GB2044705A - Boat Propulsion and Steering Device - Google Patents

Abstract

A detachable apparatus for propelling a small boat comprises a mounting which allows movement about vertical and horizontal axes and a paddle assembly having preferably three vanes consisting of a central vane 126 and a pair of pivotable vanes 132 disposed at each side of the central vane. Steering can be effected by turning the handle in the manner of a tiller. <IMAGE>

Description

SPECIFICATION Boat Propulsion and Steering Device This invention concerns means for propelling and steering small craft such as dinghies.

Conventionally, such craft are propelled by rowing with oars. However, it is difficult to control a craft accurately with oars e.g. when manoeuvering in a crowded harbour.

Furthermore, oars are long and inconvenient to transport, especially by car.

According to a first aspect of this invention there is provided a boat propulsion and steering device comprising an attachment element having means for reieasable attachment to the boat, an elongate shaft attached to the attachment element through pivot means so that the shaft descends therefrom in an upright plane and is pivotable around upright and horizontal axes, and paddle means carried by a lower end portion of the shaft spaced from said pivot means, so that rocking movement of the shaft about the horizontal axes effects reciprocal motion of the paddle means the paddle means having three vanes projecting laterally therefrom, which in use, are at least partially submerged, one said vane being fast with the shaft and the other two vanes being pivotable about an axis or respective axes extending generally longitudinally of the shaft, these two vanes being pivotable between a first position with them angularly close together, one at either side of the first said vane, and a second position with them turned outwardly to either side so as to be angularly spaced apart, the assembly also having stop means for these two vanes to prevent them turning beyond the second position, whereby in use the drag of the water during said reciprocal motion causes the submerged vanes to tend to move between the first and second positions when the direction of said reciprocal motion changes, motion of said assembly with said vanes in said second position providing a propulsive thrust which exceeds the reverse thrust applied by corresponding motion in the reverse direction with the vanes in the first position and whereby pivoting the shaft around the upright axis enables steering of the boat.

The device is particularly intended for mounting on the stern of a boat, notabiy on the transom of a dinghy. By pivoting the shaft around the upright axis the propulsive hrust will be developed at an angle to the fore and aft line of the boat, so steering it, and this aid manoeuvring in confined spaces. Also the paddle means can function as a conventional rudder while the pivotable vanes are in the first position, so that a boat can be steered by the device if there is way on the boat, without applying propulsive thrust.

Preferably a handle projects laterally from an upper end region of the shaft towards the attachment element so that reciprocal motion of the paddle means can be effected by up and down motion of the shaft, and the handle used as a conventional tiller for steering.

The vane fast with the shaft provides a stop for the pivotable vanes in their angularly close, first position and enables the paddle means to function as a rudder. However, use of a third vane, rather than some other form of step has been found to improve the opening of the blades from their first position while the boat is turning. The distal margins of the pivotable blades are preferably out-turned to assist this also.

In a second aspect, this invention provides a boat propulsion and steering device comprising an attachment element having means for releasable attachment to the boat, an elongate shaft attached to the attachment element through pivot means so that the shaft descends therefrom in an upright plane and is pivotable around upright and horizontal axes, and paddle means carried by a lower end portion of the shaft spaced from said pivot means, so that rocking movement of the shaft about thehorizontal axis effects reciprocal motion of the paddle means the paddle means including at least one vane which, in use, is at least partially submerged, and which is pivotally attached to the shaft such that, in use, the drag of the water during said reciprocal motion causes the submerged vane to tend to move between first and second positions when the direction of the reciprocal motion changes, motion of the said assembly with the vane in its second position providing a propulsive thrust which exceeds the reverse thrust applied by corresponding motion in the reverse direction with the vane in its first position, the shaft being attached to the attachment element through an intermediate arm, to which the shaft is pivotally connected by a horizontal pivot providing the said horizontal axis, the intermediate arm being pivotally connected to the attachment element by an upright pivot providing the said upright pivot axis, whereby in use the upright axis is closer to the boat than the horizontal axis, the shaft being freely pivotable around both axes simultaneously and having a handle projecting laterally from it above the pivots towards the attachment element.This geometry is advantageous in that it reduces the extent to which the inboard end of the handle must be moved across the boat to effect steering. The handle will give greater leverage for propulsion (where more is required) than for steering.

