Keel design scrutinised in UK Marine Accident report on Cheeki Rafiki

by Richard Gladwell, Sail-World.com NZL on 29 Apr 2015 Almost a year ago the Beneteau First 40.7 Cheeki Rafiki was found capsized 720nm off the coast of Nova Scotia.

Her four crew, delivering the cruiser/racer back to UK, were never found. The upturned hull of the boat sunk before it was able to be recovered.

The yacht's liferaft was found strapped into its well in the aft end of the cockpit by divers from the US Coastguard.

The relevant UK Government agency, the Marine Accident Investigation Branch has completed its investigation into the incident and released a 76 page report.

The report says its purpose is not to apportion blame, but rather to provide a factual record of the incident and make recommendations for the appropriate regulatory bodies.

In the absence of survivors and material evidence, the report says the causes of the accident remain a matter of some speculation. However, it is concluded that the yacht capsized and inverted following a detachment of its keel.

The focus of the investigation centred on the keel which had broken away from the upturned yacht. From photos it was apparent that the after keel bolt of the four was rusty, and could have been fractured.

Emails to and from the crew on the ingress of water into the yacht are featured in the report, along with messages from the yacht's owner - some of which were not received.

The keel design and specifications were referred to Southampton University's Wolfson Unit, who compared the specifications with current required design standards. They found the keel and specifications generally complied with the current standard, except that the keel washers were 3mm too narrow in diameter and thickness. They believed that with the after (rusty) keelbolt fractured, that the keel would not have stayed attached in the event of a 90 degree knockdown.

The key safety issues identified were:

• Where bonding is used to secure a matrix of stiffeners into a hull, it is possible for that bond to break down leading to weakening of the overall structure. Importantly, break down of the bond can be difficult to detect.

• A ‘light’ grounding can still cause significant undetected damage to the matrix bonding.

• Regular inspection of the hull and internal structure should help to provide early warning of possible keel detachment.

• Ocean passage contingency planning and careful routing can significantly reduce the risks of weather-related damage occurring.

• When flooding is detected, all possible sources of water ingress should be checked, including the area the keel is attached to the hull.

• An ability to send an alert and to abandon to a liferaft is essential in the event of capsize and inversion.

The following is the Synopsis from the report, which can be read in full by clicking here

At about 0400 on 16 May 2014 the UK registered yacht Cheeki Rafiki capsized approximately 720 miles east-south-east of Nova Scotia, Canada while on passage from Antigua to Southampton, UK. Despite an extensive search that found the upturned hull of the yacht, the four crew remain missing.

At approximately 0405 on 16 May an alert transmitted by the personal locator beacon of Cheeki Rafiki’s skipper triggered a major search for the yacht involving United States Coast Guard fixed-wing aircraft and surface vessels. At 1400 on 17 May, the upturned hull of a small boat was located; however, adverse weather conditions prevented a closer inspection and the search was terminated at 0940 on 18 May.

At 1135 on 20 May, following a formal request from the UK government, a second search was started. At 1535 on 23 May, the upturned hull of a yacht was located and identified as being that of Cheeki Rafiki. On investigation, it was confirmed that the vessel’s liferaft was still on board in its usual stowage position. With no persons having been found, the second search was terminated at 0200 on 24 May. Cheeki Rafiki’s hull was not recovered and is assumed to have sunk.

In the absence of survivors and material evidence, the causes of the accident remain a matter of some speculation. However, it is concluded that Cheeki Rafiki capsized and inverted following a detachment of its keel. In the absence of any apparent damage to the hull or rudder other than that directly associated with keel detachment, it is unlikely that the vessel had struck a submerged object. Instead, a combined effect of previous groundings and subsequent repairs to its keel and matrix had possibly weakened the vessel’s structure where the keel was attached to the hull. It is also possible that one or more keel bolts had deteriorated. A consequential loss of strength may have allowed movement of the keel, which would have been exacerbated by increased transverse loading through sailing in worsening sea conditions.

The yacht’s operator, Stormforce Coaching Ltd, has made changes to its internal policies and has taken a number of actions aimed at preventing a recurrence. The Maritime and Coastguard Agency has undertaken to work with the Royal Yachting Association to clarify the requirements for the stowage of inflatable liferafts on coded vessels, and the Royal Yachting Association has drafted enhancements to its Sea Survival Handbook relating to the possibility of a keel failure.

A recommendation has been made to the British Marine Federation to co-operate with certifying authorities, manufacturers and repairers with the aim of developing best practice industry-wide guidance on the inspection and repair of yachts where a glass reinforced plastic matrix and hull have been bonded together.

A recommendation has also been made to the Maritime and Coastguard Agency to provide more explicit guidance about circumstances under which commercial certification for small vessels is required, and when it is not. Further recommendations have been made to sport governing bodies with regard to issuing operational guidance to both the commercial and pleasure sectors of the yachting community aimed at raising awareness of the potential damage caused by any grounding, and the factors to be taken into consideration when planning ocean passages.