GB2477167A

GB2477167A - A luff spar for a foresail

Info

Publication number: GB2477167A
Application number: GB201005205A
Authority: GB
Inventors: Ralph Maurice Roberts
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-01-25
Filing date: 2010-03-29
Publication date: 2011-07-27
Anticipated expiration: 2030-03-29
Also published as: GB201005205D0; GB2477167B; GB201001128D0

Abstract

A luff spar is made from a carbon or glass fibre tube 1 and is adapted to increase the efficiency of a foresail, when incorporated into the luff wire (2, Fig 2) of the foresail, by improving the aerodynamic shape in the luff of the foresail. The lull spar encapsulates the luff wire of the foresail (11, Fig 6) to increase the efficiency of the foresail by creating an improved aerofoil shape (Fig 8) to the leading edge of the foresail as compared to a foresail with only a luff wire. The luff spar also eliminates the sag (Fig 7) in the luff of a foresail that occurs when the luff wire within the luff sleeve of the foresail stretches under load. The luff spar may also convert any foresail furling system into a foresail reefing system (Fig 12).

Description

Aero luff spar 1

Description:

Background:

All foresails have either a wire or rope luff (rope being used increasingly rarely today), inserted through the foresail luff sleeve, and tensioned by the foresail halyard between the bow of the boat and a point on the mast, in order to support the leading edge, or luff of the foresail.

The luff wire, usually only 3mm dia. for a small sailing craft, enclosed within the luff sleeve of a foresail provides no effective aerofoil shape to the leading edge of the sail (Fig 6).

The efficiency of a foresail is compromised by even a small amount of stretch in the luff wire, particularly when under additional pressure from a strong wind, as it causes the luff of the foresail to sag' slightly out of shape.

This increases the entry curve of the luff of the sail (Fig. 7), which reduces the efficiency of the sail, as well as the boat's ability to point as high as possible towards the wind.

A luff wire on its own has no torsional rigidity, so whilst the use of a furling drum at the bow of a boat and a swivel at the peak of the sail allows the foresail to be furled (wrapped) around the luff wire, it is not possible to use this system to reef the sail to any size, since the top of the foresail will start to unfurl whenever the foresail clew is tensioned by the foresail sheet.

What it does: There are currently no known systems or products available designed specifically to: 1. Encase the luff wire of a foresail to improve the aerofoil entry shape of the luff of the sail, as compared to entry shape obtained with only a luff wire.

2. Prevent a foresail luff from being distorted from the desired shape due to the luff wire within the luff sleeve stretching when under any increased pressure.

The Aero' luff spar provides an improved aerofoil entry shape for the wind over the luff of the sail as compared to that provided by a normal luff wire.

The Aero' luff spar, being directly secured to the ferrules of the luff wire, eliminates the problem of the luff wire stretching under load within the luff sleeve of a foresail, since there is no stretch' in the Aero' luff spar, The shape of the foresail is therefore maintained, which enhances the performance of the sail.

The Aero' luff spar converts a foresail furling system into a foresail reefing system.

Note: A foresail furling system wraps the foresail completely around its luff to conveniently stop the sail flapping about in the wind after it has been hoisted, and not in actual use.

A foresail reefing system enables the foresail to be furled around its luff to adjust its size to match the wind conditions for sailing, as well as furling the sail completely out of use whenever needed.

Key and unique features: 1. The Aero' luff spar being made from a lightweight and small diameter, Carbon or Glass Fibre tube.

2. The Aero' luff spar being secured at each end to the swaged ferrules of the luff wire, making the luff spar and luff wire one integral and torsionally rigid unit.

3. The foresail being secured at either end of the luff spar by clamps, rather than by using a length of line or a clevis pin, as is the usual method of affixing the foresail to a luff wire or reefing spar.

Improvements on existing systems: The only foresail spars currently available for small boats are those made for foresail reefing systems, and consist of either an extruded aluminium section, as used by the Bartel (0), Holman (UK), and Plastimo (F) systems, or the flexible polypropylene type material of the Helyer (UK) system.

The Bartel, Holman, and Plastimo systems all have a furling drum incorporated into the system. This makes their use for any foresail which is not reefed far less efficient than using a luff wire without any furling/reefing system, for the following reasons: 1. The size and design of the reefing spar makes the entry shape of the leading edge less efficient than a foresail with only a luff wire.

2. The furling drum of the reefing system raises the height of the foot of the foresail, causing the sad to be less efficient.

3. The additional weight of the above reefing systems at the bow of the boat reduces the sailing efficiency of a small boat.

The Helyer flexible reefing spar can be directly attached to the same points on a boat as the luff wire of any foresail, and therefore used without any furling/reefing system. It doesn't improve the efficiency of an unreefed foresail however, for the following reasons: 1. The spar, being flexible, doesn't prevent the luff of the foresail from sagging' out of shape.