According to a third aspect of this invention there is provided a boat propulsion and steering device comprising an attachment element having means for releasable attachment to the boat, an elongate shaft attached to the attachment element through pivot means so that the shaft descends therefrom in an upright plane and is pivotable around upright and horizontal axes, and paddle means carried by a lower end portion of the shaft spaced from said pivot means, so that rocking movement of the shaft about the horizontal axis effects reciprocal motion of the paddle means the paddle means including at least one vane which, in use, is at least partially submerged and which is pivotally attached to the shaft, such that, in use, the drag of water during said reciprocal motion causes the submerged vane to tend to move between first and second positions when the direction of the reciprocal motion changes motion of the said assembly with the vane in its second position providing a propulsive thrust which exceeds the reverse thrust applied by corresponding motion in the reverse direction with the vane in its first position, the vane being of sheet plastics material and having a root portion fast with the shaft and a main portion attached to the root portion through a linear zone of reduced thickness forming a hinge around which the main portion can pivot.

This is an economical method of construction and avoids possible problems with corrosion of submerged pivots. Preferably the said shaft is hollow and the or each root portion extends into the shaft through an axial slit and is secured by pins extending transversely through the shaft and root portion(s).

Two embodiments of the invention will now be described with reference to the accompanying drawings in which: Fig. 1 is an elevation of a first embodiment: Figs. 2 to 8 show details of the Fig. 1 embodiment; Figs. 2 and 3 show the paddle assembly with the paddle vanes in open and closed configurations respectively; Fig. 4 shows a paddle vane detached from the assembly; Fig. 5 shows the paddle assembly with the paddle vanes removed; Fig. 6 is a perspective view of part of the transom clamp; Fig. 7 is an elevation of a second embodiment; Fig. 8 is a plan of Fig. 7 with the propulsion arm removed; Fig. 9 is a section along IX-IX in Fig. 7 on a larger scale; Fig. 10 is a horizontal section through a paddle vane of the Fig. 7 embodiment.

The propulsion device 1 shown in Figs. 1 to 8 has a generally L-shaped propulsion arm 10. The shorter, upper section 12 of the "L" has a handgrip 14 on its end. The longer section 1 6 has near its end a paddle assembly clamp 1 7 secured thereon e.g. by welding. This provides a threaded bore for a thumbscrew 18 which can be screwed so as to project radially into the interior of the arm 10. At an intermediate region of arm secion 16, a drilled block 20 is attached, e.g. by welding.

A paddle assembly 22 has an elongate paddle arm 24. The assembly 22 is detachably securable to the tubular propulsion arm 10 by inserting an upper portion of the paddle arm 24 into it and tightening the thumbscrew 18.

A steering vane 26 and a vane back-stop 28 are fixed, e.g. by welding, in diametrically opposed relationship on the lower portion of the paddle arm 24. A pivot portion 30 of arm 24 extends a little way beneath the region of attachment of the steering vane 26. The vane 26 is T-shaped, the foot of the T being the part secured to the arm 24. The arms of the T provide vane front stops 31.

Two movable paddle vanes 32 each comprise a flat rectangular paddling portion 34 which has at the outer one of its long edges an angled flange constituting a partial return 36. The two shorter edges of each paddling portion 34 each bear a vane return 38 in the form of a narrow generally triangular element secured along one edge subsTantially in a respective plane at right angles to the portion 20. The two vane returns 38 of each vane 32 are in spaced overlying relationship.

Each has near its inner edge an aperture 40 through which the paddle arm 24 fits slidably.

Each paddle vane 32 can be made by bending a single piece of sheet metal.

