Kevin,
Those things fail where the steel rod goes across and then comes to a T. The shackle fitting is pushed outward due to the size of the weld (on some foils). A crack develops in the fitting and the result is an inverted taco for a foil, followed by the mast crashing down.
I have heard of the rod failing at the weld too. But I have never seen that one.
Here is a link to some pics:
http://darientel.net/~surfsail/xbar8.htmlThis happened to mine but I caught it before it cracked all the way through.
Hope this helps.....
AJ
Nacra 6.0 Express