Originally Posted by Sternik
First thought that comes to my mine is a german Jollenkreuzer. This one here, build in 1928, is stunning. The boat above, not so.
That is a very neat picture. The curve in the upper portion of the rig reminds me of the Herreshoff S-Boats and
some of the Skerry Cruisers (22 square meter class).
The curved upper mast was a fad which probably originates with Manfred Curry's research into aerodynamics in the early 20th century. Manfred Curry's research was pivotal in understanding the behavior of wings and sails. He had access to the Fokker wind tunnel and tested actual bird wings and metal sails to measure how they behaved. His book on sailing aerodynamics was widely read and raised the bar on the understanding of how sailboats worked. It was full of illustrations comparing bird wings to sails.
One of his main areas of research was on how to obtain the most efficient sail plan (drive to drag) with a fixed amount of sail area. He came up with a fractionally rigged sloop sail plan with a very large mainsail, with a curved masthead and a comparatively small headsail. He employed this on a number of designs the most famous of which probably was his J-Jolie boat.
While Curry's design was a sliding gunther, which permits the sail to be reefed, I have aways wondered what happens when you try to reef a rig like the S-Boat or a Skerry with their curved upper mainsails, when the curved portion of the sail hits the straight portion of the track.