A method and a device for improving the properties of a boat The present invention relates to a method and a device for improving the properties, especially the gliding properties of a boat, specifically by having influence on the propeller flows of the engine. In this text the term"boat"is meant to cover widely all objects which are moving on water and have engines. So the meaning is to cover also ships, vessels and corresponding expressions.

To improve the speed and the cruising comfort of a boat various constructions have been tested. Examples of these constructions include various plate like constructions which control the moving of the boat and also hydrofoils in certain vessels.

For the same purpose, and also for improving the speed, different constructions have been made in the bottom of the boat. This kind of construction have been shown in many publications, like e. g. in US patent publications 4756265, 4915668,4924797 and 4690086 and also in the following publications EP (A) 12098 and DE (A) 4127939.

In the cases described above various advantages have been alleged to be gained. However, the above inventions have not brought any considerable improvements in the art.

The aim of this invention is to achieve a clear improvement in the moving properties of a boat by using a construction of a boat that has been developed on a different basis compared what has been known before. This is achieved in a way the characterizing features of which have been given in the accompanied patent claims.

The basic idea of the invention is in that space is ploughed for the output flow from the propeller by using suitable structures of the bow of the boat. Another essential matter is that the output flow from the propeller is directed essentially upwards. The aforementioned properties work separately or their use together

will bring the desired improving properties. Thus the speed of the boat can be raised by the aid of the above features and the moving of the boat is, thanks to the same, controlled and smooth.

The invention is described, in the following, more closely by making reference to one embodiment of the invention described in the accompanying drawings. It is to note that the described embodiment is only one way to implement the invention and the invention is by no means restricted to only this way.

Thus: Figure 1 shows one schematic embodiment of the invention from the side and as a longitudinal section; Figure 2 shows the embodiment of Figure 1 seen directly from above; and Figure 3 shows the same embodiment seen from the stern of the boat.

It has not been the purpose to give an artistic picture in the drawings, but the purpose has been rather to give outlines to the invention by using simple basic figures.

So in Figure 1 it is shown a schematic longitudinal section, seen from the side, of the boat according to the invention. The boat itself has been described as a box 1 without taking exact position in respect of the shape of the hull of the boat, the structures of the bow or corresponding properties. The propeller rotated by an motor has been designated schematically by the reference number 2. In this example the motor is an outboard motor, without a cavitation plate, and fixed in the rear part of the boat, but in the art also other motor solutions are possible.

The motor itself has not been drawn in the figure.

The basic idea is to locate, on the bow area of the boat, guides 3 which plough water so that there will be more space for the output flow 4 from the propeller 2.

In other words the guides 3 spread the flow so that the output flow from the

propeller has more free space to leave compared with the situation when conventional structures are used. Specifically, Figure 2 shows how the guides 3 achieves the widening streams 6. The incoming streams have been schematically designated with a reference number 5. Especially, but not exclusively, the guides 3 have been articulated to the boat in a ajustable manner around a schematically shown point 7.

When the outflow is directed upwards, it will cause the bow of the boat to be pressed lower. When the speed is increasing, the lifting power of the guides 3 increases and lifts the bow of the boat upwards. According to the created phenomena the boat is gliding away from beneath of the pressing power of the propeller and the speed is increasing. The phenomena is like the one which happens when a sailing boat is sailing in side wind.

If the same condition is tried to be obtained with a conventional boat, the result is that moving of the boat is leaping and thus very uncomfortable and uneffective, among others for the reason that no equilibrium is gained between the fixed cavitation plate and the upwards directed outflow from the propeller.

In the conventional boats the outflow from the propeller is directed downwards or only marginally upwards.

When more free space is arranged for the outflow from the propeller, the created phenomena is like the one which improves the pushing power of a jet motor of an aeroplane in the higher atmosphere.

The flexibility 8 of the invention is gained when the boat has been raised, with the increasing speed, on the rear structure 3 according to the invention, loose from the surface 9 of the water. The bow structure of the boat may be such that it will lift the bow from the water when the speed is increasing. A structure like this can be a kind of a hydrofoil.

In the structure according to the invention it is suitable to use plate-like guides on the area above the propeller but also as the structure below the propeller joining

e. g. to the guides 3. The upper cavitation plate has been designated with a reference number 10 and the lower guide plate with a reference number 11. The upper cavitation plate 10 has the specific purpose to prevent air coming to the propeller. It has been fixed in a suitably snug way to the rear part of the boat so that air is prevented from going in a ejector-like and uncontrolled way to the water stream coming to the propeller.

In the solution according to the invention the position of the cavitation plate is by no means depending from the position of the propeller as is the case in conventional solutions.

