through the way in which we make the stitching of the multi-axial fibres. This involves careful adjustment of the gauge and the pattern of that stitching.’
For Gunboat, there were other issues that came into play. ‘Looking at the big picture, we decided on carbon infusion instead of pre-preg because the cost of large ovens and heat resistant moulds was out of step with the weight savings that we might have achieved,’ Jelbert says. ‘Still, we’re obsessed with precision and refining this build in every way, so for us, with the precision of the materials that Hexcel and SF supply, we can achieve a very high standard and weight savings without having to go to the cost and complexity of pre-preg.’
millimetre precision that improves build efficiency and reduces labour hours. For example, we order specific rolls of carbon at pre-defined widths of unidirectional fibres for the exact measurements that are required. I get nervous when a tape measure comes out,’ he jokes.
William Jelbert, chief operating officer at Gunboat. Based at La Grande Motte in the south of France, Jelbert has considerable experience in the field of composite construction having worked for several major builders around the world where he has been at the leading edge in the adoption and application of modern carbon composite construction. ‘Precision is the key for structural integrity and quality in modern composite construction and one of the reasons why the SF Composites/ Hexcel partnership is so important for us is that it eliminates the risk of human error,’ he says. ‘They deliver
Top: the
Gunboat 68’s platform is remarkably stiff, thanks to cutting-edge composite engineering and the high- est quality materials. Above: the first layer of carbon into the mould is woven, after that it’s all stitched
‘But seriously, with this system we can achieve better build tolerances with panels that are cut much more accurately, reducing extra material and weight. The increase in weight is not only the carbon excess but the resin this excess will absorb. So, the material supplied by SF Composites means that we are also achieving an overall weight saving.’ Hexcel’s PrimeTex – a spread tow woven fabric – is used as the first ply into the mould, providing a flatter and more uniform surface finish for the final parts which also reduces finishing time for paint preparation. ‘Due to the highly engineered VPLP structure, we use a lot of different weights and configurations of carbon and yet, in the grand scale of Hexcel’s production, we are a small operation,’ continues Jelbert. ‘There are very few big manufacturers that would be prepared to supply us with materials in such varied specifications and quantities so part of the success of our 68 has relied on the adaptability of our supplier.’
But the benefits are not simply around quantities. ‘The cloths that we have supplied for Gunboat are specifically intended to be infusion- friendly,’ says Hexcel sales engineer Frederic Pomies. ‘They are designed to ease the flow of the resin to avoid the risk of dry spots in the laminate. Broadly speaking, we achieve this
The ability to adapt materials and techniques where required is also important as is the steady evolution of the product and process. ‘We like to use stitched fibres as opposed to woven fabrics because all the fibres are aligned for all but the first layer that goes into the mould,’ Pomies continues. ‘Here we do use woven fabrics. From an aesthetic point of view, it helps avoid print through and allows a better paint finish. Using woven rovings in the outer laminate is also a means of protecting the outer laminate from peeling away in the event of any damage.’ The bottom line is that while the production of modern performance boats can easily focus on the specific materials themselves, for this partnership at least, success is based on the business relationship as well. ‘This is a story about service,’ says Pomies. ‘Communication is very important to us and so is looking to the future and proposing materials that could benefit the construction. For example products such as our DPA multi-axial fibres, which includes an adhesive that helps when it comes to aligning the fabrics, is one area that we are talking to Gunboat about for the future. These materials, which are DNV-GL approved, are easier to place in the mould and it is not necessary to spray the mould with adhesive beforehand, which helps to both save time and avoid emissions. ‘In addition, with materials like our M79 pre-pregs, our XF2 surfacing films, adhesive films, carbon fibres and honeycombs, we can offer the complete solution when it comes to advanced materials. And it is technologies like these that form the basis of conversations with Gunboat as we go forward with the objective of refining and improving the process and of course the final product itself,’ he concludes.
www.hexcel.com
www.sf-composites.com q SEAHORSE 67
SUSAN TOTH
GILLES MARTIN-RAGET
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