ORIGINAL: dirtybird
Using a servo to set the trim tab is not a new application. I saw one installed on a homebuilt more than 20 years ago.
Take a look at Servo City (Google for URL). They have many special servos that could be used for this. I am considering one to use to apply the brakes on my towed vehicle from my motor home.
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And I repeat: It was the wrong tool then and it is the wrong tool now !
What you saw 20 years ago means what ?
Simply a half baked solution then and it still is .