The UK-registered commercial yacht Tyger of London capsized while on passage from La Gomera to Tenerife, on 7 December 2017. The five persons
onboard 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. 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.
The MAIB is not aware of any similar keel failures in yachts of a comparable design. However, owners should be aware that the ‘shallow draught, lead keels’ fitted to the yachts listed above might not have been fabricated in accordance with the designer’s drawings. Where this is the case, the connection between the stainless steel keel plate and rods will not be as strong as intended. Furthermore, the condition of the connection cannot be inspected or assessed using traditional survey methods.
To prevent a similar accident, owners are recommended:
- To note that the securing bolts within the bilge of their boats, for this type of shallow draught lead keel, connect the top plate to the hull. The condition and tightness of these keel securing bolts do not indicate the true condition of the keel’s internal frame structure.
- To arrange for an out of water inspection of their vessel by a suitably qualified yacht surveyor at the earliest opportunity if the yacht has grounded, been heavily used, or if they have any concern whatsoever as to the condition of the keel, noting the difficulty of inspection of the junction between lead keel and top plate.
The MAIB’s investigation is ongoing and it is intended that a full report will be published later in the year.