Ships – Sail or control means therefor – Having airflow control device for sail
Reexamination Certificate
1998-12-30
2001-01-09
Avila, Stephen (Department: 3617)
Ships
Sail or control means therefor
Having airflow control device for sail
C114S102220
Reexamination Certificate
active
06170421
ABSTRACT:
This invention relates to apparatus used in the construction of a sail envelope for use on various types of sailing craft, including wind surfers. The invention finds a particular application in relation to sails which are made in or can be adjusted to adapt to the form of an aerofoil. Such sails are typically provided with two spaced, external sail surfaces that extend from a sail mast.
The construction of sails of such type has been wrought with difficulty. Design requirements are demanding as the sail must be lightweight but able to withstand high or gusty winds, and substantial impact loads in the event of collision or the like.
One particular problem that must be overcome is the design of the junction or interaction of the sail and the mast. The problem is more challenging when the external sail surfaces may alternate between serving as a leeward and a windward surface. Where the sail functions in this manner, the aerofoil or sail envelope ideally changes in cross-section, and thus the junction or interaction between the sail envelope and the mast should allow for this requirement.
It is felt that such junction designs have heretofore been less than satisfactory and there is a need to provide a better design of junction between a sail mast and a sail envelope for use on sailing craft.
For example, one design suggested in the past has involved positioning the mast externally of the sail envelope. However, this is undesirable as the mast, being forward of the sail envelope, mitigates the advantage of the aerofoil design.
In U.S. Pat. No. 4,699,073 there is disclosed a double surface sail wherein the sail cloth directly contacts and wraps around the mast. The cloth is able to slide around the mast to enable it to adopt alternative aerofoil profiles. The Patent teaches the use of a tubular or conventional mast, meaning that the leading edge of the sail maintains a constant circular convex shape, regardless of the aerofoil adopted by the sail envelope. In the present invention it is recognised that it would be advantageous to provide a junction between the sail envelope and the mast which enables the leading edge of the sail to change shape in a manner which optimises or at least improves the aerofoil efficiency.
However, it is recognised that it is not entirely satisfactory to profile the mast in a more aerodynamic shape, as to benefit from doing so would require the mast to rotate around its longitudinal axis in accordance with the relative direction of the wind to the craft. This would necessitate undue torsion or strain on the mast or require a complex mounting mechanism between the mast and the board of the craft.
According to the present invention there is provided a profile for use in a sail, the sail having a mast and two spaced external sail surfaces, wherein, in use, the profile is free to rotate relative to the longitudinal axis of the mast and has an outer edge upon which the inner sides of the external sail surfaces bear.
Typically the profile contacts or abuts against the mast. Preferably, the outer edge of the profile is in the form of a symmetrical aerofoil and comprises two moulded plastic components hinged together at a pivot or joint positioned forward of the mast, in use. The joint, in a preferred design, may be adapted to be dismantled without damaging the components or profile generally.
Preferably, each component is of substantially identical design and dimension.
The outer edge of the profile may be, desirably, flanged to provide greater support to the inside faces of the external sail surfaces.
The profile preferably includes means for making a mechanical connection to sail battens.
Also according to the invention there is provided a sail having a mast or spar and two spaced external surfaces capable of adopting the shape of an aerofoil, the sail further comprising a plurality of profiles as described herein.
Yet further, according to the present invention there is provided a sail having a mast or spar and two spaced external sail surfaces forming a sail envelope, wherein the mast or spar is positioned substantially within the sail envelope, and wherein the sail surfaces are held away from contact from the mast or spar by one or more profiles, wherein the profiles are shaped in the form of an aerofoil.
Preferably, the one or more profiles are free to rotate relative to the longitudinal axis of the mast or spar.
Typically, the profile and sail are for use with a windsurfer.
REFERENCES:
patent: 3332383 (1967-07-01), Wright
patent: 4369724 (1983-01-01), Weiss
patent: 4699073 (1987-10-01), Farneti
patent: 5271349 (1993-12-01), Magrini
patent: 5423276 (1995-06-01), Nishimura
patent: 5799601 (1998-09-01), Peay
Avila Stephen
Fleshner & Kim LLP
Powerfoil Limited
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