To mount a paddle vane 32 on the paddle arm 24, the upper portion of arm 24 is passed through the aperture 40 in the upper return 38a. The vane 32 is then slid down the arm 24. The materials and dimensions of the steering and paddle vanes are such that when the upper return 38 abuts the top of the steering vane 28 resilient deformation allows the pivot portion 30 of the arm 24 to be passed through the apsrture in the lower return 38b. The paddle vanes 32 are thus pivotally mounted on the arm 24, and are retained there by a retaining bolt 42 and washer 44, the bolt 42 being received by a threaded insert in the lower end of the arm 24. Each paddle vane 32 can pivot towards the steering vane 26 until the leading edges 46 of its vane returns 38 abut the vane front stops 31, and can pivot in the reverse direction until the inner edge 48 of its paddling portion abuts the vane back stop 28.

The propulsion device 1 is removably securable e.g. to the transom of a boat by means of a screwclamp 50.

This has lugs 52 which are bored to mount a pivot bolt 54 (held in place by a self-locking nut 55) with its axis generally vertical; an intermediate swivel mounting arm 56 is rotatably mounted on the bolt 54 between the lugs 52. The arm 56 provides two generally overlying webs 58 which embrance the drilled block 20 which is fast with the propulsion arm 10. A generally horizontal bolt 60 passes through an aperture 62 in one of the webs 58, through the drilled block 20, and through an aperture 64 in the second web 58, and is held in place with a self-locking nut 66. The intermediate arm 56 and the block 20 (and hence the arm 10) are relatively pivotable about the bolt 60 in a vertical plane.

In use, the device 1 is mounted on a craft with the paddle assembly 22 submerged. For propulsion, the arm section 12 is grasped by the handgrip 14 and pivoted up and down with a pumping action, so that the device pivots to and fro in a vertical plane about the bolt 60 with the paddle vanes submerged. When the paddle assembly 22 is moved in the direction of the arrow 68 (Fig. 2), the force of the water acting on the partial returns 36 urges the paddle vanes 32 to the open position shown in Fig. 2. This presents a large effective area to the water, and thus produces a large propulsive thrust for the craft, in the direction opposed to the arrow 68.When the assembly 22 is moved in the reverse direction, the water action on the other sides of the partial returns 36 rges the vanes 32 to the closed position (Fig. 3), in which they present a small effective area to the water, and cause little drag.

Thus reciprocation causes an overall propulsive force.

For steering, the arm section 12 is moved laterally, causing pivotting about pivot bolt 54.

The device may then be held stationary to act as a rudder, or may be "pumped" to produce a positive turning force..

Sharp direction changes can be effected by raising the vanes out of the water by pivotting about bolt 60, swivelling the device about bolt 54 to a new angular position then re-submerging the vanes and recommencing "pumping".

The propulsion device 101 as shown in Figs. 9 to 12 is generally similar to the first embodiment, and corresponding elements bear the same reference numerals but raised by 100.

It has an elongate shaft 110 consisting of three tubular sections, a bottom arm 124, a central section 11 Oh and an upper section 11 Oa from which a handle 112 projects laterally. This construction facilitates transport (e.g. in a car boot) and storage. The upper ends of sections 124 and 11 Ob fit into the lower ends of sections 11 Oh and 11 Oa respectively and are lockable together by means of locking screws 111 a and nuts 111 b brazed to the sections 11 Oa and 11 Oh.

The paddle assembly has a steering vane 126 and two pivotable paddle vanes 132 on either side of it. The vanes are of substantially equal size in this example, as is preferred. It should be noted that the steering vane 124 should project laterally from the arm 124 for at least a major fraction of the distance by which the pivotable vanes 1 32 project, and should have an arm which is at least a major fraction of the area of these vanes.

The arm 124 is tubular, and has a longitudinal milled slot 180 in a lower portion. Root portions of the vanes 126, 132 pass into the interior of the arm 124 through the slot 180, and are held there by roll pins 182 which pass through apertures 183 in the vanes' root portions.

