Originally Posted by
JDNSW
Certainly concrete used in hulls usually has an additive to ensure low porosity, but this need not be a proprietary additive - successful concrete hulls were being built many years before these were invented - for example, 'Helsal' a successful ocean racer of the 1950-60 period, and barges dating from as far back as the eighteenth century. I think what his discussion is missing is that concrete hulls are always adequately painted, inside and out, which prevents water absorption from being a problem.
John