Smart tech cuts down labour
The M34 build benefitted from Gurit's B³ SmartPac approach
A new wave of technology is helping to nail down both build and repair costs, writes Stevie Knight
A bit like those "shaker-maker" cakes, there’s a product that helps boatbuilders get the best out of the building process, while taking away some of the intensive – and therefore variable – labour.
Mind you, SP-High Modulus, Gurit's marine business, doesn’t exactly put it like that: it says the B³ SmartPac is a “versatile solution that helps builders manufacture composite components more efficiently and cost-effectively than ever before”. Yannick Le Morvan of SP-High Modulus adds: “Actually, it gives the builders a measure of consistent control over the product, which in itself means reduced man-hours.”
The B³ SmartPac from SP-High Modulus brings together all the reinforcement and core materials required for the jobs, pre-cut to the exact shape and size to fit the mould, and clearly labelled for alignment and location. Taking the "Ikea" approach, the materials are packed in boxes in the order of assembly, and on top is a "check box" list that guides you through the build.
If you are tempted to ask "so what?" it might be worth mentioning that the process, when applied to the M34 project, “cut down the construction time by half”, says Mr Le Morvan.
Volume and custom builds
It does reach "across the board": the approach is suitable for a wide range of processing techniques and products. Interestingly, SP-High Modulus says it’s fine for everything from volume production to both semi-custom and custom builds, on both vacuum and wet layups as well as prepreg carbons and suchlike.
However, obviously it’s not just a take-away phone order. The application and processing of composites is complex so, in order to integrate materials as diverse as adhesives, prepregs, structural cores and coating systems, SP-High Modulus’ structural engineering team have to really get involved – which they certainly did with the M34 project, the collaboration with architects Bateaux Archambault even leading to custom materials being developed to make the most of the system.
“The scope of work was precise: we had to help create a racing boat within a very tight budget which was also able to achieve high production rates,” says Mr Le Morvan. Not easy, as the “cost” part of the equation could so easily have undercut some of the other desirables.
Thinking ahead
Mr Le Morvan adds: “In terms of engineering, it was a case of not wanting to compromise on the high tech material – in fact, the boat has a particularly high number of carbon-epoxy components - so the only option was to think ahead, to reduce labour and other costs where it could be done.”
For example, it seemed processes could be improved around the laying up of the hull composites. The boat utilises an epoxy-infused sandwich design and so a special 1,100g E-glass multiaxial fabric was developed for most parts of the hull and deck. This means combining one 800g quadriaxial layer with a 300g woven layer, (these were hot melted together so the stitching wouldn’t show through the gelcoat) to take the place of the "bread" on the outside, while 15mm or 20mm thick Corecell takes the place of the "filling". “This means laying up only three, rather than five layers on site,” explains Mr Le Morvan.
There are other little touches which really help to make things go smoothly: tacky strips keep all the dry fibres in place before the vacuum is applied, these simply dissolve into the resin on infusion.
Global stiffness was a key performance factor as it gives the crew better control on forestay sag and allows maximum waterline length to be maintained while sailing upwind. In some places, such as the sidedecks and hull bottom, further stiffening was needed, so hybrid biaxial glass and unidirectional carbon plies were applied in certain areas.
Keel stress
The stresses on the keel meant a particularly detailed look at the load path, using finite element analysis. The keel fin and its supporting structure were analysed for a load equivalent to 3g transverse acceleration (knock down case) and a 2.35g grounding longitudinal acceleration. The top keel bolts transfer the load from the stainless steel top plate to the composite structure, so there’s a complex load being transferred from the keel box into the hull.
Bateaux Archambault were able to achieve a good, repeatable alignment of the keel trunk by building a mating flange pre-moulded into the hull. Further, hybrid glass and carbon reinforcements were also added to the body near the keel structure to increase the area’s load carrying capability and minimise deflections under transverse keel loads.
The approach to the stock manufacture was developed in collaboration with high tech composite specialist Isotop: two hollow sections are bonded together inside the shell, this stabilises the stock capping and provides the necessary shear strength and stiffness while also minimising manufacturing time. The longevity of the part is increased by including solid carbon inserts at key locations along the leading and the trailing edge, where the load transfers from the keel to the trunk.
All in all, there’s a balance to taking some of the direction away from the workshop and regulating it by setting out the build scheme methodically via a third party: while it makes it more of conveyorbelt scheme, it also saves on time, and time means money, now more than ever.
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