This is a response that I tried to post as a comment following a question about our windvane steering- why we chose this particular type. As with most boat-related topics, I got a little excited and wrote more than the comment box allows. So it has become a post.
I've got some more posts that I will place tomorrow but, for now, suffice to say that we arrived in Cabo San Lucas this morning and, though we're still only about 2/3rds of the way through customs, it's been a blast so far. And wifi from the cabintop... who can complain?
Ramblin from the Frigid North,
The Hydrovane has been very good to us. It steers a great course and has proven to be very adjustable to various conditions. It's drawbacks are few. However, it has trouble steering a course lower than a broad reach if the swell is close together- as a guess I might say a ten foot swell at 12 seconds means an often flogging jib and a lot of exercise for the gybe preventers on the main and mizzen if we're trying to go dead down wind. In those or similar conditions, we often sail a higher course than would be ideal. That said, I imagine that is a symptom of servo-pendulum systems as well because any windvane is a reactionary system. A human sailor can scope out the swell and the breeze before it gets to the boat and keep a much lower course using that anticipation; the vanes have to wait until the wind gets to them and are ignorant of the swell except in how it affects apparent wind.
I don't have direct experience with a servo-pendulum system, but I think they would likely have similar results. It hasn't been a problem for us, but, it's probably worth saying that Ardea is well balanced. It may just be one of the advantages of a ketch rig- again I can't claim to be an expert, as this is the first multi-masted rig that I've had substantial experience with, but we can adjust canvas and as long as we lash the main rudder in the right spot and trim the sails properly, the Hydrovane is great.
About the servo-pendulum systems- they are fantastic. One immediate consideration is that they rely on the main rudder and thus to not provide an auxiliary rudder in the event of a break down. This might matter a lot (especially if you have a fin keel/spade rudder) or it might be a fail-safe against a very low probability event (skeg-hung and, more so, keel-mounted rudders, provide more protection from impact).
Servo-pendulum vanes are great because you can be sure that the vane will always have enough power to steer the boat- it is using the main rudder, obviously designed to steer her, and the pendulum ensures that powerful water pressure will persist until the course is corrected. They're also much cheaper even new and have a much larger used market than the Hydrovane and its kin (all auxiliary rudder windvane systems- Autohelm makes one, Flemming makes one... there are more but I can't think of them now).
To sum it up, because Ardea has a full keel, the need for an auxiliary rudder did not alone outweigh the cost-saving of a servo-pendulum system (Monitor and Aeries are the two I strongly considered, both of which are readily available on the used market and, even well-used, have very good reputations). The kicker for Ardea is her worm-gear steering on the main rudder. I'm happy to send you some pictures of the system if you'd liked, but basically it means that there is a relatively high level of turns for the full range of the rudder (four turns from full starboard to full port) on a relatively small wheel. A lot of folks that have done crossings in Mariner 31s have reported that a servo-pendulum system relying on lines run through blocks to a drum on the wheel have trouble achieving enough rotation on the wheel to effectively adjust course. They will work, but require a significant amount of attention and adjustment. They also mean placing blocks and running lines in your cockpit.
I would confidently go with a used servo-pendulum system, which can be found in the western U.S. fairly easily for about 35% of the cost for a new Hydrovane, on a boat with a larger wheel or different rudder mechanism. With a tiller-steered boat (which I dream of) I feel the servo-pendulum system is even better suited. I would highly recommend finding out the experiences of folks that have owned your type of boat or something similar. The boat design is important to consider. But, in the end, if an opportunity to pick up a solid piece of gear at a really good price comes up, I think that you can probably get most of the more common windvane systems to work with just about any boat.
Sorry to be so long-winded, but I figured if I posted on the comments, it may as well be thorough. These are just the things I found in my limited experience and from the research I did when I was in your shoes. I also bought a book about windvane systems (Amazon or similar will show several that talk about general concepts as well as how to design and build your own system), which helped for sure. Feel free to keep asking questions- you're welcome to contact me via email- cddibble@gmail- as well.
Keep warm,
Connor
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