIG. 5 shows a cross-sectional view along line V-V of FIG. 3 of the hull and propeller arrangement of the present invention;

figure 6 shows a cross-sectional view along the line V-V in figure 3 of the hull and propeller arrangement of the invention.

PREFERRED EMBODIMENTS

Fig. 1 shows a motorboat 1 with a hull 2 and two propellers 3. The two propellers 3 are semi-submersible and counter-rotating, with their drive shafts extending substantially forward in the longitudinal direction of the boat 1. The hull 2 is provided with two protruding parts 4. Each of the projections 4 is streamlined and extends in the longitudinal direction of the hull 2. Each projection 4 merges at a front end 5 in the shape of a streamline with the shape of the hull 2. Each of the fore ends 5 is located longitudinally substantially in the centre of the hull 2 and laterally between the centre of the hull 2 and its edges. Each projection 4 extends to a rear end 6, which rear end 6 is located in front of and in close proximity to one of the propellers 3. The hull 2 is in the shape of a belly 7 at its front where the hull 2 is deeper than in most other places.

Reference is now made to fig. 2. The craft 1 is supported at high speed by the passing water over a relatively small support area. In this connection, the support area means the area of the hull 2 that is in direct contact with the water flowing past, on which support area a force acts to lift the hull 2. In the exemplary embodiment, two rear support areas 8 are formed on the boat 1 at high speed, which are indicated by the dash-lined areas in fig. 2, each consisting of a portion of the surface of each projecting portion 4 extending forward a relatively short distance from the rear end 6. A front support area is formed on the abdomen 7.

As can be seen in fig. 3, each propeller 3 is designed with a relatively large hub 9, while the hub 9 is designed essentially as a disc.

In fig. 4 it is shown that the hub 9 has on its periphery a peripheral limiting surface 10 forming a cylinder whose length corresponds substantially to the thickness of the disc forming the hub 9. A plurality of propeller blades 11, sixteen in this embodiment, project radially from the peripheral delimiting surface 10.

Figure 5 shows that the hub 9 has a rear delimiting surface 12, which surface 12 extends substantially radially and is oriented substantially at right angles to the peripheral delimiting surface 10. A relatively sharp hub edge 13 is formed at the intersection of the rear defining surface 12 and the peripheral defining surface 10. The hub edge 13 is able to effectively separate the water flow from the propeller 3.

Each projection 4 is substantially part-circular in cross-section at least at the rear end 6. Close to the rear end 6, the radius of the cross-section substantially corresponds to the outer diameter of the hub 9, the centre of the circle defined by the cross-section radially substantially coinciding with the centre of the propeller. At the rear end 6, each projection 4 forms an end face 14 which is substantially parallel to the propeller disc. A relatively sharp end edge 15 is formed at the junction between the end face 14 and the outer surface immediately forward of the end face 14. The end edge 15 is able to effectively separate the water flow from the protruding part 4. The distance between the end edge 15 and the propeller 3 is minimized, taking into account practical possibilities. In any case, it is significantly smaller than the length of each propeller blade 11.

Fig. 6 shows an effect of the propulsion structure of the present invention. The water flow is indicated by a straight line below the boat 1. Since the cross-sectional radius of the projecting portion 4 near the rear end 6 substantially corresponds to the outer diameter of the hub 9 and the propeller 3 is located immediately aft of the rear end 6, the surface of the water flow is located at high speed in the region where the propeller blades 11 meet the peripheral delimiting surface 10 of the hub 9.

If the boat 1 is bumped at high speed, for example, by the boat 1 driving into the waves, it will rotate substantially about a horizontal axis in the transverse direction in the region of the rear support region 8. Since each propeller 3 is located close to the rear of the respective rear support area 8 and thus close to the centre of rotation, the above-mentioned rotational movement will only result in a small vertical movement of the propeller 3.

