Boat Hull With Flow Chamber

1. Field of the Invention

The present invention relates to boat hulls, and more particularly to a boat hull having a two-stage flow chamber in which the driving propeller is disposed.

2. Description of the Prior Art

It is well known in the prior art to provide a tunnel or propeller pocket in the hull of a boat to provide additional clearance between the bottom of the hull and the bottom of the waterway. In addition, it has been suggested that such tunnels tend to improve the efficiency of the propulsion system. Early patents, such as U.S. Pat. No. 128,407, have disclosed tunnels running the entire length of the hull which effectively forms a double hull. The use of pockets or cavities at the stern of the boat in which the propeller is mounted had been taught by the following U.S. Pat. Nos. 111,462; 3,515,087; 3,611,973; 4,371,350; and 4,383,828.

Generally, these patents teach a cavity or pocket which may extend for about one-third the length of the hull at the stern. A typical design is taught by the '087 and '973 patents both issued to Stuart. Stuart shows a U-shaped tunnel running aft to the amidship line of the hull toward the stern. The tunnel smoothly increases in size and diameter as it runs aft and is opened fully at the stern. Stuart claims an advantage in that the slipstream of water in the tunnel and aft of the propeller results in a jet-like stream of water producing a reaction drive similar to a jet engine.

I have found, however, that the Stuart design having a U-shaped cavity has a serious problem in that the water received by the propeller has been foiled off of the hull causing turbulence and cavitation. The result is poor performance of the propeller. Thus, there is a need for a hull tunnel design to provide the advantages of the low draft, yet which will not sacrifice efficiency due to turbulence and cavitation in the tunnel. I refer to such a design as a "flow chamber" since water will flow with a minimum of turbulence.

My improved flow chamber for a boat hull overcomes the problems in the prior art and provides efficient propulsion with a low draft. A two stage flow chamber is provided starting approximately at the midpoint of the keel. The flow chamber starts at a point for which the hull is still in the water when the boat is planing. The first section of the flow chamber has an initial V-shape with the same angle as the hull and increases in cross-sectional area, at a shallow angle flattening out toward the stern of the boat. The second section of the flow chamber begins at the aft end of the first section, curving upward at a larger angle and curving downward slightly at the stern. A .[.keelson.]. keel is provided in the first section of the flow chamber which terminates at the beginning of the aft section of the flow chamber. I have determined that the aft flow chamber portion is most efficient when an inverted V-design is used rather than the conventional U-design of the prior art. The propeller is disposed in the tunnel with standard design clearance to the hull from the tip of the outside propeller. The propeller shaft line is splayed to port approximately five inches from the center line of the keel utilizing a righthand propeller. Splaying increases the propeller torque and efficiency and also permits backing of the boat in a straight line.

With the above-described flow chamber design, water enters the forward section of the flow chamber and is delivered to the aft section on a flat plane to prevent turbulence and cavitation. The water exits from the tunnel in a smooth laminar flow thereby reducing drag and loss of propulsion.

A rudder may be mounted along the keel line aft of the propeller in a conventional fashion. If desired, a flat metal skeg may be disposed running from the aft end of the .[.keelson.]. keel to the bottom of the rudder post for protection of the propeller, propeller strut and rudder.

Therefore, it is a principal object of my invention to provide a flow chamber design for a hull which is relatively free from turbulence and cavitation.

Another object of my invention is to provide a flow chamber hull for a boat having a shallow forward section and a deeper aft section with the forward section serving to deliver water in a flat plane to the aft section.

It is yet another object of my invention to provide a flow chamber hull for a boat in which the water flows smoothly through the tunnel with minimum turbulence and cavitation of the propeller.

It is still another object of my invention to provide a boat hull having a flow chamber for essentially enclosing the propeller which is splayed in the tunnel.

It is a further object of my invention to provide a two-stage flow chamber beginning approximately amidship in which the aft section of the tunnel is of a V-design.

These and other objects and advantages of my invention will become apparent from the following detailed description when read in conjunction with the drawings.

