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Autopilot steering with an auxiliary rudder

Jan 1, 2003

To the editor: My boat Tricia is a yawl-rigged, 30-foot, center cockpit built in Hong Kong in 1963 to a design by Bill Shaw. She is solid mahogany with a Dynal overcoat. The boat is still sound after all these years. I wanted a good solution to using an autopilot, but asking my little Tillerpilot TP 1800 to move all those cables and pulleys was perhaps asking too much.

The Chinese chaps who installed the cables and pulleys did have the foresight to install an auxiliary tiller. I wondered if that was the right place to install the Tillerpilot. But a look at the auxiliary tiller and quadrant in the after hatch convinced me there was no handy place to make the connection and there wasn’t sufficient space for the autopilot to work.

It just so happened that I had a rudder left over from another boat. This gave me the idea to make an auxiliary rudder off the stern that could be driven by the Tillerpilot. I realized that, with a little make-over, the leftover rudder would do nicely. It needed about a foot in length. Plus, I added some extra blade area to give it some balance and minimize power requirements.

The final installation worked well. The 18-inch tiller arm required by the Tillerpilot was easy to arrange and the old pintles and gudgeons were also easily installed. Tricia has a nice conventional transom that allowed for the installation of the auxiliary rudder.

On her first sea trials she seemed to wander a bit, and the Tillerpilot didn’t seem able to keep the boat on course. I checked the owner’s manual for the TP 1800, and it said that the way to get more movement of the rudder is to either adjust the gain or shorten the tiller arm. The latter gives the autopilot more “throw” but it also requires more force from the autopilot motor.

I guessed the need for this adjustment from the typical setting on the TP is the relatively small surface area for steering a 30-foot boat. Unfortunately, the rear deck area of my boat is small, and getting back there to adjust the Tillerpilot is challenging. But I am still fine-tuning this setup. I hope it will be a useful addition to my singlehanding arsenal.

Jack Morton lives in Nassau Bay, Texas.


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