1980-05-16
1982-10-05
Blix, Trygve M.
Ships
Keels
Rocking
B63B 4100
Patent
active
043523358
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to keels, and in particular to keels for yachts.
Conventional yacht keels comprise a single downwardly extending fin which is symmetrical with respect to a vertical longitudinal section through the yacht hull when the hull is not heeling. Such keels depend upon their mass and depth to counteract wind forces on the yacht sails which tend to cause the yacht to heel. They are also effective to counteract wind forces tending to push the hull sideways through the water. To provide good performance, single fin keels must be heavy and must extend to a considerable depth, greatly increasing the draught of the yacht.
A major problem with the known single fin keels is that when it is desired to dry out a fixed keel yacht hull, considerable efforts must be made to prop the hull and prevent it toppling over as would otherwise obviously occur once the single fin keel touches bottom. This is a serious problem in shallow tidal bays and often makes the use of expensive purpose built moorings essential.
It is known to provide a yacht hull with two spaced apart fin keels which serve as supports for the hull when it is dried out. Unfortunately such keels are relatively shallow and cannot provide a sailing performance comparable with that obtainable from a single keel of conventional design. In addition, although they can provide support for a dried out hull they cannot accommodate sloping surfaces such as are often found on sandbanks for example.
It is an object of the present invention to provide a keel which obviates or mitigates the above problems by providing a double fin keel the position of which can be altered to obtain good performance and which can also serve as a stable base for a dried out hull.
According to the present invention, there is provided a keel comprising two mutually inclined fins mounted on a hull, characterised in that the fins are movable together relative to the hull, and means are provided for releasably locking the fins in any one of a plurality of positions relative to the hull. Preferably the keel comprises a central hub pivotally supported by the hull, the fins being connected to the hub.
In use, the fins can be moved as desired by releasing the locking means, maneuvering the hull such that it heels to a desired angle with the keel hanging freely, and then locking the keel to the hull. The hull then effectively has an asymmetrical fixed keel which can give improved performance by restraining the heeling of the hull. When a change in direction of travel relative to the wind direction is required, the position of the keel can be reset to provide the asymmetrical keel configuration best suited to the new direction of travel.
As an alternative to relying solely on heeling of the hull to obtain desired hull/keel relative positions, means may be provided to move the keel relative to the hull. These means could be hydraulic for example.
The fins may have any desired configuration, but preferably their ends are shaped to define flat surfaces which are substantially horizontal when the keel is hanging freely. These flat surfaces provide a firm support for the hull even on soft surfaces. Furthermore, the fins may have an airfoil section such that when driven through the water hydrodynamic forces are generated to provide additional resistance to heeling.
The hub preferably comprises two shafts pivotally received in end caps secured to the hull. The locking means may comprise a releasable one way clutch ratchet device provided in each end cap, the ratchet devices being operative when engaged to prevent rotation of the hub relative to the end caps, and release of both ratchet devices allowing the hub to pivot freely on the shafts.
When it is desired to dry out the hull, the locking means are released. As the tide recedes, if at first one of the fins touches the bottom, the fins pivot until the second fin touches the bottom, and then the weight of the hull is progressively taken up by the keel. Means are provided to form the keel and hull together as a result of the weight of t
REFERENCES:
patent: 3972300 (1976-08-01), Adamski
patent: 4044703 (1977-08-01), Kurtz
Blix Trygve M.
Brahan Thomas J.
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