The paddle vanes 1 32 are made of resilient plastics material e.g. polypropylene. Each consists of a generally rectangular element having a milled channel 1 84 parallel to and adjacent one long edge, providing a zone of reduced thickness.

When the vanes 132 are held in the slot 1 80 in the arm 124, the channels 184 are outside the arm 124, and face away from the steering vane 126. The main parts of the paddle vanes hinge about their channelled sections, the outward range of hinging being limited by vane back stops provided by the splayed ends 186 of two spring clips 1 88 which are brazed onto the arm 124.

The distal portions 136 of the paddle vanes 132 are out-turned as partial returns.

The dam tube 11 Oh has a saddle 120 brazed on an intermediate region. A cast aluminium intermediate arm 156 is pivotted between the legs of the saddle 120 by means of a bolt 160 and nut 162, giving a horizontal pivot axis for the shaft 110. The inner end of the arm 156 is pivotted on an upright bolt 1 54 which is mounted between lugs 1 52 of a screw clamp 150, by means of which the device 101 is attachable e.g.

to a dinghy's transom.

The bolt 1 54 constitues an upright axis for pivotting of the shaft 11 0. In use it may be somewhat out of vertical depending on the angle of the transom to which the device is fitted. It will be appreciated that the upright axis lies very close to the transom whereas the horizontal axis lies further away from it. The horizontal axis may be at least further out from the transom than the upright axis.

The operation of the device 101 is generally the same as that of the device 1, "pumping" of the propulsion arm 110 causing reciprocation of the paddle assembly 122 through the water whereby the paddle vanes 132 are caused to alternate between closed and open configurations (shown respectively in full and ghost lines in Fig.

10).

The simplified paddle construction of this second embodiment allows paddle vanes to be produced very cheaply and easily, e.g. by injection moulding them of polypropylene, or machining from polypropylene sheet In general, suitable materials for the devices are steel (mild or stainless), cast aluminium, and high density plastics materials.

The two embodiments have been described by way of example only, and many variations are possible. For example, elements of the two embodiments may be combined Both embodiments employ partial returns (36, 136), and this is preferred since it lessens the risk of the vanes sticking in the closed configuration.

However, constructions without partial returns are possible, especially when the paddle vanes are prevented from closing completely together e.g. as in the first embodiment by abutment of vane return 38 on vane front stops 31.

As already briefly mentioned, provision of the vane 26, 126 fast with the upright shaft is advantageous. We have found that it improves the opening of the pivotable vanes 22, 1 32 while turning. It has been found that without the central vane 26, 126 whichever of the pivotable vanes 32, 132 is at the inside of a turn tends not to open properly. The central vane correspondingly enables the pivotable vanes to open properly when there is a side current, which can also interfere with proper opening of the vanes even when the boat is being propelled in a straight line.

Another advantage accruing from the provision of the central vane 26, 126 is that it enables the device to be used to take way off a boat in an analogous manner to "holding water" with oars.

For this, the vanes are raised out of the water by pivoting around the bolt 60, 160 and the device swung around the upright pivot 54, 1 54 until the intermediate arm 56, 1 56 lies generally parallel with the boat's transom and therefore transverse to the direction of movement, whereupon the paddle assembly is re-submerged and the arm 112 held firmly thereby holding the central vane 26, 126 in a submerged position transverse to the direction of forward motion of the boat.

Claims (11)