FIG. 1 is a side view of a boat hull in which my two-stage flow chamber is shown by dashed lines;

FIG. 2 is a partial cross-sectional view of the hull of FIG. 1 showing details of the flow chamber design;

FIG. 3 is a partial view of the transom of the boat of FIG. 1 showing in more detail the shape of the flow chamber;

FIG. 4 is a partial cross-sectional view of the hull of FIG. 1 showing a propeller, rudder, and skeg installation;

FIG. 5 is a stern view of the hull of FIG. 4 showing the transom, rudder, and propeller orientation;

FIG. 6 is a bottom view of the hull of FIG. 1 showing the installation of the engine, propeller shaft, and propeller to illustrate the splaying of the shaft;

FIG. 7 is a cross-sectional view of the first stage tunnel along the plane 7--7 of FIG. 2;

FIG. 8 is a cross-sectional view of the first stage tunnel along the plane 8--8 of FIG. 2;

FIG. 9 is a cross-sectional view of the first stage tunnel along the plane 9--9 of FIG. 2; and

FIG. 10 is a stern view of the hull of an alternative embodiment of the invention having twin flow chambers.

Referring first to FIG. 1, a side view of a hull 10 in accordance with the invention is shown. Hull 10 has a conventional V-bottom 20 and a stern transom 12. As shown by the dashed lines, a two-stage flow chamber 14, 16, is provided starting approximately amidship and extending to the transom 12.

Details of the flow chamber are more clearly seen in FIGS. 2 and 3. In FIG. 2, a cross-section approximately along the keel line of hull 10 is shown. The forward or first stage flow chamber 14 may be observed to curve upward at a relatively shallow angle. A .[.keelson.]. keel 15 runs approximately the length of forward flow chamber 14. At the termination of forward flow chamber 14, the aft flow chamber 16 begins which curves upward at a sharper angle than the forward flow chamber 14 and curves downward slightly at the point of connection with transom 12 as indicated by the section of surface 17. The aft flow chamber 16 comprises two upper surfaces 17 forming a shallow inverted V and two side surfaces 18, joining surfaces 17 at an obtuse angle as indicated in FIG. 3 and connecting with the hull bottom 20. The shape of .[.keelson.]. keel 15 is also apparent from the view in FIG. 3.

The cross-sectional shape of forward flow chamber 14 is important to ensure a laminar flow of water into aft flow chamber 16. Referring to FIGS. 7-9, this shape is illustrated. Flow chamber 14 starts as a V parallel with the hull bottom (see FIG. 7) and gradually decreases in angle toward the aft flow chamber 16. As noted from FIG. 8, the angle of the V along plane 8--8 of FIG. 2 is approaching 180.degree.. At the end of forward flow chamber and at the beginning of aft flow chamber 16, the angle is 180.degree., as seen in FIG. 9.

Advantageously, water is delivered to aft flow chamber 12 smoothly, without turbulence or cavitation.

Turning now to FIGS. 4 and 5, the installation of the rudder and propeller is shown. As will be noted from FIG. 4, propeller shaft 22 enters the hull near the forward end of aft flow chamber 17 and is connected to a power plant not shown. A rudder 30 is illustrated mounted just aft of propeller 26. A flat metal skeg may be connected from the aft end of .[.keelson.]. keel 15 to propeller strut 24 and rudder post 32. The skeg 28 serves to protect these elements and to provide additional rigidity. As best seen in the bottom view of hull 10 of FIG. 6, power plant 23 and propeller shaft 22 are splayed to port by an angle.

Having shown the construction of my improved hull and flow chamber of the invention, the operation thereof will not be described. When the boat is underway, the V-shaped bottom 20 tends to cause the boat to plane. The hull design 10 is such that the forward point where forward flow chamber 16 is faired into the keel area 20 remains in the water. The flow of water over the surfaces of forward flow chamber 14 is relatively flat and is thus delivered to aft flow chamber 17 without turbulence. The forward motion of the boat and the action of propeller 26 will be to guide the water into the flow chamber 16 as a clean, laminar flow and, therefore, the propeller finds a solid stream of water against which to work. Cavitation is thus prevented and very little, if any, slippage will normally occur. Therefore, the maximum effectiveness of the propeller 26 is achieved. The slight downward curve of surface 17 (see FIG. 2) at the stern prevents the usual "rooster tail" that forms from a tunnel hull at high speeds, reducing the drag which would otherwise result.

An alternative embodiment of may invention is shown in the stern view of a hull 35 in FIG. 7. As may be noted, the alternative design is for use with twin propeller drives. A pair of flow chambers 40 is disposed with one on either side of the keel. Flow chambers 40 are otherwise identical to flow chambers 14 and 16 previously described.

It is to be understood that the illustrations shown above are for exemplary purposes only and various changes may be made to my design by those of skill and art without departing from the spirit and scope of my invention.