WO1984004903A1

WO1984004903A1 - Vessel with adjustable draught

Info

Publication number: WO1984004903A1
Application number: PCT/NL1984/000016
Authority: WO
Inventors: Sjoerd Meijer
Original assignee: Sjoerd Meijer
Priority date: 1983-06-07
Filing date: 1984-06-07
Publication date: 1984-12-20
Also published as: NL8302025A; DE3490269C2; NL190717B; NL190717C; DK52985A; DE3490269T; DK52985D0; DK172026B1

Abstract

A vessel comprising a hull providing the floating power and having on the underside an upwardly re-entering hull recess and air supply means (31) for supplying pressurized air to the hull recess. Preferably the hull comprises at least two downwardly projection hull parts (22) extending in the longitudinal direction of the vessel and bounding between them the hull recess, whilst at least one flap body (25, 26) is connected with the hull so as to be movable between a rest position in which the flow resistance is at a minimum and a working position in which the hull recess is closed laterally in a manner such that it is open only on the bottom side.

Description

Vessel with adjustable draught.

The invention relates to a vessel.

The object of the invention is to provide a vessel capable of running on very shallow water, yet having sufficient stability and draught to navigate on rough water. This combination of shallow water as well as water navigable only with difficulty may occur in river mouths, bays and at the sea coast or seas such as the Dutch Shallows. The small draught required for navigating on shallow water is very unfavourable for navigation on rough water, for example, due to wind and waves.

With a vessel according to the invention said object is achieved in that the hull comprises on its underside an upwardly re-entering hull recess and air supply means for supplying pressurized air to the hull recess. For running on shallow water the air supply means are switched on so that air is pumped into the hull recess. Thus the draught of the vessel decreases whilst the water displacement remains the same. Since waves of shallow water have only a small height, it is even possible to navigate on shallow water even in rough weather. For running on water of sufficient depth the air is evacuated from the hull recess so that the vessel regains its normal draught.

In a preferred embodiment of the invention the hull comprises at least two downwardly projecting hull parts extending in the longitudinal direction of the vessel and bounding between them the hull recess, whilst at least one flap body is movable between a rest position in which the flow resistance is at a minimum and a working position in which the hull recess is laterally closed so that it is only open in downward direction. In this embodiment the vessel has an advantageous catamaran hull shape having high stability under normal navigation conditions and a low flow resistance.

OMPI In a further embodiment of the invention at least one additional flap body is used at an intermediate place in the hull recess. Thus the hull recess is divided into two or more compartments. The air pumped into these compartments remains enclosed in these compartments and cannot shift in place. Consequently during diving movements of the vessel the water level in each compartment remains constant, on an average, so that the stability of the vessel is ensured.

In an advantageous embodiment the flap body is pivot- able about a transverse shaft extending between the hull parts near the top side of the hull recess, whilst in the rest posi¬ tion the flap body extends rearwards from said shaft. In the rest position the flap is substantially integral with the top face of the hull recess and thus the flow resistance is very low. In the event of such a disturbance of the flap moving mechanism that the flap cannot be fully moved into its rest position or remains hanging loosely, the hindrance experienced in normal navigation is slight.

According to the invention a particularly advantageous hull shape is obtained when μnder normal navigation conditions the undersides of the hull parts slope down to the rear and the upper boundary wall of the hull recess extends to the front substantially up to the plane of the undersides of the two hull parts. According to the invention the air supply means comprise an en ine-driven centrifugal air pump. Such a centrifugal air pump can supply a relatively high amount of air at a low pressure. For the use concerned here this is advantageous because the hull recess can be filled within a very short time. In the event of air leakage due to movements of the vessel or the waves the loss of air is soon compen¬ sated for.

In a further development of the invention the air supply means comprise an outlet opening out in the hull recess in a manner such that during the forward movement of the vessel the air emanating from the outlet spreads in th« form of an air layer between a considerable part of the hull and the water. In the normal state of navigation, that is to say, when the flap bodies are in the rest position and the

OMPI air supply means are switched on, an air layer is formed which is capable of drastically reducing navigation resis¬ tance. This permits of attaining a high navigation speed.

According to the invention an advantageous shape of the outlet of the air supply means is obtained by a slot ex¬ tending in a transverse direction. This slot ensures a satis¬ factory distribution of the air along the width of the hull.