2. The method of attachment of the foresail to the spar is such that it raises the height of the foot of the sail, causing the foresail to work less efficiently.

3. The increased weight of the spar compared to that of a foresail with only a luff wire reduces the sailing efficiency of a small boat.

The Aero' luff spar is less than half the diameter of all current reeling spars available for small boats. The advantage of having an improved entry shape for the luff therefore extends to any reefed foresail position, in comparison to a similarly reefed foresail using any of the other reefing systems mentioned above.

Introduction to drawinQs and photos:

The following drawings illustrate the use of the Aero' foresail luff spar.

Fig 1. Illustrates a length of (Carbon or Glass) Fibre tube (1), being the main component of the Aero' luff spar (Fig 4).

Fig 2. Illustrates the luff wire (2) inserted through the centre of the Fibre tube (1), with thimbles (4) swaged onto either end.

Fig 3. Illustrates the stainless steel tubes (5), with a slot cut into one end of each tube.

Fig 4. Illustrates the stainless steel tubes (5) fitted over the ends of the Fibre tube (1) and swaged ferrules (3), and locked into position over the thimbles (4) of the luff wire (2), making up the single integrated unit of the Aero' luff spar (6).

Fig 5. Illustrates the Aero' luff spar (6), inserted through the luff sleeve of the foresail (8) and secured into position by double sided clamps (7).

Fig 6. Illustrates a cross section of a luff wire (2) inserted through the luff sleeve (8) of a foresail and tensioned to give the desired luff entry shape.

Fig 7. Illustrates a cross section of the shape of the luff of a foresail (11) after the luff wire (2) within the luff sleeve, has stretched under load and compromised the luffs shape.

Fig 8. Illustrates a cross section of an Aero' luff spar (6) inserted through the luff sleeve (8) of a foresail, demonstrating its aerofoil entry shape and the way it maintains the luff s shape under load.

Fig 9. Photo 1. Illustrates a foresail with only a luff wire, attached to the bow of the boat.

Fig 10. Photo 2. Illustrates a foresail with an Aero' luff spar, attached to the bow of the boat.

Fig 11. Photo 3. Illustrates a foresail with only a luff wire attached to the furling drum of the boat, which allows the foresail to be furled.

Fig 12. Photo 4. Illustrates a foresail with an Aero' luff spar attached to the furling drum of the boat, which allows the foresail to be reefed.

Description of the Aero' luff spar with reference to the drawings and photos: 1. A spar, cut to length from a (Carbon or Glass) Fibre tube (1), (or joined to make it longer, should this be necessary), to match the appropriate length of the luff sleeve of the foresail (8) for which it is being made (Fig 1 & Fig 5).

2. Two stainless steel tubes (5), of varying lengths, being placed over the Fibre tube (1) such that the cutout slots on one end of both stainless steel tubes (5) face the open ends of Fibre tube (1).

3. Aluff wire (2) being inserted through the centre of the Fibre tube (1), with thimbles (4) swaged on either end to make it an identical length to the luff wire of the foresail for the type of boat for which the Aero' luff spar is being made. The luff wire (2) being permanently retained within the Fibre tube (1) after assembly (Fig 2).

4. The stainless steel tubes (5), being pushed down over the swaged ferrules (3) of the thimbles (4) at each end, such that the stainless steel tubes (5) are locked onto the ferrule (3) by means of the cut-out slot engaging over the thimble (4) at the ends of the luff wire (2). The longer of the two stainless steel tubes (5) being positioned at the top (peak) end of the Fibre tube (1) to take up all the slack in the luff wire (2) (Fig 4).

5. The stainless steel tubes (5) being crimped' onto the Fibre tube (1) and locked into position such that the completed assembly becomes the single integrated unit of the Aero' luff spar (Fig 4, & (6) in Fig 5).

6. The Aero' luff spar (6) being inserted into the luff sleeve (8) of a specially made foresail, with the following features: an extended luff sleeve (8); no cringles (reinforced holes) at the tack (9) or peak (10); and reduced stiffening and sail reinforcement at the tack (9) and peak (10) of the sail. The foresail being secured to the Aero' luff spar (6) by means of two double-sided clamps (7). The luff tension along the length of the foresail luff (11) being adjusted by positioning the clamps (7) as required (Fig 5).

7. A foresail with the Aero' luff spar being fitted to the bow fitting(s) and foresail halyard of a sailing vessel, in exactly the same way as a foresail with only the normal luff wire. (Photos 1, 2, 3, and 4)

Claims

C'aims: 1. A lightweight foresail luff spar made from a Carbon or Glass fibre tube that supports the luff of a foresail and is of sufficiently small a diameter for it to create an improved aerodynamic shape in the luff of the sail.
2. A foresail luff spar that is directly secured at each end to the swaged ferrules of the luff wire, making it one integral unit.
3. A foresail luff spar to which a foresail is affixed by means of clamps securing an extended luff sleeve to the spar.