"Rodney Myrvaagnes" wrote in message
...

Our boat exhibits no prop walk that I can detect. It also can't steer
from propwash in forward. It must be moving for any steering to occur.
The prop (18-inch Martec) is 12 feet forward of the spade rudder and
fairly close to the keel, so it has little lever arm to turn the boat.

I assume that this is a sail boat, which would put this into a "large
rudder" catagory. Sailboats, by their very nature, need to be able to steer
at slow speeds without any thrust from the prop. Thus, they install a rudder
that is large enough to provide adequate steering at dead slow speeds.

A typical power boat, on the other hand, uses a very small rudder that is
located as close as possible to the prop. The rudder is rarely taller than
the prop is. Such a rudder is very effective when it can deflect the stream
of water that is being pushed by the prop, but has minimal effect when the
prop is not turning.


Rod