Originally Posted by justwaiting
So how necessary is it for the sails to be fully balanced before engaging the wind vane?
Yes, I think a good way to think about it is that trim deepens the groove the boat is in. Windvanes tend to have less of the rudder
throw available to them, on my last boat probably about half of the throw that the autopilot
had (which would go all the way to the stops). So they have less ability to get the boat back into it's groove if it gets far out of it.
So how important trim is kind of depends on the boat. Because some boats have much deeper grooves than others, and are much more forgiving of unbalanced sails. The late 70's Perry design I had would fall into very deep equillibriums, and that is one of my favorite things about that boat (and evidence of Perry's skill, IMO). I do not know design, but I feel like a powerful rudder
is important, as is a hull
shape that doesn't turn the boat as it heels. I have heard, and can see in the shape, that the traditional narrow hulls with large transom hung rudders would also have very deep grooves. I also feel like some racing
hulls with large spade rudders and an underwater shape that is balanced as it heels would also tend to have deep grooves, though it may not be obvious to the person at the helm
since the rudder has so much power.
So... On this boat the windvane would work very well without balanced sails. Before I knew trim, the windvane would steer reasonably well even with poor trim, though it would let the course wander quite a bit. It depends on the wind and seas, but it was typical for the course to wander 20 or 30 degrees to each side of our intended course with bad trim. We tended to judge the course by the middle of the extremes of the wandering, and set our average course to where we wanted to go.
In some seas this wandering is unavoidable, but in most it's not. Once I learned trim... which is when I was forced to: the Torres Strait is pretty narrow in places, and with a broken autopilot
, we were pushing ourselves to get the boat to steer within 5 degree's of our intent. It's funny
how pushing yourself to learn something will make you learn it...
Anyways, I've sailed other hulls that do not have deep grooves. I've tried to figure this out, why, so that I could see it in the lines (and avoid it in any potential Boat #2, since I know I really don't like it). And, the best I can figure out, and from conversations with designers, is that some boats have under powered rudders, and the hull
has an uneven underwater profile that tends to turn it as it heels. Some, as they heel, tend to throw a lot underwater right at their beam, and they get unbalanced in their drag. Ok, here I really don't know what I am talking about. There's a word for what the cross section of the boat at the waterline, and the thought is that if you look at how that shape changes, that will indicate this effect.
But, the point is, these hulls have shallow grooves that even autopilots have trouble keeping them from freaking out. Add poor sail trim and a windvane that only throws the rudder half or a third as much as an autopilot, and, well, it'll be pretty hard to settle that boat into an equillibrium that it'll stay on for hours on end. The small percent of waves that are randomly slightly bigger or out of sync from the others, or a gust, or whatever, will push it out of it's groove and it'll start on another course, or tack, jibe, or whatever.
So with these touchy designs I think sail trim is much more important. It's no longer about just getting the boat to stop wandering widely, but to get it to stop freaking out every few hours.
Originally Posted by justwaiting
Secondly how does the helming of the boat by the vane affect the way in which you go about trimming the sails?
As to how to trim the sails for the vane, and if it's different to trim the boat for the vane... I think we now trim for the vane the same as we trim for a person or autopilot to steer. Because it is faster and the boat sails a better course. The goal is really to get the helm to feel light, just a touch of weather
helm (if any), and for the boat to mostly stay on course if you don't move the helm at all. I guess I define it as a deep groove-- you want the boat to need only small movements of the rudder to stay on course, even as waves and gusts knock it slightly off course.
Under windvane we are more likely to use double headsails or with a reefed main, or no main, on a run or broad reach. I think we also, in general, tend to reef earlier, to keep the boat more balanced. But I do not think we lose any speed because of this, since as we approach needing to reef the weather
helm builds and we tend to be dragging the rudder and slowing ourselves down.
So, if there is an algorithm or method that I can somehow communicate through words, it's to get the boat in a groove, set the helm in a pretty neutral position, make sure the boat is staying there for a few seconds, make sure the windvane is centered (the wind paddle is straight up and down, and the pendulum in the water
is centered), and then engage the wheel
. And then... it's just pushing a small child on a bicycle and letting go-- they just kind of take off an keep going...
You can tell by watching the vane when the trim needs to be fixed. The vane will tend to be steering
to one direction more than the other. The pendulum in the water
should spend most of it's time centered, with short little corrections to either side. If the boat is getting off course enough that the paddle is going all the way over, or the boat is taking a while to get back on course-- that's the time to retrim and get everything balanced again.
Of course, an advantage of learning
good trim is that you tend to sail faster. Because the rudder is not being used as much, so it drags less. How much of a difference, I don't know. I think it's most important in light air, from barely ghosting along all the way up to a little under hull speed
Hope that helps!
PS-- An interesting thing is that, in many conditions, I feel a vane will steer better than an autopilot. Because it senses the wind and allows the boat to follow the exact wind that the sails are trimmed for. A servo pendulum vane (as opposed to an auxilary rudder type) can additionally feel the stern slew around from quartering seas, and tends to react before the compass
heading has even changed. It's pretty cool to watch.
PPS-- This is something that took me years of sailing far to learn, and, from day sailing
with other people, I know that many other people don't get it. My crew and I just kind of look at each other, kind of weirdly uncomfortable and annoyed to be on a boat being poorly sailed (it's like watching someone try to Google
something and screw it all up, you just want to take the keyboard from them), wondering if we should backseat drive or take the sheet from them and let it out eight inches or whatever...
So... I'm hopeful that there's a way to explain it through this medium, but I'm a little skeptical about a written brain download, so I think it's mostly about pushing yourself to learn it.