GB2190056A - Sail arrangement - Google Patents

Abstract

A sail arrangement for a sailboard comprises pre-formed mast 1 over which an envelope sail 2 is fitted. The mast 1 is tapered in diameter from its base to its apex and together with the sail 2 forms an aerofoil. <IMAGE>

Description

SPECIFICATION Sail arrangement This invention relates to a sail arrangement.

In the fieid of wind propelled windcraft and in particular sail boards there is a requirementto improve the efficiency of sail design.

It is an object of the present invention to obviate or mitigate the deficiencies in existing sail design.

According to the present invention there is provided a sail arrangement comprising a preformed mast over which an envelope sail is fitted.

Preferably, the pre-formed mast is tapered in diameter from its base to its apex.

Preferably, the mast and envelope sail arrangement define an aerofoil cross-section.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which Figure 1 is an elevational view of a sail arrangement made in accordance with the present invention; Figure2 is a top plan viewofthe arrangement of Figure 1; and Figures 3a-c, 4and 5 illustrate comparisons between the existing sail arrangements and the sail arrangement ofthe present invention, undervarious sailing situations.

With reference to the drawings, and in particularto Figures 1 and 2 thereof, a sail arrangement comprises a tapered preformed mast 1 oven which there is fitted an envelope sail 2 referred to as a 'sail sock'.

The outside diameter of the preformed mast 1 tapers from its base to its apex and is preferably formed of a standard stock mast core around which there is provided an expanded polystyrene outer layer. The mast is capable of being rotated by virtue of its attachment to a sail board through a conventional swivel pivot 4.

A conventional sail tensioning boom 3 is provided as in existing arrangements.

The sail arrangement of the present invention provides an aerofoil section which gives smoother airflow and creates a greater forward thrust.

The configuration of the circular cross-section tapered preformed masttogether with the envelope sail is such to allow the sail to give an aerofoil section on either tack as illustrated in Figure 3.

As compared with existing systemstheairflow section of the sail sock of the invention gives smoother airflow and creates more lift. In existing systems a wind shadow is created by the mast resulting in increased turbulence, as illustrated in Figure 3a.

With reference to Figure 4, it can be seen that even when the thrust from a standard sail layout and the thrust from the sail sock layout are equivalent the forward component of the sail sock shows a marked improvement.

Figure 5 illustrates the working relationship between a standard sail and a sail sock. Thy figure relates to sailing in a circle and the eleven conditions are asfollows: (1) headtowind (2) close hauled (3) close reach (4) beam reach (5) broad reach (6) running (7) running (8) broad reach (9) beam reach (10) close reach (11) close hauled Modifications and improvements may be incorporated without departing from the scope of the invention.

1. A sail arrangement comprising a pre-formed mast over which an envelope sail is fitted.

2. Asail arrangement as claimed in Claim 1, wherein the preformed mast is tapered in diameter from its base to its apex.

3. A sail arrangement as claimed in either preceding claim, wherein the mast and envelope combination define an aerofoil cross-section.

4. Asail arrangementsubstantially as hereinbefore described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Sail arrangement This invention relates to a sail arrangement. In the fieid of wind propelled windcraft and in particular sail boards there is a requirementto improve the efficiency of sail design. It is an object of the present invention to obviate or mitigate the deficiencies in existing sail design. According to the present invention there is provided a sail arrangement comprising a preformed mast over which an envelope sail is fitted. Preferably, the pre-formed mast is tapered in diameter from its base to its apex. Preferably, the mast and envelope sail arrangement define an aerofoil cross-section. Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which Figure 1 is an elevational view of a sail arrangement made in accordance with the present invention; Figure2 is a top plan viewofthe arrangement of Figure 1; and Figures 3a-c, 4and 5 illustrate comparisons between the existing sail arrangements and the sail arrangement ofthe present invention, undervarious sailing situations. With reference to the drawings, and in particularto Figures 1 and 2 thereof, a sail arrangement comprises a tapered preformed mast 1 oven which there is fitted an envelope sail 2 referred to as a 'sail sock'. The outside diameter of the preformed mast 1 tapers from its base to its apex and is preferably formed of a standard stock mast core around which there is provided an expanded polystyrene outer layer. The mast is capable of being rotated by virtue of its attachment to a sail board through a conventional swivel pivot 4. A conventional sail tensioning boom 3 is provided as in existing arrangements. The sail arrangement of the present invention provides an aerofoil section which gives smoother airflow and creates a greater forward thrust. The configuration of the circular cross-section tapered preformed masttogether with the envelope sail is such to allow the sail to give an aerofoil section on either tack as illustrated in Figure 3. As compared with existing systemstheairflow section of the sail sock of the invention gives smoother airflow and creates more lift. In existing systems a wind shadow is created by the mast resulting in increased turbulence, as illustrated in Figure 3a. With reference to Figure 4, it can be seen that even when the thrust from a standard sail layout and the thrust from the sail sock layout are equivalent the forward component of the sail sock shows a marked improvement. Figure 5 illustrates the working relationship between a standard sail and a sail sock. Thy figure relates to sailing in a circle and the eleven conditions are asfollows: (1) headtowind (2) close hauled (3) close reach (4) beam reach (5) broad reach (6) running (7) running (8) broad reach (9) beam reach (10) close reach (11) close hauled Modifications and improvements may be incorporated without departing from the scope of the invention. CLAIMS

1. A sail arrangement comprising a pre-formed mast over which an envelope sail is fitted.

2. Asail arrangement as claimed in Claim 1, wherein the preformed mast is tapered in diameter from its base to its apex.

3. A sail arrangement as claimed in either preceding claim, wherein the mast and envelope combination define an aerofoil cross-section.

4. Asail arrangementsubstantially as hereinbefore described with reference to the accompanying drawings.