Whenever there is a significant technical development one team always seems to be at the forefront in terms of involvement and application. That was the case again with the latest Dyneema SK90 grade, first used in small quantities – though 100kg is a lot of Dyneema – by Alinghi in Valencia. The graphic opposite shows the steep gain in modulus moving from SK78 to SK90 grade fibre – a bigger increase than might be expected even at the expense of a small loss in terms of creep characteristics
Dyneema up their game (again) as the wraps start to come off their SK90 fibre. Dobbs Davis reports To make a high-modulus fibre still stronger takes more than just technical prowess, it takes competitive incentive to justify the added expense in development, testing, retooling in production, and marketing and sales. With the continuing success of Holland-based DSM’s range of Dyneema fibre products in running and standing rigging, it seemed there couldn’t be much more to achieve for a while yet, given that the company’s latest low-creep SK78 variant is already increasingly to be seen on top grand prix programmes. But at the pinnacle of the game – yes, in 42 SEAHORSE
an event called the America’s Cup, where there used to be regular competition on the drawing board and in the water – an even higher level of performance is sought; and the funds and talent are still available to explore new ideas on how to achieve it. In this ethereal world the quest is for what is possible, not just probable, whether in new materials or in the techniques used to manipulate them to create equipment that is stronger, lighter and thus faster. In late 2004 in the run-up to the last America’s Cup, the ACC fleet was in its fifth iteration and so undergoing only subtle refinement to proven characteristics in design, so the pressure was on to find other avenues of improvement in areas such as hardware, spars and rigging. Dirk Kramers and the engineering team at Alinghi were searching for a fibre that could outperform – reliably – the best existing grades of Dyneema SK75 for rigging applications. [It transpires that while Dyneema’s use on ACC and comparable programmes has been relatively commonplace for over a
decade in rigging applications, Kramers says they also used it in the laminate schedule of America3 in 1992 to bring the boat up to the minimum hull thickness needed for the then IACC rule. The special carbon used in the hull by Bill Koch’s science-led team was already strong enough to handle the loads, so something was needed to add bulk with little or no weight. Apparently the material was plasma-treated and cured to allow its normally slippery qualities to accept resin within a laminate…] Having the highest strength-to-weight ratio and flexural strength of any comparable fibres, Dyneema SK75 was already the only choice for applications such as runner strops, halyards and halyard lock systems, jib and spinnaker sheets, and other sailtrimming applications. And though the fibre’s characteristics of light weight, high modulus, tenacity and flexural strength are impressive, Alinghi’s boffins were wondering if it couldn’t be made just a bit better … Their timing could not have been more
TH.MARTINEZ/ALINGHI
Stronger still!
perfect, since the folks at DSM Dyneema had just started an aggressive marketing and promotion programme aimed at letting the world know about the superior nature of their existing product, while actively soliciting input from high-level projects to improve on current features. ‘It’s common in Formula 1 for suppliers to partner teams to test their ideas before putting them into production in the automotive industry,’ said Dyneema marketing manager Marcel Alberts, ‘so we were looking to try a similar approach to developing Dyneema fibres for the sailing industry.’ So the fit with Alinghi was perfect, because it turns out that the manufacturing process of Dyneema – a closely guarded trade secret – lends itself to some ‘tweaking’ in which the end product’s performance characteristics can be altered slightly to suit specific applications. (The starting brew of material is no different, we’re told, but it is in the details of the extraction process that the fibre’s final characteristics are determined.) This is how certain grades of Dyneema – for example, SK62, SK75 and SK78 – can be tailored and improved, for example, in their tenacity, or modulus, or resistance to creep, without giving up too many of the fibres’ other general qualities. Alinghi were after a grade of Dyneema that could deliver its base qualities of low density, high tenacity, UV resistance and flexural strength compared with other fibres, but also with higher-modulus numbers so that less material could be used in applications where weight savings would translate into performance gains – such as in halyards. ‘If we could have a higher-modulus material to handle the loads,’ says Kramers, ‘then this would mean a few millimetres less material in each halyard. This in turn means not only less weight aloft in the line, but a smaller halyard then means a smaller and lighter halyard lock as well. This can all add up to a few hundred grammes, or even a kilo, which can be huge. And better materials generally have a snowball effect on the fittings around them – Dyneema halyards and strops are central to the best halyard locks and masthead details.’
So after more development DSM provided Alinghi with some new experimental yarn (dubbed SKX) for use wherever they thought it was of most benefit. ‘We only ever got about 100kg of this special batch, so we treated it like gold,’ claims Kramers. ‘We, with Dan Terhaar and Joao Cabecadas who did most of the development, used conventional Dyneema on applications where the strength and weight demands were not as stringent and saved the X stuff for the critical areas, like guys, sheets, halyards and runner strops.’ Those familiar with the Dyneema variants may ask why Alinghi were not content to use SK78, which was still under development at this time too and being tested in the Volvo Ocean Race on the Pirates’ programme. The difference lies in the focus of the fibre’s qualities. ‘SK78 was developed specifically to replicate the characteristics of SK75,’ says Alberts, ‘but to then also address the problem of inelastic stretch that is encountered when you apply a high load over a long period, the so-called “creep problem”. ‘But since America’s Cup racing is only ever of short duration, Alinghi were not as concerned about creep and so SKX being developed towards improving just modulus strength was perfect for their purposes.’ And improve it they did: tests at DSM found the X material to be a whopping 25% stronger in modulus strength. Kramers guesstimated that the net overall weight savings on their final V5 ACC boat SUI 100 were in the order of 20kg. So DSM Dyneema are now ready to offer this über-Dyneema SK90 more widely to other high-end programmes, with a launch scheduled for November at the METS show in Amsterdam. An amazing material just keeps getting more amazing. And just wait to see what comes out of AC33. ‘In spite of the bad press,’ says Kramers, ‘the competition on the drawing board is greater this time than in any Cup that I have participated in. It is unfortunate that the new lows on the legal side seem to overshadow any of the fantastic developments we are allowed to work on at the moment. Focus on the positives!’ ❑