Hello, Vandeusen,
There's a book by a man called Letcher,
Self Steering for Small
Boats. If you read it, it will give you some ideas to try on your Roberts. Your Boat is difficult for wind
steering, because of its shape. You really need pretty unobstructed air flow to the "fly" of the vane, so that it can respond quickly, and anything back that that gets in the way of it would be a problem.
My husband built an auxiliary
rudder type
wind vane for our first Insatiable, and it worked well for us. He copied
parts of the old
Autohelm wind
steering system, but he took the design for the
rudder out of a book for airplane wing design. In use, we took out the
weather helm by adjusting the
wheel position, and locked the steering; and the
wind vane steered, adequately, thousands of miles. But if you have
hydraulic steering, I don't personally know if you can lock it off.
If you have the skills or a mentor, you might be able to make your own wind-steering system, and good luck with it.
Ann