When first built in 1914, the Wianno One Design had a different keel/rudder arrangement compared to what is seen today. The iron ballast keel was originally tapered on both ends and the rudder was symmetrical from top to bottom.
From early on, it was determined that the boats did not have enough steerage. In the winter of 1926-1927, the design was adapted to incorporate an extension in the length of the keel and a larger rudder. For boats built earlier, a filler piece was added to their keel in order to accommodate the larger rudder and to keep them competitive with newer boats.
You may still see older hulls with the keel modifications, as shown by these photos of a hull built in 1923: