GB2032871A

GB2032871A - Improvements in or Relating to Watercraft

Info

Publication number: GB2032871A
Application number: GB7935489A
Authority: GB
Original assignee: Piaggio and C SpA
Current assignee: Piaggio and C SpA
Priority date: 1978-10-12
Filing date: 1979-10-12
Publication date: 1980-05-14
Also published as: GB2032871B; IT7828697A0; IT1100965B; FR2438580A1

Abstract

A watercraft is propelled by means of a removable motor 3 mounted abaft and contained within a caisson 2 of substantially parallelpiped shape and the caisson 2 is releasably fastened within the watercraft. The illustrated watercraft comprises an inflatable U-shaped boat and has a motor of the water-jet type. <IMAGE>

Description

SPECIFICATION Improvements in or Relating to Watercraft The present invention relates to a watercraft, particularly, but net exclusively, to a pnuematic boat equipped with a water jet propulsion unit contained within a water-tight caisson.

Such a propulsion unit is described and illustrated, for instance, in the Specification of the published Japanese patent application No.

87096/74.

As is known, common pneumatic motor boats are essentially constituted by a tubular U-shaped inflatable rubber float; between the limbos of the U-shape is fastened the bottom of the boat and at the rear side is a rigid transversal bulkhead to which an outboard propulsion unit is fixed.

It is know that one of the main advantages of that kind of watercraft as compared with boats having a rigid hull is afforded by the facility of transport on land, as is allowed by the possibility of easily separating the propulsion assembly from the boat, by lightness and by the possibility of reducing the space requirement of the hull by deflating and folding it.

Also the advantages of the water jet (hydrojet) kind of propulsion unit over the screw propeller type are known from the point of view of the safety of navigation in shallow water and in zones frequented by bathers as well as from the point of view of easy manoeuvring.

The application of the hydrojet motor propulsion unit to a pneumatic boat is not as easy as in the case of a screw propeller owing to fact that in order to avoid projections below the underbody and for reasons of good operation and hydrodynamic efficiency, the water intake of the jet should be provided at the bottom of the hull, but the conduit of the jet, where the pump is mounted, thereby takes up more space because it has to be long enough so as to avoid sharp deviations of the stream.

Hence it has not been possible to use the idea of a jet propulsion unit at the end of a strut projecting from a standard outboard motor instead of a screw propeller.

To apply a jet propulsion unit in a removable manner to watercraft having a rigid hull the proposal has been made to incorporate the unit within a floating rigid caisson to be fixed in a suitable manner to the transom of the boat so that the bottom of the caisson, in which the water intake of the jet is provided, forms an extension of the underbody of the watercraft. A container of that kind is described in Italian patent Specification No. 1002024.

The solution is not suited to be adopted in the case of a pneumatic boat without resorting to suitable integration of the construction of the boat as a matter of fact, the transverse bulkhead constituting the transom of the boat does not fine itself in the best conditions to resist the moment at fixed end caused by the motor propulsion unit owing to the deformability of its supports which are localized within a restricted region of the tubular floats. The rotation of the bulkhead with respect to the remainder of the boat is very noticeable in the case of the screw propeller outboard motor owing to the moment produced by the thrust of the screw propeller placed below the bulkhead especially during acceleration, but it does not bring about any harmful consequence in the navigation of the vessel.

However, in the case of the caisson container of a jet propulsion unit, even if the moment of the thrust is smaller than in the previous case because the jet exits at the level of the bulkhead, even a small rotation of the bulkhead due to the variation of the resultant of the weight and of the hydrodynamic lift exerted on the bottom of the caisson might produce variations of the trim of the bottom with respect to the underbody of the boat such as to prejudice the navigation of said boat.

Another problem of construction, besides the problem of avoiding.the above mentioned variations of trim, arises from of how to join the shape of the caission with the shape of the boat so as to ensure a continuity of the underbody with respect to hydrodynamic effects, the effects of the seeping of water, as well as by the opportunity of utilizing the spaces between the motor propulsion assembly and the tubular floats.

The aforesaid problems are more in evidence if the length of the container of the motor propulsion assembly is greater, the motor propulsion assembly having need of a sufficient development of the water intake conduit.

In order to overcome this difficulty the proposal was made to incorporate the motor assembly within a floating caisson provided with watertight compartments adjacent to the motor and with special lateral extension so that it can be made to rest by way of a saddle on suitably elongated tubular floats.

It has also been proposed to equip the compartments with special covers and shutters to be utilized for the locating and protection of the accessories and, finally, it has been proposed to shape the body of the caisson in such a manner as to be part of the underbody of the boat.

The solution of the problem appears to be satisfactory from the hydrodynamic and structural aspects, but it has the drawback of making transport by hand or on a vehicle more difficult, owing to the considerable space requirement and weight of the caisson. In that way the pneumatic boat would lose, at least in part, its main advantage, namely the advantage of easy transportability. A watercraft of this kind is described for instance in the specification of Italian patent application No. 23143 A/76 filed on tilth May1976. 1976.

According to the present invention, there is provided a watercraft having a removable motor mounted abaft and contained within a caisson of substantially parallelepiped shape, a seat having a shape complemental of the shape of the caisson, within which seat the caisson can be fastened in a removable manner, the caisson when so fastened being contained substantially wholly within the overall space requirement of the watercraft.

Thus the overall volume of the watercraft is not increased when the motor is fitted.

The invention will be further described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a plan view of an embodiment of the present invention shown without its covers in the interests of clarity; Fig. 2 is a longitudinal section of the boat, taken along the plane Il-Il of Figure 1; Fig. 3 is a section of the boat, taken along the plane Ill-Ill of Figure 1; Fig. 4 is a rear view of the boat; Fig. 5 is a section taken along the plane V-V of Figure 1 and to an enlarged scale; and Fig. 6 is an enlarged view of the stern of the boat and of the motor when detached from one another.

As can be seen in the drawings, the motor propulsor 1 is fastened at the inside of a caisson 2 having an approximately parallelepipedonal shape and being of a size sufficient to contain an engine 3, the gearing, the suction duct 4 and the inspectable portion of the motor. On the bottom 5 of the caisson 2 there is provided an aperture 6 of water intake of the jet whilst from the rear wall 7 of the caisson there projects the jet outlet nozzle 8 suitable provided with members for adjusting the direction of the jet. The connection between the motor and the caisson is water-tight so as to prevent flooding of the caisson and consequent damage to the engine.

The walls of the caisson are for instance made of fiberglass reinforced plastics or of other resistant material and are coated internally with a layer 9 of soundproofing material to reduce transmission to the outside of the noise of the engine (Figure 5).

Externally the caisson 2 is provided with front and rear attachments 10 and 11 respectively for fastening it to the boat and with handles 12 to enable transport even by hand.

There is provided also a special cover 13 equipped with a lock.

The volume of the caisson maybe sufficient to enable it to float.

In order to fasten the caisson 2 to the boat 14, the latter has at its rear side a special housing 1 5 of a shape which is rectangular in plan, defined in front by the rigid transverse bulkhead 1 6 (transom) connected to the tubular floats 1 7' and 1 7" and defined laterally by longitudinal walls 29' and 29" of water-tight compartments 1 8' and 1 8" respectively adjacent to the floats.

The fastening of the caisson to the beat is carried out by means of bolts or other quick hooking systems in front on the bulkhead 1 6 through the attachment 10 and at the rear side, through the attachment 11, on rigid backwalls 23' and 23" introduced and fixed into the compartments 18' and 1 8" for the purpose that will become apparent below.

The stability of the fastening is ensured by the fact that the caisson is supported in front by the beam resting on the tubular floats and constituted by the bulkhead 1 6 and at the rear by the beam resting on the same tubular members which is formed by the union, by means of aforesaid attachment 11 of the caisson with the rear walls 23' and 23" of the compartments 18' and 18" already connected by way of brackets to the respective tubular members.

In order to keep the possibility of folding the deflated boat, for the purpose of transport, the compartments 18' and 18" are made of rubberized canvas stiffened in the manner hereinafter described.

In particular the said compartments are formed by pockets of nearly paralleiepipedonal shape suspended form the respective tubular members; into the bottom of these pockets there are inserted stiffening panels 25' and 25" (Figure 5) with inclined transverse ribs 44.

