MAIB ISSUES URGENT SAFETY BULLETIN AFTER KEEL FAILURE TO A COMMERCIAL YACHT


The MAIB is investigating the keel failure and capsize of the UK registered commercial yacht Tyger of London while on passage from La Gomera to Tenerife, on 7 December 2017. The five persons on board were rescued from the water by the crew of a nearby yacht.


Tyger of London was a Comar Comet 45S designed by Vallicelli & C and built in 2007 by Comar Yachts s.r.l, at Fiumicino, Italy. In common with other vessels built by the shipbuilder, the Comet 45S could be fitted with a choice of two keels: - A 3200kg, ‘deep draught bulb keel’, consisting of a cast iron fin with a lead bulb fixed to its base; or, - A 3700kg ‘shallow draught, lead keel’, consisting of a fabricated rectangular stainless steel top plate and frame, onto which lead was cast to form the keel.


Tyger of London was fitted with the ‘shallow draught, lead keel’, which is the subject of this safety bulletin.


The post-salvage inspection of the yacht identified that the keel’s stainless steel top plate was still attached to the hull. The MAIB recovered the top plate to the UK for technical assessment. The lead section of the keel sank in deep water and could not be recovered. The technical assessment of the top plate revealed that the keel had not been manufactured in accordance with the designer’s drawing or intent. Specifically, the stainless steel rods forming the frame and their interconnecting plates had been only partially welded to the underside of the top plate.


As a result, the joins progressively failed over time (Figure 3c). The final joins failed while the yacht was underway, causing the lead keel to separate from the keel plate, following which the yacht quickly capsized and inverted.


Tyger of London had been employed as a charter vessel since 2013. It is estimated that the yacht had sailed approximately 29,000nm since build. The MAIB has been informed that prior to the accident the yacht had grounded on a number of occasions, all reportedly at slow speed and onto sand or mud.


The yacht’s manager had removed the yacht from the water 22 months before the accident, for maintenance, during which paint and filler were removed to allow the keel plate and lead keel to be inspected. The securing arrangements between the keel and the hull matrix were found to be in good condition, however the lead casting prevented the inspection of the welded joins between the keel’s fabricated frame and top plate.


Full details, safety lessons and recommendations: http://bit.ly/2ANNiQF


LOW SPEED DIESEL ENGINES SAVE ON CLAIMS IS THE FINDING OF A RECENT SWEDISH CLUB STUDY


In a recent study the Swedish Club has warned that vessels propelled by medium or high speed diesel engines have a claims frequency two and a half times higher than slow speed engines with an average claims cost of about $650,000.


Statistically, a vessel will suffer between one and two incidences of main engine damage during its life time, according to the club. However, the incidence rate varies by vessel class (and engine type).


“Our research shows that bulkers and tankers are the best performers for claims cost,” said senior technical advisor Peter Stalberg. “Most of these vessels have slow speed engines. Conversely passenger vessels/ferries have the highest frequency of main engine claims – 0.066 claims per vessel and year. Often these vessels have multiple medium speed engine installations.”


Full story: https://bit.ly/2ur4PZj


The Report • September 2018 • Issue 85 | 19


Safety Briefings


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