wind vane self steering
The system: DIY servo pendulum with variable vane to pendulum linkage, this has not been tested by ocean crossings or extreme weather, but has many years of use and is still a work in progress. The boat: 50', 19 ton steel cutter, slightly modified full keel, skeg hung balanced rudder, with statly, even majestic performance.
Operation: fix tiller with stop (1), insert vane pole and hook on clew to deploy vane (2), lower pendulum (3), connect cross link (4), tension reverse tiller lines (5), set course (6), engage with over center lever (7). A tiller stop helps but first try is rarely successful, one must disengage, move tiller and reengage with quick action of over center lever. These corrections can be very small so a sliding reference helps to track and minimalize vane and tiller movement, goal being no movement, at least in steady wind and low wave conditions.
Cross link settings: 1-3" below bellcrank pivot best offwind, 1" for DDW with lower counterweight, and even elastic damping line in high rolling conditions. Crosslink 3-6" down for upwind, 6" down and weight up for close hauled light leeward shifting wind to correct before sails stall and boat loses speed and pendulum power. This is system's most difficult point of sailing perhaps compounded by long keel. DDW there is much less speed variation and the small vane with adjustable weight works in very light air. There is no direct rudder feedback but there is progressive dampening of turning signal through linkage, high at 1" to low at 6". I expect there are hidden actions and more to learn about the " Hand of God".
If the pendulum swings due to yaw in following seas, the reverse tiller turns the wrong way, in practice, the vane signal for course correction, slightly diminished by apparent wind of roll,dictates the action and, with linkage adjustments, can develop a nice rhythmic correction. Above 3 KT boat speed, it is impossible to lift the pendulum up out of the water with the safety line against the vane signal. I disconnect linkage and rotate pendulum tab to surface the blade for easy lifting and stowing while under way.With the wide variety of wind and sea conditions, the system can sometimes be oddly cranky but adjustment of linkage ane vane weight guided by reference indicator has consistently restored performance.
Maybe too many subtle trim options here but what do exist in any system should be finely calibrated, very quick and easy to use, too much changes too fast during reset, this was the main change from design to use. Course setting: simple but inconvenient locking thumb screw on wind vane support tube (8), insensitive, pull but no push, running line leading forward on deck (9),20" wheel for finer control but fixed location (4), running line forward crossing bridgedeck and back along combings giving access from various locations, even from inside the companionway, last 2 are tough trade off, opted for (4)'s finesse. Pendulum-vane link started as standard turnbuckle, went to sliding barrel with pins, to sliding thumb screw clamps on tabs as this became highly used. Tiller line clamp was engaged by threaded rod turned by crank handle, way too slow, so onto over center lever. Since tiller location is so critical, boat will wander to correct any misplacement, improvement here really pays off; lines to jambcleats are too slow and chainlink not fine enough. For more standard forward facing tiller, a robust over center or eccentric cam stop lever, sliding on a track bolted to the top of tiller, could supply line tension, variable leverage point, fine tiller position adjustments and quick engagement. Adjustable blade sweep can be useful, especially on small boats where high cockpit loads can cause an overly balanced forward swept pendulum for some wild oversteering.
Much of this system is below deck and inboard and less susceptible to damage; it also allows the main tiller to be lifted and remain out of the cockpit, but there is the loss of awareness of developing problems and immediate access. The stem of a 30' sailboat at full speed hit the outboard end of pendulum's horizontal rotating hollow shaft (8) only damaging rubber end cap, the glory of steel sometimes shines through the rust.
Construction is mainly welded stainless steel, vane shaft is aluminum tubing, quadrant is a split 20" bicycle wheel. Bearing surfaces are all plastic except vane crankshaft pipe (10) which, grooved by a pipe cutter, rests in sharpened cutouts of split sheet metal housing to minimalize surface area, crude but effective in very light air so far.
Credit for the success of a wide variety of systems applied to so many different boats should be given to the sailors who have labored to join the two, it may never be a perfect fit but when it works- ecstasy..