VJith regard to the specific use of the vessel embody¬ ing the invention it is preferably made from light-weight material, for example, aluminium. In practice it has been found that with an overall length of 16 ms a water displace¬ ment of 15 to 20 tons can be attained with an associated very small draught of 0.4 to 0.5 m, the hull recess being complete¬ ly filled with air. Vessels having two or three hull parts extending in the direction of length of the vessel are known per se. This hull shape is used in particular for sailing vessels, but also for larger ships. In this case, however, the hull parts constitute more or less separate floats which do not form a hull recess together with flap bodies.

The invention will be described more fully herein¬ after with reference to embodiments of the invention shown in the Figures.

Fig. 1 is a perspective view of a first embodiment of a vessel in accordance with the invention.

Figs. 2 and 3 are rear views of the vessel of Fig. 1 with the flap body in the rest position and in the working position, respectively.

Fig. 4 is partly a sectional view and an elevational view of a vessel according to the invention in a different embodiment.

Fig. 5 is a schematic plan view of the bottom of the vessel of Fig. 4.

Fig. 6 is a perspective view from below of the vessel shown in Figs. 4 and 5.

Figs. 7 and 8 are elevational views partly correspond¬ ing to Figs. 4 and 5 of a further embodiment of the vessel in accordance with the invention.

Fig. 9 shows a further embodiment of the vessel in

OMPI accordance with the invention.

The vessel 1 shown in Fig. 1 is constructed in the form of a ferry boat. The ferry boat 1 has a hull 2 compris¬ ing two hull parts 3 and 4. The hull parts 3, 4 extend in the longitudinal direction of the vessel on the sides thereof. Between the hull parts 3 and 4 is bounded a hull recess 5. The hull recess 5 is bounded on the longitudinal sides by the hull parts 3 and 4 and it is open on the front and rear side and in downward direction. On the rear side and on the front side of the hull recess 5 are arranged flap bodies 6 and 8 respectively. These flap bodies are pivotally connected with the hull 2 and journalled in bearings 7 (shown schematically) on the top side of the hull recess, where the flap bodies can turn each about a transverse shaft 11. The flap bodies 6, 8 can turn out of a rest position shown in Fig. 2, in which the flap bodies are in a horizontal position, so that the flow resistance is at a minimum and from this rest position into a working position shown in Fig. 3, in which the flap bodies are vertical. In the working position of the flap bodies 6, 8 shown in Fig. 3 they close the hull recess 5 on the rear and front sides. In this situation the hull recess 5 is only open on the bottom side. According to the invention air supply means are provided in the vessel 1. These air supply means are formed by a centrifugal air pump 9 shown schematically in Fig. 3,^which has an air outlet 10 opening out in the hull recess 5. By means of the air supply 9 air can be pumped into the hull recess closed by the flap bodies 6 and 8. In the rest position of the flaps 6 and 8, in which the hull recess 5 is open at the front and at the rear, the vessel 1 has sufficient draught for navigation normally in sufficiently deep water. This is apparent in Fig. 2 from the water level 12. When the flap bodies 6, 8 are in the working position and after air is pressed into the hull recess 5, the draught of the vessel 1 has considerably decreased, which is apparent from the water level 13 indicated in Fig. 3. In this situa¬ tion the vessel 1 can run on very shallow water so that places inaccessible by the conventional ferry boat can be readily reached by the ferry boat 1 embodying the invention. Since in accordance with the invention the air supply means

-BURhA OMPI b iPO comprise a centrifugal air pump capable of supplying a large volume of air at a slightly raised pressure, the hull recess 5 can be filled with air within a short time. Thus the draught of the vessel 1 can be adapted very rapidly so that the vessel 1 can run in water of sufficient depth with the normal draught and, as soon as a region of smaller depth of the water is reached, it can run with a smaller draught matching this smaller water depth.

An additional advantage of the vessel embodying the invention resides in that, when the vessel threatens to run ashore or has run aground for example due to flux and reflux movements in shallow water, it can be simply refloated by reducing the draught in accordance with the invention.