Besides constituting supporting planes said panels serve to tension the rubberized canvas bottoms 26' and 26" and end walls 43 of the pockets. Against said end walls 43 of the pockets there are then applied rigid panels 23' and 23 wherein there are provided holes for the fastening of the appendices 11 of the caisson. The walls 28', 28". 29' and 29" of the pockets are then tensioned by hooking them (with the aid of hooking means of known kind not shown) to the bulkhead 1 6 and to the side walls of the caisson 2, after having fastened the latter to the boat.

Obviously the caisson is placed on the boat in such a manner that its bottom, suitable shaped, comes to form an integral part of the careen of the boat, such as suggested for instance in the USA Patent Specification No. 3002732.

The compartments 18' and 18" can be utilized particular for housing the fuel tank 30 and the electric storage battery 31 by providing suitable passages for the associated piping and cable in the wall of the caisson.

The caisson and the adjacent compartments can be closed by means of the covers 13, 32' and 32".

The covers or lids 321 and 32" on the channels 33' and 33" which are stuck to the tubular members 17' and 17", to the bulkhead 16 and to the rear walls of the compartments.

The cores are provided with channels 34' and 34" into which the borders 35' and 35n of the lid 1 3 of the caisson 2 can be inserted; the lid 13 can then be fastened to the caisson by means of a hinge and a lock by so doing also the lids 32' and 32" become fastened. The lids 32' and 32" come to form together with the lid 13 a platform that can be used as a seat or as a deck in which the channels 33', 33", 34' and 34" act as stiffening members and as gutters for the water.

As can be seen, in the illustrated watercraft, the motor assembly is mounted in such a way as to be entirely contained within the volume of the hull and so as not to create any gap therewith, with all the attendant advantages.

The control of the members for varying the direction of the jet is achieved by means of a rod 36 connected to the end of a pipe 37 passing through a slot provided for this purpose in the lid 1 3. The control of the accelerator of the engine may be actuated by means of a knob or handle 38 provided at the end of the rod 36.

There is also provided a control system of the kind with a steering wheel at the front portion of the watercraft.

In order to adjust the longitudinal trim of the caisson with respect to the boat there is provided an adjustable connection 39 of the bulkhead 1 6 with the rigid keel 40 of the boat. The keel too can be dismantled. This connection may be constituted by a conventional screw jack.

To discharge any water there is provided a hole 41 located at the base of the bulkhead 16 in correspondence with a passageway 42 provided for this purpose in the caisson.

Water discharge holes, provided with plugs may be formed in the caisson 2 and in the compartment 18' and 18".

The above description and the accompanying drawings relate to a non-limiting example of the present invention.

Various modifications may be made without departing from the scope of the invention. In particular, the motor need not be a jet propulsion unit but could instead be of the screw propeller kind with the engine in line or in any way connected to the shaft of the screw propeller provided it be enclosed in a caisson to be fastened to the boat in the way required by the present invention. The compartments of the boat adjacent to the caisson may be rigid, dismantleable or not and also, the whole hull may be rigid.

Claims

1. A watercraft having a removable motor mounted abaft and contained within a caisson of substantialiy parallelepiped shape, a seat having a shape complemental of the shape of the caisson, within which seat the caisson can be fastened in a removable manner, the caisson when so fastened being contained substantially within the overall space requirement of the watercraft.

2. A watercraft according to claim 1 and which comprises an inflatable boat with a pair of lateral tubular floats which extend aft of beyond a rigid transom, there being rigid brackets extending from the floats and which, with the transom create the seat for the caisson.

3. A watercraft according to claim 2, wherein the rigid brackets form part of water tight compartments fastened to the floats and to the transom.

4. A watercraft according to claims 2 and 3, wherein caisson and the compartments are equipped with rigid lids or covers adapted to form a common platform to be fastened to the boat by locking the respective lid or cover to the caisson.

5. A watercraft according to claim 3 or 4, wherein the water-tight compartments are constituted by pockets of flexible material within which the brackets are located.

6. A watercraft according to claim 5, wherein on the bottom of said pockets there are provided panels forming part of the careen or underbottom of the watercraft.

7. A watercraft according to claim 2 or any one of claims 3 to 6 and claim 2, wherein the longitudinal trim of the motor caisson with respect to the front careen of the craft is adjustable by a connecting means of variable length between the transom where the front part of the caisson is fastened and a rigid removable keel of the boat.

8. A watercraft according to any one of the preceding claims, wherein the motor is of the water jet kind.

9. A watercraft constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.