This S&S design 1780 is a very typical R.O.R.C. racing yacht. A number of these boats were built by various builders. This is right at the point in time when separate rudders were coming into fashion so the boats built to this design were from modified plans with a separate rudder. Other modifications were made to differentiate the boats, mostly with changes to the deckhouse geometry.
Information courtesy of http://sparkmanstephens.blogspot.it