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THE DESIGN AND BUILD OF A DOYLE STRATIS™ SAIL Doyle Sails has become one of the leading manufacturers of laminated sails worldwide. One of our particular fields of expertise is superyacht sails, and Doyle Sails Head of Design Richard Bouzaid explains the process for developing a STRATIS™ superyacht sail from design, through engineering and manufacturing to final finishing. “As with any sail, the first stage in the process is the sizing of the sail. This is especially important on large yachts as errors are costly and can require cranes to take sails on and off a yacht for changes to be made. Very accurate measurements are required for all the parameters of the boat to ensure that the design can proceed correctly.
THREE DIMENSIONAL DESIGN
“Our first stage in the process is to build a precise 3 dimensional model of the yacht within our design software. These models are accurate to millimetres and include all of the relevant detailing that can affect the fit and performance of the sails. Details of the sail attachment points, furling units, head swivels, mast detail with halyard positions, spreaders and other potential conflicts with the sail are included. We even take into account possible interference from radars scanners, communications equipment and stanchions as well as calculating possible positions for headsail cars.. This allows us to then fit a sail to the model with the certainty that, in real life, the sail will not only fit correctly to the 3 attachment points, namely head, tack and clew, but also where and if the sail will have other stress or chafe points due to fittings on the boat. The sails can then be suitably reinforced or the geometry altered to avoid these conflicts. “The accuracy of this type of modelling has been one of the biggest steps forward with sail design software in the last 10 years.
SHAPE OPTIMISATION AND FIBRE MAPPING
Shape optimisation is the next stage in the sail design process. Base sail shape moulds are used for certain geometries and applications and then adjusted for the requirements of the actual sail that is being designed. For example a cruising genoa will have more shape towards the back of the sail to be more effective when the sheet is eased. During this process the sails will be accurately aligned to the actual attachment points on the model so that mast bend and headstay sags can be incorporated into the sail design. Once the parameters of shape have been worked out, the orientation and density of the fibres that address the load paths of the sail can be established. We engineer ours sails to stretch by a certain amount, rather than to a % of their ultimate breaking strength. For a high performing sail we would be typically be looking for a maximum elongation anywhere in the membrane in the region of 0.15-0.2 per cent; and it is important that this elongation (stretch) is as uniform as possible throughout the membrane. During the process of establishing the correct fibre alignment and density, different combinations of fibres may be used to get the best balance between weight and overall durability. There are various fibres that we use in a STRATIS™ sail depending on the application. Performance cruising boats will typically use Vectran or a combination of Vectran and carbon fibre. Performance racing boats will use twaron (Kevlar), carbon fibre or a combination of the two fibres.
LAMINATION AND CONSOLIDATION
Once the orientation and density of the fibres has been finalised, the fibre map for the sail will be programmed into the 12m wide x-y plotters that will lay the fibres onto the surface. This base surface will become one of the sides of the finished sail. These fibres are all laid under tension to exact paths determined by the earlier studies. The final process in the membrane manufacture is the application of the top surface. This top surface is also a film sheet, often pre-coated with adhesive with a polyester taffeta on the outside. The laminated membrane is finally vacuum bagged to the table and then the laminator, using infrared heat lamps and 12000KG of downward pressure makes computer controlled passes over the membrane to activate the glue and expel any remaining air in the laminate. The STRATIS™ factory operates with two of these laminators. The membrane is left to cure for several days before being moved to the Doyle New Zealand 30,000 square foot sail loft floor for finishing or shipping to one of the many Doyle Lofts worldwide for completion.
FINISHING The completed membrane is then sent to the finishing floor to have hardware attached and any other finshing tasks completed.
STRATIS™ sails are made exclusively for the Doyle Group of Sailmakers and supplied from Doyle Sails New Zealand's custom STRATIS™ facility in Auckland |
