Fatigue in metallic fabricated welded keels is a significant mode of keel failure globally. In recent decades there have been multiple keel failures resulting in loss of life, of which the majority was due to this mode. What is being done about it?

At a recent meeting of World Sailing’s Oceanic & Offshore Committee, a decision was made to approve a recommendation from its Special Regulations Sub-Committee to introduce a regulation requiring boats with welded metal keels to undergo non-destructive testing of those welds, every ten years, effective from 2030 for category 0, 1 and 2 races. The vote was approved with 12 in favour, 1 abstention and nil against. Australian Sailing is now considering the implementation the same requirement domestically.

The naval architects and engineers involved in yacht design will likely know that ISO12215-9:2025 seeks to address fatigue failure in keels by improving fatigue-life assessment procedures and increasing the life of metal fatigue from 8 million cycles to 16 million cycles and requiring that recommended inspection methods be clearly stated in the Owner’s Manual.  This will apply to new boats with fabricated metal keels; however, this does not lower risks of fatigue in existing keels designed and built under earlier versions of ISO12215-9 or the ABS Guide for Building and Classing Offshore Yachts.

The lay person reading this should understand two things. First, their boat wasn’t designed against these new and sturdier standards. Second is the nature of the problem; that fatigue in metals is the progressive failure that occurs due to the repeated stresses and loads on the metal. Failure initiates and progresses due to cracking of the metal. But the cracking can usually be identified before ultimate failure, and that is why the non-destructive testing is being introduced; early identification.

These fatigue cracks in metal are not always visible to the human eye. These cracks that the non-destructive tests should identify may be as small as 5 microns (five-thousandths of a millimetre).

The problem being fixed by World Sailing is that, if not identified, the initiation and growth of fatigue cracks results in instantaneous catastrophic separation of the keel from the vessel’s hull, resulting in its capsize and inversion, which is what ultimately leads to loss of life.

Performing periodic non-destructive testing on metallic fabricated welded keels will reduce the likelihood of loss of life due to keel failure. This is why World Sailing has introduced the requirement and why Australian Sailing is looking at domestic implementation. It is a response to a very real risk.

Information about keel inspections is here.
Keel bolt corrosion can be read about by clicking here.
More on keel detachment can be read here.

By Glen Stanaway