Ships – Watercraft with means used in providing sailpower
Reexamination Certificate
2000-09-18
2002-02-26
Avila, Stephen (Department: 3617)
Ships
Watercraft with means used in providing sailpower
C114S132000
Reexamination Certificate
active
06349659
ABSTRACT:
FIELD OF THE INVENTION
This application relates to under-water appendages for water-borne sailing vessels with heavy ballast bulbs as required for International Americas Cup Class (IACC) Yachts and in particular to rotatable fin keels which produce an asymmetric effect when tacking for generating enhanced hydrodynamic forces to increase the Velocity Made Good (VMG) of the sailing vessel so as to quicken its passage to a windward destination.
DEFINITIONS
In the description, the following terms have the following meanings: a “canoe body” is the hull of the vessel up to the sheer line excluding appendages; an “appendage” means an underwater protrusion from the underside of the canoe body such as a keel, fin, wing, dagger board, centerboard keel, rudder, etc.; “VMG” (Velocity Made Good) means the velocity of a tacking or reaching sailing vessel towards its windward destination; “leeward drift” means the drift to leeward of a tacking or reaching vessel caused by the wind; “appendage lift” means a force generated by a submerged moving appendage in the direction to counter the leeward drift by the wind of a tacking or reaching sailing vessel; “drag” means the resistance of water passing over any submerged surface; “appendage or keel drag” means the resistance of water passing over wetted surfaces of a keel or an appendage; “water track” is the direction of the body of water moving towards and impinging upon a canoe body; “crabwise motion” of a canoe body means that it is moving into the water track with its longitudinal axis at an angle thereto; “crabwise hull drag” means the additional drag of the canoe body when it has crabwise motion; “making leeway” means that the keel or appendage is producing an asymmetrical effect to generate a hydrodynamic force vector having a component to counter the leeward drift; “angle of incidence or “leeway angle” means the angle between the longitudinal centerline of a fin or appendage and the water track; an “asymmetric effect” means the creation of a hydrodynamic force when the water track is split into two paths which are reunited, one path of the water flow being longer than the other path of the water flow; a “symmetrical appendage” means an appendage having two opposite chord surfaces each with the same camber; an “asymmetrical appendage” means an appendage having two opposite chord surfaces of different cambers; “favorable wind shift” occurs when the apparent wind angle increases; and “Lift/Drag Ratio” of an means its the quantity of lift per unit of drag produced by a moving submerged appendage, the goal being to generate maximum lift with minimum drag.
Velocity Made Good (VMG) of a tacking or reaching vessel is the component of the sailing yacht's forward velocity vector which is directed towards the windward mark.
Skippers of racing yachts desire to win races and Skippers of cruising sailboats desire to shorten the time on tacking and reaching passages. Such goals can be favorably influenced with appendage design.
BRIEF SUMMARY OF THE INVENTION
In exemplary embodiments of the invention, an appendage unit includes one or more thin fins carrying a heavy ballast which is supported in a manner to permit rotation of the fin(s) and the heavy ballast about an axis perpendicular to the canoe body's waterline plane. The rotatable appendage unit is strongly fitted to its hull so as to avoid fin(s) breakage failure by bending moments thereon in heavy seas. The fin or fins are symmetrical in shape for generating a hydrodynamic force vector by water passing there over when the fin(s) are positioned at a selective leeway angle to the on-rushing water track.
In other exemplary embodiments, an articulated appendage unit has two components, one of which is rotatable to form either a symmetrical or asymmetrical appendage of selected shape, and one of which supports a heavy ballast bulb.
In exemplary methods of the invention to increase the forward velocity of a tacking sailing vessel, steps include eliminating the extra drag of a tacking canoe body which occurs when it is not arrowing into the water track and when the rotatable keel and ballast member are making leeway for increasing the canoe body forward velocity by reducing the leeward drift.
In another exemplary method of the invention to increase the forward velocity of a tacking sailing vessel, steps include tacking into the water track with a fin keel and ballast at a selected angle of incidence thereto, rotating the canoe body directly into the water track while maintaining the fin keel and ballast at the same selected angle of incidence relative to the water track and selectively adjusting the sails to take advantage of the more favorable angle of the apparent wind to the sails when the canoe body is rotated away from the apparent wind.
REFERENCES:
patent: 3990384 (1976-11-01), Reynolds, III
patent: 4920906 (1990-05-01), Collins
patent: 5003904 (1991-04-01), Unger et al.
patent: 5313905 (1994-05-01), Calderon
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