I'm not just picking on catamarans. Just walk around a boatyard and look. This has given spade rudders a bad name. I referenced in a prior post a research paper done in Finland, in which Nautor Swan built a racer/cruiser outfitted with strain gages throughout then raced it in the Baltic. One of the results was that the rudder post stress was operating beyond its elastic limits (engineering speak for bending slightly) even though its dimensions exceeded the current ABS standard. This was a long time ago yet no lessons were heeded.

I repeat what I have said many times: there is little added cost in making critical structures - such as keel attachments and steering gear - robust enough that the hull will be shredded before these parts give up. However there are many, many boats built as though the keel and rudder were sacrificial structures. That might be fine within swimming distance of shore, but isn't desirable 300 miles off of Hatteras in January. Those Alpha posts are probably only 3' long. From McMaster-Carr (a high priced retailer) 6' of 1.5" 316 round is $176. 6' of 2.5" (about 4.6 times as strong) is $445. Alpha saved $270 on the two rudders and lost a $500K boat as a direct result, with probably a $100K CG rescue. All paid for by you and me through taxes and insurance premiums.

The Coast Guard has already taken notice. How long before departure inspections are required?