Claims

1. A boat propulsion and steering device comprising an attachment element having means for releasable attachment to the boat, an elongate shaft attached to the attachment element through pivot means so that the shaft descends therefrom in an upright plane and is pivotable around upright and horizontal axes, and paddle means carried out by a lower end portion of the shaft spaced from said pivot means, so that rocking movement of the shaft about the horizontal axis effects reciprocal motion of the paddle means the paddle means having three vanes projecting laterally therefrom, while in use, are at least partially submerged, one said vane being fast with the shaft and the other two vanes being pivotable about an axis or respective axes extending generally longitudinally of the shaft, these two vanes being pivotable between a first position with them angularly close together, one at either side of the first said vane, and a second position with them turned outwardly to either side so as to be angularly spaced apart, the assembly also having step means for these two vanes to prevent them turning beyond the second position, whereby in use the drag of the water during said reciprocal motion causes the submerged vanes to tend to move between the first and second positions when the direction of said reciprocal motion changes, motion of said assembly with said vanes in said second position providing a propulsive thrust which exceeds the reverse thrust applied by corresponding motion in the reverse direction with the vanes in the first position, and whereby pivoting the shaft around the upright axis enables steering of the boat.

2. A device according to claim 1 having a handle projecting laterally from an upper end region of the shaft towards the attachment element.

3. A device according to claim 2 wherein the shaft is the longer leg of an L-shaped member and the propulsion handle is the shorter leg thereof.

4. A device according to claim 3 wherein the shaft comprises a plurality of sections releasably attachable together.

5. A device according to any one of the preceding claims wherein each vane is composed of sheet plastics material, each has a root portion fast with the shaft and the two pivotable vanes each have a main portion attached to the root portions through a linear zones of reduced thickness forming a hinge around which the main portion can pivot.

6. A device according to claim 5 wherein, in the first position, the main portions of the pivotable vanes lie adjacent and parallel to the vane fast with the shaft, each pivotable vane having a distal margin out-turned from the vane fast with the shaft.

7. A boat propulsion and steering device comprising an attachment element having means for releasable attachment to the boat, an elongate shaft attached to the attachment element through pivot means so that the shaft descends therefrom in an upright plane and is pivotable around upright and horizontal axes, and paddle means carried by a lower end portion of the shaft spaced from said pivot means, so that rocking movement of the shaft about the horizontal axis effects reciprocal motion of the paddle means the paddle means including at least one vane which, in use, is at least partially submerged and which is pivotably attached to the shaft such that, in use, the drag of the water during said reciprocal motion causes the submerged vane to tend to move between first and second positions when the direction of the reciprocal motion changes motion of the said assembly with the vane in its second position providing a propulsive thrust which exceeds the reverse thrust applied by corresponding motion in the reverse direction with the vane in its first position, the shaft being attached to the attachment element through an intermediate arm, to which the shaft is pivotally connected by a horizontal pivot providing the said horizontal axis, the intermediate arm being pivotally connected to the attachment element by an upright pivot providing the said upright pivot axis, whereby in use the upright axis is closer to the boat than the horizontal axis, the shaft being freely pivotable around both axes simultaneously and having a handle projecting laterally from it above the pivots towards the attachment element.

8. A boat propulsion and steering device comprising an attachment element having means for releasable attachment to the boat, an elongate shaft attached to the attachment element through pivot means so that the shaft descends therefrom in an upright plane and is pivotable around upright and horizontal axes, and paddle means carried by a lower end portion of the shaft spaced from said pivot means, so that rocking movement of the shaft about the horizontal axis effects reciprocal motion of the paddle means the paddle means including at least one vane which, in use, is at least partially submerged, and which is pivotally attached to the shaft such that, in use, the drag of the water during said reciprocal motion causes the submerged vane to tend to move between first and second positions when the direction of the reciprocal motion changes, motion of the said assembly with the vane in its second position providing a propulsive thrust which exceeds the reverse thrust applied by corresponding motion in the reverse direction with the vane in its first position, the vane being of sheet plastics material and having a root portion fast with the shaft and a main portion attached to the root portion through a linear zone of reduced thickness forming a hinge around which the main portion can pivot.

9. A device according to claim 5, claim 6 or claim 9 wherein the shaft is hollow and the or each root portion extends into the shaft through an axial slit and is secured by pins extending transversely through the shaft and root portion(s).

10. A boat propulsion and steering device substantially as herein described with reference to Figs. 1 to 6 of the drawings.

11. A boat propulsion and steering device substantially as herein described with reference to Figs. 7 to 10 of the drawings.