The vessel 20 of Figs. 4 to 6 is constructed in the form of a tugboat or a working boat, in particular for use in regions of shallow water. The hull 21 of the vessel 10 com¬ prises two hull parts 22, 23. Between these hull parts 22, 23 is bounded a hull recess 18. The top boundary wall of the hull recess 18 or else the bottom 24 is sloping down towards the bow of the vessel substantially to the level of the under¬ side of the two hull parts 22, 23. The hull shape resulting therefrom, shown most clearly in Fig. 6_., imparts to the vessel 20 favourable navigation properties, such as great stability and relatively low flow resistance with higher speed. From the Figures it is apparent that the hull recess 18 is open only to the rear side and to the bottom. In order to reduce the draught it is, therefore, sufficient to use a single flap 25 on the rear side of the vessel. This flap 25 can turn about a transverse shaft 19 and journalled in a recess 29 in the bottom 24. The ends of the transverse shaft 19 are provided with arms 40, the free ends of which can be engaged by hydraulic jack screws 27. With the aid of the hydraulic jack screws 27 the flap 25 can be moved from the rest position in which it is housed in the recess 29 into a working position in which it extends vertically downwards.

The vessel 20 is provided with a second flap 26, which is arranged in a similar manner in a recess 30 and which can be turned by means of arms 41 and jack screws 28 from a rest position into a working position and conversely. The second

OMPI flap 26 is provided in order to divide the hull_^ recess 18 into two compartments, as a result of which the air pressed into the hull recess 18 closed by the flaps is better held in place, which is conducive to the longitudinal stability of the vessel 20 brought to a small draught.

In the hull 21 of the vessel 20 is arranged an air supply device 31. This air supply device 31 comprises a cen¬ trifugal air pump 32, which communicates through ducts 33 with the hull recess 18. The duct 33 is branched so that air can be supplied to each of the compartments separated from one another by the flap 26. The duct 33 includes closing members 34. In the inoperative state of the air supply device 31 these closing members prevent water from penetrating into the duct 33. Moreover, the closing members 34 permit of selec- tively supplying air to one of the compartments separated by the flap 26. In given cases the position of the vessel 20 can thus be changed.

The vessel 20 is propelled with the aid of two propellers 35 connected with engines (not shown) mounted one in each of the hull parts 22 and 23. In the middle of the hind ^"part of the ship is mounted a rotatable propelling device formed in this case by a water jet tube 36. With the aid of this rotatable propulsion the vessel 20 can be very satisfactorily manoeuvered whilst it contributes to the propulsion in running straight on. The rotatable propelling device 36 is driven by an engine 37. The transmission may effectively be a hydraulic transmission.

Fig. 4 shows the vessel 20 in the state of reduced draught. The water level is indicated at 38. By way of cora- parison the water level 39 is shown for the normal navigation conditions. It is apparent that in the state of reduced draught the vessel 20 is tilted forward with respect to the normal state of navigation. The upper boundary wall 24 of the hull recess is in this normal state of navigation substantiαl- ly parallel to the water level, whereas the undersides of t!ι<? hull parts 22, 23 are sloping to the rear. Then the vessel can start gliding at a higher speed. In view of the specifI : hull shape there is a possibility of subatmospheric pressure being created in the hull recess 18 at the front of the hull

-ft XtA

OMPI parts 22, 23 when running with relatively high speed. In order to avoid the adverse effects thereof openings 42 are provided at said place in the hull, which openings communi¬ cate with an air inlet 44 through non-return valves 45 and an air cabinet 43. In the event of subatmospheric pressure air is sucked in so that the subatmospheric pressure is obviated. The non-return valves 45 are provided for preventing air pumped into the hull recess 18 by means of the air supply device 31 from escaping through the openings 42. The vessel 50 shown in Figs. 7 and 8 comprises a hull

51 having the same shape as the hull 21 of the vessel 20 of Figs. 4 to 6. The flap 52 is pivotable about a vertical, central shaft 61. The shaft 61 is connected with a driving gear 53, which is actuated by an engine 54. The engine 54 can move, via the driving gear 53, the flap 52 from the rest position shown in the Figures into a working position trans¬ verse to the former. The working position is indicated in Fig. 8 by a broken line. In the rest position shown the flap

52 causes minimum .flow resistance. The air supply device 55 of the vessel 50 is con¬ structed in accordance with the invention in a manner such that during the forward movement of the vessel the air flow¬ ing out of the outlet opening out in the hull recess spreads out like an air layer between an appreciable part of the hull 51 and the water. The outlet of the air supply device 55 is for this purpose formed by slots. The air outlet opening out in the foremost compartment is formed by two inclined slots to which air is supplied from the pump 62 through a manifold 57 and a duct 56. With this disposition of the slots 58 they can, moreover, fulfil the same function as the openings 42 of the vessel 20. For this purpose the duct 56 includes a non¬ return valve (not shown) .

