The lack of response to my previous submission suggests that by trying to be brief, I failed to explain my idea adequately. So, here goes again:-
When I luff up, the mainsheet (or Mizzen sheet or traveller line) tension drops to zero. When sailing full and bye, the tension might be 10 kg (22 lbs in the USA). If I attached the end of the sheet to the lee side of the tiller, I would need to pull with 10 kg + the force needed to overcome the weather helm. So, I normally attach a small block to the mainsheet positioned just above the cleat. This gives me more motion and a 2:1 reduction in needed force, from 10 kg to 5 kg in this wind. If I lead this line to the mid point along my tiller, I only need an effort of 2.5 kg (plus weather helm) at the end of the tiller. This is readily supplied by a weight that is attached via a block to the end of the tiller so that the weight pulls the helm down.
In action, when the wind comes ahead, the mainsheet tension decreases and the force from the weight is greater than force from mainsheet so the boat bears away to the new course. If the boat at falls away from the wind, or the wind strengthens, the mainsheet tension increases and the force is greater than the force from the weight, so the boat comes up.
It is easy to greedy, and have the sheet lead and weight placed to get the full drive from the main in the average wind. But with this setting, in a lull, the boat will come off the wind and may gybe. So I try to arrange things so that in the average wind, my boat i hard on the wind and the main starting to luff. Then in a lull, she drops off, so the sail gets more drive and we get enough mainsheet tension to steer as outlined.
My first weights were old SCUBA weights, but a plastic milk container full of sand would do. The blocks were ones for dinghy control lines at less than $ 10 each, so my cost was less than $20.
If you have wheel steering, you may need to make a drum, but a brief experiment on a friends yacht showed that we could steer her with lines lead to spokes of the wheel. In that ship, a winch was needed for the mainsheet. So I used a lever to bend the mainsheet round 90 degree bends two points about 5 cm apart and attaching the sheet lead about a metre along the lever. This greatly reduced the force to the helm. The line was then lead to a spoke and attached close the wheel axle. The weight was attached to a spoke at a point close to the rim.
My apologies to any Physicists who object to my use of kgs as a unit of force. Yes, I know kgs are a weight, not a force, but most of us can relate to it as a force.