Luckily, the piece that broke off from the stern of my boat fit nicely back onto the boat. Most of the wood from inside the break has been replaced with thickened epoxy, yet it still mostly looks like wood from the outside. I wrapped a few pieces of fiberglass around the damaged area and onto the hull a few inches. Hopefully this will give me enough strength. If the section re-breaks my plan is to build a third rudder that follows the shape of the stern (just like a more traditional sailboat). I will attach it using gudgeon and pintles which will spread the strain. I hope this will not be needed, but that is my backup plan. I thought of building some kind of internal rudder that would kick up into a slot in the stern, but the rudder size I need to turn this boat while sailing would necessitate mounting the thing a few feet forward, pretty much halving my storage capacity. Not to mention the giant hole that I would have to cut in the bottom of my boat. Here's a couple of photos of the repair taken before sanding and varnishing. You can see that the repair took place outside, as I have lost my shop space. Thank goodness it is still warm enough for the epoxy to cure.