I built a weather vane model of the two masted schooner yacht "America" (built in England in 1851 and best known as the vessel that took the first America's Cup for her New York Yacht Club owners) for my parents nearly 35 years ago. I transferred the hull lines from plans attributed to W.P. Stevens found as Plate XV in Howard I. Chapelle's book "The History of the American Sailing Ships". I carved the hull from a clear piece of 4" x 4" pine and fitted it with a pair of brass masts, bowsprit and rigging, with heavy sheet copper sails. I embedded a brass sleeve at the midpoint of the hull with two small ball bearings into the hull that allowed the model to turn on a stainless steel shaft (turned on a metal lathe) that was affixed to the N-S-E-W mount I also made from brass and copper. The hull was painted with multiple coats of black Rustoleum and the section below the waterline done on copper paint. The center point of the sails was probably 3-4 inches aft of the bearing axis, allowing the wind to point the schooner's bow to face the wind.
This weather vane survived about 20 years atop the roof of my parents retirement "camp" above the west side of Canandaigua Lake New York (major winters) until I took it down before the property was sold 8 years ago. It still worked, even though my cross axes in the mount were somewhat corroded. I still have the hull, but it is indoors. (Sorry, I don't have a picture of it, but if desired, I could take a few).
Jeff, the vertical axis was at the midpoint of the hull, but the sail configuration put the center of the side forces created by the wind about 3-4 inches aft of the axis. If you are planning to build one that will last, I'd recommend sheet copper.
