Another keel problem on the Vendée Globe. Today Marc Guillemot reports that his keel head has come loose in its box and only lashings are keeping it precariously in place. He has just passed the Azores, so is still over 1,000 miles from the finish.

The photo right, incidentally, shows Safran’s keel fin and bulb after frequency testing and a pin test on the keel cyclinder hinge pin before her launch in 2007.

This is sad news, but what are we to make of the sudden revelation that ‘when Marc Guillemot was sailing at more than 20 knots towards the Kerguelen Islands, Safran had a violent collision with a sea mammal. This impact could well have led to the problem he is experiencing today’.

First, is it fishy that this is the first we’ve heard of it? Secondly, how peculiar that his team is already mooting a cause of the keel problem, sight unseen. Is this about liability or insurance, one is bound to wonder.

Why are so many keel failures being attributed to hitting marine mammals? It that what is really going on? Bilou said he reckoned that was the cause of his keel loss as well, and Jean Le Cam posited what I regard as an improbable reason: hitting a container.

Right, so 200 miles west of Cape Horn there was one floating just exactly the right depth below the water (Archimedes would have rated the chances of that quite low) and capable of shearing off the keel bulb but not leaving a scratch on anything else?

In contrast, Dominique Wavre, whose keel head came loose, and Mike Golding, who saw cracks in his, have both pointed the finger firmly at designer or structural engineer, though they told me they have encountered very slopey shoulders.

No one should accept the marine mammal reason as an excusable explanation for damage as catastrophic as keel failure. A keel should be engineered to withstand such as impact; it is no mystery that whales and basking sharks exist and that collisions do occur. It is not the same as hitting a rock.

Designers are going to have to do better than this. They are going to have to better understand the load criteria and increase the safety margins. And if they, or teams, think that the excuse of hitting a big fish is going to be an acceptable reason in the eyes of the public and sponsors in the long term – oh, right, of course the keel fell off! – they are deluding themselves.