CVane self made wind-vane self steering
Below is my version, the C Vane.
In Portugal I had access to the local sailing club's workshop, so I utilized a work bench, pillar drill, storage and work space to really get this thing built properly.
I found a piece of fiberglass sheet and cut it to the approximate size I wanted, with a 20% area in before the pintels. I cut a trim tab from the same material.
When sailing downwind, it is better to put the wind on one quarter or the other, so the sails are filled from one side, not goose winged. The Portuguese Tradewinds blew at force 5 to 6 and Storm Petrel was able to crash along almost down wind while I sat in the companionway playing guitar. It was a most liberating development.