On Sunday, September 29, 2019 at 5:34:08 PM UTC+2, wrote:
According to my copy of "Segelflugzeuge vom Wolf zum Discus" by Peter Selinger, water ballast tanks were offered as an option by Schempp-Hirth since July 4th 1971. I suppose Grob followed the same policy.

My father used to own Std Cirrus #11 - 1969. It was fitted with water ballast.

Clinton