Marine propulsion – Screw propeller – Having means to control flow around propeller
Reexamination Certificate
2000-11-20
2002-06-18
Avila, Stephen (Department: 3617)
Marine propulsion
Screw propeller
Having means to control flow around propeller
C114S288000
Reexamination Certificate
active
06406341
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to recreational boats used in the sport of fishing and particularly to shallow draft boats adapted to be powered by outboard motors.
Fishing is a popular sport throughout the world. Fishing is often performed from boats near the shore or in other areas having shallows which attract fish. The boats used in pursuing this activity must perform several tasks in which various attributes are important.
The boat must get fishermen and fisherwomen to the place they wish to fish quickly and comfortably. This sometimes includes long passages over open water in which waves may be encountered. Stability and speed becomes important. In a small boat (about 16-22 feet), speed is obtained by causing the boat to ride on top of the water in what is often referred to as “planing” rather than in the water in the displacement mode. Adequate power and a proper hull shape are necessary for planing. Once at the location of fishing, shallow draft characteristics become more important. Reefs, sandbars, shallow flats, and various obstructions are common near the shore, in smaller lakes and rivers. A boat with a shallow draft may ride over a particular obstruction when a boat with a deeper draft will hit it and possibly suffer damage.
With fishing boats, a shallow draft is important in two different modes of operation. When the outboard motor is in a down position providing power to the boat, the outboard motor is often the lowest portion of the boat. Thus, the shallow draft with the outboard motor down is important to protect the motor from damage. When one is fishing, one often shuts the motor off and tilts the outboard motor into the up position. In this position, the outboard motor is entirely out of the water and the draft of the boat is now determined by the most downwardly extending portion on the boat hull. This is important to fishermen and fisherwomen as the boat may drift or is sometimes polled to move it quietly through shallow areas. A shallow draft boat can quietly pass over obstructions which would stop a deeper draft boat.
Obtaining good performance characteristics and good shallow draft characteristics both with the motor down and motor up is difficult. Design elements which help in one performance or draft area often appear to hurt in another performance or draft area. Thus, conventionally, high speed planing can be traditionally addressed with a flat bottom and the propeller portion of the outboard motor extending well below the flat bottom. Additionally, the hull must be designed and constructed in a manner which allows operation in rough sea conditions with waves coming from the bow, the stem or either side. Rough sea operation is sometimes addressed with a deep V hull shape. These design considerations sometimes increase the draft of a boat.
SUMMARY OF THE INVENTION
The present invention addresses high speed performance, low speed performance, motor down draft, and motor up draft concerns by providing a short tunnel in the hull allowing one to mount an outboard motor higher with respect to the bottom of the boat while still maintaining good performance and draft characteristics.
In accordance with the present invention, a boat hull is provided having a short tunnel in the stern of the boat allowing water to flow through the tunnel past the transom where it is acted upon by the propeller of an outboard motor which is mounted higher than in a conventional boat.
Still further in accordance with the invention, the tunnel is no longer than twenty percent (20%) of the overall length of the boat.
Yet further in accordance with the invention, a tunnel is provided in a boat hull having a recess at its forward end defined by a closed bottom wall and an open back wall, the recess communicating with a vent tube having its other end open above the water line of the boat hull.
Yet further in accordance with the invention, a boat hull is provided having a rear planing surface and a tunnel near the stem, the tunnel having a recess at its forward end and a vent tube connecting the recess to a port in the transom of the boat above the water line.
Yet further in accordance with the present invention, a short tunnel is provided at the stem of the boat having a planing surface, the tunnel being defined by planar walls.
The principal object of the present invention is to provide a boat with good operating characteristics both at low and high speed and with a shallow draft in both the motor down and motor up configurations.
It is another object of the present invention to provide a boat on which an outboard motor can be mounted higher in relation to the planing surface of the boat whereby the boat may be operated in relatively shallow water when the boat is in a plane configuration.
It is still another object of the present invention to provide a boat with a tunnel allowing the outboard motor to be higher than is conventional but still having good high speed characteristics both for traveling in a straight line and when turning, and good characteristics when operating in rough water both in oncoming and following seas.
It is still another object of the present invention to provide a boat having planar surfaces in the stem including planar surfaces in a central tunnel whereby the boat is more stable and less tippy than other designs.
It is yet another object of the present invention to provide a boat with a tunnel having a minimal volume whereby the buoyance lost at the stem caused by the tunnel is minimal.
It is yet another object of the present invention to provide a boat having a tunnel vent communicating with the forward portion of the tunnel allowing improved water flow through the tunnel and efficient operation of an outboard motor positioned at the rear of the tunnel.
It is another object of the present invention to provide a boat having a tunnel allowing improved operating characteristics and draft characteristics which is simple and inexpensive to manufacture and simple and inexpensive to maintain.
These and other objects and advantages of the present invention will become apparent from the following detailed description of a preferred embodiment thereof and from the accompanying drawings.
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Avila Stephen
Hell's Bay Boat Works Co.
Vickers Daniels & Young
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