The whole you can do anything with concrete movement has received a shot in the arm recently as a result of a do-it-yourself experiment dreamed up by a naval architect, an engineer, and two building architects in Fort Lauderdale, Florida. Their project: the construction of a 28 foot racing yawl of reinforced concrete using the Ferro-Cemento principles of Italian architect Pier Luigi Nervi. Interestingly enough, the racing yawl taking shape in Fort Lauderdale seems to offer some economic advantages. It is estimated that construction cost will run about 50 percent less than for a conventional sailboat of the same size and type. Additional advantages are anticipated as a result of lower maintenance costs with concrete than with more conventional materials.