Trim Tab Windvane Recommendations

[Klaus-Marco]

Hi cruising folk !
I have recently acquired a Sadler 29 Bilge keeler and plan to go this summer
from Portland, Dorset, to S Portugal and beyond.
This is a boat with a stern-hung rudder, so I want to use a trim tab on the main rudder, activated by a horizontal vane.
Im my 30's I built a 35ft Fin keeler and for our E/W Atlantik crossing I copied a frenchman's servo rudder with trim tab activated by a small horizontal wind vane -
i.o.words a separate steering system. I t worked well, except in very light winds, for 15.000 Miles.
My question to the enlightened cruising community :
1. Has anyone had experience with this kind of self-steering on a small boat with either fin- or bilge keel ? with a view to steering reliability, but also design and DIY compatibility.
2. Mike Lukas , the Yachtman's Oracle in all things Sadler, recommended a Sea-Feather, and I can see it's good kit, and at 2200.-very competitively priced. Still, a lot of money for me, when I can build the trim tab version mostly myself,
and it also means less clutter at the stern..

[Benz]

The only thing I can say about a trim-tab is that unless you make a cutout in the rudder to acommodate the trim tab, it will effectively make your rudder bigger. If you put it further aft on a strut, a la Pardey, it will REALLY make your rudder seem bigger.
Even allowing my prototype one to "freewheel," as it were, the force required to turn the tiller was exponentially magnified. Add to that the bother off feeling the thing swing around back there when not in use, and thinking about the additional strain on the gudgeons, made me scrap it rather than fine-tune it.
If I was a better engineer, no doubt I could have made a better unit that wasn't so awkward--and if I do something like that again, I'll keep the trim tab close, rather than strut it out aft. But:
I have a Sailomat servo-pendulum unit now, and I really like taking the whole circus out of the water when not in use, and having my rudder just be a rudder and giving the tiller really good feedback.
Everyone else's mileage may vary.