Marine propulsion – Oar or paddle
Patent
1990-12-04
1993-01-26
Peters, Jr., Joseph F.
Marine propulsion
Oar or paddle
440 13, 440 17, 440 21, B63H 130
Patent
active
051818728
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a manually operable water propulsion device, which is especially suitable for use as an emergency auxiliary means of propelling a small boat.
BACKGROUND TO THE INVENTION
It can be extremely important to have as an alternative some means of manual propulsion for watercraft in the event of motor failure or absence of wind. In the past various types of oars and paddles have served to propel boats through the water in such circumstances. However, such conventional paddles and oars are ineffective in propelling larger pleasure craft, such as motor launches, cabin cruisers and sailing yachts.
In many cases, there is simply no place on such craft from which a sailor can effectively use a paddle or oars. The maximum propulsive force that can be obtained with a conventional paddle is relatively minor compared to the forces resisting propulsion arising from water pressure against the hull, wind, inertia and so forth. Furthermore, it is very difficult in such craft to direct the little propulsive force that can be obtained with a paddle in a suitable direction to propel the craft in a direct course. Typically, paddling causes the boat to rotate, rather than to move forwards.
THE PRIOR ART
Previously, some attempts have been made to design a water propulsion device that consists of a scoop or envelope at the end of a handle. The device is thrust longitudinally from the rear of the boat to provide forward movement. Patent publications such as U.S. Pat. No. 3,800,734 WHANG, U.S. Pat. No. 4,098,219 TESAN, and U.S. Pat. No. 4,578,038 LENTAN provide examples. WHANG shows an umbrella-like design, with webbed ribs. The problems with designs like this are that the device is not durable enough, and is therefore unsafe, for the conditions to which it is exposed in the boating environment. Furthermore, the "umbrella" takes too long to open: a sailor can only exert thrust over a limited length of stroke, i.e. up to approximately 1.5 or 2 meters, and it may well take almost all of that stroke for an umbrella-like device to fully open out.
GENERAL DESCRIPTION OF THE INVENTION
The invention provides a propulsion device which comprises a scoop attached to a handle. The scoop is collapsible, in that the scoop comprises two panels which are hinged together in such a manner as to allow the panels to close together or spread apart. In use, preferably the axis of the hinge lies in the horizontal plain, and perpendicular to the direction of thrust.
The scoop is so arranged that, when the scoop is thrust away from the boat, hydrodynamic forces cause the two panels to spread apart; and when the scoop is drawn towards the boat, the hydrodynamic forces cause the two panels to close together. The panels have substantial area, so that once the panels start to spread, water action quickly forces them wide apart. This may be compared with an umbrella-like device, in which, because the device opens from a point, rather than along a hinge-line, only a small increase in area takes place as the umbrella starts to open. This is why so much of the stroke is wasted just in opening the scoop out, when the scoop is based on an umbrella construction.
The device of the invention is therefore able to open quickly to a configuration in which it presents a large area to the water, for powerful thrusting, and yet the device is able also to collapse quickly, which keeps down resistance on the return stroke. The fact that the scoop is collapsible means also that the propulsion device of the invention can be easily stored on the boat during periods of non-use.
One requirement of a manual propulsion device, if it is to be successful, is that the device should be easy to control. When the device is thrust into the water, there should be no tendency for the device to plunge below the surface, nor to rise up out of the water, nor to slip sideways. Ideally, the device should be self-guiding, so that the scoop remains just below the surface, and has no tendency to move to right or left. It is recognised, in the invention, that such forc
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Brahan Thomas J.
Peters Jr. Joseph F.
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