1. Field of the Invention
This invention relates to marine craft and particularly sailing vessels having keel structure for enhancing not only the stability of the boat under varying wind conditions but also to control the extent of heel-over in strong cross winds.
In its preferred embodiment, the keel structure is of the winged type and is divided into two separate mirror image sections that are pivotally supported beneath the vessel's hull for independent swinging movement transversely of the boat.
2. Description of the Prior Art
Sailboats have long been provided with relatively large, heavy keels which depend from the central lower section of the hull and provide ballast against heeling. The types of keels which have been employed vary widely. Many sailboats have keels that can be raised in some manner to decrease the draft of the vessel in shallow water conditions. Smaller boats, for example, have been provided with vertically moveable dagger boards. Boats of intermediate size often are provided with swingable center boards that can be raised by pulling upwardly on one end of the keel member. Larger sailing boats generally have fixed keels because it is usually impractical to raise a mass weighing many hundreds to several thousand pounds. Keels which extend below the bottom of the hull several feet, however, severely limit shallow water operation of the boat.
Efforts have been made to increase the effectiveness of keel structure without adversely effecting the overall speed and maneuverability of the boat, but have not met with great success, primarily because of cost considerations. In recent years, the functionality of keel structure for sailboats has been increased by adding outwardly projecting "wings" which serve to stabilize the vessel and further minimize heel-over in strong cross winds. In fact, by decreasing the degree of heel-over, a winged keel boat may actually go somewhat faster than its non-winged counterpart under the same cross wind conditions.
Shallow draft operation is still limited even with wing keels, and it is not possible to provide optimum compensation against heel over for different wind conditions. Various suggestions for mounting a keel member on the bottom of the boat hull so that it will move laterally have not found widespread usage because of the difficulty of swinging a relatively heavy weight, and the complexity of the mechanism required to move a heavy keel through small increments and within a useful time span.
Many prior laterally movably keel designs have employed a simple fin element which is swingable about a fore and aft axis adjacent the keel board of the boat. Exemplary in this respect, is the pivoted center fin of the boat as illustrated in U.S. Pat. No. 2,553,372. A somewhat more complicated pivotal fin which is also said to serve as a hydrofoil is shown and described in U.S. Pat. No. 3,324,815.
Efforts have even been made to solve the heel-over problem by swinging the mast laterally along with the keel structure to maintain the keel and mast in general symmetrical relationship. Exemplary in this respect are U.S. Pat. Nos. 3,903,827, 3,972,300, 4,094,263 and 4,117,797. However, moving the mast as well as the keel adds to the complexity of the operating mechanism and increases the initial cost of the boat as well as maintenance expenses required to keep the components fully operational.