Tiki 21 Autopilot

I have wanted to be freed from the "tyranny of the tiller" for quite some time, and did some homework on fitting an autopilot to the Tiki 21. I followed Rory McDougal's posts on Harry the homemade Bill Belcher designed wind vane, and got the book and plans from the library. Its a great design but best suited to the open ocean and long passage making. Although I do aspire to such adventures, most of my sailing is around the SF Bay in highly changeable wind conditions and short tacks. This sort of sailing is better suited to an electronic tiller pilot.

I splashed out and bought a Raymarine ST1000 tiller pilot, but that was the easy part. The ST1000 is designed to attach to the tiller around 18" from the the turning center of a rudder in the easily accessible cockpit of a monohull. On the Tiki 21, or any other wharram, 18" from the rudder is way down the back of the rear hull and completely inaccessible except in the calmest of conditions. The problem is how to bring that 18" turning center closer where it can be safely operated by the skipper in any conditions.

See above my rough plan which I came up with after seeing pictures of Boatsmith's Tiki 30 Abaco and from the Bill Belcher book (thanks Boatsmith). Basically lines are tied to the tillers at 18" and then carried through blocks to a center along the rear beam under the tiller bar. The tiller pilot is mounted on the rear beam and the ram is connected to a pin mounted on a small jib slide car and track just behind the rear beam. Instead of connecting the lines directly to the pin, the line is connected to 12" of chain that can be dropped over the pin to engage the lines. The tiller pilot is then dropped over the pin and turned on.

Chain disengaged next to pin

Chain on pin. The pin is a 6mm stud threaded into the jib car.

Ram dropped over pin - auto steering engaged

Steering the boat

Steering lines bound 18" from rudder pivot

Steering lines starboard side

Turning block at starboard rear beam

View to port side

Simple tensioning system using lashings on starboard side of chain

Rear bulkhead power cable attachment. The pilot is powered by a U1 AGM battery.

So why got to the trouble of using the chain instead of leaving the lines permanently connected to the pin? Sailing on a course, the tiller is often loaded up on one side - that is, the skipper is holding the tiller to port or starboard to keep the boat on course. If the line was permanently attached that would mean that when the tiller pilot ram is dropped over the pin, the pin my already be over to one side of the track and there is not enough travel to maintain a course. With the chain, the skipper can load up the tiller before dropping the chain over the pin in the center of travel. This means that the ram is centered even though the tiller is loaded up to one side keeping the boat on course. Clear as mud? Another great advantage of the chain, is that it is easy to entirely disengage the steering lines from the steering when sailing without the autopilot.

So how does it work? Amazingly well! I've used it now for 100 NM around the bay and outside the bay and find that it works way better than I expected. I managed to overpower it running downwind in 20 knots in a 6 foot swell with full sail, but it worked fine again once I reefed the sails down. There are limitations of course. The autopilot can hold a course as long as I can hold a course i.e. the sails are balanced for the conditions and the course is holding without too much weather helm before the autopilot is engaged. It is not magic and can't hold a course if I am struggling to hold a course without the pilot. See video below of my first test sail from a previous post.

Apart from the ST 1000 tiller pilot, I coughed up about $30 for a Ronstan small jib car and track, and $20 or so for the line and one foot of chain. I already had some spare blocks and hardware. The U1 AGM battery powering the tiller pilot was around $70.

Making it better: Reducing friction would allow the self steering to work more accurately and smoothly but would cost. A mainsheet traveller car and track would be smoother than the budget jib car, but would cost several hundred dollars. Using a better quality traveller car would also allow rigging up two pins or attachments - one for the ram and one for the chain. This would allow the ram to be permanently installed on the car, and engaging the steering would only require dropping the chain over the pin. Bigger blocks, say 40mm air blocks would also run a bit smoother. If money is no object, then the ST 2000 has a quicker action and would probably work overall better than the ST 1000 (but would also use more power).