Originally Posted by wind_magic
I have heard this term "balanced boat" a number of times but never really understood what it means. I assume it means that the boat goes in a straight line and doesn't head up into the wind or fall off of it, but I don't know for sure. Someone earlier in this thread was, I think, trying to explain it to me but I didn't completely understand what was being said.
As you said a balanced boat is a boat that doesn’t have any tendency to take off on her own and change course unexpectedly. A lot of things need to be in place if you want to succeed at this. First the rig and boat need to work together. The shape of the boat itself is important because as the boat heels its center of lateral resistance will change if the boat changes trim. So a modern boat with a wide transom and the center of buoyancy more then 54% of the waterline aft and a fin keel and spade rudder will be almost imposable to make balanced under anything but the calmest conditions. As the boat heals the stern raises and pushes the bow done and the center of area in the sailplan moves relative to the center of lateral resistance. The boat will wander as she rolls because of this. It’s hard on a windvane system or helmsmen.
An older design such as one designed under the CCA rule tend to have longer ends then a modern boat and more importantly the distribution of volume under the waterline is more even forward and aft with the center of buoyancy closer to amidships. As this boat rolls she will not change trim so you don’t need rudder input to go straight while rolling. If you need to keep adjusting the rudder while sailing you will never be able to sail just by balancing the boat. Try this with your boat, go out on a gusty day and if you need to add much rudder as the boat heals in a gust then you will have trouble getting her to selfsteer without a windvane or the use of the rudder. If you want to be on the safe side and avoid having someone outside during bad weather playing with lines and jury-rigs to steer after you have rudder problems because your boat doesn’t steer straight by herself you might want to consider a different boat. I don’t like double-enders but that hull form is the most balanced and its one of the reasons the type got its reputation for safety offshore. No mater what else happened you could at least depend on keeping control of a double ender and that’s one of the reasons the shape was used as a sailing lifeboat in the north sea.
Your choice of sails is just as important. If you are using a large overlapping Genoa there is no change of forces in the rig as you start to turn until the boat has changed course beyond the recovery point. But if you have a 110% jib and set up the trim correctly you will have very large changes in force with small changes in course. The boat will be able to correct the course before the turn gets away from you. You should also note that the CCA style of boat has a larger main and smaller fortriangle then a modern boat. This makes your choice of sails a little more difficult on a modern boat to get the same balance as on the older style of boat especially with the difference between the semi full keel in the older boat and the fin in the newer boats. The longer ends in the older boat also move the center of effort of the headsail farther forward relative to the end of the waterline then the modern boat.
But how do you really do it? It varies quite a bit boat to boat so you need to experiment on your own boat but the short answer is simple. Let me oversimplify it a bit just to make it easy to understand. Close hauled and reaching are similar in setup with the difference being just one of degree. After you trim the boat and sails on reach so the rudder has just a small bit of weather helm you can then trim the headsail in a little more and trim the main out a little bit and then tie off the tiller. If the boat wanders off the wind the main becomes more effective and the headsail less so and the boat rounds up to the course. If the boat wanders towards the wind then the headsail is now trimmed better and the main loses drive because it's grossly under trimmed so the boat falls off to the course. In either case the boat sails a course of gentle s turns each way but averaging a better course then you would after a few hours at the helm. The amount of over or under trim is greater for reaching then close hauled and in fact I found that if the conditions were right the boat would go to windward by herself trimmed very closely to what you would consider proper.
If you are doing this because you lost the rudder everything is the same except the slight weather helm part. The boat will wander more without having some weather helm to start with but it works just the same otherwise.
I hope this makes sense to you but if I didn’t explain it in a way that you understand just ask and I will try to do a better job. Also you can point to a lot of other factors that have some affect on steering such as the shape of the leading edge of the keel and the presence of a centerboard but this is a quick overview and I hope it will get you started in the right direction so you can experiment with your own boat.
All the best,