To make a high-modulus fibre still strongertakes more than just technical prowess, ittakes competitive incentive to justify theadded expense in development, testing,retooling in production, and marketingand sales. With the continuing success ofHolland-based DSM’s range of Dyneemafibre products in running and standingrigging, it seemed there couldn’t be muchmore to achieve for a while yet, given thatthe company’s latest low-creep SK78variant is already increasingly to be seenon top grand prix programmes.

But at the pinnacle of the game – yes, in

an event called the America’s Cup, wherethere used to be regular competition on thedrawing board and in the water – an evenhigher level of performance is sought; andthe funds and talent are still available toexplore new ideas on how to achieve it. Inthis ethereal world the quest is for what ispossible, not just probable, whether in newmaterials or in the techniques used tomanipulate them to create equipment thatis stronger, lighter and thus faster.

In late 2004 in the run-up to the lastAmerica’s Cup, the ACC fleet was in itsfifth iteration and so undergoing only subtlerefinement to proven characteristics indesign, so the pressure was on to find otheravenues of improvement in areas such ashardware, spars and rigging. Dirk Kramersand the engineering team at Alinghi weresearching for a fibre that could outperform– reliably – the best existing grades ofDyneema SK75 for rigging applications.

[It transpires that while Dyneema’s useon ACC and comparable programmes hasbeen relatively commonplace for over a

decade in rigging applications, Kramerssays they also used it in the laminateschedule of America3 in 1992 to bring theboat up to the minimum hull thicknessneeded for the then IACC rule. The specialcarbon used in the hull by Bill Koch’sscience-led team was already strongenough to handle the loads, so somethingwas needed to add bulk with little or noweight. Apparently the material wasplasma-treated and cured to allow itsnormally slippery qualities to accept resinwithin a laminate…]

Having the highest strength-to-weightratio and flexural strength of any compar-able fibres, Dyneema SK75 was already theonly choice for applications such as runnerstrops, halyards and halyard lock systems,jib and spinnaker sheets, and other sail-trimming applications. And though thefibre’s characteristics of light weight, highmodulus, tenacity and flexural strength areimpressive, Alinghi’s boffins were wonder-ing if it couldn’t be made just a bit better …

Their timing could not have been more

42 SEAHORSE

Dyneema up theirgame (again) as thewraps start to comeoff their SK90 fibre.Dobbs Davis reports

Stronger still!

Whenever there is a significant technicaldevelopment one team always seems to beat the forefront in terms of involvement andapplication. That was the case again withthe latest Dyneema SK90 grade, first usedin small quantities – though 100kg is a lotof Dyneema – by Alinghi in Valencia. Thegraphic opposite shows the steep gain inmodulus moving from SK78 to SK90 gradefibre – a bigger increase than might beexpected even at the expense of a smallloss in terms of creep characteristics

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perfect, since the folks at DSM Dyneemahad just started an aggressive marketingand promotion programme aimed at let-ting the world know about the superiornature of their existing product, whileactively soliciting input from high-levelprojects to improve on current features.

‘It’s common in Formula 1 for suppliersto partner teams to test their ideas beforeputting them into production in the auto-motive industry,’ said Dyneema marketingmanager Marcel Alberts, ‘so we were look-ing to try a similar approach to developingDyneema fibres for the sailing industry.’

So the fit with Alinghi was perfect,because it turns out that the manufacturingprocess of Dyneema – a closely guardedtrade secret – lends itself to some ‘tweak-ing’ in which the end product’s perfor-mance characteristics can be alteredslightly to suit specific applications. (Thestarting brew of material is no different,we’re told, but it is in the details of theextraction process that the fibre’s finalcharacteristics are determined.) This ishow certain grades of Dyneema – forexample, SK62, SK75 and SK78 – can betailored and improved, for example, intheir tenacity, or modulus, or resistance tocreep, without giving up too many of thefibres’ other general qualities.

Alinghi were after a grade of Dyneemathat could deliver its base qualities of lowdensity, high tenacity, UV resistance andflexural strength compared with otherfibres, but also with higher-modulusnumbers so that less material could beused in applications where weight savingswould translate into performance gains –such as in halyards.

‘If we could have a higher-modulusmaterial to handle the loads,’ says Kramers,‘then this would mean a few millimetresless material in each halyard. This in turnmeans not only less weight aloft in the line,but a smaller halyard then means a smallerand lighter halyard lock as well. This canall add up to a few hundred grammes, oreven a kilo, which can be huge. And bettermaterials generally have a snowball effecton the fittings around them – Dyneemahalyards and strops are central to the besthalyard locks and masthead details.’

So after more development DSM pro-vided Alinghi with some new experimentalyarn (dubbed SKX) for use wherever theythought it was of most benefit.

‘We only ever got about 100kg of thisspecial batch, so we treated it like gold,’claims Kramers. ‘We, with Dan Terhaarand Joao Cabecadas who did most of thedevelopment, used conventional Dyneemaon applications where the strength andweight demands were not as stringent andsaved the X stuff for the critical areas, likeguys, sheets, halyards and runner strops.’

Those familiar with the Dyneemavariants may ask why Alinghi were notcontent to use SK78, which was still underdevelopment at this time too and beingtested in the Volvo Ocean Race on thePirates’ programme. The difference lies inthe focus of the fibre’s qualities.

‘SK78 was developed specifically toreplicate the characteristics of SK75,’ saysAlberts, ‘but to then also address the prob-lem of inelastic stretch that is encounteredwhen you apply a high load over a longperiod, the so-called “creep problem”.

‘But since America’s Cup racing is onlyever of short duration, Alinghi were not as concerned about creep and so SKXbeing developed towards improving justmodulus strength was perfect for theirpurposes.’

And improve it they did: tests at DSMfound the X material to be a whopping25% stronger in modulus strength.Kramers guesstimated that the net overallweight savings on their final V5 ACC boatSUI 100 were in the order of 20kg.

So DSM Dyneema are now ready to offerthis über-Dyneema SK90 more widely toother high-end programmes, with a launchscheduled for November at the METS showin Amsterdam. An amazing material justkeeps getting more amazing.

And just wait to see what comes out ofAC33. ‘In spite of the bad press,’ saysKramers, ‘the competition on the drawingboard is greater this time than in any Cupthat I have participated in. It is unfortunatethat the new lows on the legal side seem toovershadow any of the fantastic develop-ments we are allowed to work on at themoment. Focus on the positives!’ ❑

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