Originally Posted by Andrew
I'm looking for a Blondie Hasler trim tab self steering vane/or plans
Why? These things are expensive and excessively complex IMHO. Here's a better system, and it integrates seamlessly with both manual and linear ram drives as well:
1. You have a transom mounted semi-balanced rudder with an open stainless pipe rising on the axis.
2. Mount a trim-tab on the trailing edge of this rudder with a tiller at 90 degrees and rod connected to it by a bolt.
3. The wind vane sits in the tube with cog on it.
4 The trim tab rod connects to an arm also mounted on the wind vane post which has a track on it.
5. A worm drive is mounted on a car on the track.
6. A shock cord engages the worm with the cog, completing the coupling.
7. A rope with a cleat disengages the vane.
8. The worm can be adjusted whilst operating by turning it, changing the engagement angle
(or just disengage, steer boat, then re-engage).
This system allows a tiny wind vane to drive a massive boat, because the wind vane is directly coupled to the trim tab, which makes it move in the "wrong" direction with no effort, since the trim tab is quite small. The trim tab can also be driven by a linear ram from a tiller autopilot of the smallest size (uses almost no electricity) coupled to the rudder (not to the boat!)
The trim tab drives the trailing edge of the rudder in the opposite direction to its own trailing edge, which then steers the boat in the right direction. The torque of the trim tab is the product of its area and distance from the rudder axis (and so it can be as small as you like if you're willing to trail it far enough behind the main rudder).
Because the drive is not coupling the rudder to the boat, it can be simultaneously steered manually without disengaging the autopilot (but you will be fighting the torque of the trim tab).
Note the wind system is instantly responsive, so it will track the smallest wind shifts faithfully .. which may not be desirable.