The outlet of the aif supply device 55 opening out in the hindmost compartment of the hull recess is formed by a slot 60 extending in a transverse direction. To this slot 60 is supplied air from the pump 62 through a manifold 59 and the duct 56. \/hen the draught of the vessel 50 has to be reduced in the manner described above, the flap 53 is turned downwards and the flap 52 is moved into the transverse posi- tion. Then, in the manner described above, the pump 62 sup¬ plied air to the hull recess so that the draught decreases. The specific shape of the air outlets formed by slots 58, 60 is used for normal navigation. The flaps 53 and 52 are then in the rest position and the hull recess is normally filled with water. By actuating the air supply device 55 suring this normal navigation air is pressed out of the slots 58 and 60. This air is carried along by the water flowing alongside and spreads like a thin air layer along the upper boundary wall of the hull recess or the bottom 63. Thus the flow resistance is reduced in a manner known per se so that the vessel 50 can attain a higher speed or it consumes less energy at its same speed.

The vessel 71 of Fig. 9 has a hull recess 78 bounded on both longitudinal sides by hull parts 72 and 73, whilst the boundaries on the front and rear sides are formed by the bottom 74 extending downwards to the plane going through the undersides of the hull parts 72, 73. The air supply means (not shown here) open out at 75 in the hull recess. For a satisfactory streamline it is desirable for the bottom to extend smoothly.

In order to benefit to the optimum from the advan¬ tages of the vessel embodying the invention it is made from a light-weight material such as aluπiniuπ. The overall weight of the vessel and hence the water displacement thus remain low so that also the minimum draught m y be very small. In order to obtain sufficient draught for satisfactory stability when navigating in rough weather in water of adequate depth, ballast tanks may be used in the vessel.

Claims

C L A I M S

1. A vessel comprising a hull providing the floating power c h a r a c t e r i z e d in that the hull comprises on the underside an upwardly re-entering hull recess and air supply means for supplying pressurized air to the hull recess.

2. A vessel as claimed in Claim 1 c h a r a c t e r ¬ i z e d in that the hull comprises at least two downwardly projecting hull parts extending in the longitudinal direction of the vessel, said parts bounding between them the hull recess and in that at least one flap body is connected with the hull so as to be movable between a rest position in which the flow resistance is at a minimum and a working position in which the hull recess is closed laterally in a manner such that it is open only on the bottom side.

3. A vessel as claimed in Claim l or 2 c h a r a c - t e r i z e d by at least one additional flap body arranged at an intermediate place in the hull recess.

4. A vessel as claimed in anyone of the preceding Claims c h a r a c t e r i z e d in that the flap body is pivotable about a transverse shaft extending between the hull parts near the top side of the hull recess and extends rear- wardly from said shaft in the rest position.

5. A vessel as claimed in anyone of the preceding Claims c h a r a c t e r i z e d in that under the normal navigation conditions the undersides of the hull parts are sloping to the rear and in that the upper boundary wall of the hull recess extends to the front substantially up to the plane going through the undersides of the two hull parts.

6. A vessel as claimed in anyone of the preceding Claims c h a r a c t e r i z e d in that the air supply means comprise an engine-driven centrifugal air pump.

7. A vessel as claimed in anyone of the preceding

Claims c h a r a c t e r i z e d in that the air supply means comprise an outlet opening out in the hull recess in a manner such that the air emanating from the outle "spreads like an air layer between an appreciable part of the hull and the water during the forward movement of the vessel.

8. A vessel as claimed in Claim 7 c h a r a c t e r ¬ i z e d in that the outlet is formed by a slot extending in a transverse direction.

9. A vessel as claimed in anyone of the preceding Claims c h a r a c t e r i z e d in that it is made from a light-weight material such as aluminium.

OMPI ^,p