A situation analysis regarding Ecover’s keel |
| Saturday, 12 February 2005 |
| There are a many factors that could be involved in the failure of a
component such as keel. No conclusions should be drawn that simply because a keel is a swing keel and even of the same material type, that the failures recently are intricately linked. It is quite possible that there are contributory factors in all cases and possibly over time more than one factor involved in any failure. It is too early to draw any conclusions as the boat has not yet returned to the UK and an inspection has not yet been made.
In order to answer some of the most routinely answered questions in the last week we have prepared the following information:
The keel that failed in the last fifty miles of Mike Golding's Vendee Globe Race had a fabricated steel fin, the latest to be manufactured by Robert Stones Ltd in New Zealand. This company is a large and respected heavy engineering firm that also carries out welding for offshore oil/gas installations, manufacture of pressure vessels and other such work for oil refineries and heavy industry. As with the other keels built for Owen Clarke in this facility the personnel undertaking the work are coded for the particular weld procedures used and the welds are pre-qualified. That is to say, they adhere to strict internationally recognised regulations as to preparation and the manner in which welds are completed and inspected.
Robert Stones were chosen because of their expertise and quality control procedures inherent in such a large company. In addition to the inspection work carried out internally, Owen Clarke Design secured the services of an external inspector who carried out ultrasonic and other NDT (non destructive testing) inspection throughout the manufacture of the keel as it was assembled. Ecover's keel was then inspected again on the return from the Transat race last year and found to be free of defects.
Ecover's keel was of a conservative design, with an allowable stress 30% below the limit suggested by the ABS scantling guide for Offshore Racing Yachts. It was also engineered against a benchmark of what had previously been successful in completing the Vendee Globe.
Roger Scammel worked with Owen Clarke Design on the Ecover project as the consulting engineer for the keel design. The design of this keel was to make the keel 20% stronger (a reduction in the design stress of 20%) in real terms than previous Owen Clarke keel design models. After analysis we felt we were able to do this with no appreciable decrease in performance whilst increasing the safety factor of what is obviously a critical component.
The Vendee Globe represents the harshest environment for any racing yacht, just under thirty thousand miles without the ability to inspect and repair. To put this into context, that's almost twice a normal years sailing for these yachts or the equivalent of nine transatlantic races, back to back.
Obviously then the security of the vessel is not an area where a sailor, project or design office would want to cut corners and that is why the safety factors for this keel were raised. As outlined above, we feel all reasonable steps were taken in the construction and design of the keel to prevent failure but the keel still failed.
The question is why? It is now important for the good of the IMOCA class and the confidence of sailors in swing keel designs in general that we endeavour to find the causes of the failure last week to Ecover's keel, move forward and avoid undue speculation. |
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