Eighteen feet of 1/4" Samson Amsteel Blue (though it is really grey) arrived this afternoon. The shackle which held the line in place as the centerboard pendant will be replaced with a larger and stronger one, the thimble will be reused.
I spent some time trying to recall both the name and the technique for the very simple splice I had used to put the thimble in the line. As with all things these days, the answer was found with a google search. The name remains elusive, but the splice can be seen here (though I did it with a screw driver and a straw). Very simple, and in fact the only splice that I can successfully make.