Using the mainsheet on Busca works only from about a beam reach on up to close-hauled but it offers simplicity and comparative ease of tacking in exchange. I've used it even when sailing on tacks as short as a quarter mile or less and as long as about 15 miles. The procedure when tacking is just to swap the elastic return and the turning block to the opposite sides. No need to untie from the mainsheet or tiller.
In an attempt to get Busca to self-steer on other points of sail, I tried using the jib sheet. It succeeded much better than I would have guessed it would and Busca has sailed many miles off the wind. In flat water and light air she has even sailed virtually dead downwind (within a few degrees) for miles on end. So far I haven't used this setup with my full suite of foresails; mainly the 155% genny.
As you can see, this arrangement is more involved to set up than the one using the mainsheet, so I only use it when I can sail for a fair distance. Basically, there is a line tied to the tiller that runs through a block on the weather coaming then up through one sheave of a double block on the boom and then to a block on the clew of the jib where it makes a 180 and goes back to the second sheave of the boom block and then essentially ties off to the coaming again. It's what they call a "fool's purchase" on the jib. Not all boats will necessarily be rigged this way; it's just what works on Busca.
The procedure when tacking involves first unhooking from the clew, unhooking from the boom, then swapping the elastic and coaming turning block, then tacking, then hooking to the boom and then finally to the clew. Definitely not something for a short tack.
Here is a more recent pic showing my latest method for attaching/adjusting lines. As shown, the base clamped onto the tiller should be mounted further aft for it to work as I had envisioned. The plan was to be able to flip the lines off of the brass knob while tacking but with the cam cleats as far forward as they are, that still doesn't create enough slack in the control lines. I was trying to avoid mounting a bunch of hardware on the coamings, but probably having the cleats on the coamings would work better. We'll see.
What I find so great about this, besides just plain being fun to see it in action, is how well it works. The key to it is first understanding the principles involved so that you know what you are striving for and then in the initial experimenting so that you learn how to set it up properly. Once you get it figured out then subsequent set-up times are pretty minimal and don't require much fooling around. The sweet-spot is found, according to Dr. Letcher, when the boat will sail herself without input from you from very light air all the way up until it is time to reef. If you have to make adjustments as the wind strength varies then you don't quite have it right. Probably the most common misperception about sheet-to-tiller is that it requires constant adjustment.
Basically, it boils down to balancing the pull of the helm with the pull of the sheets. There is a concept that many people (myself included) get hung up on when it is first presented but it helps to wade through it and get it sorted out in your mind. I'll try to explain it here without muddying the waters too much.
Every sailor sailing a dinghy has felt the pull of the sheet drastically increase when they bear off without easing the sheet. That experience is what causes the difficulty in understanding why sheet-to-tiller steering works. It is true that the pull of the sheet does increase. You can feel it! But what is happening is that the airflow over the sails is changing from pretty smooth attached flow to lots of drag as the sail becomes more square to the wind and the wind breaks away in swirls. Before that happens, before the wind breaks away from the sail to whirl away in a swirly mess, the pull actually decreases. It is a lot more subtle so it isn't noticed, but it is there nonetheless. This change in pull -before the wind breaks away in a swirly mess- is what causes sheet-to-tiller steering to work. The pull decreases because the wind that the sail sees is slower, and the wind is slower for the same reason you feel more wind when you walk into it than you do when you walk crossways to it or with it.
Okay, so there is a subtle decrease in sheet pull when the boat starts to bear off and a subtle increase in sheet pull as the boat starts to head up. I say starts because these tendencies only happen over a small range. Bear off too far and the wind separates in swirls or head up too far and the sail starts luffing.
Picture this: As the boat sails along, she heads up a little bit. What does the skipper need to do? Pull on the tiller to bear off a little. But wait! As the boat was heading up, the sheets were (briefly) pulling harder! So....connect the tiller to the sheet and voila, as the boat starts to head up the sheet pulls harder on the tiller thus bearing back off again. Conversely, picture this: The boat sails along and bears off a little bit. What does the skipper need to do? Not pull so hard on the tiller (assuming the boat is set up with a bit of weather helm). But if we recall, the sheet is not pulling as hard. So....if the sheet was pulling on the tiller, it is pulling less than it was...just like the skipper would have done.
