The keel bolts are designed to carry 7 times the weight of the keel.
That is just plain silly. Where did you come up with that idea? It makes absolutely no sense at all and bears no resemblance to reality. When dropping off a wave while heeled the side force on a keel and the sudden deacceleration can result in a tensile load on the bolts that can approach a range that is 20-40 times the weight of the keel. Or to look at this from another approach, each of those bolts has roughly a 50,000- 55,000 lb tensile strength and the keel only weighs 3748 lbs that is something in the range of 14 times the weight of the keel for each bolt.
Shouldn't there have been some stringers across?
It couldn't just have been bolted through the laminate with backplates?
If you look at the first set of pictures you can see that there are transverse frames (what Denise rightly calls floors) that are sheered off where they turn down into the bilge. The photos of the top of the keel show gaps where these frames were located and there torn fibers which are probably from the biaxial cloth used as reinforcing in this area of the boat and which were withdrawn from the hull and frames . Having the bolts through thickened laminate between the frames is pretty typical construction for a glass boat with a bolt on keel, but the failure mode is not very typical at all.
The backing plates look bent up on the port side, giving the appearance of failure due to leverage from the side. Are there any pics of the keel that show where it was impacted? I wonder if it drove up onto a ledge, with the boat falling off to one side. Jury is out on whether this is a manufacturing issue or just a freak failure scenario. It will be very interesting to find out.
p.s. those keel bolts look better than mine (which are being replaced this Fall.
I noticed the bent plates as well. It looks like there was a blow from the port side that pushed the keel towards the starboard. The port side of the base plates appear to have sheered downward through the laminate and were bent in the process. I still don't understand what happened have created such a clean cut. After all, even if the plates sheered down through the laminate, you would have expected the adjacent laminate to be peeled apart. Similarly, if the keel sheered upward from through the laminate on the starboard side you would have expected the transverse frames to be crushed on that side which they don't appear to be.
This looks like a lead keel and the paired bolts on a lead keel of this model are actually one U-shaped rod that is threaded on both ends to take a nut. The single bolts are J-bolts and you can see how well they faired with the aft bolt literally being torn out of the keel. Compared to many of the newer race boats, that is actually a pretty big root area.
It will be interesting to hear what is learned as the story develops.
Does anyone know if everyone on board was okay?