BOATYARD
dependent of toe-in or toe-out), a cer-
tain number of degrees, depending on
the vehicle. Thanks to geometry, when
the steering is put hard over, the inside
wheel, or rudder, is turned more than
the outside one, by half as many de-
grees as the toe-in of the tillers. Dave
Gerr recommends a toe-in angle of 10
degrees for boats that have a beam of
10 feet or more, and 7 degrees for nar-
rower craft. Catamaran sailors, who want minimum rudder drag in
tight maneuvers, sometimes toe-in their tillers as much as 20 degrees.
Toe-in geometry is more complex with cars than with boats, of
course, since the rear wheels come into play. With boats, there are
only the rudders to worry about, and if things aren’t adjusted pre-
cisely, the only effect is turbulence around the rudders and a little
extra drag—no big deal. But using the Ackermann principle to fine-
tune steering can add that little bit extra to the boat’s handling. It’s
easy to do when setting up the steering: It only requires cutting the
keyways on the rudder posts 10 degrees, give or take, inboard from
the centerline. Once installed, the rudders behave in much the same
way as any other conventional, tie-bar steering system.The End of the Tie Bar?
You probably won’t find many powerboats that make use of the
Ackermann principle these days, and most of the preceding likely
will be moot in a few years, as boatbuilders turn more to electronic
steering with individual rudder control. Eventually, the tie bar
will be as outdated as the rumble seat. If each rudder can turn
independently, it can assume the most efficient angle whether
running straight or cranked over in a hard turn. All that’s needed
is intelligent control, which comes from a computer that crunches
data input from various sources and determines how much to
deflect each rudder. Toe-in or toe-out is adjusted from the helm for
maximum straight-line speed; the computer handles the rest.
Viking Yachts was ahead of the curve with this, developing their VI-
PER steering in 2007. VIPER stands for Viking Independent Program-
mable Electro-hydraulic Rudder, and how it works is all in the name.
Electric impulses from the wheel are sent to controllers, which activate
hydraulic steering cylinders to turn the rudders. In the latest VIPER in-
carnation, the controllers are integral with the cylinders. There’s no tie
bar. Viking senior mechanical engineer Eric Metz said that some skip-Determining rudders’ optimal
toe-in geometry equals
improved performance.