Figure 5 shows how a part of the propeller 3 is located in a recess 16 in the hull 2. According to the invention, the drive shaft 17 abuts against the propeller hub 9 through the location of the lead-in hole 18 of the hull 2, which simplifies the mounting of the propeller 3, since no additional bearings and corresponding fastening structures outside the hull 2 are required.

Positioning each propeller 3 immediately behind the respective projecting portion 4 and vertically thereof makes the propeller semi-submersible even at least relatively high speeds of movement of the boat 1. This is also facilitated by the fact that each propeller 3 is relatively large.

The motorboat 1 in the embodiment described is provided with two propellers 3 which are spaced apart from each other in the transverse direction of the hull 2. They are arranged in such a way that the pitch angle of the propeller blades 11 can be adjusted for each propeller 3, respectively, when the motorboat 1 is in motion. As a result, the steering of the boat 1 can be completed without rudder. The omission of rudders reduces the number of parts in contact with the water during travel of the boat 1 and in this way reduces the drag during propulsion of the boat 1.

The blades 11 on each propeller 3 are preferably arranged in such a way that the pitch angle can be adjusted during travel to adapt it to the operating speed of the boat, which in turn means a more efficient use of the propulsion source of the boat 1.

Claims (6)

1. Hull and propeller arrangement for a water craft (1), provided with two propellers (3), which propellers (3) are semi-submerged at the high speed of the craft and are arranged in such a way that only the propeller blades (11) or a part thereof are submerged at the high speed of the craft (1), characterized in that,

-the hull (2) is provided with a belly part (7) and two streamlined protrusions (4) extending substantially in the longitudinal direction of the hull (2),

-the outer shape of each protruding portion (4) has an end edge (15) at its rear end (6), which end edge (15) extends at least partially substantially perpendicular to the longitudinal direction of the protruding portion (4),

-each propeller (3) is located immediately aft of the respective end edge (15), a portion of each propeller (3) extending radially beyond the defining surface of the respective projecting portion (4),

-said belly part (7) and protrusions (4) are arranged in such a way that at high speed of the vessel (1) on each protrusion a rear bearing area (8) for the vessel (1) is formed, which rear bearing area (8) is mainly constituted by a part of the surface of the respective protrusion (4) located immediately in front of the end edge (15) and at the very bottom of the protrusion (4), and on the belly part (7) a front bearing area is formed, whereby the vessel is supported by water flowing through the bearing area, on which bearing area forces act to hold the hull up.

2. Hull and propeller arrangement according to claim 1, wherein each protruding portion (4) has, adjacent to the respective propeller (3), a cross-section which is at least partly substantially shaped like a portion of a circle, the center of which, adjacent to the propeller (3), substantially coincides radially with the center of the propeller, the radius of which, adjacent to the propeller (3), is smaller than the radius of the circumference of the propeller.

3. Hull and propeller arrangement according to claim 2, wherein the radius of the circle formed by the cross-section of the protruding part (4) at the location of the propeller (3) is substantially equal to the radius of an imaginary circle formed by the area of intersection of the propeller blades (11) with the propeller hub (9) when the propeller (3) is rotated.

4. The hull and propeller arrangement according to any one of the preceding claims, characterized in that each propeller (3) is designed with a relatively large hub (9) for the propeller blades (11), which hub (9) has at its periphery a peripheral delimiting surface (10) shaped substantially as a cylinder, which hub (9) has a rear delimiting surface (12), the junction between the rear delimiting surface (12) and the peripheral delimiting surface (10) being designed as a relatively sharp hub edge (13).

5. A hull and propeller arrangement according to any one of the preceding claims 1-3, wherein the propellers (3) are spaced apart in the transverse direction of the hull (2), and they are arranged in such a way that the pitch angle of the propeller blades (11) can be adjusted for each propeller (3) separately when the vessel (1) is in motion.

6. A hull and propeller arrangement according to any one of the preceding claims 1-3, characterised in that the drive shaft (17) is located in the immediate vicinity of the propeller hub (9) through the introduction aperture (18) of the hull (2).