Doyle Sails enters the 'fourth dimension'
Phil Bennett, Managing Director at Doyle Sails UK, has provided Boating Business with an insight into the development of a new type of sailcloth the company has developed, which it is calling D4.
"Recognising and understanding the load paths within a sail allowed the designers of the sails to produce a structure where the warp direction of the material is aligned as closely as possible with the principal load paths within the sail", explained Bennett. "This was achieved by creating a 'radially constructed' sail, whereby the fabric was cut into a series of panels, triangles and wedges, then joined to create a structure where the warp direction of the material follows the load paths within the structure".
This kind of radial construction does have some disadvantages, however, because of the inability to align the warp yarns to the multiple load paths - which can result in a complete breakdown in the laminate or loss of sail shape.
"Recognising the potential disadvantages of this kind of construction, we embarked on an extensive research and development programme, which, we believe, has resulted a sail that is ideally suited to the needs of performance yachtsmen, Grand Prix Racers, club racers, or discerning cruising sailors".
As Bennett explained, unlike a conventional radial panel sail, which incorporates panels made from laminates with parallel yarns, a D4 sail is constructed using sub assemblies featuring 'non parallel' fibres within the body of the sail. This allows a 'zero bias' change between adjacent sub panels. Accurate yarn placement and superior lamination ensures better shape retention and improved longevity.
The drawing reproduced here shows a simplified yarn map for a D4 mainsail. Each line represents a number of individual yarns.
Compared with a typical radial panel sail, it is noticeable how the yarns converge to the high load points in the head and clew. In the body panels there is a zero bias angle change between adjacent sub panels made from the converging/diverging sailcloth.
For reefing sails, additional yarn structures are applied along the load path internally within the laminate. This results in a sail that is much smoother when set, holds its shape better and lasts longer than a conventional panel sail.
According to Bennett, "every square" of a D4 sail is custom designed to handle not only the principle loads under normal sailing conditions, but those that are generated when a sail is reefed. The yarn map of the mainsail shows the primary yarn array plus a series of load bearing yarns that radiate from the new clew and tack corners when the sail is reefed. This ensures there is no distortion to the sail when reefed, or worse, the breakdown of the laminate that might occur in a conventional panel sail.
Bennett says that in addition to the advantages outlined above, the thermoplastic resin used in the D4 laminate has stronger bond characteristic than that used in the production of standard sail laminates. Also, as the sections are laminated in a flat form before shaping, there is no practical limit to the external pressure used during the bonding process. This is essential to ensure that delamination will not occur during the use of the sail. It also means the sail can be made considerably lighter than other sails, as less adhesive is required to form the lamination.
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