Apparently a possibility on the "older" (whenever that was) J/120s...apparently now fixed on the newer J/120s. Don't know which (older or newer) J/120 it was that was sunk. But I'd say that a rudder dropping out of a boat after being hit qualifies as a structural failure --that being said, being in a pod of whales offshore and being rammed by one or more of them would probably uncover just about any boat's structural weaknesses... ;-) Arguably, though, some --some-- boats with skeg-hung rudders might have fared better and not have sunk...but who knows. See thread here: http://forums.sailinganarchy.com/index.php?s=&showtopic=98284&view=findpost&p=2537778

Seeing lots and lots of huge humpback whales breach and spin nearby the boat up in the Alaska this summer was at once incredibly awesome, and scary...they're awe-inspiring animals, even when not aggressive. The only marine mammals I don't mind being too close to are Stellar sea lions, but the bulls (males) themselves are about 10 feet long and weigh well over 1000 lbs. Fortunately, they don't seem too interested in boats...but just don't step into their jealously-guarded harems on shore! See the big boy in the middle of the pic, head raised, and howl-grunt-barking very loudly.

Below, in Inian Passage, Icy Strait, outside Glacier Bay, AK this summer. (The smell and sound of the Stellers at close range is pretty impressive.)