The elastic that you see in the pictures above serves two purposes: it is a simple spring return and it also is a means of properly balancing the forces, so the stiffness of it is important. Determining how strong of an elastic is part of the experimenting. It is important because selecting the proper stiffness will help the boat to hold her course even when the wind picks up or lightens. Too weak of an elastic and the boat is likely to bear off as the wind picks up. Too strong and the boat will likely round up when a gust comes. You can verify that for yourself by intentionally using extra strong or weak elastic. Sailing on a close reach will likely require a different strength elastic than on a broad reach. Likewise, different sheet-to-tiller arrangements may require different strengths. I keep a couple of them handy and add or remove elastics based on the need.
Another adjustment availble is to vary the way the control line attaches to the sheet. For example, in the first photo you will notice that there is a bit of bend in the mainsheet. Varying the amount of bend will vary the force that the sheet is able to transmit: lots of bend, more pull on the tiller; less bend, less pull on the tiller.
Surgical tubing seems to be the elastic of choice because it has nice uniform stretchiness unlike cloth-covered shock cords. Its main shortcoming is that it succumbs to UV degradation. Mine lasts about a season of weekend/vacation use and then I have to replace it. The good news is that it is incredibly inexpensive and is readily available at any medical supply shop.
Everyone seems to have their own way to hook the elastic up to the coaming and tiller; my choice was to use the plastic shock-cord hooks that are available at your local marine store. Since the elastic is a hollow tube which tends to collapse when stuck into the hooks, I took a 1/2" long bit of wire and stuck in the end of the tubing where the hook clamps. I'll have to take a pic of it to add to this page.
On Lake Erie, Busca has sailed from a midday lull with barely enough wind for steerage into a nice brisk late afternoon breeze without input from me, sailing about 15 miles. On the Chesapeake, she has sailed diagonally across the Bay on a near run in light air while I finished off a book I was reading (frequently looking around...don't need anyone telling stories along the lines of "Yup, I guess the skipper was so engrossed in some book that he just let the boat sail herself right in to shore"). On Penobscot Bay, she held a course all night long heading out to sea in a light drizzle past Matinicus Rock, allowing me to leave the helm for brief stints to warm up in the cabin and check my location on the chart. On that night, we started out in very light, flat water and it gradually picked up during the night to the point Busca was washing her gunwale in seven foot seas.
In short, this technique works, and works well. Dr. Letcher sailed his Island Girl many thousands of miles in the Pacific using this extremely inexpensive method
Now that isn't to say it isn't without shortcomings. It doesn't work while motoring. It doesn't work while you are changing headsails. And it takes a bit of effort to learn how to do it. And trying to get it to work on some points of sail under certain conditions could be more than a little frustrating.
One noteable item for those who sail smaller boats is that crew weight affects it. On Busca, if I set it up while sitting to weather and then move to leeward, I have to tweak it a bit to compensate for the change in heel (and helm) my weight causes. Change in heel due to changing wind strength doesn't require compensating because the sheets transmit the extra helm force needed automatically. I find that on Busca while using the mainsheet to steer I need to tighten the control line about 3" if I want to shift my postition from the weather side to the leeward side of the cockpit. (or conversely loosen it if moving to the weather bench.
This is a different approach to getting a boat to steer herself. There are many types of windvane mechanisms and most use a windvane as more of a sensor telling the boat which way to head and providing only a little bit of power from the vane to actuate something immersed in the water which in turn provides the power to turn the helm. It is sometimes possible to use the vane itself to turn the helm directly.
I'm in the middle of making my first one, so I'll add more info as the work progresses. There are a number of photos and installation diagrams available for viewing at the various commercial web pages but the definitive web page with lots of information about them including plans for building your own is at Walt Murray's Web Page. Walt is a retired engineer who's hobby is, you guessed it, designing windvanes for the home builder. Isn't that amazing? His page includes a link to (don't you love this internet thing??) Paul Vandenbosch's windvane forum! And in addition to the wealth of information that Walt posesses, there is another gentleman, Jan Alkema, who has designed a windvane simulation program that models the forced, damped oscillations of a boat with differential equations. A number of adjustable parameters match the dimensions and ratios of the particular vane and boat in question. According to Jan, the progam has already been used to help design successful vanes.
There are many sorts of windvane steering designs, but not all are suitable for all boats. The design that offers the most certainty of satisfactory operation is the servo-pendulum type. It introduces a resistance to yawing (i.e. course stability) that not all boat inherently have and so it is the design that most manufacturers offer. Ideally, a servo-pendulum system can be designed to match a particular boat, with windvane and pendulum (oar) only large enough to work well. An example/summary of rational proportions for the oar and vane, taken from Letcher's book, is here. Hopefully I've added enough commentary to make it understandable. If not, please E-mail me and I'll try to revise it with more discussion. For a full discussion, see Letcher's book.
