Ships – Displacement-type hull
Reexamination Certificate
2000-05-31
2001-12-04
Basinger, Sherman (Department: 3617)
Ships
Displacement-type hull
C114S138000, C114S140000, C114S141000
Reexamination Certificate
active
06325009
ABSTRACT:
TECHNICAL FIELD
The invention relates generally to an improved sailboat design for sailing in shallow water and, more specifically to a larger-style sailboat which can sail windward in about three feet of water or less.
BACKGROUND OF RELATED ART
The ability to control side slipping or leeway is a major factor in allowing a boat to sail windward, i.e. into the general direction of the wind, a necessary feature in any sailboat. In order to prevent a sailboat from slipping side ways as the result of wind pressure on the sail being transferred to the hull, appendages are provided which extend below the hull. Thus, fixed keels, as well as centerboards, lee boards and dagger boards have been used to prevent such side slipping and to allow sailboats to sail generally into the wind. Centerboards, lee boards and dagger boards are used in place of fixed keels in order to allow a sailboat to both sail and be beached in shallow water. Such boards are generally thin and may be retracted (i.e. raised) and extended (i.e. lowered), as required, so as to reduce and increase the draft or distance of the board below the water line, respectively. Generally, the board is raised when the wind is about aft (i.e., rear) of the mid-ship point, and generally is completely raised when sailing before the wind and when pulling the boat ashore.
Although acceptable for beaching sailboats, retractable boards do not allow a sailboat to sail well in shallow water because the boards must be raised to reduce draft and performance of the boat in sailing toward the wind suffers. For example, a 30 foot catamaran sailboat with a centerboard has a draft of only about 18 inches with the centerboard fully retracted, but has a draft of about 4 feet with the board fully lowered. In order to effectively sail to windward, the centerboard of the catamaran must be fully lowered. With the board fully raised to the 18 inch draft in shallow water, the boat will slip side ways and be largely uncontrollable when sailing windward. Thus, although such boats can be powered by a motor or the like in shallow water and thereafter beached, they cannot sail effectively in shallow water.
In order to achieve performance type sailing, especially to windward, relatively deep fixed keels or deep movable appendages need to be utilized. However, such deep keels and appendages do not allow the boat to sail in shallow or shoal water. When the water becomes too shallow, a sailboat with a fixed keel will go aground and fall over on it's side if there is not enough water to support the hull. Reduced depth, fixed keel boats have been tried in the art, however, such boats cannot be beached or grounded without problem. In addition, sailing performance characteristics of reduced depth, fixed keels are adversely affected because the shape of the keel must be compromised to reduce draft. To improve the sailing performance of such reduced depth keels, small horizontal wings have been added to the bottoms of the keels. Even with the reduced depth keels having wings, the draft is still fixed at about 4.5 feet of draft. Another approach has been to include an appendage
111
which is extendable from the bottom
113
of a keel
118
as shown in FIG.
15
. However, to sail in shallow water the appendage must be retracted and, again, sailing performance (especially to windward) is adversely affected. To date, there are no performance sailboats, monohulls or multihull boats over 25 feet in length which provide true windward sailing in about 3 feet of water or less. Since over 75% of the inshore, cruising waters on the Atlantic and Gulf Coasts are 3 feet or less in depth, such waters are only accessible by sailboats over 25 feet which are under power and with appendages raised.
Another problem encountered with such reduced depth, fixed keel boats is the provision of headroom beneath the deck in the cabin. In order to create a shallow hull and keel, the area between the waterline of the boat and the deck line (also known as the freeboard) must be raised, as must the trunk cabin height in order to obtain standing headroom (i.e., 6′4″) in the cabin interior. It has been found that raising the freeboard and the deck height negatively affects the center of gravity of the boat which, in turn, adversely affects sailing performance.
Accordingly, there is needed in the art a sailboat capable of sailing to windward in water which is relatively shallow (i.e. about 3 feet or less), which does not compromise sailing performance, and which can be readily beached.
SUMMARY
One object of the present invention is to provide a sailboat capable of sailing to windward in water which is relatively shallow, without adversely compromising sailing performance.
In accordance with one aspect, there is provided a sailboat having a novel hull shape along with a fixed, shallow keel, dual rudders, and retractable, shallow dagger boards. The combination of these features allows the boat to achieve performance sailing at all points of wind, and in both deep and shallow water. The hull preferably has a hydrodynamic shape which provides lift and lateral resistance to the hull when sailing. In addition, the shape of the hull is turned inward and upward, so as to form a modified “U” shape. By turning the hull inward and upward, a pronounced hollow or convex configuration in the bottom portion of the hull is formed below the waterline. The wetted surface area of the hull (i.e. surface area of the boat immersed in water) remains substantially the same for the present embodiment as for a conventional sailboat of the same size. The shape of the hull also preferably flattens out toward the aft, or rear of the boat. The preferred hull shape creates lateral and directional stability on all points of sail while also allowing for sufficient room (including headroom) below the deck in the cabin of the boat.
In addition to the shape of the hull, the boat may preferably be provided with a long, shallow keel which allows the boat to sail in shallow water. The draft of the keel is preferably related to the length of the hull measured along the waterline and is preferably about ⅓ the total draft of the boat. In a preferred embodiment, there is 1 inch of total draft (hull+keel+lowered appendages) for every 1 foot of waterline. For example, a 30 foot length boat (measured along the waterline stern to bow) would preferably have a 30 inch total draft, with the draft of the keel being about 10 inches. In one embodiment, the keel may also preferably taper from the bottom of the boat inward, and include a flat bottom to facilitate beaching.
The boat may also preferably include a set of retractable dagger boards supported by the hull and located on opposite sides of the keel. A dagger board may be extended on the leeward side of the boat when the wind exceeds about 15 knots, in order to reduce side slippage or leeway. In a preferred embodiment, the draft of the dagger boards does not exceed that of the shallow keel so as to not increase the overall draft. Dual rudders may also be provided on the stern to help prevent leeway. Again, the rudders should preferably be sized so as to not increase the overall draft of the sailboat.
The shape of the hull, dual rudders, and use of dagger boards allows for performance sailing, while minimizing the draft of the boat by utilizing a long, shallow keel (and shallow dagger boards, as needed) allows the boat to be sailed in shallow water and beached.
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Carter George J.
Schulz Walter A.
Basinger Sherman
Salter & Michaelson
Shoalsailer, LLC
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