BACKGROUND OF THE INVENTION. This invention relates to a mast, and more particularly to a mast of a sailboat, which is equipped with the means to reduce drag across its surface.

The mast of a sailboat together with the boom, which is attached to the mast, provides the necessary structure to hold in place the sail which catches the wind and converts its force into the forward motion of the sailboat. The amount of forward velocity a sailboat may achieve, depends to a large degree on the strength of the wind and the efficiency of the sail arrangement. Air flow over the sail is affected by the turbulent wake created by the surface of the mast, resulting in a base drag condition which greatly reduces the efficiency of the sail. Furthermore, the combination of wake or low pressure on one side of the mast and the corresponding high pressure on the opposite thereof, creates a weight condition which greatly influences the effect of gravity on the mast, which needs to be calculated into the design and construction of a sailboat, especially with respect to the keel.

It is a general rule, that a pound of weight or pressure on a mast at a height of 32 feet from the centre of gravity of a boat needs to be countered by at least 30 pounds of weight below the centre of gravity at the keel, in order to maintain proper balance.

As the weight of the keel is considered "dead weight", any reduction of it would be directly expressed in increased boat performance.

It is therefore most desirous to have available a means to reduce the amount of base drag occurring behind mast and boom of a sailboat, thereby increasing its sail efficiency.

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SUMMARY OF THE INVENTION

Although one aspect of the present invention relates to a mast and boom application for a sailboat, the scope of the present invention generally embraces all continuous single curvature elongated bodies, such as tubes, rods, cables, wires and the like, which are located adjacent a fluid in relative motion and thereby experiencing significant amounts of base drag.

In accordance with the present invention, a single curvature elongated body includes in its surface a pattern of surface discontinuities arranged along at least a portion of the surface of such elongated body. Preferably, the surface discontinuities include discrete, generally spheroidal, concave sub-surfaces extending below the surface of such elongated body. Regular, discretely shaped surface discontinuities have the advantage of dealing uniformly with changing flow patterns and are independent of the angle of attack the flow takes across the surface of such single curvature elongated bodies. As already mentioned, the present invention has a broad range of application, and covers a variation of continuous single curvature elongated bodies. In accordance with one aspect of the invention, for example, the surface is moving and the fluid is generally stationary. Examples of this aspect of the invention includes exterior surfaces of tubular struts and bracings of landing gears and fixed wheel arrangements on small aircraft and on helicopters and the like.

In the case of a mast and boom of a sailboat, both the surface and the fluid are in motion.

In another aspect of the invention only the movement of the fluid provides the relative motion between the exterior surface and the fluid. Applications of this type include exterior surfaces of tubular shapes used in the construction of ocean drill platforms, especially for below

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the waterline. Further examples include exterior surfaces of parts of high towers and bridges and the like, using tubular shapes in their construction.

In general, fluid passing across a smooth exterior surface of a single curvature elongated body, such as a tube, rod or wire, produces turbulent flow creating a low pressure or base drag condition behind such body.

The present invention therefore, assists in changing fluid flow behaviour across elongated bodies, such as tubes, rods, wires and the like, thereby significantly reducing the low pressure area or the resulting base drag and increasing overall efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 of the drawings depicts a preferred embodiment of the present invention, comprising a portion of a sail arrangement, including part of a mast and boom.

Figure 2 of the drawings depicts a section view through the mast or boom, indicated as *S-S\' in Figure 1. Figure 3 of the drawings depicts a section view through the mast or boom, indicated as \'S-S\' in Figure 1 showing an alternative arrangement.

Figure 4 of the drawings depicts a portion of a tube or wire, indicating the direction of relative fluid motion and the location of the corresponding low pressure area. Figure 5 of the drawings depicts a section view through the tube at \'S-S\' , as indicated in Figure 4.

Figure 6 of the drawings depicts an alternate section view through the tube at \'S-S\' as indicated in Figure 4. Figure 7 of the drawings depicts a variety of exterior surface discontinuities.

DETAILED DESCRIPTION OF THE DRAWINGS

For the purpose of understanding the principle of the present invention, reference will now be made to the embodiment illustrated in the drawings, and specific

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language will be used to describe the same. It will nevertheless be understood that no limitations of the scop of the invention is hereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

Figure 1 of the drawings shows an elevated view of a portion of a sail (a), including a portion of the mast (b) and the boom (c). Both boom and mast include in their surface a pattern of surface discontinuities (e), designed to affect fluid flow behaviour across such surface areas. Figure 2 of the drawings depicts a view through section line *S-S\', through mast or boom, as indicated in Figure 1 of the drawings. This view illustrates the surface discontinuities (e) as depressions in the surface (d) of such mast or boom.

Figure 3 of the drawings depicts a view through section line \'S-S\', through mast or boom, as indicated in Figure 1 of the drawings, but this time illustrating the surface discontinuities (e) as protrusions in the surface (d) of such mast or boom.

Figure 4 of the drawings depicts a more general shape of a portion of a continuous curvature elongated body, suc as a tube, rod or wire, with its surface equipped with a pattern of surface discontinuities (e), and illustrating the direction of relative fluid motion over its surface with arrow (h) and the location of the low pressure area opposite as indicated by arrows (j).

Figure 5 of the drawings depicts a section through section line \'S-S\' , as indicated in Figure 4, showing an alternative oval shaped circumference of such tube, rod or wire, and including in its surface (d) a pattern of surfac discontinuities (e).

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Figure 6 of the drawings shows again another alternative to the shape of the circumference of such tube, rod or wire, as indicated in Figure 4, this time illustrating an uneven shape, and including in its surface (d) a pattern of surface discontinuities (e) .

Figure 7 of the drawings depicts a variety of shapes of surface discontinuities, as viewed through section line \'S-S\' as indicated in Figure 4 of the drawings. The discontinuities illustrated here show a selection of possible depressions (b), (d), (i) , (j) and (k) , and protrusions (1) and ( ), demonstrating some of the varieties of surface discontinuities able to affect fluid flow behaviour over the surface of a continuous single curvature elongated body.

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