Technically I think a
centerboard would be
wood. A swing
keel or retractable
keel would be heavy. :>) Not
aluminum.. too many
corrosion issues and not heavy enough, Stainless would be too expensive. If it's a shape that could be done out of
steel that would be great, even better if you could have it galvanized..? Many traditional boats had a
steel keel, Thunderbirds etc. Could you take your old one as a pattern and have one cast from cast iron or cast steel? Cast iron might be better than steel.
Bronze would be the ultimate, but with today's copper value......