Unveiling the truth

Merfyn Owen of Owen Clarke Design explains their latest understanding about why Ecover's keel broke

Today we publish, courtesy of the Royal Institute of Naval Architects, the paper presented by Liz Tier of Owen Clarke Design at the recent High Performance Yacht Design conference in Auckland.

First Merfyn Owen of Owen Clarke Design provides a brief introduction to the paper:

This paper has a great deal to take in as it is about canting keel design in general, although I expect that many people might read the whole paper, they will primarily be interested in the failure of Ecover's keel and will want to know the answer to four main questions: What happened to Ecover's keel? How are we approaching the design of keels for our latest boats? Is this linked to the other failures in the Open 60 and Volvo fleet? Where does this leave canting keel technology in the future? I'll also answer a question of my own: Why did we publish our thoughts on canting keels?

a) What happened to Ecover's keel?

The keel failed due to fatigue from service stresses exceeding the fatigue strength of the material. This much was clear from the investigations, but the reason as to why the fatigue crack was initiated in the first place and why this happened during what should have been the mid-lifespan of the keel was unclear. You'll have to read the report to get a complete picture to the issues behind the failure as there is no 'cut and dry' reason and so no single solution. What we were able to do was rule out some of the speculative thoughts as to how this happened and validate choices such as material type, weld procedures etc.

b) How are we approaching the design of keels for our latest boats?

We have addressed each of the possible initiators of the fatigue failure separately as if they were solely the reason for the failure. Details are contained in our action list as the end of the report. The result of this is a targeted engineered approach rather than a 'cover all' general increase in safety factor. Increasing the safety factor in isolation would reduce mean stress levels and may give the same overall result but would miss tackling the fundamental reasons for the failure. A less targeted methodology would also lead to a less competitive keel and although this approach could be considered to be 'belt and braces,' our clients still will continue to demand high performance from us. Our primary goal with this component remains safety however and for Owen Clarke Design it is necessary to regain a reference point in keel design after the completion of the next Vendee Globe, in the same way that we had after Kingfisher completed the 2000 race.

c) Is this linked to the other failures in the Open 60 and Volvo fleet?

So far as the Volvo fleet all have canting keels and are subject to the dynamic loads of sailing around the world, yes, but from a designer's point of view though - absolutely not. That would be like linking all airplane crashes together - of course there are fundamental similarities in each crash, gravity being one of them. It's such a simplistic viewpoint that as an engineer I consider it almost laughable if the results were not so serious.

We can't even link the failure of Ecover's keel with other Open 60s [such as Skandiaor Armor Lux] because elements of each keel's construction, design, maintenance and operation are completely different. With respect to Volvo what problems they have had have resulted in some ill-informed speculations causing hydraulic, composite and general design issues to be grouped under the banner of 'canting keels are unsafe'.

Am I or any of the other yacht designers involved in canting keels hiding our heads in the sand when I write in such a way? I don't believe so. All of us involved at this sector of sailing know there are challenges, some of them inevitably hidden as we break new ground.

d) Where does this leave canting keel technology in the future?

Carbon masts and carbon rudder stocks are now standard on some production cruisers. I bet when Ian Proctor produced the first aluminium mast tube there were failures and plenty of detractors who said that it would not catch on. Canting keels are here to stay both on high performance cruisers like our Spirit of Adventure and of course on race boats of all sizes and sectors of our sport. There is no fundamental problem with fabricated canting keels or other types, nor the hydraulic and associated composite structures. We are confident of this and so are our clients. Dominique Wavre has chosen a fabricated keel for the new Temenos and Mike Golding has ordered a new fabricated keel from us again for Ecover in time for this year's Route de Rhum. Spirit of Adventure has a solid forged lifting and canting keel and is in her third season of sailing around the Pacific with no problems reported. Next year she will sail round Cape Horn to Africa.

When something goes wrong at this level of a sport such as ours there are always cries of alarm. The finger pointing blame mongers of our 'couch potato' modern society stand up to be counted and widely different events are sometimes tenuously linked in order to make a point or expound a theory. That's wrong - each individual case has to be analysed on its own. Of course there's risk when you're innovating at the leading edge of any sport but the designers, engineers, sailors and their sponsors are aware of this, otherwise we'd all be playing golf. This is the cutting edge, despite everyone's best efforts wheels will fall off as in Formula 1, fighter aircraft planes will crash more often than civil airliners, especialy during combat! I'm not saying that as engineers and designers there is no responsibility to get it right, but an unhealthy blame culture limits innovaton, stifles design and inhibits progress on many fronts. To win, we know our sailors first have to finish. Let's move on, solve the challenges through good design, methodology and produce ever more exciting and safer boats.

e) Why did we publish our thoughts on canting keels?

Self-interest is the simple answer. Although we have published some data which many might consider sensitive and to our detriment, both by handing over details of our design, raking up memories of past events best forgotten and thereby also opening ourselves to criticism, we want any lessons that can be learnt to be learnt by everyone. Keel failures, hydraulics and structural problems such as those we saw prior to and during the Vendee Globe and Volvo races brought these fantastic boats into disrepute. I hope that the lessons learnt on the Volvo will also become publicly available in time, either through the designers themselves or suppliers.

If anyone has an idea of how to create or if a suitable forum where these topics can be discussed and displayed openly then Owen Clarke Design would certainly contribute honestly to it. In my mind this has gone way past issues of small gains in performance. If the information that prevents other sailors having similar problems in the next Vendee Globe or the next Volvo race is sat on someone's C Drive then it should be available to all.

As I said, our publicising was self-interest. We don't want to see other designers having the same thing happen to them as we encountered with Ecover and we'd like to have our designs in the next Volvo too. It's in the sport's best interest and particularly those of us involved in canting keel designs to share information and minimise the possibility of similar events happening in the next running of these races.

As well as presenting at the HPYD we have circulated the Ecover report to all the members of IMOCA already and that by itself ensures that all the designers in the Open 60 class have it. By publishing this paper thedailysail will hopefully reach 90% of the other interested parties and save us a lot of admin time. Thank you James and Andy.

To download the pdf document of Owen Clark Design's full presentation 'Practical Aspects of Canting Keel Design' click on the image below. Please note that this paper is published courtesy of the Royal Institute of Naval Architects (RINA) and the High Performance Yacht Design conference. All papers from the conference are available directly from the RINA



NB: Owen Clark Design weren't involved in the design of the SkandiaOpen 60's second keel. "We don't have a view on why it failed. It's service and maintenance life was markedly different and at the moment we think it unlikely that there's a direct correlation between the failure on the two keels as the circumstances were so markedly different."

Read part one and part two of the article we published last year about Open 60 canting keel problems.