Sailboard with slotted winglets
Inactive Publication Date: 2013-11-14
KELLER JOHN H
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Benefits of technology
[0017]The thickness of the winglet may vary, either or both in a transverse direction and a longitudinal direction. This can result, for example, in the nose and/or outside edge of the winglet having thicknesses which are thinner than at other points of the winglet. The nose of the winglet may, for example, have a thickness of about 50% (half) the maximum thickness of the winglet. This reduces spray off of the nose of the winglet. Meanwhile, the slot allows energized water from under the front of the board to produce a Coanda effect (lift) over the top surface of the winglet.
[0018]The winglets according to this invention may have a slot formed on the top of (that is to say, above) a portion or the entirety of the winglet, particularly near the end of the winglet such that the turbulence and wave drag at the back of the board is decreased. That is, a top slot allows the winglet to be extended under a top portion of the board (under a hull part having a top surface on which a user stands or is situated when using the sailboard and a bottom surface forming a slot with the winglet.) This also allows the top surface of the sailboard, which is above the top slot, to have a foot strap and a larger top surface area for sailing and jibing the sailboard.
[0019]The transverse end of a forward slot, i.e. the outside, can be covered or partially covered so that water and waves, particularly on the windward side do not enter the slot or strike the nose of the winglet when sailing at high planing speeds, such as over 15 mph. When partially covered by a cover or partial cover (which can be part of the hull), an opening/gap between the cover or partial cover and the winglet can be provided to allow any weeds or grass which enter the slot to escape.
[0020]While the nose of the winglet can be perpendicular, angled back, angled forward, or curved, it is preferred that it be angled or swept back. This will both allow it to shed weeds and direct the water passing on top of the winglets away from the front foot straps.
Problems solved by technology
Also, the flow over the top of the front of the winglet may stop at a slower board speed than desired, while the camber of the winglet is limited by the thickness to length ratio.
However, each winglet has drag from the separation of the water at its nose to pass over and under the winglet, thus if the number of winglets is too large there will be increased drag from this wing grid.
Method used
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[0027]Referring now to the drawings, and more particularly to FIGS. 1A-1E, a cross section of a side part of a sailboard hull 1 is shown with a preferred embodiment of a winglet 2 with a front slot 3 and a top back slot 6. ‘Front slot’ and ‘forward slot’ are treated as substantially synonymous terms and may be used interchangeably herein. A ‘front slot’ or ‘forward slot’ may include an ‘opening’ or ‘forward opening’ which should also be understood as substantially synonymous. The term ‘top slot’ includes ‘back slot’ and ‘top black slot’. Hereafter a ‘winglet’2 may also be called a ‘slotted winglet’2 to emphasize the presence of a slot above the winglet. Winglet 2 has a length, in a longitudinal direction of the sailboard hull, at least 2 or 3 times its transverse width on each side of attachment to the main body. Thus it is distinguished from a fin or skeg at the side of the hull as in some racing catamaran sailboats. Winglet 2 may be integral with the sailboard hull such that the hull
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A sailboard hull has at least one pair of winglets or foils beneath the top of the board. Each winglet or foil has above it a slot and allows dynamic lift from both the top and bottom surface of the winglet and reduction of drag when the board is traveling at a transition speed between displacement mode and planing mode. At high planing speed it does not normally have lift from the top surface of the winglet. There may be multiple pairs of winglets or foils. Back slots may be provided at the rear of the sailboard hull providing a higher ratio of winglet width to maximum hull width. A top slot may cover at least half the winglet area, and a winglet may have a camber/slope step on the planing surface.
Description
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