Flounder,
Like you, I had a love hate relationship with the nacra rudder system. It has the advantage of extreme simplicity, the disadvantage is the dificulty in getting it to stay in the correct position.

Lets start with the basics. If it is a Nacra 6.0 we are talking about, the first thing you should do is redrill the rudders. Fill the pivit hole in the rudder with west systems and microballons. Redrill the pivit hole aprox 1 pivot hole diameter farther towards the front of the blade. This allows you to balance the helm by toeing the rudders much farther under the boat.

Second, Replace the plastic clam cleats on the pivomatics. They cost about 3 $ each. Just drill out the rivits in the old ones and reuse everything else. Make sure the rivit that sticks up through the cleat is not too long or the cleat won't work.

Third, consider changing to a 2:1 mechanical advantage for the kick up mechanism. This lowers the load on the line in the cleat by a factor of 2.

Fouth, experiment with lines. You want a soft spun knoby polyester line with moderately low stretch. Generaly I find 1/4" is best.

The last thing you can try is powercleating. To do this, snap the pivimatic in the up position. Next pull the rudder pulldown line all the way (rudder in the down position). Lock the line in to the clam cleat, then snap the pivimatic down onto the rudder arm. At this point the rudder should be solidly locked down.

The bottom line is the Nacra rudder system can be made to work reliably if you try. I like it because I can fix any part of it easily and I can lock the rudders 1/2 way down when sailing over sandbars and the like.

As far as other rudder systems go, I think Dart made the best rudder systems I have ever tried.

Eric Anderson
Nacra 6.0
Hobie 14
DN 5193