Caution, these are disturbing pictures.
I glassed the hull/deck joint over wiht 2 layers of woven matting. The cheesey rub rail manufactures offer are no match for my ability to "RUB" docks, pilings etc. In a move to save some dollars I thought to install a wood rubrail 1"x3" teal. I drilled and bolted to the now smoother hull/deck joint. I've very satisfied with this modification, stiffer and a good look as well. I could drive old rusty nails into it to hang fenders, eh?
Here's some pictures I have of a Helms that sunk at the dock and was later cut apart. Looking at the profile of the hull the ballast added is evident in the keel. I can't make out a lot of detail of thickness but you can look for yourself and perhaps draw some conclusions. I know it's solid, not cored.
Caution the first 2 pix could be disturbing to Helms owners, it is the dismembered hull of a 1972 25'er.
3rd is my hull deck joint.