America's Cup HY-80 keel failure

Developed case study illustrating zone-three preheat for 4340 steel. Jerry Milgram (MIT ocean engineering) calls Tom because the HY130 keel of an America's Cup prototype bent during sea trials; four-inch HY130 was the strongest plate available and it wasn't strong enough. Tom develops a welding procedure for 4340 using the structural welding code methodology just taught.

The story I'll tell you in the last couple of minutes — by the way, you can have Monday off, it's a holiday. The story I'll tell you, I don't think I've told this story — maybe I told it last year, I apologize. Did I tell you the story about the America's Cup? Yeah. If I did you don't remember, but maybe you do.

Used to illustrate that 130 ksi welded keel beam, four feet wide and eight inches thick, bent under sail loads — concentrating force in a single bending moment was beyond what HY130 could carry at that geometry. Tom names it as HY130 (the Navy submarine steel), not HY-80; the canonical cluster name may need reconciliation against other lectures.

They use it in the keel of the America's Cup yacht. This was about ten or fifteen years ago. In the America's Cup yacht keel beam, they'd used HY130, which was what the Navy wanted to use for submarines. But they built one and they went out and tested it and it bent. 130 ksi, like four feet wide, eight inches thick — a lot of force on those things, a lot of sail area, and you concentrate it all in a bending moment with a big knot. And I say keel — it's actually the piece that sticks down. It's not the rudder, but it's the centerpiece, and you want a bunch of weight in the bottom, down low.