A skeg or rudder can increase efficiency. They can also add a lot of drag. You need a good foil shape to begin with. You should also steer with the rudder as little as possible.

> I was paddling with a guy three years ago who took 2nd in the
> Blackburn Challenge. He uses a Wave x-L or a X-par missel. the interesting
> thing is that these racing hulls come with both skegs and rudders.
> You don't want to think about corrective strokes if you're a die-hard
> racer. This guy would use the rudder just dipped into the surface
> (as needed) he would add in the skeg if the seas fo so rough that
> the stern was lifting out of the water. His boat was 20 ' x 19"
> - kevlar - super thin and weighed nothing. He was also in excellent
> shape. He told me that he trained for a month by paddling about 3
> hours ever day (he was unemployed) including some 15 minute sprints
> as hard as he could paddle.