The purpose of the plate 11, if it is in use, is to stabilize the moving position of the boat. It may be, if so desired, wedge-like and help then the directing of the outflow from the propeller upwards. The structures described above are not seen in the conventional solutions.

In the above description it has been referred to the guides 3 only in the meaning to show that the guides widen the streams so that there is free space for the propeller streams. It is self-evident that this kind of"ploughing"can be achieved with many kind of guides. The basic type is an approximately plate-like structure, which is in a desired position corresponding to the using circumstances and is located so that the rear edges are, advantageously, often in a broader position than the lead edge on the side of the coming stream. However, in the figure it has been shown a type of a guide which has been assembled from two plate-like parts 31 and 32. The part 32 is approximately upright and the part 31 is on its behalf horizontal.

In many situations it has been shown advantageous to place the guides in a way that is shown clearly in Figure 1 which means that the end of the guide, which is the rear end in the direction of the water flow, is lower that the opposite end which is the lead end in the direction of the flow. However, with the adjustability of the guides it is sought the optimum position in respect of the use by making corrections when the speed is changing.

It is clear that the form of the guides 3 is insignificant in respect of the basic idea of the invention, as far as the desired ploughing effect is gained. So also other forms which have effect on the moving of the boat and with which the properties of the boat are controlled, can be joined to the ploughing effect. The guides can thus be groove-like, the curves being"soft"or angular. On the other hand, by combining horizontal components to the guides, the same can have considerable effect on the steering of the boat.

One matter having its effect on the position of the guides is the position of the propeller. It is advantageous that the horizontal distance between the leading edges, in the direction of the stream, of the guides is, advantageously, only slightly bigger than the rotation circle of the propeller 2. On the same way the starting point of the guides is, in the longitudinal direction, approximately by the rotation plane of the propeller 2. However, it is to be noted, that the afore mentioned positions are probably suitable, but for certain purposes the positions may be changed.

When designing the components, their sizes and positions, it is naturally taken into account the using circumstances in question, whereby the optimum circumstances are applicable.

To describe the versatile optimization of the function it can be stressed the quick increasing of the speed at the cost of the flexibility by increasing the supporting surface, among others, of the guides 3. If it is the purpose to utilize wide flexibility 8 under certain circumstances, it is to be taken into account, in addition to the dimensioning of the plate constructions, the load, the speed and the height of the waves. It is essential, in respect of the total working under different circumstances e. g. the position of the propeller 2 in the direction of the transverse and longitudinal axis of the boat in relation to the bow of the boat and the guide piece 3, as well as to the height direction, especially if the highest point of the rotation plane of the propeller 2 is above the water surface 9. It must be taken into account, naturally, that when one part of the total system is changed, the relative working of the other parts may be changed.

In the structure according to the invention the propeller 2 is, advantageously, leaned so that its leaving stream 4 is directed essentially incline upwards as shown especially in Figure 1. The guides 3, the cavitation plate 10 and the plate 11 together with the position and the properties of the propeller 2 and other properties of the boat, like the structure of the bow, load and speed define in the first instance the moving position of the boat, stability and height 8 of the bottom of the hull from the water surface 9, the height 8 working as the flexibility.

It is evident that the joint 7 mentioned before is only an example and the adjustments are in practice such that they make the versatile adjustment of the different parts possible. The adjustment points may be located in suitable places for the adjustment. These places are not described more precisely here and also they are not restricted by any way. Also the propeller is, advantageously, ajustable so, that e. g. when driving with low speed, e. g. when starting the moving of the boat, the exiting stream from the propeller may be directed straight backwards or perhaps downwards, but when the speed is increasing it is advantageous to direct the exit streams from the propeller suitably incline upwards and at the same time the exit edge of the part 3 incline downwards.

The optimum result which corresponds to the moving situation in question is possible to obtain by making possible the adjustments and by dimensioning the sizes, the relative sizes, places and positions, the relative places and relative positions, the inclinations, forms and curvatures and the relative inclinations suitably in relation to the size, load, shape, power of the motor, the properties of the propeller, the desired speed and the desired streams that are formed and other properties of the boat.

It is evident that, within the scope of the basic idea of the invention, one or several of the described parts may be left away and also other parts, the purpose of which is to affect any property of the boat and that are not described here, may be joined to the structure. This kind of modifications still belong to the scope of the invention. Additionally it is clear that even though the above described structure is to be located in the rear area of the boat, in practice the structure may be positioned in other parts of the bottom of the boat or in the vicinity of the same. It is also clear that, if so desired, there may be two or more structures according to the invention located in the boat.