According to UK MAIB, during a training passage on the south coast of England a commercially operated sailing yacht experienced a catastrophic rigging failure that led to it being dismasted. There were no injuries and the mast was cut free and released overboard.
The incident
The yacht was on passage with a skipper/ instructor and six students on board conducting RYA competent crew training. The vessel was sailing on a port tack with the main and headsail up, when a loud bang was heard, and the mast fell over the starboard side of the vessel.
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The skipper checked how the students were, assessed the damage and informed the coastguard. He then cut the remaining rigging free, dropping it to the seabed, and returned to port under engine power.
Probable cause
The yacht’s shrouds were secured via stainless steel tie bars that spanned between the deck and the hull structure. The investigation into the cause of the failure found that the weld between the tie bar and lateral retaining member embedded within the GRP of the hull structure, had failed (Figure 3).
Metallurgical testing of the failed tie bar also found that:
- The weld fracture occurred as a result of cyclic loading;
- The weld was not a full penetration weld;
- Surface corrosion was found close to the point of failure but was not considered a causal factor.
This boat had been in commercial ownership for a number of years and had recorded a lot of miles. The cyclic loading on the tie bar would have been high, and led to the failure of the welded joint.
Lessons learned
- This vessel recently had all of its standing rigging renewed; it was not deemed practical to inspect the tie bar securing point as it was inaccessible without removing a significant amount of the internal fixtures. However, owners and surveyors should carefully consider the risk of a failure such as this occurrence given a yacht’s age and usage when deciding which critical elements of structure should be examined.
- In this case, there were no injuries and the vessel was able to continue on to port, having contacted the coastguard. This case demonstrates the benefit of having well practised emergency procedures.
- The skipper was able to cut the rigging to jettison the mast before motoring safely into port; having the ability to cut the rigging was critical for this. Had the vessel not been carrying wire cutters, this might have been much more difficult. Consideration should be given to having an appropriate level of emergency equipment on board a yacht to deal with emergencies.
