In my research for resources, I stopped off at a local friendly tire store, one I have dealt with for years, and asked how they "dispose" of thier old weights. Takes them down to local recycler on occasion he tells me. SO I tell him I am interested in making taking them off his hands for a keel. The thought of boatbuilding made him smile and he said, no problem I could have all I wanted and that he had at least 3 ea. 5 gallon buckets full already. He then tells me that a 5 gallon bucket of tire weights weighs about 700# !!!. I told him I would be back when I had something other than my 1966 Mini to cary them in....