Years a go I saw an ingenious system devised by an American yacht designer whose name escapes me for the moment. I'll try to describe it. A horizontal rod in line with the boat's centreline passes through the upper part of the sternpost. It engages into a slot in the rudder head. Where it leaves the sternpost, it is bent downward at an angle of 40 degrees. At its inboard end it is geared to the steering wheel shaft, which is parallel to it and just above it. As the rudder shaft rotates, the bent part moves the rudder from side to side. Given the forces which can apply to such a shaft, it needs to be very strong, probably about 1" diameter. The gearing ratio is up to you, but I would imagine that around 3 or 4 to 1 might be appropriate. A lever can be clamped and keyed to this shaft, and a normal push-pull Autohelm attached to the lever, all of this being below the aft deck. The longer the lever, the easier it would be for the autohelm, but the limitation is the length of 'throw' of the autohelm.
Peter.
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